Alinaghi, Pouriya; Janssens, Martin; Choudhury, Goutam; Goren, Tom; Siebesma, A. Pier; Glassmeier, FranziskaAlinaghi, P., M. Janssens, G. Choudhury, T. Goren, A. P. Siebesma, F. Glassmeier, 2024: Shallow cumulus cloud fields are optically thicker when they are more clustered. Quarterly Journal of the Royal Meteorological Society, n/a(n/a). doi: 10.1002/qj.4783. Shallow trade cumuli over subtropical oceans are a persistent source of uncertainty in climate projections. Mesoscale organization of trade cumulus clouds has been shown to influence their cloud radiative effect (CRE) through cloud cover. We investigate whether organization can explain CRE variability independently of cloud-cover variability. By analyzing satellite observations and high-resolution simulations, we show that more clustered cloud fields feature geometrically thicker clouds with larger domain-averaged liquid water paths, smaller cloud droplets, and consequently larger cloud optical depths. The relationships between these variables are shaped by the mixture of deep cloud cores and shallower interstitial clouds or anvils that characterize cloud organization. Eliminating cloud-cover effects, more clustered clouds reflect up to 20 W/m 2\ ^2 \ more instantaneous shortwave radiation back to space. cloud microphysics; cloud organization; cloud radiative effect; partial correlation
Atlas, R. L.; Bretherton, C. S.; Sokol, A. B.; Blossey, P. N.; Khairoutdinov, M. F.Atlas, R. L., C. S. Bretherton, A. B. Sokol, P. N. Blossey, M. F. Khairoutdinov, 2024: Tropical Cirrus Are Highly Sensitive to Ice Microphysics Within a Nudged Global Storm-Resolving Model. Geophysical Research Letters, 51(1), e2023GL105868. doi: 10.1029/2023GL105868. Cirrus dominate the longwave radiative budget of the tropics. For the first time, the variability in cirrus properties and longwave cloud radiative effects (CREs) that arises from using different microphysical schemes within nudged global storm-resolving simulations from a single model, is quantified. Nudging allows us to compute radiative biases precisely using coincident satellite measurements and to fix the large-scale dynamics across our set of simulations to isolate the influence of microphysics. We run 5-day simulations with four commonly-used microphysics schemes of varying complexity (SAM1MOM, Thompson, M2005 and P3) and find that the tropical average longwave CRE varies over 20 W m−2 between schemes. P3 best reproduces observed longwave CRE. M2005 and P3 simulate cirrus with realistic frozen water path but unrealistically high ice crystal number concentrations which commonly hit limiters and lack the variability and dependence on frozen water content seen in aircraft observations. Thompson and SAM1MOM have too little cirrus. anvil; global cloud-resolving model; tropical cirrus; global storm-resolving model; ice microphysics; longwave cloud radiative effect
Baba, Yuya; Ujiie, Masashi; Ota, Yukinari; Yonehara, HitoshiBaba, Y., M. Ujiie, Y. Ota, H. Yonehara, 2024: Implementation and evaluation of a spectral cumulus parametrization for simulating tropical cyclones in JMA-GSM. Quarterly Journal of the Royal Meteorological Society, n/a(n/a). doi: 10.1002/qj.4689. A spectral cumulus parametrization (spectral scheme) developed using a cloud-resolving model simulation was implemented in Global Spectral Model of the Japan Meteorological Agency (JMA-GSM, GSM hereafter). The performance of the spectral scheme in terms of mean state, variability, and tropical cyclone (TC) properties was evaluated using atmosphere-only model experiments by comparing results of the original convection scheme (based on Arakawa–Schubert scheme, AS scheme) and the spectral scheme. Parameter tunings were first conducted for the spectral scheme, through which the climatological errors of the cloud cover in the Southern Ocean and temperature were greatly improved. The spectral scheme showed comparable climatological errors to the AS scheme in the increased resolutions. The spectral scheme greatly improved tropical variability, that is, response to El Niño/Southern Oscillation and Madden–Julian Oscillation. Analyses on TC statistical data revealed that the spectral scheme improved TC properties in terms of genesis frequency, intensity, and the response of TC to tropical variability. Specifically, significant improvements were seen in the Northern Hemisphere. Further analyses on the TC structure revealed that higher TC intensity was sustained for longer times by the spectral scheme than by the AS scheme. The reason for this is that the spectral scheme better simulates convective heating by considering coexistence of different cloud types with parametrized vertically varying entrainment rates, especially from low to mid-altitudes. The convective heating leads to a sharper vertical-radial circulation in the TC structure, causing stronger incoming moisture flux toward the TC centre, and resulting in a stronger TC intensity. Consequently, the spectral scheme can simulate a comparable mean state, better variability, and better TC properties compared with the original scheme by simulating a more detailed convective structure. Therefore, it has a potential to increase the TC forecast skill for operational GSM. convection scheme; tropical variability; atmospheric general circulation model; tropical cyclone
Bao, Fangling; Letu, Husi; Shang, Huazhe; Ri, Xu; Chen, Deliang; Yao, Tandong; Wei, Lesi; Tang, Chenqian; Yin, Shuai; Ji, Dabin; Lei, Yonghui; Shi, Chong; Peng, Yiran; Shi, JianchengBao, F., H. Letu, H. Shang, X. Ri, D. Chen, T. Yao, L. Wei, C. Tang, S. Yin, D. Ji, Y. Lei, C. Shi, Y. Peng, J. Shi, 2024: Advancing Cloud Classification Over the Tibetan Plateau: A New Algorithm Reveals Seasonal and Diurnal Variations. Geophysical Research Letters, 51(13), e2024GL109590. doi: 10.1029/2024GL109590. The cloud classification algorithm widely used in the International Satellite Cloud Climatology Project (ISCCP) tends to underestimate low clouds over the Tibetan Plateau (TP), often mistaking water clouds for high-level clouds. To address this issue, we propose a new algorithm based on cloud-top temperature and optical thickness, which we apply to TP using Advanced Himawari Imager (AHI) geostationary satellite data. Compared with Clouds and the Earth's Radiant Energy System cloud-type products and ISCCP results obtained from AHI data, this new algorithm markedly improved low-cloud detection accuracy and better aligned with cloud phase results. Validation with lidar cloud-type products further confirmed the superiority of this new algorithm. Diurnal cloud variations over the TP show morning dominance shifting to afternoon high clouds and evening mid-level clouds. Winter is dominated by high clouds, summer by mid-level clouds, spring by daytime low clouds and nighttime high clouds, and autumn by low and mid-level clouds. cloud classification; cloud-type algorithm; low clouds; Tibetan Plateau
Baran, Anthony J.; Manners, James; Field, Paul; Hill, AdrianBaran, A. J., J. Manners, P. Field, A. Hill, 2024: A novel new coupled two-moment parametrization for cirrus radiative properties and its impact in a cloud-aerosol resolving model (CASIM). AIP Conference Proceedings, 2988(1), 080003. doi: 10.1063/5.0183481. The latest assessment of the Intergovernmental Panel on Climate Change (IPCC) report that there is significant uncertainty in the radiative effect of aerosol-ice interactions on the Earth’s atmosphere radiation balance. This is partly owing to the lack of knowledge of the interaction between aerosol and ice, and how this interaction evolves the ice particle shapes, and particle size distribution (PSD). This is further exacerbated by the fact that current cloud-aerosol interaction models cannot adequately address this radiative uncertainty owing to an inherent lack of consistency between the two-moment microphysics and the evolving radiation fields. Here, we address this lack of consistency by directly coupling the global CASIM prognostic moments (i.e. mass and number) to the ice optical properties through the same assumed PSD (i.e. the generalized gamma function). We examine the impact of this consistent coupling on the outgoing top-of-atmosphere (TOA) short- and long-wave irradiance fields in the Met Office’s regional model, which was centered around Darwin, Australia, and compare them to the CERES short- and long-wave local midday irradiance measurements. We show that the consistent moment–ice optical coupling better describes the probability density function (PDF) of the CERES short-wave irradiance measurements than the current operational model ice optical parametrization. However, the PDF of the CERES long-wave measurements is better described by the current operational model parametrization than the consistent moment–ice optical coupling. This inconsistency between the short-wave and long-wave results is further discussed together with its potential resolution.
Barnett, Michelle L.; Kemp, Alan E. S.; Hickman, Anna E.; Purdie, Duncan A.Barnett, M. L., A. E. S. Kemp, A. E. Hickman, D. A. Purdie, 2024: Environmental controls on the interannual variability in chlorophyll and phytoplankton community structure within the seasonal sub surface chlorophyll maximum in the western English channel. Continental Shelf Research, 277, 105253. doi: 10.1016/j.csr.2024.105253. The subsurface chlorophyll maximum (SCM) is increasingly recognised as an important but understudied locus of primary production particularly in shelf seas. Here we report the results of a 4 year, repeat station, summer sampling programme (2013–2016) of a seasonally recurrent SCM in the Western English Channel. Interannual variability in phytoplankton community structure and chlorophyll distribution and intensity was strongly related to water column stability at the depth interval of the SCM and also to water temperature. The phytoplankton community was statistically distinct in each year. High stability, as evidenced by large Richardson numbers and a well-developed strong thermocline appeared to favour the growth of larger dinoflagellates (autotrophs or mixotrophs) and diatoms. Such conditions led to development of the most intense SCMs and these were sometimes dominated by a single or a few key species most prominently in 2015 with near monospecific concentrations of the dinoflagellate Tripos fusus with average peak SCM chlorophyll concentrations of 7.3 ± 4.4 μg l−1. By contrast, in years with low water column stability and intermittent turbulence at the thermocline (2014, 2016) there was greater chlorophyll dispersal and less intense SCM. In these low stability conditions, red fluorescent nano-phytoplankton, such as naked dinoflagellates, chlorophytes and prymnesiophytes, made a greater contribution to the community, possibly as a result of the advantages that motility and enhanced light utilisation efficiency confer within an SCM exposed to turbulence. It is also likely that turbulence disrupted the stability required by the larger dinoflagellates and diatoms. Several of the key SCM taxa were absent from surface waters including the dinoflagellates Tripos fusus, Tripos lineatus, and most of the Rhizosolenia/Proboscia diatoms, consistent with adaptations more suited to survival at depth in stratified waters. These traits include luxury nutrient uptake and storage and survival in low light (both groups) and mixotrophy (dinoflagellates). On the other hand, in 2013, diatoms including Pseudo-nitzschia spp. were abundant in both surface, SCM and bottom waters. The relatively cooler waters (11.6–12.1 °C on average in 2013 and 2016) were characterised by smaller diatoms (Chaetoceros spp. and Pseudo-nitzschia spp.) whereas the warmer waters (13.1 °C on average in 2014) contained larger diatoms (large Rhizosolenia spp., Lauderia annulata and Leptocylindrus danicus). There did not appear to be continuity of key species between years, other than for the dinoflagellate Tripos lineatus, which was significant in both 2013 and 2014 and present in 2015. In any given year, there was no correspondence between the key spring bloom phytoplankton species as monitored in the nearby Western Channel Observatory L4 station and the key SCM taxa. Phytoplankton community structure; Subsurface chlorophyll maximum; Thermocline stratification; Turbulence; Western English Channel
Barrientos-Velasco, Carola; Cox, Christopher J.; Deneke, Hartwig; Dodson, J. Brant; Hünerbein, Anja; Shupe, Matthew D.; Taylor, Patrick C.; Macke, AndreasBarrientos-Velasco, C., C. J. Cox, H. Deneke, J. B. Dodson, A. Hünerbein, M. D. Shupe, P. C. Taylor, A. Macke, 2024: Estimation of the radiation budget during MOSAiC based on ground-based and satellite remote sensing observations. EGUsphere, 1-53. doi: 10.5194/egusphere-2024-2193. Abstract. An accurate representation of the radiation budget is essential for investigating the radiative effect that clouds have on the climate system, especially in the Arctic, an environment highly sensitive to complex and rapid environmental changes. In this study, we analyse a unique dataset of observations from the central Arctic made during the MOSAiC (Multidisciplinary drifting Observatory for the Study of Arctic Climate) expedition in conjunction with state-of-the-art satellite products from CERES (Clouds and the Earth's Radiant Energy System) to investigate the radiative effect of clouds and radiative closure at the surface and the top of the atmosphere (TOA). We perform a series of radiative transfer simulations using derived cloud macro- and microphysical properties as inputs to the simulations for the entire MOSAiC period, comparing our results to collocated satellite products and ice-floe observations. The radiative closure biases were generally within the instrumental uncertainty, indicating that the simulations are sufficiently accurate to realistically reproduce the radiation budget during MOSAiC. Comparisons of the simulated radiation budget relative to CERES show similar values in the terrestrial flux but relatively large differences in the solar flux, which is attributed to a lower surface albedo and a possible underestimation of atmospheric opacity by CERES. While the simulation results were consistent with the observations, more detailed analyses reveal an overestimation of simulated cloud opacity for cases involving geometrically thick ice clouds. In the annual mean, we found that the presence of clouds leads to a loss of 5.2 W m-2, of the atmospheric-surface system to space, while the surface gains 25 W m-2, and the atmosphere is cooled by clouds by 30.2 W m-2, during the MOSAiC expedition.
Barrientos-Velasco, Carola; Deneke, Hartwig; Griesche, Hannes J.; Hünerbein, Anja; Macke, Andreas; Seifert, Patric; Shupe, Matthew; Witthuhn, JonasBarrientos-Velasco, C., H. Deneke, H. J. Griesche, A. Hünerbein, A. Macke, P. Seifert, M. Shupe, J. Witthuhn, 2024: Investigation of the annual cycle of the cloud radiative effect based on CERES and Polarstern observations during MOSAiC. AIP Conference Proceedings, 2988(1), 060005. doi: 10.1063/5.0183726. The unique in-situ and remote-sensing observations obtained during the Multidisciplinary drifting Observatory for the Study of Arctic Climate (MOSAiC) expedition from the ice-breaker Polarstern (from September 2019 to October 2020) were used to evaluate the Clouds and the Earth’s Radiant Energy System (CERES) satellite products over the central Arctic. Within the scope of this analysis, the consistency among CERES products, radiative transfer simulations based on shipborne remote-sensing observations (named T-CARS) and observed downward solar (SOL) and terrestrial (TER) radiative fluxes are assessed. It was found that during polar night (27 October 2019 to 13 March 2020), CERES products had systematic deviations around 0.2-21.6 Wm−2 compared to the observed broadband downward TER flux at the surface. During polar day (14 March 2020 to 30 September 2020), the flux differences of CERES relatively decreased to 2.2-15.8 Wm−2. T-CARS simulations show a good agreement for all conditions during polar night with mean biases around 0.6-6.4 Wm−2. Still, significant flux differences were found for the downward TER and SOL radiative fluxes for polar day. Preliminary calculations of the cloud radiative effect based on shipborne and satellite-based simulations indicate a warming effect of clouds at the surface of around 41 Wm−2 and 15 Wm−2 for polar night and polar day, respectively.
Bayoumi, S.; Moharram, N. A.; Shehata, A. I.; Imam, M. M.; El-Maghlany, W. M.Bayoumi, S., N. A. Moharram, A. I. Shehata, M. M. Imam, W. M. El-Maghlany, 2024: A multi-criteria performance assessment of concentrated solar power plants for site and technology selection in Egypt. International Journal of Environmental Science and Technology, 21(3), 2989-3004. doi: 10.1007/s13762-023-05114-1. The objective of this research is to investigate the implementation of two concentrated solar power (CSP) technologies in the 28 devoted locations in Egypt, in order to select the optimum site-specific CSP technology. This may be achieved by a validated thermo-economic simulation of power plants using the Sam advisory model and an investigation of the two proposed CSP technologies’ configurations to fulfill the power plant’s thermal demand. Simulations take into consideration the environmental, technical, financial, and economic aspects of the projects. Among many simulated parameters, three are considered to compare the two proposed technologies' configurations in the 28 locations utilizing geographic information system aid. Those parameters are the annual power production, the levelized cost of energy, and water consumption. A comparative analysis indicated that the solar tower requires 25% more land than the parabolic trough. The additional collecting area raised the net capital cost of the solar tower system by 15% over the parabolic trough model. As a result, the solar tower arrangement reduces the levelized cost of energy while increasing the yearly power generated and water required by the power plant. Simulation results favored the proposed solar tower configuration over the parabolic trough and recommended the implementation of such concentrated solar power projects in the central and eastern locations of Egypt. Sustainability; Concentrated solar power; Geographic information system; Multi-criteria decision analysis; Parabolic trough; Solar tower
Bhatti, Yusuf A.; Revell, Laura E.; McDonald, Adrian J.; Archibald, Alex T.; Schuddeboom, Alex J.; Williams, Jonny; Hardacre, Catherine; Mulcahy, Jane; Lin, DongqiBhatti, Y. A., L. E. Revell, A. J. McDonald, A. T. Archibald, A. J. Schuddeboom, J. Williams, C. Hardacre, J. Mulcahy, D. Lin, 2024: Aerosol and Dimethyl Sulfide Sensitivity to Sulfate Chemistry Schemes. Journal of Geophysical Research: Atmospheres, 129(12), e2023JD040635. doi: 10.1029/2023JD040635. Dimethyl sulfide (DMS) is the largest source of natural sulfur in the atmosphere and undergoes oxidation reactions resulting in gas-to-particle conversion to form sulfate aerosol. Climate models typically use independent chemical schemes to simulate these processes, however, the sensitivity of sulfate aerosol to the schemes used by CMIP6 models has not been evaluated. Current climate models offer oversimplified DMS oxidation pathways, adding to the ambiguity surrounding the global sulfur burden. Here, we implemented seven DMS and sulfate chemistry schemes, six of which are from CMIP6 models, in an atmosphere-only Earth system model. A large spread in aerosol optical depth (AOD) is simulated (0.077), almost twice the magnitude of the pre-industrial to present-day increase in AOD. Differences are largely driven by the inclusion of the nighttime DMS oxidation reaction with NO3, and in the number of aqueous phase sulfate reactions. Our analysis identifies the importance of DMS-sulfate chemistry for simulating aerosols. We suggest that optimizing DMS/sulfur chemistry schemes is crucial for the accurate simulation of sulfate aerosols. AOD; chemistry; clouds; DMS; modeling; sulfate
Bock, Lisa; Lauer, AxelBock, L., A. Lauer, 2024: Cloud properties and their projected changes in CMIP models with low to high climate sensitivity. Atmospheric Chemistry and Physics, 24(3), 1587-1605. doi: 10.5194/acp-24-1587-2024. Since the release of the first Coupled Model Intercomparison Project version 6 (CMIP6) simulations, one of the most discussed topics is the higher effective climate sensitivity (ECS) of some of the models, resulting in an increased range of ECS values in CMIP6 compared to previous CMIP phases. An important contribution to ECS is the cloud climate feedback. Although climate models have continuously been developed and improved over the last few decades, a realistic representation of clouds remains challenging. Clouds contribute to the large uncertainties in modeled ECS, as projected changes in cloud properties and cloud feedbacks also depend on the simulated present-day fields. In this study, we investigate the representation of both cloud physical and radiative properties from a total of 51 CMIP5 and CMIP6 models. ECS is used as a simple metric to group the models, as the sensitivity of the physical cloud properties to warming is closely related to cloud feedbacks, which in turn are known to have a large contribution to ECS. Projected changes in the cloud properties in future scenario simulations are analyzed by the ECS group. In order to help with interpreting the projected changes, model results from historical simulations are also analyzed. The results show that differences in the net cloud radiative effect as a reaction to warming among the three model groups are driven by changes in a range of cloud regimes rather than individual regions. In polar regions, high-ECS models show a weaker increase in the net cooling effect of clouds, due to warming, than the low-ECS models. At the same time, high-ECS models show a decrease in the net cooling effect of clouds over the tropical ocean and the subtropical stratocumulus regions, whereas low-ECS models show either little change or even an increase in the cooling effect. Over the Southern Ocean, the low-ECS models show a higher sensitivity of the net cloud radiative effect to warming than the high-ECS models.
Brendecke, Jordann; Dong, Xiquan; Xi, Baike; Zhong, Xiang; Li, Jiangnan; Barker, Howard W.; Pilewskie, PeterBrendecke, J., X. Dong, B. Xi, X. Zhong, J. Li, H. W. Barker, P. Pilewskie, 2024: Evaluation of clear-sky surface downwelling shortwave fluxes computed by three atmospheric radiative transfer models. Journal of Quantitative Spectroscopy and Radiative Transfer, 328, 109164. doi: 10.1016/j.jqsrt.2024.109164. In this study the clear-sky total, direct, and diffuse shortwave (SW) fluxes at the surface, have been calculated by three radiation transfer models (RTMs) – MODTRAN6.0 (M6.0), Canadian Centre for Climate Modelling and Analysis (CCCma), and Langley-modified Fu-Liou (NASA CERES). These calculations have been evaluated by surface measurements collected from seven sites that represent different climatological regimes with various surface scene types including ocean, grassland/continental, desert, and snow/sea ice. For pristine atmospheric conditions, SW fluxes predicted by CCCma and M6.0 shows little variation, which lays a baseline for further analysis. Note that computing time required by CCCma is ∼1000 times smaller than M6.0. Based on all samples collected from seven sites, mean differences of total, direct, and diffuse fluxes between surface measurements and CCCma / M6.0 / Fu-Liou are [5.3 / 2.4 / 0.9], [-2.2 / -5.1 / -13.7], and [7.5 / 7.5 / 14.6] W m-2, respectively. Histograms of differences between the three RTM calculations and surface measurements show that CCCma computed direct and diffuse fluxes have the smallest biases with standard deviations similar to those for M6.0, while Fu-Liou values have the largest biases and standard deviations. While Fu-Liou outperforms for total flux, especially for desert conditions, it is hampered by large biases for direct and diffuse across all scene types. The three RTMs are consistent with showing the least error for total flux and the largest in diffuse based on bias, correlation, and root mean square error. MODTRAN, CERES, Correlated -distribution, Shortwave Flux; Radiative transfer
Cao, Yunfeng; Yin, Mengxi; Tian, Jiaxin; Liang, ShunlinCao, Y., M. Yin, J. Tian, S. Liang, 2024: Increased summertime wildfire as a major driver of the clear-sky dimming in the Siberian Arctic from 2000 to 2020. Atmospheric Research, 306, 107458. doi: 10.1016/j.atmosres.2024.107458. A warming Arctic is expected to exacerbate wildfires in Siberia, potentially creating a critical feedback to the Arctic climate change. However, our understanding of these fire-climate interactions remains limited. This study investigated changes in East Siberian wildfires and their influence on fire emissions, aerosol optical depth (AOD), and the surface clear-sky insolation across the Siberian Arctic from 2000 to 2020 using satellite observations. Our analysis reveals a substantial increase in wildfires, with fire counts doubling (a 114% increase) and fire radiative power surging by 8.4 × 106 MW compared to the early 21st century. Over 93% of this increase occurred during the boreal summer months. These intensified wildfires led to a significant rise in aerosol emission (organic carbon, PM2.5, and black carbon) exceeding 75% in East Siberia. Consequently, fire-season AOD in the Siberian Arctic increased by 33% (6.0 × 10−2), with 85% (5.1 × 10−2) attributable to wildfire changes. The wildfire-associated increase in AOD resulted in enhanced clear-sky dimming of 4.1 ± 3.2 W m−2 across the Siberian Arctic from 2000 to 2020. These findings suggest a critical feedback mechanism: a warming Arctic drives increased wildfires in Siberia, which in turn significantly impact the Arctic surface radiative budget through enhanced clear-sky dimming. Future simulations and projections for the Arctic should prioritize incorporating the feedback effects of intensifying wildfires. Aerosol optical depth; Arctic amplification; Clear-sky dimming; Siberia wildfire
Carrigg, Joseph; Yu, Lisan; Menezes, Viviane V.; Chen, YanxuCarrigg, J., L. Yu, V. V. Menezes, Y. Chen, 2024: Autumnal Equinox Shift in Arctic Surface Energy Budget: Beaufort-Chukchi Seas Case Study. Journal of Geophysical Research: Oceans, 129(5), e2023JC020788. doi: 10.1029/2023JC020788. This study examines the annual cycle of the Surface Energy Budget (SEB) in the Beaufort-Chukchi seas, focusing on the autumn transition. Shipboard measurements from NASA's Salinity and Stratification at the Sea Ice Edge (SASSIE) experiment (8 September–2 October 2022) and satellite flux analysis for the entire 2022 were utilized to provide a comprehensive perspective of the SEB's seasonal dynamics. An important finding is the alignment of SEB’s autumnal transition with the September 22 equinox, marking the onset of prolonged Arctic darkness. This transition involved a shift from the summertime radiative heating to cooling conditions, characterized by outgoing longwave radiation surpassing incoming solar radiation and a notable increase in synoptic turbulent latent and sensible heat flux variability. The increased turbulent heat fluxes after the equinox were associated with increased occurrences of short-duration cold air outbreaks. These outbreaks seem to originate from cold mesoscale surface winds transitioning from cooling landmasses or ice caps to the warmer seas, driven by differential cooling rates between land/ice and ocean as solar irradiance declined. Turbulent heat losses, outpacing longwave emission by more than fivefold, accelerated ocean surface cooling in the subsequent 2 months, leading to the complete freeze-up of the Beaufort-Chukchi seas by late November. These findings underscore the substantial influence of astronomical seasons on the SEB, emphasizing their crucial role in Arctic climate dynamics. Arctic Ocean; autumnal equinox; Beaufort-Chukchi seas; cold air outbreaks; energy autumn transition; surface energy budget
Castant, Jérôme; Vantrepotte, Vincent; Frouin, Robert; Beaugrand, GrégoryCastant, J., V. Vantrepotte, R. Frouin, G. Beaugrand, 2024: Comprehensive gridded dataset of photosynthetically active radiation in the upper ocean from 1958 to 2022. Remote Sensing of Environment, 311, 114305. doi: 10.1016/j.rse.2024.114305. Photosynthetically Active Radiation (PAR) plays a crucial role in shaping marine ecosystems, influencing primary production, species interaction, and phytoplankton seasonal dynamics. However, comprehensive long-term (gap-free) datasets for both surface PAR and the diffuse Attenuation Coefficient of Photosynthetically Active Radiation (KdPAR) are currently lacking. In this study, we introduce two new extensive global 4D PAR gap-free datasets (Longitude x Latitude x Day x Depth) at a resolution of 0.25o latitude x 0.25o longitude from surface to 250 m covering the periods 1998–2022 and 1958–2022. The first dataset (1998–2022) is primarily derived from Globcolour (surface PAR and Chlorophyll-a), supplemented with missing surface PAR data estimated using the Environmental String Model (ESM) with key climatic ERA5 variables. Missing Chlorophyll-a data are interpolated by applying the DINEOF method (Data Interpolating Empirical Orthogonal Functions) and transformed into KdPAR. Visual and numerical evaluations closely approximate observations, demonstrating the accuracy of our approach. Subsequently, we extend our dataset back to 1958 using exclusively the ESM based on key climatic ERA5 variables. The ESM outperforms the Generalized Regression on Neural Network (GRNN) in computational efficiency while yielding similar results. Validation against in-situ measurements confirms the reliability of PAR and KdPAR surface products. Although the 1958–2022 dataset exhibits limited daily variability in PAR compared to the 1998–2022 dataset, it effectively captures critical spatial-temporal patterns, as demonstrated by correlative and comparative studies with El Niño indices. Furthermore, the similarity observed between euphotic depth (Zeu) derived from our ESM-based 4D PAR dataset (1958–2022), and the Mercator-Ocean hindcast model, along with in-situ data, underscores the robustness of our approach in capturing light availability at depth. Beer-Lambert law; Diffuse Attenuation Coefficient of Photosynthetically Active Radiation (KPAR); Environmental String Model (ESM); ERA5; Photosynthetically Active Radiation (PAR); Remote sensing
Cesana, Grégory V.; Pierpaoli, Olivia; Ottaviani, Matteo; Vu, Linh; Jin, Zhonghai; Silber, IsraelCesana, G. V., O. Pierpaoli, M. Ottaviani, L. Vu, Z. Jin, I. Silber, 2024: The correlation between Arctic sea ice, cloud phase and radiation using A-Train satellites. Atmospheric Chemistry and Physics, 24(13), 7899-7909. doi: 10.5194/acp-24-7899-2024. Climate warming has a stronger impact on Arctic climate and sea ice cover (SIC) decline than previously thought. Better understanding and characterization of the relationship between sea ice and clouds and the implications for surface radiation is key to improving our confidence in Arctic climate projections. Here we analyze the relationship between sea ice, cloud phase and surface radiation over the Arctic, defined as north of 60° N, using active- and passive-sensor satellite observations from three different datasets. We find that all datasets agree on the climatology of and seasonal variability in total and liquid-bearing (liquid and mixed-phase) cloud covers. Similarly, our results show a robust relationship between decreased SIC and increased liquid-bearing clouds in the lowest levels (below 3 km) for all seasons (strongest in winter) but summer, while increased SIC and ice clouds are positively correlated in two of the three datasets. A refined map correlation analysis indicates that the relationship between SIC and liquid-bearing clouds can change sign over the Bering, Barents and Laptev seas, likely because of intrusions of warm air from low latitudes during winter and spring. Finally, the increase in liquid clouds resulting from decreasing SIC is associated with enhanced radiative cooling at the surface. Our findings indicate that the newly formed liquid clouds reflect more shortwave (SW) radiation back to space compared to the surface, generating a cooling effect of the surface, while their downward longwave (LW) radiation is similar to the upward LW surface emission, which has a negligible radiative impact on the surface. This overall cooling effect should contribute to dampening future Arctic surface warming as SIC continues to decline.
Chao, Li-Wei; Zelinka, Mark D.; Dessler, Andrew E.Chao, L., M. D. Zelinka, A. E. Dessler, 2024: Evaluating Cloud Feedback Components in Observations and Their Representation in Climate Models. Journal of Geophysical Research: Atmospheres, 129(2), e2023JD039427. doi: 10.1029/2023JD039427. This study quantifies the contribution of individual cloud feedbacks to the total short-term cloud feedback in satellite observations over the period 2002–2014 and evaluates how they are represented in climate models. The observed positive total cloud feedback is primarily due to positive high-cloud altitude, extratropical high- and low-cloud optical depth, and land cloud amount feedbacks partially offset by negative tropical marine low-cloud feedback. Seventeen models from the Atmosphere Model Intercomparison Project of the sixth Coupled Model Intercomparison Project are analyzed. The models generally reproduce the observed moderate positive short-term cloud feedback. However, compared to satellite estimates, the models are systematically high-biased in tropical marine low-cloud and land cloud amount feedbacks and systematically low-biased in high-cloud altitude and extratropical high- and low-cloud optical depth feedbacks. Errors in modeled short-term cloud feedback components identified in this analysis highlight the need for improvements in model simulations of the response of high clouds and tropical marine low clouds. Our results suggest that skill in simulating interannual cloud feedback components may not indicate skill in simulating long-term cloud feedback components. CERES; cloud feedback; climate modeling; pattern effect
Chapman-Dutton, H. R.; Webster, M. A.Chapman-Dutton, H. R., M. A. Webster, 2024: The Effects of Summer Snowfall on Arctic Sea Ice Radiative Forcing. Journal of Geophysical Research: Atmospheres, 129(14), e2023JD040667. doi: 10.1029/2023JD040667. Snow is the most reflective natural surface on Earth. Since fresh snow on bare sea ice increases the surface albedo, the impact of summer snow accumulation can have a negative radiative forcing effect, which would inhibit sea ice surface melt and potentially slow sea-ice loss. However, it is not well known how often, where, and when summer snowfall events occur on Arctic sea ice. In this study, we used in situ and model snow depth data paired with surface albedo and atmospheric conditions from satellite retrievals to characterize summer snow accumulation on Arctic sea ice from 2003 to 2017. We found that, across the Arctic, ∼2 snow accumulation events occurred on initially snow-free conditions each year. The average snow depth and albedo increases were ∼2 cm and 0.08, respectively. 16.5% of the snow accumulation events were optically thick (>3 cm deep) and lasted 2.9 days longer than the average snow accumulation event (3.4 days). Based on a simple, multiple scattering radiative transfer model, we estimated a −0.086 ± 0.020 W m−2 change in the annual average top-of-the-atmosphere radiative forcing for summer snowfall events in 2003–2017. The following work provides new information on the frequency, distribution, and duration of observed snow accumulation events over Arctic sea ice in summer. Such results may be particularly useful in understanding the impacts of ephemeral summer weather on surface albedo and their propagating effects on the radiative forcing over Arctic sea ice, as well as assessing climate model simulations of summer atmosphere-ice processes. albedo; Arctic; radiation; sea ice; snow
Chatterjee, Dwaipayan; Schnitt, Sabrina; Bigalke, Paula; Acquistapace, Claudia; Crewell, SusanneChatterjee, D., S. Schnitt, P. Bigalke, C. Acquistapace, S. Crewell, 2024: Capturing the Diversity of Mesoscale Trade Wind Cumuli Using Complementary Approaches From Self-Supervised Deep Learning. Geophysical Research Letters, 51(12), e2024GL108889. doi: 10.1029/2024GL108889. At mesoscale, trade wind clouds organize with various spatial arrangements, shaping their effect on Earth's energy budget. Representing their fine-scale dynamics even at 1 km scale climate simulations remains challenging. However, geostationary satellites (GS) offer high-resolution cloud observation for gaining insights into trade wind cumuli from long-term records. To capture the observed organizational variability, this work proposes an integrated framework using a continuous followed by discrete self-supervised deep learning approach, which exploits cloud optical depth from GS measurements. We aim to simplify the entire mesoscale cloud spectrum by reducing the image complexity in the feature space and meaningfully partitioning it into seven classes whose connection to environmental conditions is illustrated with reanalysis data. Our framework facilitates comparing human-labeled mesoscale classes with machine-identified ones, addressing uncertainties in both methods. It advances previous methods by exploring transitions between regimes, a challenge for physical simulations, and illustrates a case study of sugar-to-flower transitions. artificial intelligence; cloud system transition; cloud variability; mesoscale cloud organization; self-supervision; tropical clouds
Chen, Yan; Wang, Guiling; Seth, AnjiChen, Y., G. Wang, A. Seth, 2024: Climatic Drivers for the Variation of Gross Primary Productivity Across Terrestrial Ecosystems in the United States. Journal of Geophysical Research: Biogeosciences, 129(8), e2024JG008168. doi: 10.1029/2024JG008168. Temperature and water stress are important factors limiting the gross primary productivity (GPP) in terrestrial ecosystems, yet the extent of their influence across ecosystems remains uncertain. This study examines how surface air temperature, soil water availability (SWA) and vapor pressure deficit (VPD) influence ecosystem light use efficiency (LUE), a critical metric for assessing GPP, across different ecosystems and climatic zones at 80 flux tower sites based on in situ measurements and data assimilation products. Results indicate that LUE increases with temperature in spring, with higher correlation coefficients in colder regions (0.79–0.82) than in warmer regions (0.68–0.78). LUE reaches a plateau earlier in the season in warmer regions. LUE variations in summer are mainly driven by SWA, exhibiting a positive correlation indicative of a water-limited regime. The relationship between the daily LUE and daytime temperature shows a clear seasonal hysteresis at many sites, with a higher LUE in spring than in fall under the same temperature, likely resulting from younger leaves being more efficient in photosynthesis. Drought stress influences LUE through SWA in all ranges of water availability; VPD variation under moderate conditions does not have a clear influence on LUE, but extremely high VPD (exceeding the threshold of 1.6 kPa, often observed during extreme drought-heat events) causes a dramatic reduction of LUE. Our findings provide insight into how ecosystem productivities respond to climate variability and how they may change under the influence of more frequent and severe heat and drought events projected for the future. hysteresis; light use efficiency; soil water availability; temperature; vegetation responses
Chen, Yanxu; Yu, LisanChen, Y., L. Yu, 2024: Mesoscale Meridional Heat Transport Inferred From Sea Surface Observations. Geophysical Research Letters, 51(5), e2023GL106376. doi: 10.1029/2023GL106376. The ocean regulates the Earth's climate by transporting heat from the equator to the poles. Here, we use satellite-based sea surface observations of air-sea heat fluxes and eddy detection to investigate the mesoscale heat transport. “Mesoscale” refers to both the Eulerian perspective as the spatio-temporal scales of ∼100 km and ∼1 month, as well as the Lagrangian aspect as isolated vortices identified from the dynamic topography. Paradoxically, there are a considerable number of mesoscale eddies inconsistent between their surface thermal and dynamic signals, that is, cold-core anticyclones and warm-core cyclones are globally prevalent. On account of such inconsistency, we show that the mesoscale meridional heat transport carried by geostrophic components is 10 times larger than (and opposite in direction to) that of the wind-driven Ekman components. An offset between SSH-SST coherent and incoherent eddies in the Ekman heat transport is apparent, whereas the geostrophic heat transport is contained within coherent eddies.
Chen, Ying; Haywood, Jim; Wang, Yu; Malavelle, Florent; Jordan, George; Peace, Amy; Partridge, Daniel G.; Cho, Nayeong; Oreopoulos, Lazaros; Grosvenor, Daniel; Field, Paul; Allan, Richard P.; Lohmann, UlrikeChen, Y., J. Haywood, Y. Wang, F. Malavelle, G. Jordan, A. Peace, D. G. Partridge, N. Cho, L. Oreopoulos, D. Grosvenor, P. Field, R. P. Allan, U. Lohmann, 2024: Substantial cooling effect from aerosol-induced increase in tropical marine cloud cover. Nature Geoscience, 17(5), 404-410. doi: 10.1038/s41561-024-01427-z. With global warming currently standing at approximately +1.2 °C since pre-industrial times, climate change is a pressing global issue. Marine cloud brightening is one proposed method to tackle warming through injecting aerosols into marine clouds to enhance their reflectivity and thereby planetary albedo. However, because it is unclear how aerosols influence clouds, especially cloud cover, both climate projections and the effectiveness of marine cloud brightening remain uncertain. Here we use satellite observations of volcanic eruptions in Hawaii to quantify the aerosol fingerprint on tropical marine clouds. We observe a large enhancement in reflected sunlight, mainly due to an aerosol-induced increase in cloud cover. This observed strong negative aerosol forcing suggests that the current level of global warming is driven by a weaker net radiative forcing than previously thought, arising from the competing effects of greenhouse gases and aerosols. This implies a greater sensitivity of Earth’s climate to radiative forcing and therefore a larger warming response to both rising greenhouse gas concentrations and reductions in atmospheric aerosols due to air quality measures. However, our findings also indicate that mitigation of global warming via marine cloud brightening is plausible and is most effective in humid and stable conditions in the tropics where solar radiation is strong. Climate change; Atmospheric science
Cheng, Lijing; Abraham, John; Trenberth, Kevin E.; Boyer, Tim; Mann, Michael E.; Zhu, Jiang; Wang, Fan; Yu, Fujiang; Locarnini, Ricardo; Fasullo, John; Zheng, Fei; Li, Yuanlong; Zhang, Bin; Wan, Liying; Chen, Xingrong; Wang, Dakui; Feng, Licheng; Song, Xiangzhou; Liu, Yulong; Reseghetti, Franco; Simoncelli, Simona; Gouretski, Viktor; Chen, Gengxin; Mishonov, Alexey; Reagan, Jim; Von Schuckmann, Karina; Pan, Yuying; Tan, Zhetao; Zhu, Yujing; Wei, Wangxu; Li, Guancheng; Ren, Qiuping; Cao, Lijuan; Lu, YayangCheng, L., J. Abraham, K. E. Trenberth, T. Boyer, M. E. Mann, J. Zhu, F. Wang, F. Yu, R. Locarnini, J. Fasullo, F. Zheng, Y. Li, B. Zhang, L. Wan, X. Chen, D. Wang, L. Feng, X. Song, Y. Liu, F. Reseghetti, S. Simoncelli, V. Gouretski, G. Chen, A. Mishonov, J. Reagan, K. Von Schuckmann, Y. Pan, Z. Tan, Y. Zhu, W. Wei, G. Li, Q. Ren, L. Cao, Y. Lu, 2024: New Record Ocean Temperatures and Related Climate Indicators in 2023. Advances in Atmospheric Sciences. doi: 10.1007/s00376-024-3378-5. The global physical and biogeochemical environment has been substantially altered in response to increased atmospheric greenhouse gases from human activities. In 2023, the sea surface temperature (SST) and upper 2000 m ocean heat content (OHC) reached record highs. The 0–2000 m OHC in 2023 exceeded that of 2022 by 15 ± 10 ZJ (1 Zetta Joules = 1021 Joules) (updated IAP/CAS data); 9 ± 5 ZJ (NCEI/NOAA data). The Tropical Atlantic Ocean, the Mediterranean Sea, and southern oceans recorded their highest OHC observed since the 1950s. Associated with the onset of a strong El Niño, the global SST reached its record high in 2023 with an annual mean of ∼0.23°C higher than 2022 and an astounding > 0.3°C above 2022 values for the second half of 2023. The density stratification and spatial temperature inhomogeneity indexes reached their highest values in 2023. climate; global warming; ocean heat content; salinity; stratification
Choudhury, Goutam; Goren, TomChoudhury, G., T. Goren, 2024: Thin Clouds Control the Cloud Radiative Effect Along the Sc-Cu Transition. Journal of Geophysical Research: Atmospheres, 129(10), e2023JD040406. doi: 10.1029/2023JD040406. In situ and spaceborne studies reveal the prevalence of thin clouds in the major Stratocumulus-to-Cumulus Transition (SCT) regions. Using instantaneous satellite and reanalysis data, this study investigates the properties of thin clouds in the Southeast Pacific Ocean and their impact on the cloud radiative effect (CRE). Our findings demonstrate that thin clouds are intrinsic to the SCT. The overcast stratocumulus-dominated regime exhibits a minimal presence of thin clouds, which become notably prominent after the clouds breakup into the cumulus-dominated regime. The regime dependence of the occurrence of thin clouds is also observed in terms of the marine cold-air outbreak parameter and the sea surface temperature. Thin clouds at a given cloud cover significantly modulate the shortwave (SW) and longwave (LW) components of CRE. SW CRE decreases by 46 %–65 % with increasing thin cloud cover. They account for a larger variance in cloud albedo than the combined influence of the liquid water path and effective radius. Furthermore, LW CRE decreases by about 12 %–52 % with thin cloud cover. An increase in the fraction of thin clouds also leads to a larger fraction of negative SW CRE offset by positive LW CRE at a given cloud cover. This LW compensation ranges from approximately 8 % at overcast cloud cover to as much as 19 % at about 50 % cloud cover. These findings elucidate the crucial role of thin clouds, and thus cloud morphology, in modulating CRE and underscore the necessity of their accurate representation in climate models. CERES; cloud morphology; cloud radiative effect; MODIS; stratocumulus-to-cumulus transition; thin clouds
Christensen, Matthew W.; Wu, Peng; Varble, Adam C.; Xiao, Heng; Fast, Jerome D.Christensen, M. W., P. Wu, A. C. Varble, H. Xiao, J. D. Fast, 2024: Aerosol-induced closure of marine cloud cells: enhanced effects in the presence of precipitation. Atmospheric Chemistry and Physics, 24(11), 6455-6476. doi: 10.5194/acp-24-6455-2024. The Weather Research Forecasting (WRF) version 4.3 model is configured within a Lagrangian framework to quantify the impact of aerosols on evolving cloud fields. Kilometer-scale simulations utilizing meteorological boundary conditions are based on 10 case study days offering diverse meteorology during the Aerosol and Cloud Experiments in the Eastern North Atlantic (ACE-ENA). Measurements from aircraft, the ground-based Atmosphere Radiation Measurement (ARM) site at Graciosa Island in the Azores, and A-Train and geostationary satellites are utilized for validation, demonstrating good agreement with the WRF-simulated cloud and aerosol properties. Higher aerosol concentration leads to suppressed drizzle and increased cloud water content in all case study days. These changes lead to larger radiative cooling rates at cloud top, enhanced vertical velocity variance, and increased vertical and horizontal wind speed near the base of the lower-tropospheric inversion. As a result, marine cloud cell area expands, narrowing the gap between shallow clouds and increasing cloud optical thickness, liquid water content, and the top-of-atmosphere outgoing shortwave flux. While similar aerosol effects are observed in lightly to non-raining clouds, they tend to be smaller by comparison. These simulations show a relationship between cloud cell area expansion and the radiative adjustments caused by liquid water path and cloud fraction changes. The adjustments are positive and scale as 74 % and 51 %, respectively, relative to the Twomey effect. While higher-resolution large-eddy simulations may provide improved representation of cloud-top mixing processes, these results emphasize the importance of addressing mesoscale cloud-state transitions in the quantification of aerosol radiative forcing that cannot be attained from traditional climate models.
Christophersen, H.; Nachamkin, J.; Davis, W.Christophersen, H., J. Nachamkin, W. Davis, 2024: Regional Cloud Forecast Verification Using Standard, Spatial, and Object-Oriented Methods. Wea. Forecasting, 39(3), 563-579. doi: 10.1175/WAF-D-23-0197.1. Abstract This study assesses the accuracy of the Coupled Ocean–Atmosphere Mesoscale Prediction System (COAMPS) forecasts for clouds within stable and unstable environments (thereafter refers as “stable” and “unstable” clouds). This evaluation is conducted by comparing these forecasts against satellite retrievals through a combination of traditional, spatial, and object-based methods. To facilitate this assessment, the Model Evaluation Tools (MET) community tool is employed. The findings underscore the significance of fine-tuning the MET parameters to achieve a more accurate representation of the features under scrutiny. The study’s results reveal that when employing traditional pointwise statistics (e.g., frequency bias and equitable threat score), there is consistency in the results whether calculated from Method for Object-Based Diagnostic Evaluation (MODE)-based objects or derived from the complete fields. Furthermore, the object-based statistics offer valuable insights, indicating that COAMPS generally predicts cloud object locations accurately, though the spread of these predicted locations tends to increase with time. It tends to overpredict the object area for unstable clouds while underpredicting it for stable clouds over time. These results are in alignment with the traditional pointwise bias scores for the entire grid. Overall, the spatial metrics provided by the object-based verification methods emerge as crucial and practical tools for the validation of cloud forecasts. Significance Statement As the general Navy meteorological and oceanographic (METOC) community engages in collaboration with the broader scientific community, our goal is to harness community tools like MET for the systematic evaluation of weather forecasts, with a specific focus on variables crucial to the Navy. Clouds, given their significant impact on visibility, hold particular importance in our investigations. Cloud forecasts pose unique challenges, primarily attributable to the intricate physics governing cloud development and the complexity of representing these processes within numerical models. Cloud observations are also constrained by limitations, arising from both top-down satellite measurements and bottom-up ground-based measurements. This study illustrates that, with a comprehensive understanding of community tools, cloud forecasts can be consistently verified. This verification encompasses traditional evaluation methods, measuring general qualities such as bias and root-mean-squared error, as well as newer techniques like spatial and object-based methods designed to account for displacement errors.
Dai, AiguoDai, A., 2024: The diurnal cycle from observations and ERA5 in precipitation, clouds, boundary layer height, buoyancy, and surface fluxes. Climate Dynamics. doi: 10.1007/s00382-024-07182-6. Diurnal variations in precipitation, clouds and other related fields are of interest for many applications. Here I analyze surface and satellite observations and ERA5 data to quantify these variations and evaluate ERA5’s performance. Results show that ERA5 captures the observed seasonal climatology of precipitation and cloud amount remarkably well. Surface observations show that warm-season precipitation exhibits a robust diurnal cycle with an amplitude of ~ 20 to 50% of the daily mean and a peak around 14–18 local solar time (LST) over most land areas and 04–08 LST over most oceans. ERA5 approximately reproduces these features with a slightly earlier peak (by ~ 2 h) over both land and ocean and a stronger amplitude over land, mainly due to biases in its convective precipitation. The IMERG satellite product captures mainly the diurnal cycle of convective precipitation with a peak around 16–20 LST during the warm season. ERA5 oceanic precipitation shows robust diurnal variations that are comparable to observations despite its dampened marine surface diurnal cycle due to its use of daily-mean SST. This suggests a free-tropospheric control of oceanic precipitation diurnal cycle. Surface and satellite observations show more clouds (mainly from low clouds) during daytime (nighttime) over land (ocean). ERA5 total cloud diurnal anomalies are more comparable to surface observations than to ISCCP satellite product. Cloud base height shows a minimum in early afternoon and a maximum around midnight with a diurnal amplitude of ~ 150 m over warm-season land in surface observations; ERA5 approximately captures this diurnal cycle with a slightly stronger amplitude and earlier phase. Land planetary boundary layer height (PBLH) in ERA5 is around 250 m at night but increases after sunrise to a peak around 14–15 LST of about 1500–1900 m in the warm season and ~ 650 to 1100 m in the cold season, with largest diurnal amplitudes over summer drylands. ERA5 marine PBLH is higher in the cold season (~ 1000 m) than in the warm season (~ 530 m) in the extra-tropics, suggesting a dominant role by low-level wind-induced mixing. ERA5 CAPE shows out-of-phase diurnal variations over land and ocean, with near-noontime peak (minimum) and an early morning minimum (peak) over land (ocean). ERA5 CIN’s diurnal cycle is approximately out of phase with CAPE. ERA5 captures well the diurnal cycles and their land–ocean and seasonal differences in surface net shortwave and longwave (LWnet) radiation seen in CERES satellite product, with a near-noontime peak in land LWnet. A near-noontime peak is also seen in ERA surface sensible and latent heat fluxes over land, while oceanic PBLH, LWnet and heat fluxes show little diurnal variation in ERA5, which may be partly due to its use of daily-mean SST. Boundary layer; Clouds; Diurnal cycle; ERA5; Precipitation; Surface fluxes
Donahue, A. S.; Caldwell, P. M.; Bertagna, L.; Beydoun, H.; Bogenschutz, P. A.; Bradley, A. M.; Clevenger, T. C.; Foucar, J.; Golaz, C.; Guba, O.; Hannah, W.; Hillman, B. R.; Johnson, J. N.; Keen, N.; Lin, W.; Singh, B.; Sreepathi, S.; Taylor, M. A.; Tian, J.; Terai, C. R.; Ullrich, P. A.; Yuan, X.; Zhang, Y.Donahue, A. S., P. M. Caldwell, L. Bertagna, H. Beydoun, P. A. Bogenschutz, A. M. Bradley, T. C. Clevenger, J. Foucar, C. Golaz, O. Guba, W. Hannah, B. R. Hillman, J. N. Johnson, N. Keen, W. Lin, B. Singh, S. Sreepathi, M. A. Taylor, J. Tian, C. R. Terai, P. A. Ullrich, X. Yuan, Y. Zhang, 2024: To Exascale and Beyond—The Simple Cloud-Resolving E3SM Atmosphere Model (SCREAM), a Performance Portable Global Atmosphere Model for Cloud-Resolving Scales. Journal of Advances in Modeling Earth Systems, 16(7), e2024MS004314. doi: 10.1029/2024MS004314. The new generation of heterogeneous CPU/GPU computer systems offer much greater computational performance but are not yet widely used for climate modeling. One reason for this is that traditional climate models were written before GPUs were available and would require an extensive overhaul to run on these new machines. In addition, even conventional “high–resolution” simulations don't currently provide enough parallel work to keep GPUs busy, so the benefits of such overhaul would be limited for the types of simulations climate scientists are accustomed to. The vision of the Simple Cloud-Resolving Energy Exascale Earth System (E3SM) Atmosphere Model (SCREAM) project is to create a global atmospheric model with the architecture to efficiently use GPUs and horizontal resolution sufficient to fully take advantage of GPU parallelism. After 5 years of model development, SCREAM is finally ready for use. In this paper, we describe the design of this new code, its performance on both CPU and heterogeneous machines, and its ability to simulate real-world climate via a set of four 40 day simulations covering all 4 seasons of the year. cloud-resolving scales; diurnal cycle; E3SM; exascale; global atmosphere model; global climate model; global storm-resolving model; GPUs; heterogeneous computing; high-resolution global model; Kokkos
Donohoe, A.; Fajber, R.; Cox, T.; Armour, K. C.; Battisti, D. S.; Roe, G. H.Donohoe, A., R. Fajber, T. Cox, K. C. Armour, D. S. Battisti, G. H. Roe, 2024: Model Biases in the Atmosphere-Ocean Partitioning of Poleward Heat Transport Are Persistent Across Three CMIP Generations. Geophysical Research Letters, 51(8), e2023GL106639. doi: 10.1029/2023GL106639. The observed partitioning of poleward heat transport between atmospheric and oceanic heat transports (AHT and OHT) is compared to that in coupled climate models. Model ensemble mean poleward OHT is biased low in both hemispheres, with the largest biases in the Southern Hemisphere extratropics. Poleward AHT is biased high in the Northern Hemisphere, especially in the vicinity of the peak AHT near 40°N. The significant model biases are persistent across three model generations (CMIP3, CMIP5, CMIP6) and are insensitive to the satellite radiation and atmospheric reanalyzes products used to derive observational estimates of AHT and OHT. Model biases in heat transport partitioning are consistent with biases in the spatial structure of energy input to the ocean and atmosphere. Specifically, larger than observed model evaporation in the tropics adds excess energy to the atmosphere that drives enhanced poleward AHT at the expense of weaker OHT. climate models; climate dynamics; atmospheric circulation; ocean circulation
Dramé, Mamadou Simina; N'Diaye, Pape Mbagnick; Niang, Serigne Abdoul Aziz; Diallo, Ismaila; Sarr, Astou; Gueye, Ahmed; Niang, Demba NdaoDramé, M. S., P. M. N'Diaye, S. A. A. Niang, I. Diallo, A. Sarr, A. Gueye, D. N. Niang, 2024: On the characterization of Cloud occurrence and its impact on solar radiation in Mbour, Senegal. Journal of Atmospheric and Solar-Terrestrial Physics, 261, 106284. doi: 10.1016/j.jastp.2024.106284. The objective of this study is to evaluate the clouds seasonal occurrence characteristics, and to estimate their impact on solar radiation in Mbour, Senegal, West Africa. Here, we use datasets from various sources including: i) observations from the Clouds and Earth's Radiant Energy System satellite sensors, ii) in situ shortwave radiation measurement obtained from the Mbour station, and iii) the outgoing longwave radiation (OLR) obtained from the National Centers for Environmental Prediction reanalysis data. Results show a marked seasonality, associated with high spatial variation in terms of cloud occurrence over Senegal. The maximum cloud occurrences are observed during the wet summer season (June–October), whilst the minimum cloud occurrences are recorded during the long-dry season from November to May. During the monsoon season the cloud activity becomes more intense with a total cloud cover of about 80%, a cloud optical depth of around 7, and a high convective activity illustrated by a low OLR (below 240 W/m2). Likewise, across Senegal a strong north-south gradient of the cloud characteristics is observed. Based on quantitative comparison between cloud occurrence and radiation measurement, results show an important seasonal impact on available solar potential in Mbour. Conversely to the cloud occurrence, the maximum of both direct normal and global solar potentials is recorded during the dry season, coinciding with the period with clean sky. An investigation of the cloud influence on solar radiation on selected study cases indicates a decrease of 60% (80%) for the total (direct normal) radiation during the peak of the summer monsoon season. Clouds; Seasonal variation; Senegal; Solar potential; West Africa
Du, Yihan; Wang, Tianxing; Zhou, Yu; Letu, Husi; Li, Dahui; Xian, YuyangDu, Y., T. Wang, Y. Zhou, H. Letu, D. Li, Y. Xian, 2024: Toward User-Friendly All-Sky Surface Longwave Downward Radiation from Space: General Scheme and Product. doi: 10.1175/BAMS-D-23-0126.1. Longwave downward radiation (LWDR) is an important driving parameter in climate and hydrological models. Compared to traditional ground-based measurements, remote sensing has unique advantages in estimating global LWDR. However, for current remote sensing missions, as the typical available satellite-derived LWDR product with global coverage and hourly temporal resolution, the Clouds and the Earth’s Radiant Energy System-Synoptic (CERES-SYN) top of atmosphere and surface fluxes and clouds has a low spatial resolution (1° × 1°). There is still much room for improvement of the existing remote sensing LWDR products in terms of accuracy, spatiotemporal resolutions, and the ability to explain and quantify the changes of longwave radiation at various scales. To overcome these limitations, this paper developed a new global LWDR product with improved accuracy (RMSE < 30 W m−2 over the globe), high temporal resolution (hourly), and spatial resolution (5 km) based on Moderate Resolution Imaging Spectroradiometer (MODIS) measurements. It serves as a LWDR product within the Long-term Earth System spatiotemporally Seamless Radiation budget dataset (referred to as LessRad). As the first long-term high-resolution, spatiotemporally continuous LWDR product (2002–22, 1 h, 5 km), the LessRad reveals its advantages in studying the spatiotemporal variability of LWDR on finer scales. It also provides a valuable data source for various applications, such as analyzing land–atmosphere interactions and quantifying climate feedback, and thus is potentially helpful for understanding Earth’s energy budget and dynamics. Climate change; Longwave radiation; Radiation budgets
Dunn, R. J. H.; Blannin, J.; Gobron, N.; Miller, J. B.; Willett, K. M.; Ades, Melanie; Adler, Robert; Alexe, Mihai; Allan, Richard P.; Anderson, John; Anneville, Orlane; Aono, Yasuyuki; Arguez, Anthony; Pascual, Dolores Armenteras; Arosio, Carlo; Asher, Elizabeth; Augustine, John A.; Azorin-Molina, Cesar; Baez-Villanueva, Oscar M.; Barichivich, J.; Beck, Hylke E.; Bellouin, Nicolas; Benedetti, Angela; Blenkinsop, Stephen; Bock, Olivier; Bodin, Xavier; Bonte, Olivier; Bosilovich, Michael G.; Boucher, Olivier; Buehler, Stefan A.; Byrne, Michael P.; Campos, Diego; Cappucci, Fabrizio; Carrea, Laura; Chang, Kai-Lan; Christiansen, Hanne H.; Christy, John R.; Chung, Eui-Seok; Ciasto, Laura M.; Clingan, Scott; Coldewey-Egbers, Melanie; Cooper, Owen R.; Cornes, Richard C.; Covey, Curt; Crétaux, Jean-Francois; Crimmins, Theresa; Crotwell, Molly; Culpepper, Joshua; Cusicanqui, Diego; Davis, Sean; Jeu, Richard A. M. de; Degenstein, Doug; Delaloye, Reynald; DiGangi, Elizabeth; Dokulil, Martin T.; Donat, Markus G.; Dorigo, Wouter A.; Duchemin, Diane; Dugan, Hilary; Durre, Imke; Dutton, Geoff; Duveiller, Gregory; Estilow, Thomas W.; Estrella, Nicole; Fereday, David; Fioletov, Vitali E.; Flemming, Johannes; Foster, Michael J.; Frederikse, Thomas; Frith, Stacey M.; Froidevaux, Lucien; Füllekrug, Martin; Garforth, Judith; Garg, Jay; Godin-Beekmann, Sophie; Goodman, Steven; Goto, Atsushi; Grimm, Alice; Gruber, Alexander; Gu, Guojun; Guglielmin, Mauro; Hahn, Sebastian; Haimberger, Leopold; HalDunn, R. J. H., J. Blannin, N. Gobron, J. B. Miller, K. M. Willett, M. Ades, R. Adler, M. Alexe, R. P. Allan, J. Anderson, O. Anneville, Y. Aono, A. Arguez, D. A. Pascual, C. Arosio, E. Asher, J. A. Augustine, C. Azorin-Molina, O. M. Baez-Villanueva, J. Barichivich, H. E. Beck, N. Bellouin, A. Benedetti, S. Blenkinsop, O. Bock, X. Bodin, O. Bonte, M. G. Bosilovich, O. Boucher, S. A. Buehler, M. P. Byrne, D. Campos, F. Cappucci, L. Carrea, K. Chang, H. H. Christiansen, J. R. Christy, E. Chung, L. M. Ciasto, S. Clingan, M. Coldewey-Egbers, O. R. Cooper, R. C. Cornes, C. Covey, J. Crétaux, T. Crimmins, M. Crotwell, J. Culpepper, D. Cusicanqui, S. Davis, R. A. M. d. Jeu, D. Degenstein, R. Delaloye, E. DiGangi, M. T. Dokulil, M. G. Donat, W. A. Dorigo, D. Duchemin, H. Dugan, I. Durre, G. Dutton, G. Duveiller, T. W. Estilow, N. Estrella, D. Fereday, V. E. Fioletov, J. Flemming, M. J. Foster, T. Frederikse, S. M. Frith, L. Froidevaux, M. Füllekrug, J. Garforth, J. Garg, S. Godin-Beekmann, S. Goodman, A. Goto, A. Grimm, A. Gruber, G. Gu, M. Guglielmin, S. Hahn, L. Haimberger, . Hal, 2024: Global Climate. doi: 10.1175/BAMS-D-24-0116.1. "Global Climate" published on 22 Aug 2024 by American Meteorological Society.
Eastman, Ryan; McCoy, Isabel L.; Schulz, Hauke; Wood, RobertEastman, R., I. L. McCoy, H. Schulz, R. Wood, 2024: A survey of radiative and physical properties of North Atlantic mesoscale cloud morphologies from multiple identification methodologies. Atmospheric Chemistry and Physics, 24(11), 6613-6634. doi: 10.5194/acp-24-6613-2024. Three supervised neural network cloud classification routines are applied to daytime MODIS Aqua imagery and compared for the year 2018 over the North Atlantic Ocean. Routines surveyed here include the Morphology Identification Data Aggregated over the Satellite-era (MIDAS), which specializes in subtropical stratocumulus (Sc) clouds; sugar, gravel, flowers, and fish (SGFF), which is focused on shallow cloud systems in the tropical trade winds; and the community record of marine low-cloud mesoscale morphology supported by the NASA Making Earth System Data Records for Use in Research Environments (MEaSUREs) dataset, which is focused on shallow clouds globally. Comparisons of co-occurrence and vertical and geographic distribution show that morphologies are classified in geographically distinct regions; shallow suppressed and deeper aggregated and disorganized cumulus are seen in the tropical trade winds. Shallow Sc types are frequent in subtropical subsidence regions. More vertically developed solid stratus and open- and closed-cell Sc are frequent in the mid-latitude storm track. Differing classifier routines favor noticeably different distributions of equivalent types. Average scene albedo is more strongly correlated with cloud albedo than cloud amount for each morphology. Cloud albedo is strongly correlated with the fraction of optically thin cloud cover. The albedo of each morphology is dependent on latitude and location in the mean anticyclonic wind flow over the North Atlantic. Strong rain rates are associated with middling values of albedo for many cumuliform types, hinting at a complex relationship between the presence of heavily precipitating cores and cloud albedo. The presence of ice at cloud top is associated with higher albedos. For a constant albedo, each morphology displays a distinct set of physical characteristics.
Francis, Diana; Fonseca, RicardoFrancis, D., R. Fonseca, 2024: Recent and projected changes in climate patterns in the Middle East and North Africa (MENA) region. Scientific Reports, 14(1), 10279. doi: 10.1038/s41598-024-60976-w. Observational and reanalysis datasets reveal a northward shift of the convective regions over northern Africa in summer and an eastward shift in winter in the last four decades, with the changes in the location and intensity of the thermal lows and subtropical highs also modulating the dust loading and cloud cover over the Middle East and North Africa region. A multi-model ensemble from ten models of the Coupled Model Intercomparison Project—sixth phase gives skillful simulations when compared to in-situ measurements and generally captures the trends in the ERA-5 data over the historical period. For the most extreme climate change scenario and towards the end of the twenty-first century, the subtropical highs are projected to migrate poleward by 1.5°, consistent with the projected expansion of the Hadley Cells, with a weakening of the tropical easterly jet in the summer by up to a third and a strengthening of the subtropical jet in winter typically by 10% except over the eastern Mediterranean where the storm track is projected to shift polewards. The length of the seasons is projected to remain about the same, suggesting the warming is likely to be felt uniformly throughout the year. Climate change; Climate sciences; Atmospheric science
Francis, Diana; Fonseca, Ricardo; Nelli, Narendra; Yarragunta, YesobuFrancis, D., R. Fonseca, N. Nelli, Y. Yarragunta, 2024: Unusually low dust activity in North Africa in June 2023: Causes, impacts and future projections. Atmospheric Research, 309, 107594. doi: 10.1016/j.atmosres.2024.107594. Dust activity during the pre-monsoon season in Africa has an impact on the monsoon circulation and the Atlantic hurricane season. During early June 2023 the atmosphere was relatively clear over West Africa and the eastern tropical Atlantic, in contrast with the dustier June 2020. The negative phase of the North Atlantic Oscillation suppressed dust lifting, with an equatorward shifted African Easterly Jet limiting its downstream advection. On the other hand, dust accumulated in the atmosphere over northeastern Africa, with the negative dust aerosol optical depth (DAOD) anomalies over western Africa and the positive anomalies over eastern Africa more than two standard deviations away from the climatological mean. The lack of dust led to an up to 55 W m−2 increase in the surface downward shortwave radiation flux and a 35 W m−2 decrease in the longwave flux, and is in line with the record-breaking sea surface temperatures over the eastern tropical Atlantic and the active start to the Atlantic hurricane season. In order to explore future projections of DAOD, a multi-model ensemble (MME) is constructed from 29 models that integrate the sixth phase of the Coupled Model Intercomparison Project (CMIP6). It captures the positive trend in the June DAOD over the eastern tropical Atlantic during 1980–2014, although the amplitude is roughly a factor of six smaller than the 0.0017 year−1 in the reanalysis dataset. The CMIP6 MME projects a further increase in DAOD in the region at a rate of up to 0.0003 year−1 in the most extreme climate change scenario for 2066–2100, which is comparable to that seen during the historical period, even though the mean values are projected to decrease by 0.03–0.06. While lower dust loadings may lead to improved air quality, they will likely further fuel pre-season and early season storms in the North Atlantic, which have become more frequent in recent decades. African Easterly Jet; Circumglobal Wavetrain; CMIP6; Dust aerosol optical depth; North Atlantic Oscillation; Radiation fluxes
Fu, Zhen; Zhang, Yi; Li, Xiaohan; Rong, XinyaoFu, Z., Y. Zhang, X. Li, X. Rong, 2024: Intercomparison of two model climates simulated by a unified weather-climate model system (GRIST), part I: mean state. Climate Dynamics. doi: 10.1007/s00382-024-07205-2. This study made an intercomparison of two model climates, simulated by a unified weather-climate model system (GRIST), under the Atmospheric Model Intercomparison Project (AMIP) experimental protocol. These two model AMIP simulations with PhysW and PhysC (AMIPW and AMIPC hereafter) are configured with different physics suites, but both generated by a unified dynamical core framework. PhysW and PhysC are originally designed for weather forecasting and climate simulation, respectively. Both AMIPW and AMIPC reach statistical equilibrium in the climate integration. They overall produce comparable model climates, while distinctive bias features also exist. Compared with the AMIP experiments of 54 climate models from CMIP6, both AMIPW and AMIPC demonstrate competitive performances in the mean state simulations. They capture the observed spatial distribution of large-scale circulation and precipitation, as well as replicate the seasonal migration and primary frequency-intensity structures of precipitation. However, due to different parameterization schemes such as convection and microphysics being utilized, the most notable differences between the models lie in processes related to moist physics. For instance, AMIPW tends to overestimate (underestimate) global shortwave (longwave) cloud radiative forcing, while AMIPC provides a more balanced estimation, with a significantly stronger longwave cloud radiative forcing over the tropics. In addition, AMIPC well reproduces cloud fraction and liquid content but underestimates cloud ice water content, whereas AMIPW significantly overestimates all these variables. Overall, the similarity between two model climates is higher than their discrepancy. The results demonstrate that the extent to which the selection of two distinct physics suites can influence the simulated model climate, within a unified model system. AMIP simulations; Mean state; Model comparison; Unified weather-climate model system
Gettelman, A.; Christensen, M. W.; Diamond, M. S.; Gryspeerdt, E.; Manshausen, P.; Stier, P.; Watson-Parris, D.; Yang, M.; Yoshioka, M.; Yuan, T.Gettelman, A., M. W. Christensen, M. S. Diamond, E. Gryspeerdt, P. Manshausen, P. Stier, D. Watson-Parris, M. Yang, M. Yoshioka, T. Yuan, 2024: Has Reducing Ship Emissions Brought Forward Global Warming?. Geophysical Research Letters, 51(15), e2024GL109077. doi: 10.1029/2024GL109077. Ships brighten low marine clouds from emissions of sulfur and aerosols, resulting in visible “ship tracks”. In 2020, new shipping regulations mandated an ∼80% reduction in the allowed fuel sulfur content. Recent observations indicate that visible ship tracks have decreased. Model simulations indicate that since 2020 shipping regulations have induced a net radiative forcing of +0.12 Wm−2. Analysis of recent temperature anomalies indicates Northern Hemisphere surface temperature anomalies in 2022–2023 are correlated with observed cloud radiative forcing and the cloud radiative forcing is spatially correlated with the simulated radiative forcing from the 2020 shipping emission changes. Shipping emissions changes could be accelerating global warming. To better constrain these estimates, better access to ship position data and understanding of ship aerosol emissions are needed. Understanding the risks and benefits of emissions reductions and the difficultly in robust attribution highlights the large uncertainty in attributing proposed deliberate climate intervention. aerosols; climate; global warming; sulfur
Gomez, James L.; Allen, Robert J.; Li, King-FaiGomez, J. L., R. J. Allen, K. Li, 2024: California wildfire smoke contributes to a positive atmospheric temperature anomaly over the western United States. Atmospheric Chemistry and Physics, 24(11), 6937-6963. doi: 10.5194/acp-24-6937-2024. Wildfires in the southwestern United States, particularly in northern California (nCA), have grown in size and severity in the past decade. As they have grown larger, they have been associated with large emissions of absorbing aerosols and heat into the troposphere. Utilizing satellite observations from MODIS, CERES, and AIRS as well as reanalysis from MERRA-2, the meteorology associated with fires during the wildfire season (June–October) was discerned over the nCA-NV (northern California and Nevada) region during the period 2003–2022. Wildfires in the region have a higher probability of occurring on days of positive temperature (T) anomalies and negative relative humidity (RH) anomalies, making it difficult to discern the radiative effects of aerosols that are concurrent with fires. To attempt to better isolate the effects of large fire emissions on meteorological variables, such as clouds and precipitation, variable anomalies on high fire emission days (90th percentile) were compared with low fire emission days (10th percentile) and were further stratified based on whether surface relative humidity (RHs) was anomalously high (75th percentile) or low (25th percentile) compared with typical fire season conditions. Comparing the simultaneously high fire emission and high RHs data with the simultaneously low fire emission and high RHs data, positive tropospheric T anomalies were found to be concurrent with positive AOD anomalies. Further investigation found that due to shortwave absorption, the aerosols heat the atmosphere at a rate of 0.041 ± 0.016 to 0.093 ± 0.019 K d−1, depending on whether RH conditions are anomalously positive or negative. The positive T anomalies were associated with significant negative 850–300 hPa RH anomalies during both 75th percentile RHs conditions. Furthermore, high fire emission days under high RHs conditions are associated with negative CF anomalies that are concurrent with the negative RH anomalies. This negative CF anomaly is associated with a significantly negative regional precipitation anomaly and a positive net top-of-atmosphere radiative flux anomaly (a warming effect) in certain areas. The T, RH, and CF anomalies under the simultaneously high fire emission and high RHs conditions compared with the simultaneously low fire emission and high RHs conditions have a significant spatial correlation with AOD anomalies. Additionally, the vertical profile of these variables under the same stratification is consistent with positive black carbon mass mixing ratio anomalies from MERRA-2. However, causality is difficult to discern, and further study is warranted to determine to what extent the aerosols are contributing to these anomalies.
Gomez, James L.; Allen, Robert J.; Li, King-FaiGomez, J. L., R. J. Allen, K. Li, 2024: Satellite Observations Reveal Northern California Wildfire Aerosols Reduce Cloud Cover in California and Nevada Through Semi-Direct Effects. EGUsphere, 1-32. doi: 10.5194/egusphere-2023-2827. Abstract. Wildfires in the southwestern United States, particularly in northern California (nCA), have grown in size and severity in the past decade. As they have grown larger, they have been associated with large emissions of absorbing aerosols in to the troposphere. Utilizing satellite observations from MODIS, CERES, AIRS, and CALIPSO, the meteorological effects of aerosols associated with fires during the wildfire season (June–October) were discerned over the nCA-NV (northern California and Nevada) region in the 2003–2022 time frame. As higher temperatures and low relative humidity RH dominate during high surface pressure ps atmospheric conditions, the effects of the aerosols on high (90th percentile) fire days compared to low fire (10th percentile) days were stratified based on whether ps was anomalously high or anomalously low (10th percentile). An increase in tropospheric temperatures was found to be concurrent with more absorbing aerosol aloft, which is associated with significant reductions in tropospheric RH during both 90th and 10th percentile ps conditions. Furthermore, high fire days under low ps conditions are associated with reduced cloud fraction CF, which is consistent with the traditionally-defined aerosol- cloud semi-direct effect. The reduced CF, in turn, is associated with reduced T OA SW radiative flux, a warmer surface, and less precipitation. These changes could create a positive feedback that could intensify fire weather, and therefore extend fire lifetime and impacts.
Green, J. K.; Zhang, Y.; Luo, X.; Keenan, T. F.Green, J. K., Y. Zhang, X. Luo, T. F. Keenan, 2024: Systematic Underestimation of Canopy Conductance Sensitivity to Drought by Earth System Models. AGU Advances, 5(1), e2023AV001026. doi: 10.1029/2023AV001026. The response of vegetation canopy conductance (gc) to changes in moisture availability (γgcm {\gamma _gc^m\) is a major source of uncertainty in climate projections. While vegetation typically reduces stomatal conductance during drought, accurately modeling how and to what degree stomata respond to changes in moisture availability at global scales is particularly challenging, because no global scale gc observations exist. Here, we leverage a collection of satellite, reanalysis and station-based near-surface air and surface temperature estimates, which are physically and statistically linked to γgcm {\gamma _gc^m\ due to the local cooling effect of gc through transpiration, to develop a novel emergent constraint of γgcm {\gamma _gc^m\ in an ensemble of Earth System Models (ESMs). We find that ESMs systematically underestimate γgcm {\gamma _gc^m\ by ∼33%, particularly in grasslands, croplands, and savannas in semi-arid and bordering regions of the Central United States, Central Europe, Southeastern South America, Southern Africa, Eastern Australia, and parts of East Asia. We show that this underestimation occurs because ESMs inadequately reduce gc when soil moisture decreases. As gc controls carbon, water and energy fluxes, the misrepresentation of modeled γgcm {\gamma _gc^m\ contributes to biases in ESM projections of gross primary production, transpiration, and temperature during droughts. Our results suggest that the severity and duration of droughts may be misrepresented in ESMs due to the impact of sustained gc on both soil moisture dynamics and the biosphere-atmosphere feedbacks that affect local temperatures and regional weather patterns. land surface temperature; emergent constraint; biosphere-atmosphere feedbacks; canopy conductance; Earth System Models; vegetation water stress
Griesche, Hannes Jascha; Barrientos-Velasco, Carola; Deneke, Hartwig; Hünerbein, Anja; Seifert, Patric; Macke, AndreasGriesche, H. J., C. Barrientos-Velasco, H. Deneke, A. Hünerbein, P. Seifert, A. Macke, 2024: Low-level Arctic clouds: a blind zone in our knowledge of the radiation budget. Atmospheric Chemistry and Physics, 24(1), 597-612. doi: 10.5194/acp-24-597-2024. Quantifying the role of clouds in the earth's radiation budget is essential for improving our understanding of the drivers and feedback mechanisms of climate change. This holds in particular for the Arctic, the region currently undergoing the most rapid changes. This region, however, also poses significant challenges to remote-sensing retrievals of clouds and radiative fluxes, introducing large uncertainties in current climate data records. In particular, low-level stratiform clouds are common in the Arctic but are, due to their low altitude, challenging to observe and characterize with remote-sensing techniques. The availability of reliable ground-based observations as reference is thus of high importance. In the present study, radiative transfer simulations using state-of-the-art ground-based remote sensing of clouds are contrasted with surface radiative flux measurements to assess their ability to constrain the cloud radiative effect. Cloud radar, lidar, and microwave radiometer observations from the PS106 cruise in the Arctic marginal sea ice zone in summer 2017 were used to derive cloud micro- and macrophysical properties by means of the instrument synergy approach of Cloudnet. Closure of surface radiative fluxes can only be achieved by a realistic representation of the low-level liquid-containing clouds in the radiative transfer simulations. The original, most likely erroneous, representation of these low-level clouds in the radiative transfer simulations led to errors in the cloud radiative effect of 54 W m−2. In total, the proposed method could be applied to 11 % of the observations. For the data, where the proposed method was utilized, the average relative error decreased from 109 % to 37 % for the simulated solar and from 18 % to 2.5 % for the simulated terrestrial downward radiative fluxes at the surface. The present study highlights the importance of jointly improving retrievals for low-level liquid-containing clouds which are frequently encountered in the high Arctic, together with observational capabilities both in terms of cloud remote sensing and radiative flux observations. Concrete suggestions for achieving these goals are provided.
Guendelman, Ilai; Merlis, Timothy M.; Cheng, Kai-Yuan; Harris, Lucas M.; Bretherton, Christopher S.; Bolot, Maximilien; Zhou, Linjiong; Kaltenbaugh, Alex; Clark, Spencer K.; Fueglistaler, StephanGuendelman, I., T. M. Merlis, K. Cheng, L. M. Harris, C. S. Bretherton, M. Bolot, L. Zhou, A. Kaltenbaugh, S. K. Clark, S. Fueglistaler, 2024: The Precipitation Response to Warming and CO2 Increase: A Comparison of a Global Storm Resolving Model and CMIP6 Models. Geophysical Research Letters, 51(7), e2023GL107008. doi: 10.1029/2023GL107008. Global storm-resolving models (GSRMs) that can explicitly resolve some of deep convection are now being integrated for climate timescales. GSRMs are able to simulate more realistic precipitation distributions relative to traditional Coupled Model Intercomparison Project 6 (CMIP6) models. In this study, we present results from two-year-long integrations of a GSRM developed at Geophysical Fluid Dynamics Laboratory, eXperimental System for High-resolution prediction on Earth-to-Local Domains (X-SHiELD), for the response of precipitation to sea surface temperature warming and an isolated increase in CO2 and compare it to CMIP6 models. At leading order, X-SHiELD's response is within the range of the CMIP6 models. However, a close examination of the precipitation distribution response reveals that X-SHiELD has a different response at lower percentiles and the response of the extreme events are at the lower end of the range of CMIP6 models. A regional decomposition reveals that the difference is most pronounced for midlatitude land, where X-SHiELD shows a lower increase at intermediate percentiles and drying at lower percentiles. climate change; precipitation; cloud resolving models
Gunnarson, Jacob L.; Stuecker, Malte F.; Zhao, SenGunnarson, J. L., M. F. Stuecker, S. Zhao, 2024: Drivers of future extratropical sea surface temperature variability changes in the North Pacific. npj Climate and Atmospheric Science, 7(1), 1-11. doi: 10.1038/s41612-024-00702-5. Under anthropogenic warming, future changes to climate variability beyond specific modes such as the El Niño-Southern Oscillation (ENSO) have not been well-characterized. In the Community Earth System Model version 2 Large Ensemble (CESM2-LE) climate model, the future change to sea surface temperature (SST) variability (and correspondingly marine heatwave intensity) on monthly timescales and longer is spatially heterogeneous. We examined these projected changes (between 1960–2000 and 2060–2100) in the North Pacific using a local linear stochastic-deterministic model, which allowed us to quantify the effect of changes to three drivers on SST variability: ocean “memory” (the SST damping timescale), ENSO teleconnections, and stochastic noise forcing. The ocean memory declines in most areas, but lengthens in the central North Pacific. This change is primarily due to changes in air-sea feedbacks and ocean damping, with the shallowing mixed layer depth playing a secondary role. An eastward shift of the ENSO teleconnection pattern is primarily responsible for the pattern of SST variance change. Atmospheric dynamics; Physical oceanography
Guo, Hao; Tian, Yunfei; Li, Junli; Meng, Xiangchen; Lv, Xiaoyu; Wang, Wei; Bao, Anming; Zhu, Li; Nzabarinda, Vincent; De Maeyer, PhilippeGuo, H., Y. Tian, J. Li, X. Meng, X. Lv, W. Wang, A. Bao, L. Zhu, V. Nzabarinda, P. De Maeyer, 2024: Unveiling the spatiotemporal impacts of the 2021 Central Asian drought on vegetation: A comprehensive quantitative analysis. Ecological Indicators, 165, 112238. doi: 10.1016/j.ecolind.2024.112238. In the growing season of 2021, a severe drought occurred in Central Asia impacting various local ecosystems and socio-economic conditions. However, there is limited research on the spatiotemporal characteristics of this drought and its effects on local vegetation. To address this gap, this study utilizes the standardized precipitation evapotranspiration index (SPEI) to quantitatively evaluate the spatiotemporal drought characteristics, and standardized anomalies to assess drought impacts on vegetation greenness and productivity. The drought-induced reduction in vegetation greenness and production was also decomposed into environmental drivers based on a random forest model. Our findings can be summarized as follows: During the 2021 growing season, Central Asia experienced one of the most severe drought events in the past 40 years, with approximately 42.57 % of the region facing record-breaking drought conditions. Abnormally low precipitation (PRE), prolonged high temperatures (TMP) and evapotranspiration also occurred during the drought event. The drought had a significant detrimental effect on vegetation, leading to an approximately 10 % reduction in vegetation greenness and around 13 % in productivity. Soil moisture (SM) was found to be the most critical factor influencing vegetation greenness loss during drought conditions. Leaf Area Index (LAI) and SM emerged as the primary drivers for the reduction of Gross Primary Productivity (GPP) and Solar-Induced Fluorescence (SIF). The antecedent environmental conditions had a significant impact on the decline in vegetation greenness and productivity during the 2021 drought event, accounting for approximately 30 %–35 % and 52–69 % of the respective losses. The findings of this study highlight the importance of taking into account antecedent climate factors when studying the impacts of drought on vegetation. Central Asia; Drought impacts; Extreme drought; Greenness and production; Vegetation response
Guo, Mengfei; Cheng, Jie; Zeng, QiGuo, M., J. Cheng, Q. Zeng, 2024: A data-driven model for estimating clear-sky surface longwave downward radiation over polar regions. IEEE Transactions on Geoscience and Remote Sensing, 1-1. doi: 10.1109/TGRS.2024.3418205. Polar regions play a crucial role in global climate change. Surface longwave downward radiation (SLDR) is a primary energy source for the polar surface, plays an essential role for studies of polar hydrology, temperature and climate. Therefore, accurately estimating the SLDR over polar regions is highly important. However, the accuracies of existing polar SLDR datasets and SLDR inversion methods are insufficient to meet the requirements of relevant research. In this study, we developed a data-driven model for high spatial resolution clear-sky SLDRs estimated from Moderate Resolution Imaging Spectroradiometer (MODIS) imagery in polar regions. The model comprises two layers: the first layer incorporates three machine learning models, namely, XGBoost, CNN and Transformer, while the second layer consists of a stacking meta-model. The ground measurements collected from 51 sites were used to train and validate the developed model. The bias, RMSE and R2 of the model training are zero, 14.15 W/m2 and 0.95, respectively, whereas the values for the validation are 0.49, 15.35 W/m2 and 0.9, respectively. We also compared the accuracies of the ERA5 and CERES-SYN SLDR data with the SLDR estimated by the developed model. The results indicate that the developed model is superior to the ERA5 and CERES-SYN SLDR models when evaluated at the validation sites. Additionally, we analyzed the performance of the developed model under different elevations and seasons, demonstrating its robustness in different situations. Climate change; Data models; Spatial resolution; Hydrology; MODIS; Machine learning; CNN; Surface Radiation Budget; Convolutional neural networks; Machine Learning; Polar Region; Radiation monitoring; Stacking; Surface longwave downward radiation (SLDR); Transformer; Transformers; XGBoost
Hakuba, Maria Z.; Fourest, Sébastien; Boyer, Tim; Meyssignac, Benoit; Carton, James A.; Forget, Gaël; Cheng, Lijing; Giglio, Donata; Johnson, Gregory C.; Kato, Seiji; Killick, Rachel E.; Kolodziejczyk, Nicolas; Kuusela, Mikael; Landerer, Felix; Llovel, William; Locarnini, Ricardo; Loeb, Norman; Lyman, John M.; Mishonov, Alexey; Pilewskie, Peter; Reagan, James; Storto, Andrea; Sukianto, Thea; von Schuckmann, KarinaHakuba, M. Z., S. Fourest, T. Boyer, B. Meyssignac, J. A. Carton, G. Forget, L. Cheng, D. Giglio, G. C. Johnson, S. Kato, R. E. Killick, N. Kolodziejczyk, M. Kuusela, F. Landerer, W. Llovel, R. Locarnini, N. Loeb, J. M. Lyman, A. Mishonov, P. Pilewskie, J. Reagan, A. Storto, T. Sukianto, K. von Schuckmann, 2024: Trends and Variability in Earth’s Energy Imbalance and Ocean Heat Uptake Since 2005. Surveys in Geophysics. doi: 10.1007/s10712-024-09849-5. Earth’s energy imbalance (EEI) is a fundamental metric of global Earth system change, quantifying the cumulative impact of natural and anthropogenic radiative forcings and feedback. To date, the most precise measurements of EEI change are obtained through radiometric observations at the top of the atmosphere (TOA), while the quantification of EEI absolute magnitude is facilitated through heat inventory analysis, where ~ 90% of heat uptake manifests as an increase in ocean heat content (OHC). Various international groups provide OHC datasets derived from in situ and satellite observations, as well as from reanalyses ingesting many available observations. The WCRP formed the GEWEX-EEI Assessment Working Group to better understand discrepancies, uncertainties and reconcile current knowledge of EEI magnitude, variability and trends. Here, 21 OHC datasets and ocean heat uptake (OHU) rates are intercompared, providing OHU estimates ranging between 0.40 ± 0.12 and 0.96 ± 0.08 W m−2 (2005–2019), a spread that is slightly reduced when unequal ocean sampling is accounted for, and that is largely attributable to differing source data, mapping methods and quality control procedures. The rate of increase in OHU varies substantially between − 0.03 ± 0.13 (reanalysis product) and 1.1 ± 0.6 W m−2 dec−1 (satellite product). Products that either more regularly observe (satellites) or fill in situ data-sparse regions based on additional physical knowledge (some reanalysis and hybrid products) tend to track radiometric EEI variability better than purely in situ-based OHC products. This paper also examines zonal trends in TOA radiative fluxes and the impact of data gaps on trend estimates. The GEWEX-EEI community aims to refine their assessment studies, to forge a path toward best practices, e.g., in uncertainty quantification, and to formulate recommendations for future activities. Argo; Earth’s energy imbalance; GEWEX; Ocean heat content; Radiation budget; Reanalysis
Hakuba, Maria Z.; Reynerson, Charles M.; Quadrelli, Marco B.; Wiese, David N.; Mccullough, ChristopherHakuba, M. Z., C. M. Reynerson, M. B. Quadrelli, D. N. Wiese, C. Mccullough, 2024: Modeling Radiation Pressure Accelerations: Earth Radiance Anisotropy, Spacecraft Shape and Global Sampling. 2024 IEEE Aerospace Conference, 1-7. doi: 10.1109/AERO58975.2024.10521289. In this study, we investigate the feasibility of a direct measurement of Earth’s Energy Imbalance (EEI) from space via radiation pressure accelerations. EEI represents one of the most challenging Earth observations for climate change research and quantifies the fundamental rate of global heating in response to radiative forcings and feedbacks. Using state-of-the-art mission design and orbit determination software, we simulate Sun’s and Earth’s radiative pressure impact on spacecrafts of different shapes. We derive the Earth radiation (shortwave and longwave) intercepted by the spacecraft from observed radiative fluxes (Clouds and Earth’s Radiant Energy System, CERES) and correct for radiance anisotropy using anisotropy factors derived from historical Earth Radiation Budget (ERB) missions. Anisotropy is a function of solar and satellite viewing geometry, as well as of scene type (surface and atmospheric properties) of each Earth element in view of the satellite at any point in time. In addition, we test the sensitivity of confounding forces, such as aerodynamic drag and Yarkovsky effects to spacecraft shape, and present preliminary results of a sampling study to quantify the bias of daily global mean net radiative flux associated with a sun-synchronous orbit crossing Earth’s equator at 12 pm local time. Our investigations and software development will inform instrument and mission requirements relevant to the accurate measurement of EEI. Earth; Extraterrestrial measurements; Satellites; Space vehicles; Anisotropic magnetoresistance; Sensitivity; Shape
Haslehner, Kerstin; Gasparini, Blaž; Voigt, AikoHaslehner, K., B. Gasparini, A. Voigt, 2024: Radiative Heating of High-Level Clouds and Its Impacts on Climate. Journal of Geophysical Research: Atmospheres, 129(12), e2024JD040850. doi: 10.1029/2024JD040850. The interactions of clouds with radiation influence climate. Many of these impacts appear to be related to the radiative heating and cooling from high-level clouds, but few studies have explicitly tested this. Here, we use simulations with the ICON-ESM model to understand how high-level clouds, through their radiative heating and cooling, influence the large-scale atmospheric circulation and precipitation in the present-day climate. We introduce a new method to diagnose the radiative heating of high-level clouds: instead of defining high-level clouds as all clouds at temperatures colder than −35°C, we define them as all clouds with a cloud top at temperatures colder than −35°C. The inclusion of the lower cloud parts at temperatures warmer than −35°C circumvents the creation of artificial cloud boundaries and strong artificial radiative heating at the temperature threshold. To isolate the impact of high-level clouds, we analyze simulations with active cloud-radiative heating, with the radiative heating from high-level clouds set to zero, and with the radiative heating from all clouds set to zero. We show that the radiative interactions of high-level clouds warm the troposphere and strengthen the eddy-driven jet streams, but have no impact on the Hadley circulation strength and the latitude of the Intertropical Convergence Zone. Consistent with their positive radiative heating and energetic arguments, high-level clouds reduce precipitation throughout the tropics and lower midlatitudes. Overall, our results confirm that the radiative interactions of high-level clouds have important impacts on climate and highlight the need for better representing their radiative interactions in models. climate modeling; cloud-radiative heating; high-level clouds
Hingmire, Dipti; Hirasawa, Haruki; Singh, Hansi; Rasch, Philip J.; Kim, Sookyung; Hazarika, Subhashis; Mitra, Peetak; Ramea, KalaiHingmire, D., H. Hirasawa, H. Singh, P. J. Rasch, S. Kim, S. Hazarika, P. Mitra, K. Ramea, 2024: South Asian Summer Monsoon Precipitation Is Sensitive to Southern Hemisphere Subtropical Radiation Changes. Geophysical Research Letters, 51(11), e2024GL108499. doi: 10.1029/2024GL108499. We study the sensitivity of South Asian Summer Monsoon (SASM) precipitation to Southern Hemisphere (SH) subtropical Absorbed Solar Radiation (ASR) changes using Community Earth System Model 2 simulations. Reducing positive ASR biases over the SH subtropics impacts SASM, and is sensitive to the ocean basin where changes are imposed. Radiation changes over the SH subtropical Indian Ocean (IO) shifts rainfall over the equatorial IO northward causing 1–2 mm/day drying south of equator, changes over the SH subtropical Pacific increases precipitation over northern continental regions by 1–2 mm/day, and changes over the SH subtropical Atlantic have little effect on SASM precipitation. Radiation changes over the subtropical Pacific impacts the SASM through zonal circulation changes, while changes over the IO modify meridional circulation to bring about changes in precipitation over northern IO. Our findings suggest that reducing SH subtropical radiation biases in climate models may also reduce SASM precipitation biases. ITCZ; monsoon; precipitation bias
Hodnebrog, Øivind; Myhre, Gunnar; Jouan, Caroline; Andrews, Timothy; Forster, Piers M.; Jia, Hailing; Loeb, Norman G.; Olivié, Dirk J. L.; Paynter, David; Quaas, Johannes; Raghuraman, Shiv Priyam; Schulz, MichaelHodnebrog, Ø., G. Myhre, C. Jouan, T. Andrews, P. M. Forster, H. Jia, N. G. Loeb, D. J. L. Olivié, D. Paynter, J. Quaas, S. P. Raghuraman, M. Schulz, 2024: Recent reductions in aerosol emissions have increased Earth’s energy imbalance. Communications Earth & Environment, 5(1), 1-9. doi: 10.1038/s43247-024-01324-8. The Earth’s energy imbalance is the net radiative flux at the top-of-atmosphere. Climate model simulations suggest that the observed positive imbalance trend in the previous two decades is inconsistent with internal variability alone and caused by anthropogenic forcing and the resulting climate system response. Here, we investigate anthropogenic contributions to the imbalance trend using climate models forced with observed sea-surface temperatures. We find that the effective radiative forcing due to anthropogenic aerosol emission reductions has led to a 0.2 ± 0.1 W m−2 decade−1 strengthening of the 2001–2019 imbalance trend. The multi-model ensemble reproduces the observed imbalance trend of 0.47 ± 0.17 W m−2 decade−1 but with 10-40% underestimation. With most future scenarios showing further rapid reductions of aerosol emissions due to air quality legislation, such emission reductions may continue to strengthen Earth’s energy imbalance, on top of the greenhouse gas contribution. Consequently, we may expect an accelerated surface temperature warming in this decade. Atmospheric science; Climate and Earth system modelling; Attribution
Hofer, Stefan; Hahn, Lily C.; Shaw, Jonah K.; McGraw, Zachary S.; Bruno, Olimpia; Hellmuth, Franziska; Pietschnig, Marianne; Mostue, Idunn Aa; David, Robert O.; Carlsen, Tim; Storelvmo, TrudeHofer, S., L. C. Hahn, J. K. Shaw, Z. S. McGraw, O. Bruno, F. Hellmuth, M. Pietschnig, I. A. Mostue, R. O. David, T. Carlsen, T. Storelvmo, 2024: Realistic representation of mixed-phase clouds increases projected climate warming. Communications Earth & Environment, 5(1), 1-12. doi: 10.1038/s43247-024-01524-2. Clouds are the main source of uncertainties when projecting climate change. Mixed-phase clouds that contain ice and supercooled-liquid particles are especially hard to constrain, and climate models neither agree on their phase nor their spatial extent. This is problematic, as models that underestimate contemporary supercooled-liquid in mixed-phase clouds will underestimate future warming. Furthermore, it has recently been shown that supercooled-liquid water in mixed-phase clouds is not homogeneously-mixed, neither vertically nor horizontally. However, while there have been attempts at observationally constraining mixed-phase clouds to constrain uncertainties in future warming, all studies only use the phase of the interior of mixed-phase clouds. Here we show, using novel satellite observations that distinguish between cloud-top and interior phase in mixed-phase clouds, that mixed-phase clouds are more liquid at the cloud top globally. We use these observations to constrain the cloud top phase in addition to the interior in a global climate model, leading to +1 °C more 21st century warming in NorESM2 SSP5-8.5 climate projections. We anticipate that the difference between cloud top and interior phase in mixed-phase clouds is an important new target metric for future climate model development, because similar mixed-phase clouds related biases in future warming are likely present in many climate models. Projection and prediction; Atmospheric science; Climate and Earth system modelling
Hsiao, Wei-Ting; Maloney, Eric D.Hsiao, W., E. D. Maloney, 2024: The Longwave Cloud-Radiative Feedback in Tropical Waves Derived by Different Precipitation Data Sets. Geophysical Research Letters, 51(11), e2024GL109143. doi: 10.1029/2024GL109143. Anomalous tropical longwave cloud-radiative heating of the atmosphere is generated when convective precipitation occurs, which plays an important role in the dynamics of tropical disturbances. Defining the observed cloud-radiative feedback as the reduction of top-of-atmosphere longwave radiative cooling per unit precipitation, the feedback magnitudes are sensitive to the observed precipitation data set used when comparing two versions of Global Precipitation Climatology Project, version 1.3 (GPCPv1.3) and the newer version 3.2 (GPCPv3.2). GPCPv3.2 contains larger magnitudes and variance of daily precipitation, which yields a weaker cloud-radiative feedback in tropical disturbances at all frequencies and zonal wavenumbers. Weaker cloud-radiative feedbacks occur in GPCPv3.2 at shorter zonal lengths on intraseasonal timescales, which implies a preferential growth at planetary scales for the Madden-Julian oscillation. Phase relationships between precipitation, radiative heating, and other thermodynamic variables in eastward-propagating gravity waves also change with the updated GPCPv3.2. cloud-radiative effect; convection; Madden-Julian oscillation; tropical waves
Hsiao, Wei-Ting; Maloney, Eric D.; Leitmann-Niimi, Nicolas M.; Kummerow, Christian D.Hsiao, W., E. D. Maloney, N. M. Leitmann-Niimi, C. D. Kummerow, 2024: Observed Relationships between Sea Surface Temperature, Vertical Wind Shear, Tropical Organized Deep Convection, and Radiative Effects. J. Climate, 37(4), 1277-1293. doi: 10.1175/JCLI-D-23-0262.1. Abstract Organized deep convective activity has been routinely monitored by satellite precipitation radar from the Tropical Rainfall Measuring Mission (TRMM) and Global Precipitation Mission (GPM). Organized deep convective activity is found to increase not only with sea surface temperature (SST) above 27°C, but also with low-level wind shear. Precipitation shows a similar increasing relationship with both SST and low-level wind shear, except for the highest low-level wind shear. These observations suggest that the threshold for organized deep convection and precipitation in the tropics should consider not only SST, but also vertical wind shear. The longwave cloud radiative feedback, measured as the tropospheric longwave cloud radiative heating per amount of precipitation, is found to generally increase with stronger organized deep convective activity as SST and low-level wind shear increase. Organized deep convective activity, the longwave cloud radiative feedback, and cirrus ice cloud cover per amount of precipitation also appear to be controlled more strongly by SST than by the deviation of SST from its tropical mean. This study hints at the importance of non-thermodynamic factors such as vertical wind shear for impacting tropical convective structure, cloud properties, and associated radiative energy budget of the tropics. Significance Statement This study uses tropical satellite observations to demonstrate that vertical wind shear affects the relationship between sea surface temperature and tropical organized deep convection and precipitation. Shear also affects associated cloud properties and how clouds affect the flow of radiation in the atmosphere. Although how vertical wind shear affects convective organization has long been studied in the mesoscale community, the study attempts to apply mesoscale theory to explain the large-scale mean organization of tropical deep convection, cloud properties, and radiative feedbacks. The study also provides a quantitative observational baseline of how vertical wind shear modifies cloud radiative effects and convective organization, which can be compared to numerical simulations.
Huang, Chuan Jiang; Wang, Gang; Chen, Siyu; Guo, Jingsong; Qiao, FangliHuang, C. J., G. Wang, S. Chen, J. Guo, F. Qiao, 2024: An effective parameterization of broadband ocean surface albedo applicable to all skies. Ocean Modelling, 190, 102394. doi: 10.1016/j.ocemod.2024.102394. The ocean surface albedo (OSA) is an important parameter in ocean and climate models for air-sea heat flux calculations. Current OSA schemes are either too simple, making them only suitable for clear sky conditions, or too complex, because they depend on parameters that are not often measured in conventional ocean observations. Using radiation observations at a fixed offshore platform, we propose a simple but effective parameterization scheme of OSA, in which the broadband OSA is an analytical function of both the solar zenith angle and atmospheric transparency. It depends only on the downward shortwave radiation measured at the ocean surface and applies to all sky conditions. During our 15-month radiation observations, the correlation coefficient between the calculated OSA and the observations reached 0.90 for all skies, and the root mean square deviation was 0.0130. Three other OSA observation datasets are also introduced to verify this scheme. Albedo; Heat flux; Numerical models; Parameterization; Solar radiation
Huang, Guan; Chen, Yonghang; Liu, Qiong; Wang, Pengtao; He, Qianshan; He, Qing; Li, Shuai; Shao, Weiling; Fan, TingHuang, G., Y. Chen, Q. Liu, P. Wang, Q. He, Q. He, S. Li, W. Shao, T. Fan, 2024: Accurate Shortwave Radiation Simulation with a Two-Layer Aerosol Model in Xinjiang Region. Journal of Meteorological Research, 38(1), 69-87. doi: 10.1007/s13351-024-3133-y. To harness the rich solar energy resources in Xinjiang Region of Northwest China, this study tries to address the issue of lack of downward surface shortwave radiation (DSSR) observations and the need to improve the accuracy of satellite retrieval and numerical simulation of DSSR under varied sky and meteorological conditions. (1) A two-layer aerosol model specific to Xinjiang was developed to capture the vertical distributions of aerosols based on multiple data sources including lidar, GPS sounding, ground meteorological observations, and profiles from the ECMWF reanalysis version 5 (ERA5) data. The results show that the ERA5/PBLH (planetary boundary layer height) and ERA5/ALH (aerosol layer height) could be used to establish the two-layer aerosol model and characterize the vertical distribution of aerosols in Xinjiang Region. (2) Using the Santa Barbara Discrete Atmospheric Radiative Transfer (SBDART) model, a localized inverse model of clear-sky DSSR was established. After parameter adjustment and using the optimal combination of input parameters for DSSR simulation together with the two-layer aerosol model, the model-simulated DSSR (DSSRSBD) under clear-sky conditions improved significantly compared to the initial results, with all fitting indices greatly improved. (3) In addition, the study demonstrated that the impact of the two-layer aerosol model on DSSR was more pronounced under dust conditions than clear-sky conditions. (4) Using the localized clear-sky DSSR inversion model and its required parameters, simulations were also conducted to capture the spatiotemporal distribution of DSSR under clear-sky conditions in Xinjiang from 2017 to 2019. The annual average DSSRSBD under clear-sky conditions in Xinjiang during 2017–2019 was 606.78 W m−2, while DSSR from CERES (DSSRCER) under the same conditions was generally higher (703.95 W m−2). (5) It is found that satellite remote sensing products experienced data loss in high-altitude snow areas, where numerical simulation technology could serve as a valuable complement. Clouds and the Earth’s Radiant Energy System (CERES); aerosol vertical distribution; downward surface shortwave radiation (DSSR); Santa Barbara Discrete Atmospheric Radiative Transfer (SBDART); Xinjiang
Huang, Han; Huang, Yi; Wei, Qiang; Hu, YongyunHuang, H., Y. Huang, Q. Wei, Y. Hu, 2024: Band-by-band spectral radiative kernels based on the ERA5 reanalysis. Scientific Data, 11(1), 237. doi: 10.1038/s41597-024-03080-y. Radiative kernel is a widely adopted method for diagnosing radiation variability and climate feedback. However, most of the existing radiative kernels are broadband flux kernels and lack the spectral information. Motivated by the growing interest in the spectral changes of the Earth radiation budget, we generate a new set of band-by-band radiative kernels based on the fifth generation European Center for Medium-Range Weather Forecasts (ERA5) reanalysis, which can be used for analyzing the spectrally decomposed changes in the top of atmosphere, surface and atmospheric radiation. The radiative sensitivity quantified by the ERA5 band-by-band kernel is compared to another spectral kernel and validated in a spectral radiation closure test. The use and benefits of the new ERA5 kernels are then demonstrated in an analysis of spectral feedbacks of an ensemble of global climate models (GCMs). Climate change; Atmospheric science
Jadhav, Ashwin Vijay; Rahul, P. R. C.; Kumar, Vinay; Dumka, Umesh Chandra; Bhawar, Rohini L.Jadhav, A. V., P. R. C. Rahul, V. Kumar, U. C. Dumka, R. L. Bhawar, 2024: Spatiotemporal Assessment of Surface Solar Dimming in India: Impacts of Multi-Level Clouds and Atmospheric Aerosols. Climate, 12(4), 48. doi: 10.3390/cli12040048. Surface solar radiation (SSR) is a fundamental energy source for an equitable and sustainable future. Meteorology-induced variability increases uncertainty in SSR, thereby limiting its reliability due to its intermittent nature. This variability depends on several meteorological factors, including clouds, atmospheric gases, and aerosol concentrations. This research investigates the detailed impact of different levels of clouds and aerosols on SSR across India. Utilizing satellite data with reanalysis retrievals, the research covers a span of three decades (30 years), from 1993 to 2022. Aerosols contributed to an average attenuation of ~13.33% on SSR, while high, mid, and low cloud conditions showed much stronger impacts, with an attenuation of ~30.80%, ~40.10%, and ~44.30%, respectively. This study reveals an alarming pattern of increasing cloud impact (Cimpact) on SSR in the recent decade, with a significant increasing rate of ~0.22% year−1 for high cloud (HCimpact) and ~0.13% year−1 for mid cloud (MCimpact) impact, while low cloud impact (LCimpact) showed minimal change. The trend of aerosol impact (Aimpact) also showed an average increase of ~0.14% year−1 across all regions. The findings underscore the imperative of considering climatic variables while studying the growing solar dimming. Our findings also will assist policymakers and planners in better evaluating the solar energy resources across India. India; surface solar radiation; aerosol impact; cloud impact; National Solar Mission; solar dimming; solar energy potential
Jia, H.; Hasekamp, O.; Quaas, J.Jia, H., O. Hasekamp, J. Quaas, 2024: Revisiting Aerosol–Cloud Interactions From Weekly Cycles. Geophysical Research Letters, 51(13), e2024GL108266. doi: 10.1029/2024GL108266. Weekly cycles (WCs) in cloud properties have been reported and linked to aerosol effects. Yet the extent to which human activities contribute to their occurrence remains unclear. Here, we revisit aerosol–cloud interactions from the WCs over central Europe using long-term satellite and reanalysis data. Significant WCs in aerosol and cloud droplet number concentration (Nd) are detected with minima/maxima on Monday/Friday, indicating a clear signal of the Twomey effect. Notably, Nd–to–aerosol sensitivity from WCs is found to decrease at larger aerosol concentrations, confirming the nonlinear behavior of the aerosol–Nd relation (in log–log space) reported previously, but from a distinct perspective. Nevertheless, no discernible WCs in liquid water path are found. The pronounced WCs in cloud cover are demonstrated to be driven by natural variability. Our results indicate that the WCs offer a useful pathway for investigating the Twomey effect, but are not as effective for detecting cloud adjustments. aerosol; aerosol-cloud interactions; cloud; weekly cycles
Jia, Jiajia; Zeng, Zhaoliang; Zhang, Wenqian; Zheng, Xiangdong; Wang, Yaqiang; Ding, MinghuJia, J., Z. Zeng, W. Zhang, X. Zheng, Y. Wang, M. Ding, 2024: The Performance of Downward Shortwave Radiation Products from Satellite and Reanalysis over the Transect of Zhongshan Station to Dome A, East Antarctica. Advances in Atmospheric Sciences, 41(8), 1574-1588. doi: 10.1007/s00376-023-3136-0. The downward shortwave radiation (DSR) is an important part of the Earth’s energy balance, driving Earth’s system’s energy, water, and carbon cycles. Due to the harsh Antarctic environment, the accuracy of DSR derived from satellite and reanalysis has not been systematically evaluated over the transect of Zhongshan station to Dome A, East Antarctica. Therefore, this study aims to evaluate DSR reanalysis products (ERA5-Land, ERA5, MERRA-2) and satellite products (CERES and ICDR) in this area. The results indicate that DSR exhibits obvious monthly and seasonal variations, with higher values in summer than in winter. The ERA5-Land (ICDR) DSR product demonstrated the highest (lowest) accuracy, as evidenced by a correlation coefficient of 0.988 (0.918), a root-mean-square error of 23.919 (69.383) W m−2, a mean bias of −1.667 (−28.223) W m−2 and a mean absolute error of 13.37 (58.99) W m−2. The RMSE values for the ERA5-Land reanalysis product at seven stations, namely Zhongshan, Panda 100, Panda 300, Panda 400, Taishan, Panda 1100, and Kunlun, were 30.938, 29.447, 34.507, 29.110, 20.339, 17.267, and 14.700 W m−2, respectively; with corresponding bias values of 9.887, −12.159, −19.181, −15.519, −8.118, 6.297, and 3.482 W m−2. Regarding seasonality, ERA5-Land, ERA5, and MERRA-2 reanalysis products demonstrate higher accuracies during spring and summer, while ICDR products are least accurate in autumn. Cloud cover, water vapor, total ozone, and severe weather are the main factors affecting DSR. The error of DSR products is greatest in coastal areas (particularly at the Zhongshan station) and decreases towards the inland areas of Antarctica. downward shortwave radiation; East Antarctic; Environmental Chemistry; reanalysis product; satellite product; validation; 东南极; 再分析产品; 卫星产品; 地表向下短波辐射; 验证研究
Jin, Yubin; Zeng, Zhenzhong; Chen, Yuntian; Xu, Rongrong; Ziegler, Alan D.; Chen, Wenchuang; Ye, Bin; Zhang, DongxiaoJin, Y., Z. Zeng, Y. Chen, R. Xu, A. D. Ziegler, W. Chen, B. Ye, D. Zhang, 2024: Geographically constrained resource potential of integrating floating photovoltaics in global existing offshore wind farms. Advances in Applied Energy, 100163. doi: 10.1016/j.adapen.2024.100163. Marine renewable energy is gaining prominence as a crucial component of the energy supply in coastal cities due to proximity and minimal land requirements. The synergistic potential of integrating floating photovoltaics with offshore wind turbines presents an encouraging avenue for boosting power production, amplifying spatial energy generation density, and mitigating seasonal output fluctuations. While the global promise of offshore wind-photovoltaic hybrid systems is evident, a definitive understanding of their potential remains elusive. Here, we evaluate the resource potential of the hybrid systems under geographical constraints, offering insights into sustainable and efficient offshore energy solutions. We compile a database with 11,198 offshore wind turbine locations from Sentinel-1 imagery and technical parameters from commercial project details. Our analysis reveals an underutilization of spatial resources within existing offshore wind farms, yielding a modest 26 kWh per square meter. Furthermore, employing realistic climate-driven system simulations, we find an impressive potential photovoltaic generation of 1,372 ± 18 TWh annually, over seven times higher than the current offshore wind capacity. Notably, floating photovoltaics demonstrated remarkable efficiency, matching wind turbine output with a mere 17% of the wind farm area and achieving an average 76% increase in power generation at equivalent investment costs. Additionally, the hybrid wind and photovoltaic systems exhibit monthly-scale complementarity, reflected by a Pearson correlation coefficient of -0.78, providing a consistent and reliable power supply. These findings support the notion that hybrid offshore renewable energy could revolutionize the renewable energy industry, optimize energy structures, and contribute to a sustainable future for coastal cities. energy complementarity; hybrid energy system; offshore photovoltaic power; offshore wind power
Johnson, G. C.; Lumpkin, R.; Alexander, Michael A.; Amaya, Dillon J.; Beckley, Brian; Boyer, Tim; Bringas, Francis; Carter, Brendan R.; Cetinić, Ivona; Chambers, Don P.; Chan, Duo; Cheng, Lijing; Dong, Shenfu; Elipot, Shane; Feely, Richard A.; Franz, Bryan A.; Fu, Yao; Gao, Meng; Garg, Jay; Giglio, Donata; Gilson, John; Goes, Marlos; Graham, Garrett; Hamlington, Benjamin D.; Hobbs, Will; Hu, Zeng-Zhen; Huang, Boyin; Ishii, Masayoshi; Jacox, Michael G.; Jersild, Annika; Jevrejeva, Svetlana; Johns, William E.; Killick, Rachel E.; Kuusela, Mikael; Landschützer, Peter; Leuliette, Eric; Liu, Chao; Locarnini, Ricardo; Lozier, Susan M.; Lyman, John M.; Merrifield, Mark A.; Mishonov, Alexey; Mitchum, Gary T.; Moat, Ben I.; Nerem, R. Steven; Oe, Mitsuho; Perez, Renellys C.; Pita, Ivenis; Purkey, Sarah G.; Reagan, James; Sato, Kanako; Schmid, Claudia; Smeed, David A.; Smith, Ryan H.; Stackhouse, Paul W.; Sukianto, Thea; Sweet, William; Thompson, Philip R.; Triñanes, Joaquin A.; Volkov, Denis L.; Wanninkhof, Rik; Weller, Robert A.; Westberry, Toby K.; Widlansky, Matthew J.; Willis, Josh K.; Yin, Xungang; Yu, Lisan; Zhang, Huai-minJohnson, G. C., R. Lumpkin, M. A. Alexander, D. J. Amaya, B. Beckley, T. Boyer, F. Bringas, B. R. Carter, I. Cetinić, D. P. Chambers, D. Chan, L. Cheng, S. Dong, S. Elipot, R. A. Feely, B. A. Franz, Y. Fu, M. Gao, J. Garg, D. Giglio, J. Gilson, M. Goes, G. Graham, B. D. Hamlington, W. Hobbs, Z. Hu, B. Huang, M. Ishii, M. G. Jacox, A. Jersild, S. Jevrejeva, W. E. Johns, R. E. Killick, M. Kuusela, P. Landschützer, E. Leuliette, C. Liu, R. Locarnini, S. M. Lozier, J. M. Lyman, M. A. Merrifield, A. Mishonov, G. T. Mitchum, B. I. Moat, R. S. Nerem, M. Oe, R. C. Perez, I. Pita, S. G. Purkey, J. Reagan, K. Sato, C. Schmid, D. A. Smeed, R. H. Smith, P. W. Stackhouse, T. Sukianto, W. Sweet, P. R. Thompson, J. A. Triñanes, D. L. Volkov, R. Wanninkhof, R. A. Weller, T. K. Westberry, M. J. Widlansky, J. K. Willis, X. Yin, L. Yu, H. Zhang, 2024: Global Oceans. doi: 10.1175/BAMS-D-24-0100.1. "Global Oceans" published on 22 Aug 2024 by American Meteorological Society.
Jones, William K.; Stengel, Martin; Stier, PhilipJones, W. K., M. Stengel, P. Stier, 2024: A Lagrangian perspective on the lifecycle and cloud radiative effect of deep convective clouds over Africa. Atmospheric Chemistry and Physics, 24(9), 5165-5180. doi: 10.5194/acp-24-5165-2024. The anvil clouds of tropical deep convection have large radiative effects in both the shortwave (SW) and longwave (LW) spectra with the average magnitudes of both over 100 W m−2. Despite this, due to the opposite sign of these fluxes, the net average of the anvil cloud radiative effect (CRE) over the tropics is observed to be neutral. Research into the response of the anvil CRE to climate change has primarily focused on the feedbacks of anvil cloud height and anvil cloud area, in particular regarding the LW feedback. However, tropical deep convection over land has a strong diurnal cycle which may couple with the shortwave component of the anvil cloud radiative effect. As this diurnal cycle is poorly represented in climate models it is vital to gain a better understanding of how its changes impact the anvil CRE. To study the connection between the deep convective cloud (DCC) lifecycle and CRE, we investigate the behaviour of both isolated and organised DCCs in a 4-month case study over sub-Saharan Africa (May–August 2016). Using a novel cloud tracking algorithm, we detect and track growing convective cores and their associated anvil clouds using geostationary satellite observations from the Meteosat Spinning Enhanced Visible and Infrared Imager (SEVIRI). Retrieved cloud properties and derived broadband radiative fluxes are provided by the Community Cloud retrieval for CLimate (CC4CL) algorithm. By collecting the cloud properties of the tracked DCCs, we produce a dataset of anvil cloud properties along their lifetimes. While the majority of DCCs tracked in this dataset are isolated, with only a single core, the overall coverage of anvil clouds is dominated by those of clustered, multi-core anvils due to their larger areas and lifetimes. We find that the anvil cloud CRE of our tracked DCCs has a bimodal distribution. The interaction between the lifecycles of DCCs and the diurnal cycle of insolation results in a wide range of the SW anvil CRE, while the LW component remains in a comparatively narrow range of values. The CRE of individual anvil clouds varies widely, with isolated DCCs tending to have large negative or positive CREs, while larger, organised systems tend to have a CRE closer to 0. Despite this, we find that the net anvil cloud CRE across all tracked DCCs is close to neutral (−0.94 ± 0.91 W m−2). Changes in the lifecycle of DCCs, such as shifts in the time of triggering, or the length of the dissipating phase, could have large impacts on the SW anvil CRE and lead to complex responses that are not considered by theories of LW anvil CRE feedbacks.
Jordan, G.; Henry, M.Jordan, G., M. Henry, 2024: IMO2020 Regulations Accelerate Global Warming by up to 3 Years in UKESM1. Earth's Future, 12(8), e2024EF005011. doi: 10.1029/2024EF005011. The International Maritime Organization (IMO) introduced new regulations on the sulfur content of shipping emissions in 2020 (IMO2020). Estimates of the climatic impact of this global reduction in anthropogenic sulfate aerosols vary widely. Here, we contribute to narrowing this uncertainty with two sets of climate model simulations using UKESM1. Using fixed sea-surface temperature atmosphere-only simulations, we estimate an IMO2020 global effective radiative forcing of 0.139 ± 0.019 Wm−2 and show that most of this forcing is due to aerosol-induced changes to cloud properties. Using coupled ocean-atmosphere simulations, we note significant changes in cloud top droplet number concentration and size across regions with high shipping traffic density, and—in the North Atlantic and North Pacific—these microphysical changes translate to a decrease in cloud albedo. We show that IMO2020 increases global annual surface temperature on average by 0.046 ± 0.010°C across 2020–2029; approximately 2–3 years of global warming. Furthermore, our model simulations show that IMO2020 helps to explain the exceptional warming in 2023, but other factors are needed to fully account for it. The year 2023 also had an exceptionally large decrease in reflected shortwave radiation at the top-of-atmosphere. Our results show that IMO2020 made that more likely, yet the observations are within the variability of simulations without the reduction in shipping emissions. To better understand the climatic impacts of IMO2020, a model intercomparison project would be valuable whilst the community waits for a more complete observational record. aerosol-cloud interactions; marine cloud brightening; shipping regulations
Joseph, Lionel P.; Deo, Ravinesh C.; Casillas-Pérez, David; Prasad, Ramendra; Raj, Nawin; Salcedo-Sanz, SanchoJoseph, L. P., R. C. Deo, D. Casillas-Pérez, R. Prasad, N. Raj, S. Salcedo-Sanz, 2024: Short-term wind speed forecasting using an optimized three-phase convolutional neural network fused with bidirectional long short-term memory network model. Applied Energy, 359, 122624. doi: 10.1016/j.apenergy.2024.122624. Wind energy is an environment friendly, low-carbon, and cost-effective renewable energy source. It is, however, difficult to integrate wind energy into a mixed energy grid due to its high volatility and intermittency. For wind energy conversion systems to be reliable and efficient, accurate wind speed (WS) forecasting is fundamental. This study cascades a convolutional neural network (CNN) with a bidirectional long short-term memory (BiLSTM) in order to obtain a model for hourly WS forecasting by utilizing several meteorological variables as model inputs to study their effects on predicted WS. For input selection, the mutation grey wolf optimizer (TMGWO) is used. For efficient optimization of CBiLSTM hyperparameters, a hybrid Bayesian Optimization and HyperBand (BOHB) algorithm is used. The combined usage of TMGWO, BOHB, and CBiLSTM leads to a three-phase hybrid model (i.e., 3P-CBiLSTM). The performance of 3P-CBiLSTM is benchmarked against the standalone and hybrid BiLSTMs, LSTMs, gradient boosting (GBRs), random forest (RFRs), and decision tree regressors (DTRs). The statistical analysis of forecasted WS reveals that the 3P-CBiLSTM is highly effective over the other benchmark forecasting methods. This objective model also registers the highest percentage of forecasted errors (≈ 53.4 – 81.8%) within the smallest error range ≤ |0.25| ms−1 amongst all tested study sites. Despite the remarkable results achieved, the CBiLSTM model cannot be generally understood, so the eXplainable Artificial Intelligence (xAI) technique was used for explaining local and global model outputs, based on Local Interpretable Model-Agnostic Explanations (LIME) and SHapley Additive exPlanations (SHAP). Both of the xAI methods determined that the antecedent WS is the most significant predictor of the short-term WS forecasting. Therefore, we aver that the proposed model can be employed to help wind farm operators in making quality decisions in maximizing wind power integration into the grid with reduced intermittency. Feature selection; Bidirectional LSTM; Convolutional neural networks; eXplainable Artificial Intelligence; Wind speed forecasting
Jouan, Caroline; Myhre, GunnarJouan, C., G. Myhre, 2024: Satellite-based analysis of top of atmosphere shortwave radiative forcing trend induced by biomass burning aerosols over South-Eastern Atlantic. npj Climate and Atmospheric Science, 7(1), 1-8. doi: 10.1038/s41612-024-00631-3. This study investigates long-term changes in the shortwave direct aerosol radiative effect (DARE) at the top of the atmosphere (TOA) induced by biomass burning aerosol (BBA) transported from southern Africa to the south-eastern Atlantic (SEA) stratocumulus region during extended fire seasons. The evolution since 2002 of aerosol, cloud properties, and TOA shortwave outgoing radiation from advanced passive satellite sensors are presented, as well as the observational trend in clear-sky DAREclr and the retrieval trend in all-sky DAREall. Supplemented by chemical transport model simulations, we estimate that DAREclr has become more negative (−0.09 ± 0.06 W m−2 yr−1) due to increased aerosol presence in SEA. Meanwhile, DAREall has become more positive ( + 0.04 ± 0.15 W m−2 yr−1) due to aerosols in cloudy sky regions. This study reveals satellite capabilities in capturing complex BBA-cloud-solar radiation interactions for accurate radiative forcing estimates and projections. Atmospheric dynamics; Atmospheric chemistry
Kang, Hyoji; Choi, Yong-Sang; Jiang, Jonathan H.Kang, H., Y. Choi, J. H. Jiang, 2024: Factors determining tropical upper-level cloud radiative effect in the radiative-convective equilibrium framework. Scientific Reports, 14(1), 13419. doi: 10.1038/s41598-024-62587-x. Investigation of the major factors determining tropical upper-level cloud radiative effect (TUCRE) is crucial for understanding cloud feedback mechanisms. We examined the TUCRE inferred from the outputs of historical runs and AMIP runs from CMIP6 models employing a radiative-convective equilibrium (RCE). In this study, we incorporated the RCE model configurations of atmospheric dynamics and thermodynamics from the climate models, while simplifying the intricate systems. Using the RCE model, we adjusted the global mean surface temperature to achieve energy balance, considering variations in tropical cloud fraction, regional reflectivity, and emission temperature corresponding to each climate model. Subsequently, TUCRE was calculated as a unit of K/%, representing the change in global mean surface temperature (K) in response to an increment in the tropical upper-level clouds (%). Our RCE model simulation indicates that the major factors determining the TUCRE are the emission temperatures of tropical moist-cloudy and moist-clear regions, as well as the fraction of tropical upper-level clouds. The higher determination coefficients between TUCRE and both the emission temperature of tropical moist regions and the upper-level cloud fraction are attributable to their contribution to the trapping effect on the outgoing longwave radiations, which predominantly determines TUCRE. Consequently, the results of this study underscore the importance of accurately representing the upper-level cloud fraction and emission temperature in tropical moist regions to enhance the representation of TUCRE in climate models. Atmospheric dynamics; Climate and Earth system modelling
Karumuri, Rama Krishna; Dasari, Hari Prasad; Gandham, Harikishan; Kunchala, Ravi Kumar; Attada, Raju; Ashok, Karumuri; Hoteit, IbrahimKarumuri, R. K., H. P. Dasari, H. Gandham, R. K. Kunchala, R. Attada, K. Ashok, I. Hoteit, 2024: Investigation of Dust-Induced Direct Radiative Forcing Over the Arabian Peninsula Based on High-Resolution WRF-Chem Simulations. Journal of Geophysical Research: Atmospheres, 129(13), e2024JD040963. doi: 10.1029/2024JD040963. This study investigates the impact of dust on radiation over the Arabian Peninsula (AP) during the reported high, low, and normal dust seasons (March–August) of 2012, 2014, and 2015, respectively. Simulations were performed using the Weather Research and Forecasting model coupled to a Chemistry module (WRF-Chem). The simulated seasonal horizontal and vertical dust concentrations, and their interannual distinctions, match well with those from two ground-based AERONET observations, and measurements from MODIS and CALIOP satellites. The maximum dust concentrations over the dust-source regions in the southern AP reach vertically upto 700 hPa during the high dust season, but only upto 900–950 hPa during the low/normal dust seasons. Stronger incoming low-level winds along the southern Red Sea and those from Iraq bring in higher-than-normal dust during the high dust summers. We conducted a sensitivity experiment by switching-off the dust module to assess the radiative perturbations due to dust. The results suggest that active dust-module improved the fidelity of simulated radiation fluxes distributions at the surface and top of the atmosphere vis-à-vis Clouds and the Earth's Radiant Energy System (CERES) measurements. Dust results in a 26 Wm−2 short-wave (SW) radiative forcing in the tropospheric-column over the AP. The SW radiative forcing increases by another 6–8 Wm−2 during the high dust season due to the increased number of extreme dust days, which also amplifies atmospheric heating. During extreme dust days, the heating rate exhibits a dipolar structure, with cooling over the Iraq region and warming of 40%–60% over the southern-AP. Arabian Peninsula; dust optical depth; heating rate; radiative forcing; WRF-chem
Kim, Doyeon; Kang, Sarah M.; Kim, Hanjun; Taylor, Patrick C.Kim, D., S. M. Kang, H. Kim, P. C. Taylor, 2024: Quantifying Changes in the Arctic Shortwave Cloud Radiative Effects. Journal of Geophysical Research: Atmospheres, 129(15), e2023JD040707. doi: 10.1029/2023JD040707. The shortwave cloud radiative effect (SWCRE) is important for the Arctic surface radiation budget and is a major source of inter-model spread in simulating Arctic climate. To better understand the individual contributions of various radiative processes to changes in SWCRE, we extend the existing Approximate Partial Radiative Perturbation (APRP) method by adding the absorptivity for the upward beam, considering differences in reflectivity between upward and downward beams, and analyzing the cloud masking effect resulting from changes in surface albedo. Using data from CMIP model experiments, the study decomposes the SWCRE over the Arctic surface and analyzes inter-model differences in quadrupled CO2 simulations. The study accounts for the influence of surface albedo, cloud amount, and cloud microphysics in the response of SWCRE to Arctic warming. In the sunlit season, CMIP models exhibit a strong, negative SWCRE with a large inter-model spread. Arctic clouds dampen the surface albedo feedback by reflecting incoming solar radiation and further decrease the shortwave radiation reflected by surface, a fraction of which is scattered back to the surface by clouds. Specifically, this accounts for the majority of the inter-model spread in SWCRE. In addition, increased (decreased) cloud amount and cloud liquid water reduce (increase) incoming shortwave fluxes at the surface, but they are found to be not critical to the Arctic surface radiation budget and its inter-model variation. Overall, the extended APRP method offers a useful tool for analyzing the complex interactions between clouds and radiative processes, accurately decomposes the individual SWCRE responses at the Arctic surface.
Kuhlbrodt, Till; Swaminathan, Ranjini; Ceppi, Paulo; Wilder, ThomasKuhlbrodt, T., R. Swaminathan, P. Ceppi, T. Wilder, 2024: A Glimpse into the Future: The 2023 Ocean Temperature and Sea Ice Extremes in the Context of Longer-Term Climate Change. Bull. Amer. Meteor. Soc., 105(3), E474-E485. doi: 10.1175/BAMS-D-23-0209.1. Abstract In the year 2023, we have seen extraordinary extrema in high sea surface temperature (SST) in the North Atlantic and in low sea ice extent in the Southern Ocean, outside the 4σ envelope of the 1982–2011 daily time series. Earth’s net global energy imbalance (12 months up to September 2023) amounts to +1.9 W m−2 as part of a remarkably large upward trend, ensuring further heating of the ocean. However, the regional radiation budget over the North Atlantic does not show signs of a suggested significant step increase from less negative aerosol forcing since 2020. While the temperature in the top 100 m of the global ocean has been rising in all basins since about 1980, specifically the Atlantic basin has continued to further heat up since 2016, potentially contributing to the extreme SST. Similarly, salinity in the top 100 m of the ocean has increased in recent years specifically in the Atlantic basin, and in addition in about 2015 a substantial negative trend for sea ice extent in the Southern Ocean began. Analyzing climate and Earth system model simulations of the future, we find that the extreme SST in the North Atlantic and the extreme in Southern Ocean sea ice extent in 2023 lie at the fringe of the expected mean climate change for a global surface-air temperature warming level (GWL) of 1.5°C, and closer to the average at a 3.0°C GWL. Understanding the regional and global drivers of these extremes is indispensable for assessing frequency and impacts of similar events in the coming years.
Li, Dahui; Wang, Tianxing; Zheng, Xiaopo; Zhang, Peng; Zheng, Lilin; Leng, Wanchun; Du, Yihan; Chen, Lin; Zhang, WanchunLi, D., T. Wang, X. Zheng, P. Zhang, L. Zheng, W. Leng, Y. Du, L. Chen, W. Zhang, 2024: Multi-Dimensional matrix MAPping (MDMAP): A new algorithm framework to derive top-of-atmosphere outgoing longwave radiation from space. Remote Sensing of Environment, 304, 114031. doi: 10.1016/j.rse.2024.114031. Outgoing Longwave Radiation (OLR) is an important component of the Earth's radiation budget and a key parameter for coupled models of the atmosphere, ocean, land, and other systems. It is of significant importance in studies related to Earth sciences such as weather forecasting, climate research, and disaster monitoring. Since narrowband sensors are more widely available and have higher spatial resolutions than broadband sensors, high-resolution OLR data are currently frequently estimated using narrowband sensors. This study proposes a novel physical method, namely the Multi-Dimensional matrix MAPping algorithm (MDMAP) framework, inspired by the scene classification ideas of Cloud and Earth's Radiant Energy System (CERES) and the differential absorption theory. The new framework aims to accurately retrieve OLR from the multi-channel infrared sensor, such as Moderate Resolution Imaging Spectroradiometer (MODIS). Corresponding to traditional algorithms, such as the polynomial regression algorithm (POLY) and lookup table algorithm (LUT), the new framework provides two distinct implementations of the MDMAP algorithm framework (MDMAP:POLY and MDMAP:LUT). The performances of both the traditional and the newly proposed algorithms are evaluated based on the radiative transfer simulation dataset and CERES SSF OLR products. The results show that the MDMAP algorithms behave more accurately than the traditional ones under most conditions, especially under clear-sky conditions. Specifically, a comprehensive analysis indicates that the new algorithms demonstrate smaller RMSEs than the traditional ones under various conditions, particularly in desert regions with the RMSE reduction exceeding 3 W/m2 (>30%). Moreover, the two new algorithms reveal enhanced robustness to noise uncertainties, and demonstrate remarkable generality and computational efficiency, implying their potential and better applicability in deriving believable OLR from most infrared sensors. Cloud and Earth's radiant energy system (CERES); Moderate resolution imaging Spectroradiometer (MODIS); Multi-Dimensional matrix MAPping (MDMAP); Outgoing longwave radiation (OLR); Polynomial regression; Radiation transfer simulation
Li, Na; Zhao, Ping; Zhou, ChangyanLi, N., P. Zhao, C. Zhou, 2024: The spatiotemporal variation of land surface heat fluxes in Tibetan Plateau during 2001–2022. Atmospheric Research, 297, 107081. doi: 10.1016/j.atmosres.2023.107081. The surface energy budget is important for understanding of energy and water cycle processes in the Tibetan Plateau (TP). In this study, the daily sensible (SH) and latent (LE) heat fluxes at the horizontal resolution of 1° are first estimated using the maximum entropy production (MEP) model (hereinafter SHMEP and LEMEP) in the entire TP during 2001–2022. The MEP model is built on physical and statistical principles to simulate surface heat fluxes. The surface net radiation, soil moisture (SM), and land surface temperature (LST) are the main driving variables for MEP model. To select the relatively accurate MEP input data, the merged surface net radiation (Rn–merged) under all-sky conditions are generated from CERES, ISCCP-FH, and ERA5 using the Bayesian Model Averaging scheme. Besides, the TP SM and LST from various data sources are evaluated using the in-situ observations at site scale. Based on the daily Rn–merged, ERA5 SM, CERES LST, and the MEP model, the daily SH and LE are estimated in the entire TP. The results show the daily SHMEP and LEMEP perform well at the validation sites, with the regional mean correlation coefficient (R) above 0.7, root-mean-square error (RMSE) of Latent heat flux; Maximum entropy production model; Multi-Source datasets; Sensible heat flux; Tibetan Plateau
Li, Ruixue; Jian, Bida; Li, Jiming; Wen, Deyu; Zhang, LijieLi, R., B. Jian, J. Li, D. Wen, L. Zhang, 2024: Understanding the variation of Reflected Solar Radiation: A Latitude- and month-based Perspective. EGUsphere, 1-45. doi: 10.5194/egusphere-2023-2882. Abstract. The hemispheric symmetry of planetary albedo (PA) is crucial for the Earth's energy budget. However, our understanding of hemispheric albedo is still limited, particularly regarding its variations at finer spatial and temporal scales. Using 21 years of radiation data from CERES-EBAF, this study quantifies the contribution rates of different latitudes to the hemispheric reflected solar radiation and examines their seasonal variations. Statistical results show that the northern latitudinal zones of 0° to 40° contribute more reflected radiation than the corresponding southern latitudes, but the southern latitudinal zones of 50° to 90° compensate for this. From the equator to 40°, the latitudinal contribution to the hemisphere is high in autumn and winter and low in spring and summer; however, after 50°, the situation is reversed. And even during extreme cases, anomalies of the cloud component contribution play a dominant role in anomalies of the total reflected radiation contribution of the latitudinal zone in most latitudinal zones. Additionally, this study evaluates the performance of four radiation data (including: satellite and reanalysis data) in reproducing hemisphere albedo and its hemispheric symmetry compared to CERES-EBAF data. Under different symmetry criteria, the applicability of different datasets to hemispheric symmetry of PA studies varies. Note that the Cloud_cci AVHRR performs better in capturing hemispheric symmetry. However, none of these datasets can decompose the different components of reflected radiation well. These results contribute to advancing our understanding of hemispheric symmetry variations and compensation mechanisms, reducing the uncertainty of model simulations, and improving algorithms for different radiation datasets.
Li, Tianci; Xin, Xiaozhou; Zhang, Hailong; Yu, Shanshan; Li, Li; Ye, Zhiqiang; Liu, Qinhuo; Cai, HeLi, T., X. Xin, H. Zhang, S. Yu, L. Li, Z. Ye, Q. Liu, H. Cai, 2024: Evaluation of Six Data Products of Surface Downward Shortwave Radiation in Tibetan Plateau Region. Remote Sensing, 16(5), 791. doi: 10.3390/rs16050791. The quantitative characterization of the thermal conditions in the Tibetan Plateau has long been a focal point of global research. Downward shortwave radiation, as a crucial component, plays an important role in numerous land surface processes while also serving as a significant indicator of the plateau’s thermal state. In order to gain a more comprehensive understanding of the Earth’s radiation budget in the Tibetan Plateau region, this study undertook an evaluation of six radiation products (ISCCP-FH, CERES-SYN, GLASS DSR, Himawari-8, MCD18A1, and ERA5). Two sets of ground measurements (downward shortwave radiation values from 10 CMA sites and 6 sites provided by the National Tibetan Plateau Data Center) in 2015 and 2016 were used as validation data to verify the accuracy of the remote sensing products. The results show that in the Tibetan Plateau region, CERESC products show the highest accuracy among the six data products with a bias (relative bias) of −7.57 W/m2 (3.46%), RMSE (relative RMSE) of 32.77 W/m2 (14.99%), and coefficient of determination of 0.80. Among all products, only the ERA5 products overestimated the value of downward shortwave radiation in the Tibetan Plateau region with a bias (relative bias) of 15.62 W/m2 (7.14%). By employing a spatial resolution upscaling approach, we assessed the influence of varying spatial resolutions on the validation accuracy, with the results indicating minimal impact. Through an analysis of the impact of cloud factors and aerosol factors on the validation accuracy, it is deduced that ERA5, Himawari-8, and MCD18A1 products are significantly influenced by cloud factors, whereas the CERES-SYN product is notably affected by aerosol factors. Tibetan Plateau; ERA5; CERES-SYN; downward shortwave radiation; aerosol optical depth; cloud optical thickness
Li, Xiaohan; Chu, Wenchao; Zhang, Yi; Wang, YimingLi, X., W. Chu, Y. Zhang, Y. Wang, 2024: Extending a dry-environment convection parameterization to couple with moist turbulence and a baseline evaluation in the GRIST model. Quarterly Journal of the Royal Meteorological Society, n/a(n/a). doi: 10.1002/qj.4763. This study presents an extension of a dry-environment convection scheme (Tiedtke–Bechtold) to couple with a boundary-layer moist turbulence scheme. The deep and shallow convective updraught is modified to develop in a moist environment and the large-scale budget of cloud condensate takes account of the influence of compensation subsidence. An ambiguous layer is introduced in the sub-cloud layer transport of shallow convection to mimic the non-local transport that is ignored in the moist local turbulence scheme. Long-term global simulation suggests that the modified convection and moist turbulence improve low cloud and short-wave cloud radiative forcing. This includes a more realistic climatological structure of stratocumulus-to-cumulus transition and ameliorated biases in liquid water path. For short to mid-term hindcasts in June 2021, the modified convection coupled with moist turbulence mitigates some regional over-forecasts of precipitation. They improve the forecast ability for light and moderate precipitation. The modified model still retains the capability to capture the diurnal features of continental rainfall. Convective parametrization; global cloud and precipitation modeling; physics–physics interaction
Li, Xuehua; Chen, Yunhao; Li, Kangning; Liu, Xiuyu; Gao, Shengjun; Ji, Weizhen; Cui, YingLi, X., Y. Chen, K. Li, X. Liu, S. Gao, W. Ji, Y. Cui, 2024: Generating station-like downward shortwave radiation data by using sky condition-guided model based on ERA5-Land data. Energy, 306, 132417. doi: 10.1016/j.energy.2024.132417. Accurate downward shortwave radiation (DSR) data is essential for the utilization of solar energy resources. However, existing various DSR data have certain limitations in applications. Among these, ERA5-Land DSR data is considered a relatively high-quality dataset. Nevertheless, it is reported notable deviations under different sky conditions, resulted from deficiencies in cloud and aerosol simulations. Therefore, this study aims to generate high-quality DSR data based on ERA5-Land data. We propose a sky condition-guided model using deviation characteristics of ERA5-Land DSR across different sky conditions as guidance, incorporating reliable cloud and aerosol parameters to provide atmosphere information. Consequently, station-like DSR data with accuracy close to station data is generated. Our model achieves high accuracy under different sky conditions, with RMSE below 32.19 W/m2. At the individual-station scale, 86.04 % of validation sites exhibit R values exceeding 0.9. At the seasonal scale, R values consistently surpass 0.87. Moreover, our data exhibits better accuracy compared to mainstream DSR datasets. Furthermore, it depicts the spatiotemporal variation of DSR and further reveals the photovoltaic potential in China, with relatively high values in the Tibetan Plateau and northwest China. The station-like DSR data is promising to advance the utilization of solar energy and accelerate the energy transition. Downward shortwave radiation; ERA5-Land reanalysis; Machine learning; Photovoltaic potential; Sky conditions; Solar energy
Li, Yize; Ge, Jinming; Du, Jiajing; Peng, Nan; Su, Jing; Hu, Xiaoyu; Zhang, Chi; Mu, Qingyu; Li, QinghaoLi, Y., J. Ge, J. Du, N. Peng, J. Su, X. Hu, C. Zhang, Q. Mu, Q. Li, 2024: Projection of Low Cloud Variation Through Robust Meteorological Linkage and Its Comparison With CMIP6 Models at the SACOL Site. Journal of Geophysical Research: Atmospheres, 129(16), e2023JD040668. doi: 10.1029/2023JD040668. Low clouds significantly influence Earth's energy budget by reflecting solar radiation. Consequently, inadequate representation of these clouds in models introduces the largest uncertainty in predicting future climate change. This study investigates low cloud cover (LCC) variation using 6 years (2014–2019) of high-precision ground-based Ka-band Zenith Radar (KAZR) observations at the Semi-Arid Climate and Environment Observatory of Lanzhou University (SACOL). We analyze the relationship between observed low cloud properties and four large-scale meteorological factors: 700 hPa relative humidity, estimated inversion strength, low-level wind shear, and 700 hPa vertical velocity. These factors are identified as key parameters influencing low cloud evolution over this semi-arid region. We utilize principal component analysis to integrate these parameters into a single meteorological predictor (PC1) and establish a robust linkage between meteorological conditions and low cloud properties. By comparing LCC fluctuations derived from the meteorological factors with those directly simulated by models over the same period, we assess the projected LCC trends under various carbon emission scenarios. Contrary to the declining LCC projected by CMIP6 models outcomes, the LCC form PC1 shows a rising tendency by 2100 under global warming. This discrepancy implies that CMIP6 models may exaggerate the extent of future warming at the SACOL site. Our approach can be applied to a broader global distribution of low clouds to examine the differences between low cloud variations constrained by meteorological fields and those from direct model simulations. This will enhance our understanding of low cloud feedback on future climate change. KAZR; large scale meteorology; low cloud; principal component analysis; SACOL
Liang, Hui; Jiang, Bo; Liang, Shunlin; Wen, Jianguang; He, Tao; Zhang, Xiaotong; Peng, Jianghai; Li, Shaopeng; Han, Jiakun; Yin, XiuwanLiang, H., B. Jiang, S. Liang, J. Wen, T. He, X. Zhang, J. Peng, S. Li, J. Han, X. Yin, 2024: A novel Terrain Correction Sinusoidal Model for improving estimation of daily clear-sky downward shortwave radiation. IEEE Transactions on Geoscience and Remote Sensing, 1-1. doi: 10.1109/TGRS.2024.3452791. Downward shortwave radiation (DSR) is greatly affected by rugged terrains, which account for about 24% of the world’s surface. Yet, existing DSR products do not take into account topographical effects. Some topographic correction algorithms have been developed for estimating the clear-sky instantaneous DSR over rugged terrains (DSRins-rugged), but no specific algorithms are available to get the daily average DSR over rugged terrains (DSRdaily-rugged). The objective of this study is to develop an efficient and robust model to retrieve the clear-sky DSRdaily-rugged based on DSR satellite products. After examining ground measurements collected from several mountainous sites over the Chengde Experimental Area in China, we found that the clear-sky DSRins-rugged over a day follows a pseudo-sine curve, depending on aspect, slope, and other terrain factors, which form the foundation of our Terrain Correction Sinusoidal Model (TCSM). TCSM also includes a new simple shadow correction method. Validation against ground measurements showed that shadow-corrected clear sky TCSM DSRdaily-rugged estimated from in situ measurements, is highly accurate with an RMSE of 9.69 Wm-2, Bias of 0.93 Wm-2 and R2 of 0.99. After applying TCSM to correct the topographic effects of both the CERES SYN1degEd4A and MCD18A1 C6 DSR products, the accuracies significantly improved, with the validated RMSE reduced from 63.60 and 64.51 to 14.03 and 12.60 Wm-2, the Bias from -38.58 and -36.93 to 5.53 and -7.17 Wm-2, and R2 from 0.46 and 0.44 to 0.97 and 0.98, respectively. Additionally, the TCSM can be easily applied to other DSR products that do not consider the topographic effects. Accuracy; Area measurement; CERES; clear-sky; daily downward shortwave radiation; estimation; Estimation; Land surface; MCD18; remote sensing; Remote sensing; rugged terrain; Solar radiation; Surface topography; Terrain Correction Sinusoidal Model
Liang, Lusheng; Su, Wenying; Sejas, Sergio; Eitzen, Zachary; Loeb, Norman G.Liang, L., W. Su, S. Sejas, Z. Eitzen, N. G. Loeb, 2024: Next-generation radiance unfiltering process for the Clouds and the Earth's Radiant Energy System instrument. Atmospheric Measurement Techniques, 17(7), 2147-2163. doi: 10.5194/amt-17-2147-2024. The filtered radiances measured by the Clouds and the Earth's Radiant Energy System (CERES) instruments are converted to shortwave (SW), longwave (LW), and window unfiltered radiances based on regressions developed from theoretical radiative transfer simulations to relate filtered and unfiltered radiances. This paper describes an update to the existing Edition 4 CERES unfiltering algorithm (Loeb et al., 2001), incorporating the most recent developments in radiative transfer modeling, ancillary input datasets, and increased computational and storage capabilities during the past 20 years. Simulations are performed with the updated Moderate Resolution Atmospheric Transmission (MODTRAN) 5.4 version. Over land and snow, the surface bidirectional reflectance distribution function (BRDF) is characterized by a kernel-based representation in the simulations, instead of the Lambertian surface used in the Edition 4 unfiltering process. Radiance unfiltering is explicitly separated into four seasonally dependent land surface groups based on the spectral radiation similarities of different surface types (defined by the International Geosphere-Biosphere Programme); over snow, it is separated into fresh snow, permanent snow, and sea ice. This differs from the Edition 4 unfiltering process where only one set of regressions was used for land and snow, respectively. The instantaneous unfiltering errors are estimated with independent test cases generated from radiative transfer simulations in which the “true” unfiltered radiances from radiative transfer simulations are compared with the unfiltered radiances calculated from the regressions. Overall, the relative errors are mostly within ±0.5 % for SW, within ±0.2 % for daytime LW, and within ±0.1 % for nighttime LW for both CERES Terra Flight Model 1 (FM1) and Aqua FM3 instruments. The unfiltered radiances are converted to fluxes and compared to CERES Edition 4 fluxes. The global mean instantaneous fluxes for Aqua FM3 are reduced by 0.34 to 0.45 W m−2 for SW and increased by 0.25 to 0.46 W m−2 for daytime LW; for Terra FM1, they are reduced by 0.24 to 0.34 W m−2 for SW and increased by 0.08 to 0.28 W m−2 for daytime LW. Nighttime LW flux differences are negligible for both instruments.
Lin, Haoxian; Ding, Ke; Huang, Xin; Lou, Sijia; Xue, Lian; Wang, Zilin; Ma, Yue; Ding, AijunLin, H., K. Ding, X. Huang, S. Lou, L. Xue, Z. Wang, Y. Ma, A. Ding, 2024: Impacts of Northward Typhoons on Autumn Haze Pollution Over North China Plain. Journal of Geophysical Research: Atmospheres, 129(6), e2023JD040465. doi: 10.1029/2023JD040465. Although air quality in China has improved substantially over recent years, haze pollution events still occur frequently, especially over the North China Plain (NCP). Previous studies showed that typhoons are conducive to regional pollution events in eastern China; however, the underlying mechanism and quantitative understanding of the typhoons' impact on haze pollution remain unclear there. Here, based on ground-based and satellite observations, reanalysis data, and model simulations, we show that northward typhoons approaching China are essential for autumn haze pollution over NCP. Elevated relative humidity levels and enhanced pollution accumulation, caused by northward typhoons and the corresponding high-pressure systems, are responsible for the pollution enhancements over NCP. Compared with episodes without typhoon influence, cities near Taihang and Yan Mountain suffer from heavier haze pollution when typhoons approach, with PM2.5 concentrations increasing from 87.1 to 106.4 μg m−3. More water vapor from the Yellow and Bohai Seas and pollutants from eastern China are transported to these cities by typhoon-induced southeasterly wind anomalies, facilitating the chemical formation of aerosols there. In addition, by the block of mountains, these southeasterly wind anomalies also lead to stronger local accumulation over cities and an elevation of pollutants along the mountains. What is more, with the implementation of emission reduction, the relative changes of PM2.5 concentrations between typhoon-induced episodes and no-typhoon episodes increase. This work highlights the importance of understanding the impact of synoptical weather on PM2.5 transport, accumulation, and formation processes in haze pollution mitigation in eastern China.
Lin, Meiyun; Horowitz, Larry W.; Zhao, Ming; Harris, Lucas; Ginoux, Paul; Dunne, John; Malyshev, Sergey; Shevliakova, Elena; Ahsan, Hamza; Garner, Steve; Paulot, Fabien; Pouyaei, Arman; Smith, Steven J.; Xie, Yuanyu; Zadeh, Niki; Zhou, LinjiongLin, M., L. W. Horowitz, M. Zhao, L. Harris, P. Ginoux, J. Dunne, S. Malyshev, E. Shevliakova, H. Ahsan, S. Garner, F. Paulot, A. Pouyaei, S. J. Smith, Y. Xie, N. Zadeh, L. Zhou, 2024: The GFDL Variable-Resolution Global Chemistry-Climate Model for Research at the Nexus of US Climate and Air Quality Extremes. Journal of Advances in Modeling Earth Systems, 16(4), e2023MS003984. doi: 10.1029/2023MS003984. We present a variable-resolution global chemistry-climate model (AM4VR) developed at NOAA's Geophysical Fluid Dynamics Laboratory (GFDL) for research at the nexus of US climate and air quality extremes. AM4VR has a horizontal resolution of 13 km over the US, allowing it to resolve urban-to-rural chemical regimes, mesoscale convective systems, and land-surface heterogeneity. With the resolution gradually reducing to 100 km over the Indian Ocean, we achieve multi-decadal simulations driven by observed sea surface temperatures at 50% of the computational cost for a 25-km uniform-resolution grid. In contrast with GFDL's AM4.1 contributing to the sixth Coupled Model Intercomparison Project at 100 km resolution, AM4VR features much improved US climate mean patterns and variability. In particular, AM4VR shows improved representation of: precipitation seasonal-to-diurnal cycles and extremes, notably reducing the central US dry-and-warm bias; western US snowpack and summer drought, with implications for wildfires; and the North American monsoon, affecting dust storms. AM4VR exhibits excellent representation of winter precipitation, summer drought, and air pollution meteorology in California with complex terrain, enabling skillful prediction of both extreme summer ozone pollution and winter haze events in the Central Valley. AM4VR also provides vast improvements in the process-level representations of biogenic volatile organic compound emissions, interactive dust emissions from land, and removal of air pollutants by terrestrial ecosystems. We highlight the value of increased model resolution in representing climate–air quality interactions through land-biosphere feedbacks. AM4VR offers a novel opportunity to study global dimensions to US air quality, especially the role of Earth system feedbacks in a changing climate. drought; precipitation; extremes; air quality-climate interactions; Earth system feedbacks; high-resolution
Liu, Huancai; Shang, Lina; Li, Man; Zheng, Xiaoyu; Shi, PeihongLiu, H., L. Shang, M. Li, X. Zheng, P. Shi, 2024: WRF numerical simulation of summer precipitation and its application over the mountainous southern Tibetan Plateau based on different cumulus parameterization schemes. Atmospheric Research, 309, 107608. doi: 10.1016/j.atmosres.2024.107608. The extreme scarcity of meteorological observation data caused by harsh natural environments greatly limits our understanding of precipitation and related atmospheric processes over the mountainous regions of the southern Tibetan Plateau and its surrounding areas (hereafter mountainous southern TP). Precipitation simulation has been challenging in this region due to the complex topography and large elevation differences. Considering the high sensitivity of precipitation to the choice of cumulus parameterization scheme (CPS) over the TP, this study systematically evaluated the precipitation simulation performance of 11 CPSs in July 2018 using the WRF model. The characteristics of atmospheric circulation and gradient variation of precipitation were also revealed based on the optimal CPS over this region. The results indicated that the scale-aware schemes (KIAPS SAS [KSAS] and multi-scale Kain–Fritsch [MSKF]) demonstrated excellent potential for precipitation simulations. Due to the reasonable expression of atmospheric stability and the resulting accurate simulation of the timing and amount of regional heavy precipitation events, the KSAS scheme was superior to the MSKF scheme. The output of the KSAS-configured experiment revealed two main water vapor transport channels for the mountainous southern TP in summer, namely the southern monsoonal channel and the western westerly channel. Based on the precipitation profiles along the typical paths of these two channels (longitudinal path of 95.5°E and latitudinal path of 29.5°N), two precipitation belts and one precipitation belt existed on the southern and western slopes of the TP, respectively. Cumulus parameterization scheme; Evaluation; Gradient variation of precipitation; Mountainous southern Tibetan Plateau; WRF
Liu, Shuchang; Zeman, Christian; Schär, ChristophLiu, S., C. Zeman, C. Schär, 2024: Dynamical Downscaling of Climate Simulations in the Tropics. Geophysical Research Letters, 51(5), e2023GL105733. doi: 10.1029/2023GL105733. The long-existing double-Intertropical Convergence Zone (ITCZ) problem in global climate models (GCMs) hampers accurate climate simulations in the tropics. Using a regional climate model (RCM) over the tropical and sub-tropical Atlantic with a horizontal resolution of 12 km and explicit convection, we develop a bias-corrected downscaling methodology to produce limited-area simulations with a realistic ITCZ, despite the double ITCZ in the driving GCM. The methodology effectively removes GCM biases in the RCM boundary conditions, such as to produce more realistic large-scale driving conditions. We show that the double-ITCZ problem persists with conventional dynamical downscaling, but with bias-corrected downscaling the RCM simulations yield credible ITCZ with a realistic seasonal cycle. Detailed analysis attributes the main cause of the double-ITCZ problem of the selected GCM to the sea surface temperature bias. Compared to the GCM's AMIP simulations, RCMs with higher resolution allow explicit deep convection and enable a better simulation of tropical convection and clouds. regional climate model; bias-corrected downscaling; double-ITCZ; dynamical downscaling; pseudo-global warming approach
Lock, A. P.; Whitall, M.; Stirling, A. J.; Williams, K. D.; Lavender, S. L.; Morcrette, C.; Matsubayashi, K.; Field, P. R.; Martin, G.; Willett, M.; Heming, J.Lock, A. P., M. Whitall, A. J. Stirling, K. D. Williams, S. L. Lavender, C. Morcrette, K. Matsubayashi, P. R. Field, G. Martin, M. Willett, J. Heming, 2024: The performance of the CoMorph-A convection package in global simulations with the Met Office Unified Model. Quarterly Journal of the Royal Meteorological Society, n/a(n/a). doi: 10.1002/qj.4781. The impact on global simulations of a new package of physical parametrizations in the Met Office Unified Model is documented. The main component of the package is an entirely new convection scheme, CoMorph. This has a mass-flux structure that allows initiation of buoyant ascent from any level and the ability for plumes of differing originating levels to coexist in a grid box. It has a different form of closure, where the mass flux of initiation is dependent on local instability, and an implicit numerical solution for detrainment that yields smooth timestep behaviour. The scheme is coupled more consistently to the cloud, microphysics, and boundary-layer parametrizations and, as a result, significant changes to these have also been made. The package, called CoMorph-A, has been tested in a variety of single-column and idealized regimes. Here we test it in global configurations and evaluate it against observations using a range of standard metrics. Overall it is found to perform well against the control. Biases in the climatologies of the radiative fluxes are significantly reduced across the Tropics and subtropics, tropical and extratropical cyclone statistics are improved, and the Madden–Julian oscillation and other propagating tropical waves are strengthened. It also improves overall scores in numerical weather prediction trials, without revisions to the data assimilation. There is still work to do to improve the diurnal cycle of precipitation over land, where the peak remains too close to the middle of the day. convection; evaluation; global; parametrization; unified model
Loeb, Norman G.; Doelling, David R.; Kato, Seiji; Su, Wenying; Mlynczak, Pamela E.; Wilkins, Joshua C.Loeb, N. G., D. R. Doelling, S. Kato, W. Su, P. E. Mlynczak, J. C. Wilkins, 2024: Continuity in Top-of-Atmosphere Earth Radiation Budget Observations. doi: 10.1175/JCLI-D-24-0180.1. The Clouds and the Earth’s Radiant Energy System (CERES) Energy Balanced and Filled (EBAF) product combines CERES and Moderate Resolution Imaging Spectroradiometer (MODIS) instruments on the Terra and Aqua satellites to create a record of Earth’s Radiation Budget (ERB) and the associated cloud properties. As the Terra and Aqua orbits are no longer maintained at a fixed mean local time, EBAF recently transitioned to the CERES and Visible Infrared Imaging Radiometer Suite (VIIRS) instruments on NOAA-20 to avoid introducing a time-dependent bias in the record. To ensure smooth transitions between the Terra, combined Terra and Aqua (Terra+Aqua), and NOAA-20 portions of the record, regional climatological adjustments derived from the overlap period between missions are applied to anchor the entire record to Terra+Aqua. We estimate the random error in global monthly anomalies following the transitions to be
Loeb, Norman G.; Ham, Seung-Hee; Allan, Richard P.; Thorsen, Tyler J.; Meyssignac, Benoit; Kato, Seiji; Johnson, Gregory C.; Lyman, John M.Loeb, N. G., S. Ham, R. P. Allan, T. J. Thorsen, B. Meyssignac, S. Kato, G. C. Johnson, J. M. Lyman, 2024: Observational Assessment of Changes in Earth’s Energy Imbalance Since 2000. Surveys in Geophysics. doi: 10.1007/s10712-024-09838-8. Satellite observations from the Clouds and the Earth’s Radiant Energy System show that Earth’s energy imbalance has doubled from 0.5 ± 0.2 Wm−2 during the first 10 years of this century to 1.0 ± 0.2 Wm−2 during the past decade. The increase is the result of a 0.9 ± 0.3 Wm−2 increase absorbed solar radiation (ASR) that is partially offset by a 0.4 ± 0.25 Wm−2 increase in outgoing longwave radiation (OLR). Despite marked differences in ASR and OLR trends during the hiatus (2000–2010), transition-to-El Niño (2010–2016) and post-El Niño (2016–2022) periods, trends in net top-of-atmosphere flux (NET) remain within 0.1 Wm−2 per decade of one another, implying a steady acceleration of climate warming. Northern and southern hemisphere trends in NET are consistent to 0.06 ± 0.31 Wm−2 per decade due to a compensation between weak ASR and OLR hemispheric trend differences of opposite sign. We find that large decreases in stratocumulus and middle clouds over the sub-tropics and decreases in low and middle clouds at mid-latitudes are the primary reasons for increasing ASR trends in the northern hemisphere (NH). These changes are especially large over the eastern and northern Pacific Ocean, and coincide with large increases in sea-surface temperature (SST). The decrease in cloud fraction and higher SSTs over the NH sub-tropics lead to a significant increase in OLR from cloud-free regions, which partially compensate for the NH ASR increase. Decreases in middle cloud reflection and a weaker reduction in low-cloud reflection account for the increase in ASR in the southern hemisphere, while OLR changes are weak. Changes in cloud cover in response to SST increases imply a feedback to climate change yet a contribution from radiative forcing or internal variability cannot be ruled out. Climate change; Clouds; Earth radiation budget; Earth’s energy imbalance; Satellite
Lopes, Francisco M.; Dutra, Emanuel; Trigo, Isabel F.; Wild, MartinLopes, F. M., E. Dutra, I. F. Trigo, M. Wild, 2024: Evaluation of Downward Surface Longwave Flux Estimates Using Meteosat Cloud Observations. Journal of Geophysical Research: Atmospheres, 129(6), e2023JD040306. doi: 10.1029/2023JD040306. The downward surface longwave flux (DSLF) plays a relevant role in the Earth’s surface radiative budget, which is crucial to monitor, understand and model the impact of changes at local and global scales on surface temperature and surface conditions. This study focuses on the evaluation and intercomparison of four DSLF products: (a) a recently developed all-weather DSLF product based on the multivariate adaptive regression splines (MARS) algorithm driven by satellite cloud information from the Meteosat Second Generation (MSG) and ERA5 reanalysis screen variables; (b) the Satellite Application Facility on Land Surface Analysis (LSA SAF); (c) CERES Synoptic top-of-atmosphere and surface fluxes and clouds (CERES-SYN1deg) and (d) ERA5 reanalysis. The study covers the period 2005–2021 and the MSG region focusing on monthly means. The evaluation performed against 48 ground stations from the Baseline Surface Radiation Network (BSRN) and FLUXNET2015 networks showed that the MARS product outperforms the remaining products, particularly the LSA SAF, while ERA5 and CERES show similar performance metrics. The fours products are intercompared in terms of their mean spatial variability and temporal mean annual cycles and inter-annual variability in four selected regions, showing a high level of agreement, particularly between MARS, ERA5 and CERES. Our results highlight the clear added value of MARS with respect to LSA SAF, while providing higher spatial resolution (0.05°), constrained by satellite cloud information, when compared with ERA5 (0.25°) or CERES (1°). machine learning; all-weather; downward surface longwave fluxes; ECMWF-ERA5; Meteosat Second Generation; multivariate adaptive regression splines
Lu, Lu; Li, Ying; Liang, Lingjun; Ma, QianLu, L., Y. Li, L. Liang, Q. Ma, 2024: Diurnal Variation in Surface Incident Solar Radiation Retrieved by CERES and Himawari-8. Remote Sensing, 16(14), 2670. doi: 10.3390/rs16142670. The diurnal variation of surface incident solar radiation (Rs) has a significant impact on the Earth’s climate. Satellite-retrieved Rs datasets display good spatial and temporal continuity compared with ground-based observations and, more importantly, have higher accuracy than reanalysis datasets. Facilitated by these advantages, many scholars have evaluated satellite-retrieved Rs, especially based on monthly and annual data. However, there is a lack of evaluation on an hourly scale, which has a profound impact on sea–air interactions, climate change, agriculture, and prognostic models. This study evaluates Himawari-8 and Clouds and the Earth’s Radiant Energy System Synoptic (CERES)-retrieved hourly Rs data covering 60°S–60°N and 80°E–160°W based on ground-based observations from the Baseline Surface Radiation Network (BSRN). Hourly Rs were first standardized to remove the diurnal and seasonal cycles. Furthermore, the sensitivities of satellite-retrieved Rs products to clouds, aerosols, and land cover types were explored. It was found that Himawari-8-retrieved Rs was better than CERES-retrieved Rs at 8:00–16:00 and worse at 7:00 and 17:00. Both satellites performed better at continental sites than at island/coastal sites. The diurnal variations of statistical parameters of Himawari-8 satellite-retrieved Rs were stronger than those of CERES. Relatively larger MABs in the case of stratus and stratocumulus were exhibited for both hourly products. Smaller MAB values were found for CERES covered by deep convection and cumulus clouds and for Himawari-8 covered by deep convection and nimbostratus clouds. Larger MAB values at evergreen broadleaf forest sites and smaller MAB values at open shrubland sites were found for both products. In addition, Rs retrieved by Himawari-8 was more sensitive to AOD at 10:00–16:00, while that retrieved by CERES was more sensitive to COD at 9:00–15:00. The CERES product showed larger sensitivity to COD (at 9:00–15:00) and AOD (at 7:00–10:00) than Himawari-8. This work helps data producers know how to improve their future products and helps data users be aware of the uncertainties that exist in hourly satellite-retrieved Rs data. Himawari-8; CERES; diurnal variation; BSRN; solar radiation
Ma, Qianhui; Zhang, Chunyan; Wang, Donghai; Pang, ZihaoMa, Q., C. Zhang, D. Wang, Z. Pang, 2024: Summer Atmospheric Water Cycle under the Transition Influence of the Westerly and Summer Monsoon over the Yarlung Zangbo River Basin in the Southern Tibetan Plateau. Advances in Atmospheric Sciences. doi: 10.1007/s00376-023-3094-6. This study compares the summer atmospheric water cycle, including moisture sources and consumption, in the upstream, midstream, and downstream regions of the Yarlung Zangbo River Basin in the southern Tibetan Plateau. The evolutions of moisture properties under the influence of the westerly and summer southerly monsoon are examined using 5-yr multi-source measurements and ERA5 reanalysis data. Note that moisture consumption in this study is associated with clouds, precipitation, and diabatic heating. Compared to the midstream and downstream regions, the upstream region has less moisture, clouds, and precipitation, where the moisture is brought by the westerly. In early August, the vertical wet advection over this region becomes enhanced and generates more high clouds and precipitation. The midstream region has moisture carried by the westerly in June and by the southerly monsoon from July to August. The higher vertical wet advection maximum here forms more high clouds, with a precipitation peak in early July. The downstream region is mainly affected by the southerly-driven wet advection. The rich moisture and strong vertical wet advection here produce the most clouds and precipitation among the three regions, with a precipitation peak in late June. The height of the maximum moisture condensation is different between the midstream region (325 hPa) and the other two regions (375 hPa), due to the higher upward motion maximum in the midstream region. The diabatic heating structures show that stratiform clouds dominate the upstream region, stratiform clouds and deep convection co-exist in the midstream region, and deep convection systems characterize the downstream region. constrained variational analysis; atmospheric water cycle; moisture source and consumption; Yarlung Zangbo River Basin
Mardani, Masoud; Hoseinzadeh, Siamak; Garcia, Davide AstiasoMardani, M., S. Hoseinzadeh, D. A. Garcia, 2024: Developing particle-based models to predict solar energy attenuation using long-term daily remote and local measurements. Journal of Cleaner Production, 434, 139690. doi: 10.1016/j.jclepro.2023.139690. Iran has an annual average of 2.8–5.4 kW h/m2d of radiation and has a high capacity for extracting electricity from its solar resources. Tehran, the capital of Iran, is one of the most polluted cities in the world in terms of atmospheric aerosols. Due to the rising air pollution in Tehran, the existing research is outdated. An analysis of the loss of electricity generation due to particulates can significantly affect the feasibility of a photovoltaic power plant in Tehran. Several factors affect the electricity generation of photovoltaic systems. The most critical is solar radiation. The amount of solar radiation transmitted and, ultimately, the amount of electricity generated depends on several atmospheric factors. One of the most important factors is the concentration of suspended particles of different sizes. In the present work, linear models based on observed suspended particle concentrations, including PM10 and PM2.5, have been proposed for Tehran from 2014 to 2020 to anticipate the aerosol attenuation index due to aerosols. Based on the correlation coefficient values (R), in the first and last months of the year, November, December, and January, the models performed better to predict the aerosol attenuation index based on PM2.5. The R values were, in order, 0.1553, 0.2926, and 0.1341. As remote measurements, the NASA CERES syn 1-deg product parameters and, as ground observations, Surface Solar Radiation (SSR) and PM10 and PM2.5 concentrations were used to estimate the impacts of aerosols on radiation. With the help of the CERES syn 1-deg product, it is declared that, on average, 8.30% of the total radiation received was wasted due to the presence of aerosols. Considering observed SSR, CERES syn 1-deg product performance was validated, with RMSE and MBD values of 14.09% and 10.89%, respectively. Solar energy; Aerosols; Energy and environment analysis; Feasibility study; Pollution; Solar mapping
Masunaga, Hirohiko; Takahashi, HaniiMasunaga, H., H. Takahashi, 2024: The Energetics of the Lagrangian Evolution of Tropical Convective Systems. J. Atmos. Sci., 81(4), 783-799. doi: 10.1175/JAS-D-23-0141.1. Abstract The convective life cycle is often conceptualized to progress from congestus to deep convection and develop further to stratiform anvil clouds, accompanied by a systematic change in the vertical structure of vertical motion. This archetype scenario has been developed largely from the Eulerian viewpoint, and it has yet to be explored whether the same life cycle emerges itself in a moving system tracked in the Lagrangian manner. To address this question, Lagrangian tracking is applied to tropical convective systems in combination with a thermodynamic budget analysis forced by satellite-retrieved precipitation and radiation. A new method is devised to characterize the vertical motion profiles in terms of the column import or export of moisture and moist static energy (MSE). The bottom-heavy, midheavy, and top-heavy regimes are identified for every 1° × 1° grid pixel accompanying tracked precipitation systems, making use of the diagnosed column export/import of moisture and MSE. The major findings are as follows. The Lagrangian evolution of convective systems is dominated by a state of dynamic equilibrium among different convective regimes rather than a monotonic progress from one regime to the next. The transition from the bottom-heavy to midheavy regimes is fed with intensifying precipitation presumably owing to a negative gross moist stability (GMS) of the bottom-heavy regime, whereas the transition from the midheavy to top-heavy regimes dissipates the system. The bottom-heavy to midheavy transition takes a relaxation time of about 5 h in the equilibrating processes, whereas the relaxation time is estimated as roughly 20 h concerning the midheavy to top-heavy transition.
Mayer, Michael; Kato, Seiji; Bosilovich, Michael; Bechtold, Peter; Mayer, Johannes; Schröder, Marc; Behrangi, Ali; Wild, Martin; Kobayashi, Shinya; Li, Zhujun; L’Ecuyer, TristanMayer, M., S. Kato, M. Bosilovich, P. Bechtold, J. Mayer, M. Schröder, A. Behrangi, M. Wild, S. Kobayashi, Z. Li, T. L’Ecuyer, 2024: Assessment of Atmospheric and Surface Energy Budgets Using Observation-Based Data Products. Surveys in Geophysics. doi: 10.1007/s10712-024-09827-x. Accurate diagnosis of regional atmospheric and surface energy budgets is critical for understanding the spatial distribution of heat uptake associated with the Earth’s energy imbalance (EEI). This contribution discusses frameworks and methods for consistent evaluation of key quantities of those budgets using observationally constrained data sets. It thereby touches upon assumptions made in data products which have implications for these evaluations. We evaluate 2001–2020 average regional total (TE) and dry static energy (DSE) budgets using satellite-based and reanalysis data. For the first time, a consistent framework is applied to the ensemble of the 5th generation European Reanalysis (ERA5), version 2 of modern-era retrospective analysis for research and applications (MERRA-2), and the Japanese 55-year Reanalysis (JRA55). Uncertainties of the computed budgets are assessed through inter-product spread and evaluation of physical constraints. Furthermore, we use the TE budget to infer fields of net surface energy flux. Results indicate biases Earth’s energy imbalance; Energy budget; Reanalysis; Remote sensing; Surface energy flux
McKim, Brett; Bony, Sandrine; Dufresne, Jean-LouisMcKim, B., S. Bony, J. Dufresne, 2024: Weak anvil cloud area feedback suggested by physical and observational constraints. Nature Geoscience, 17(5), 392-397. doi: 10.1038/s41561-024-01414-4. Changes in anvil clouds with warming remain a leading source of uncertainty in estimating Earth’s climate sensitivity. Here we develop a feedback analysis that decomposes changes in anvil clouds and creates testable hypotheses for refining their proposed uncertainty ranges with observations and theory. To carry out this storyline approach, we derive a simple but quantitative expression for the anvil area feedback, which is shown to depend on the present-day measurable cloud radiative effects and the fractional change in anvil area with warming. Satellite observations suggest an anvil cloud radiative effect of about ±1 W m−2, which requires the fractional change in anvil area to be about 50% K−1 in magnitude to produce a feedback equal to the current best estimate of its lower bound. We use quantitative theory and observations to show that the change in anvil area is closer to about −4% K−1. This constrains the area feedback and leads to our revised estimate of 0.02 ± 0.07 W m−2 K−1, which is many times weaker and more constrained than the overall anvil cloud feedback. In comparison, we show the anvil cloud albedo feedback to be much less constrained, both theoretically and observationally, which poses an obstacle for bounding Earth’s climate sensitivity. Climate change; Atmospheric dynamics; Climate and Earth system modelling
Michibata, TakuroMichibata, T., 2024: Radiative effects of precipitation on the global energy budget and Arctic amplification. npj Climate and Atmospheric Science, 7(1), 1-11. doi: 10.1038/s41612-024-00684-4. Radiative forcing is an essential metric for accurate climate prediction. Clouds are a well-known source of uncertainty, but the radiative effects of precipitation (REP) are poorly understood and excluded from most general circulation models (GCMs). This is because conventional GCMs treat precipitation diagnostically, and thus, are transparent to shortwave and longwave radiation. In this study, we investigated the REP at global and regional scales by employing three sub-models incorporating (1) diagnostic precipitation, (2) prognostic precipitation without REP, and (3) prognostic precipitation with REP. We found that REP alters not only the local thermodynamic profile but also the remote precipitation rate and distribution through changes in atmospheric circulation. The polar surface temperature increases by more than 1 K in the winter when considering REP. The 34 CMIP6 models show systematic differences in Arctic amplification depending on REP, emphasising that GCMs should include REP to improve confidence in simulating atmosphere-ocean-cryosphere interactions. Cryospheric science; Atmospheric science
Mishra, Anoop Kumar; Tomar, Chander Singh; Kumar, Gajendra; Mitra, Ashim K.; Bhan, Subhash ChanderMishra, A. K., C. S. Tomar, G. Kumar, A. K. Mitra, S. C. Bhan, 2024: Performance Evaluation of INSAT-3D Derived Outgoing Long Wave Radiation Over India Using Remotely Sensed Observations. Journal of the Indian Society of Remote Sensing. doi: 10.1007/s12524-023-01800-2. This research work focuses on the comparison of Outgoing Long Wave Radiation (OLR) derived from the current operational Indian National SATellite-3D (INSAT-3D) with that from Clouds and the Earth’s Radiant Energy System (CERES), Advanced Very High Resolution Radiometer (AVHRR) and High Resolution Infra-Red Sounder (HIRS) at various temporal scales ranging from daily to monthly. INSAT-3D OLR was averaged over a 2.5° × 2.5° grid to enable comparison between the INSAT-3D, AVHRR, HIRS and CERES OLR. Results show that INSAT-3D derived OLR shows good comparison with HIRS and CERES. AVHRR underestimates, especially over the arid and semiarid regions, which may be attributed to the fact that OLR at the top of atmosphere is also sensitive to the vertical distribution of moisture and thus exclusion of Water Vapor (WV) channel from AVHRR OLR might have resulted in lower values of OLR. Also, the temporal sampling is important as INSAT-3D uses 48 half-hourly observations for computing the daily average, whereas, CERES, HIRS and AVHRR have only 2–3 diurnal samples for daily averages. Quantitative comparison of INSAT-3D OLR at daily scale shows a CC of 0.98, 0.91 and 0.88 with HIRS, CERES and AVHRR, respectively. Positive biases of 1.12 W/m2 and 5.93 W/m2 in INSAT-3D OLR have been reported with respect to HIRS and AVHRR, respectively. INSAT-3D shows a negative bias of − 5.09 W/m2 with CERES observations which is consistent with a previous study. On a monthly scale, INSAT-3D shows excellent agreement with CERES with a bias of 0.45 W/m2. The OLR monthly bias from INSAT-3D increases slightly to 7.98 W/m2 with respect to AVHRR at a monthly scale. Results reported in this study highlights the applicability of INSAT-3D for various meteorological and climatological studies. Clouds; Satellite; Convection; Radiation feedback; Sounder
Mishra, Manoj Kumar; Singh, Randhir; Vadnathani, Rakesh; Thapliyal, P. K.Mishra, M. K., R. Singh, R. Vadnathani, P. K. Thapliyal, 2024: Impact of vegetation greening on TOA clear-sky shortwave radiation in Northwest India. Climate Dynamics. doi: 10.1007/s00382-024-07321-z. Since 2000, Clouds and the Earth's Radiant Energy System (CERES) instruments on Aqua and Terra satellites have recorded top-of-atmosphere (TOA) clear-sky outgoing radiation fluxes. Over northwest India, analysis of these two decades of data revealed significant negative trends in reflected shortwave radiation, indicating positive shortwave radiative forcing. Aerosols; Climate change; Climate mitigation strategies; Land surface temperature; Northwest India; Top-of-atmosphere (TOA) shortwave flux; Vegetation dynamics
Motlaghzadeh, S.; Vasiuta, M.; Bister, M.; Navarro Trastoy, A.; Tuppi, L.; Mayer-Gürr, T.; Järvinen, H.Motlaghzadeh, S., M. Vasiuta, M. Bister, A. Navarro Trastoy, L. Tuppi, T. Mayer-Gürr, H. Järvinen, 2024: Weather-Induced Satellite Orbit Perturbations. Journal of Geophysical Research: Atmospheres, 129(8), e2023JD040009. doi: 10.1029/2023JD040009. Satellites in Earth's orbit are exposed to Earth radiation, consisting of reflected solar and emitted thermal radiation, thereby exerting a non-conservative force that causes acceleration and affects the orbits. Gravity Recovery and Climate Experiment Follow-On (GRACE-FO) mission aiming to retrieve the Earth's gravity potential is critically dependent on accounting for this force and all other non-gravitational forces. There are both diurnal and seasonal variations in the Earth's radiation pressure, of which the seasonal variability can be represented by climatology. Nevertheless, the daily variations in the Earth's radiation pressure, due to the transient changes in the weather; for example, clouds and their properties, are not accounted for in the orbit perturbations studies. We show here that the top-of-atmosphere radiation fluxes computed with a numerical weather prediction (NWP) model explain most of the measured short-term variations in the radial acceleration of the GRACE-FO satellite. Our physics-based modeling corrects a hitherto unexplained lack of power spectral density in the measured accelerations. For example, we can accurately model the accelerations associated with a tropical storm in the Indian Ocean in December 2020, which would not be possible when using climatological data. Our results demonstrate that using a global numerical weather prediction model significantly improves the simulation of non-gravitational effects in the satellites' orbits. In the 7-day data set, OpenIFS-simulated acceleration exhibited higher accuracy than climatological-data-simulated acceleration (2.5 compared to 2.6 nms−2) and an improved precision (2.6 compared to 3.0 nms−2). This advancement contributes to a more precise orbit determination across various applications in Earth sciences. orbit; GRACE-FO; accelerometer
Moustaka, Anna; Korras-Carraca, Marios-Bruno; Papachristopoulou, Kyriakoula; Stamatis, Michael; Fountoulakis, Ilias; Kazadzis, Stelios; Proestakis, Emmanouil; Amiridis, Vassilis; Tourpali, Kleareti; Georgiou, Thanasis; Solomos, Stavros; Spyrou, Christos; Zerefos, Christos; Gkikas, AntonisMoustaka, A., M. Korras-Carraca, K. Papachristopoulou, M. Stamatis, I. Fountoulakis, S. Kazadzis, E. Proestakis, V. Amiridis, K. Tourpali, T. Georgiou, S. Solomos, C. Spyrou, C. Zerefos, A. Gkikas, 2024: Assessing Lidar Ratio Impact on CALIPSO Retrievals Utilized for the Estimation of Aerosol SW Radiative Effects across North Africa, the Middle East, and Europe. Remote Sensing, 16(10), 1689. doi: 10.3390/rs16101689. North Africa, the Middle East, and Europe (NAMEE domain) host a variety of suspended particles characterized by different optical and microphysical properties. In the current study, we investigate the importance of the lidar ratio (LR) on Cloud-Aerosol Lidar with Orthogonal Polarization–Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observations (CALIOP-CALIPSO) aerosol retrievals towards assessing aerosols’ impact on the Earth-atmosphere radiation budget. A holistic approach has been adopted involving collocated Aerosol Robotic Network (AERONET) observations, Radiative Transfer Model (RTM) simulations, as well as reference radiation measurements acquired using spaceborne (Clouds and the Earth’s Radiant Energy System-CERES) and ground-based (Baseline Surface Radiation Network-BSRN) instruments. We are assessing the clear-sky shortwave (SW) direct radiative effects (DREs) on 550 atmospheric scenes, identified within the 2007–2020 period, in which the primary tropospheric aerosol species (dust, marine, polluted continental/smoke, elevated smoke, and clean continental) are probed using CALIPSO. RTM runs have been performed relying on CALIOP retrievals in which the default and the DeLiAn (Depolarization ratio, Lidar ratio, and Ångström exponent)-based aerosol-speciated LRs are considered. The simulated fields from both configurations are compared against those produced when AERONET AODs are applied. Overall, the DeLiAn LRs leads to better results mainly when mineral particles are either solely recorded or coexist with other aerosol species (e.g., sea-salt). In quantitative terms, the errors in DREs are reduced by ~26–27% at the surface (from 5.3 to 3.9 W/m2) and within the atmosphere (from −3.3 to −2.4 W/m2). The improvements become more significant (reaching up to ~35%) for moderate-to-high aerosol loads (AOD ≥ 0.2). CERES; AERONET; BSRN; clear-sky; CALIOP–CALIPSO; DREs; lidar ratio; NAMEE; RTM; SW
Nikolov, Ned; Zeller, Karl F.Nikolov, N., K. F. Zeller, 2024: Roles of Earth’s Albedo Variations and Top-of-the-Atmosphere Energy Imbalance in Recent Warming: New Insights from Satellite and Surface Observations. Geomatics, 4(3), 311-341. doi: 10.3390/geomatics4030017. Past studies have reported a decreasing planetary albedo and an increasing absorption of solar radiation by Earth since the early 1980s, and especially since 2000. This should have contributed to the observed surface warming. However, the magnitude of such solar contribution is presently unknown, and the question of whether or not an enhanced uptake of shortwave energy by the planet represents positive feedback to an initial warming induced by rising greenhouse-gas concentrations has not conclusively been answered. The IPCC 6th Assessment Report also did not properly assess this issue. Here, we quantify the effect of the observed albedo decrease on Earth’s Global Surface Air Temperature (GSAT) since 2000 using measurements by the Clouds and the Earth’s Radiant Energy System (CERES) project and a novel climate-sensitivity model derived from independent NASA planetary data by employing objective rules of calculus. Our analysis revealed that the observed decrease of planetary albedo along with reported variations of the Total Solar Irradiance (TSI) explain 100% of the global warming trend and 83% of the GSAT interannual variability as documented by six satellite- and ground-based monitoring systems over the past 24 years. Changes in Earth’s cloud albedo emerged as the dominant driver of GSAT, while TSI only played a marginal role. The new climate sensitivity model also helped us analyze the physical nature of the Earth’s Energy Imbalance (EEI) calculated as a difference between absorbed shortwave and outgoing longwave radiation at the top of the atmosphere. Observations and model calculations revealed that EEI results from a quasi-adiabatic attenuation of surface energy fluxes traveling through a field of decreasing air pressure with altitude. In other words, the adiabatic dissipation of thermal kinetic energy in ascending air parcels gives rise to an apparent EEI, which does not represent “heat trapping” by increasing atmospheric greenhouse gases as currently assumed. We provide numerical evidence that the observed EEI has been misinterpreted as a source of energy gain by the Earth system on multidecadal time scales. albedo; CERES; climate; energy imbalance; ENSO; gas law; IPCC; radiation; temperature; thermodynamics
Norris, Jesse; Thackeray, Chad W.; Hall, Alex; Madakumbura, Gavin D.Norris, J., C. W. Thackeray, A. Hall, G. D. Madakumbura, 2024: Historical sensible-heat-flux variations key to predicting future hydrologic sensitivity. npj Climate and Atmospheric Science, 7(1), 1-10. doi: 10.1038/s41612-024-00676-4. Under anthropogenic climate change (CC), the global hydrological cycle intensifies at a rate known as hydrologic sensitivity (HS). Global climate models (GCMs) exhibit substantial uncertainty in HS. Past work suggests that another form of HS, derived from internal climate variability (IV), is useful for constraining this uncertainty. However, these two forms of HS are weakly related. Here we show that decomposing HS under both CC and IV, based on the global energy budget, provides insight into the likely range of future HS. We find that sensible heat exchange between the atmosphere and ocean is not accounted for in the atmospheric energy budget under IV, masking the connection between HS under IV and CC. Removing this term, a closer relationship emerges. We use observations in conjunction with this relationship to suggest an upward shift in the likely range of future HS (66% confidence interval: 2.00–2.36 W m−2 K−1). Atmospheric dynamics; Projection and prediction
Ohishi, Shun; Miyoshi, Takemasa; Kachi, MisakoOhishi, S., T. Miyoshi, M. Kachi, 2024: Impact of atmospheric forcing on SST biases in the LETKF-based ocean research analysis (LORA). Ocean Modelling, 102357. doi: 10.1016/j.ocemod.2024.102357. In the previous study, the authors have produced an eddy-resolving ocean ensemble analysis product called the local ensemble transform Kalman filter (LETKF)-based ocean research analysis (LORA) over the western North Pacific and Maritime Continent regions using an ocean data assimilation system driven by the Japanese operational atmospheric reanalysis dataset known as the JRA-55. However, the LORA includes warm biases in sea surface temperature (SST) in coastal regions during the boreal winter. In this study, we perform sensitivity experiments with atmospheric forcing using an ocean forcing dataset known as the JRA55-do, which adjusts the JRA-55 to high-quality reference datasets to reduce biases and uncertainties. The results show that the nearshore warm SST biases are significantly improved by the JRA55-do. During the boreal autumn, the improvement comes from mainly two factors: (i) enhancement of surface cooling by latent heat releases caused by removing contamination of weak winds at the land grid cells, and (ii) weakening surface heating by downward shortwave radiation through the adjustment in the JRA55-do. During the boreal winter, enhanced cooling by the analysis increments suppresses the growth of the warm SST biases when the JRA55-do is used. However, if the JRA-55 dataset is used, the adaptive observation error inflation (AOEI) scheme acts negatively to keep the nearshore SST biases in winter. Based on the innovation statistics, the AOEI inflates the observation errors when the differences between the squared observation-minus-forecast innovations and the squared forecast ensemble spreads are larger than the prescribed observation error variance, and improves the accuracy in the open ocean, especially around the frontal regions. However, when substantial warm SST biases are formed in the previous season, AOEI's observation error inflation makes the analysis increments smaller and cannot suppress the warm biases. We also validate the analysis accuracy using various data such as sea surface height and horizontal velocities and find that the JRA55-do has significant advantages. Therefore, continuous maintenance and development of ocean forcing datasets are essential for ocean modeling and data assimilation. atmospheric reanalysis; SST bias; Ensemble Kalman filter; LORA; mixed-layer temperature budget; ocean forcing dataset
Okamoto, Hajime; Sato, Kaori; Nishizawa, Tomoaki; Jin, Yoshitaka; Nakajima, Takashi; Wang, Minrui; Satoh, Masaki; Suzuki, Kentaroh; Roh, Woosub; Yamauchi, Akira; Horie, Hiroaki; Ohno, Yuichi; Hagihara, Yuichiro; Ishimoto, Hiroshi; Kudo, Rei; Kubota, Takuji; Tanaka, ToshiyukiOkamoto, H., K. Sato, T. Nishizawa, Y. Jin, T. Nakajima, M. Wang, M. Satoh, K. Suzuki, W. Roh, A. Yamauchi, H. Horie, Y. Ohno, Y. Hagihara, H. Ishimoto, R. Kudo, T. Kubota, T. Tanaka, 2024: JAXA Level2 algorithms for EarthCARE mission from single to four sensors: new perspective of cloud, aerosol, radiation and dynamics. Atmospheric Measurement Techniques Discussions, 1-21. doi: 10.5194/amt-2024-101. Abstract. This article gives the overview of the Japan Aerospace Exploration Agency (JAXA) level 2 (L2) Standard and Research algorithms and products by Japanese science teams for EarthCARE Clouds, Aerosols and Radiation Explorer (EarthCARE), which is a JAXA and the European Space Agency (ESA) joint satellite mission. First three single sensor algorithms for 94GHz cloud profiling radar (CPR)-only, 355nm-atmospheric lidar with high spectral resolution function (ATLID)-only, and multi-spectral imager (MSI)-only retrievals, and their products were briefly reviewed. CPR-echo algorithms provide radar reflectivity factor, Doppler velocity, normalized radar cross section and path integral attenuation. CPR-only, CPR-ATLID synergy and CPR-ALTID-MSI synergy algorithms for standard cloud products provide cloud detection, cloud particle type and cloud microphysics, and the research products further provide Doppler velocity, terminal velocity and vertical air motion inside clouds. ATLID standalone algorithms produce aerosol, cloud and clear sky classification products as well as total aerosol extinction and extinction and number concentration of each aerosol types. ATLID-MSI synergy algorithms are developed to retrieve effective radius for each aerosol species in addition to the ATLID-only products. MSI algorithms retrieve cloud effective radius, ice and water content and cloud top pressure. Four sensor algorithms are prepared to produce shortwave and longwave radiative fluxes at the top of atmosphere, those at the surface and also heating rate profiles by using the outputs from CPR, ATLID and their synergy algorithms. The shortwave and longwave fluxes from the four sensor algorithms will then be compared with broad band radiation (BBR) to examine the consistency of the JAXA L2 retrievals. The algorithms are developed and evaluated by using observational data from satellites and ground-based instruments, and simulation data from the Japanese global cloud-resolving model, the Nonhydrostatic Icosahedral Atmospheric Model (NICAM) with Joint simulator. As for space-borne data, existing space-borne satellites data such as CloudSat, CALIPSO, MODIS and CERES datasets are intensively used. For ground-based observations, High-sensitivity Ground-based Super Polarimetric Ice-crystal Detection and Explication Radar (HG-SPIDER) with a minimum sensitivity of -40 dBZ at 15 km and over -60 dBZ at 1 km, Electronic Scanning SPIDER (ES-SPIDER), 355 nm high spectral resolution lidar, multiple-field-of-view multiple scattering lidar and Doppler lidars are installed at EarthCARE super-site in Koganei, Tokyo and offers unique opportunities to evaluate and analyse EarthCARE data.
Olonscheck, Dirk; Rugenstein, MariaOlonscheck, D., M. Rugenstein, 2024: Coupled Climate Models Systematically Underestimate Radiation Response to Surface Warming. Geophysical Research Letters, 51(6), e2023GL106909. doi: 10.1029/2023GL106909. A realistic representation of top-of-the-atmosphere (TOA) radiation response to surface warming is key for trusting climate model projections. We show that coupled models with freely evolving ocean-atmosphere interactions systematically underestimate the observed global TOA radiation trend during 2001–2022 in 552 simulations. Locally, even if a simulation spontaneously reproduces observed surface temperature trends, TOA radiation trends are more likely under- than overestimated. This response bias stems from the models' inability to reproduce the observed large-scale surface warming pattern and from errors in the atmospheric physics affecting short- and longwave radiation. Models with a better representation of the TOA radiation response to local surface warming have a relatively low equilibrium climate sensitivity. Our bias metric is a novel process-based approach which links a model's current response to climate change to its behavior in the future. climate sensitivity; model evaluation; radiation; ocean-atmosphere interaction; pattern effect; large ensembles
Park, J. Minnie; McComiskey, Allison C.; Painemal, David; Smith Jr., William L.Park, J. M., A. C. McComiskey, D. Painemal, W. L. Smith Jr., 2024: Long-Term Trends in Aerosols, Low Clouds, and Large-Scale Meteorology Over the Western North Atlantic From 2003 to 2020. Journal of Geophysical Research: Atmospheres, 129(11), e2023JD039592. doi: 10.1029/2023JD039592. A continuous decrease in aerosols over the Western North Atlantic Ocean (WNAO) on a decadal timescale provides a long-term benchmark to evaluate how various natural and anthropogenic processes affect the manifestation of aerosol-cloud interactions in this region. Furthermore, the WNAO serves as a natural laboratory with diverse aerosol sources, marine boundary layer clouds more variable than those in marine stratocumulus deck regions, and unique flow regimes established by the Gulf Stream and the semi-permanent Bermuda High. We investigate how satellite-retrieved macrophysical and microphysical properties of low clouds and the surface shortwave irradiance changed from 2003 to 2020, in tandem with this aerosol decrease. The decadal changes in large-scale meteorology related to the North Atlantic Oscillation (NAO) are also examined. We find a reduction in low-cloud optical thickness, accompanied by fewer and larger cloud droplets, yet observe no significant changes in low-cloud fraction and liquid water path. Despite the reduction in low-cloud optical thickness together with aerosol decrease, a corresponding increase in the trends of surface shortwave irradiance, also known as surface brightening, is lacking. This absence of brightening is potentially related to concomitant changes found in large-scale meteorology associated with NAO—Bermuda High strengthening, sea surface warming, and atmospheric moistening— as well as an increase in high-level cloud fraction that can counteract the surface brightening. Ultimately, our findings suggest that spatial patterns of decadal meteorological variability introduce complexities in the surface cloud radiative effect over the WNAO, thereby complicating the isolation and examination of aerosol-cloud interactions. aerosol-cloud interactions; cloud radiative effect; dimming and brightening; marine boundary layer clouds; North Atlantic Oscillation
Park, Sungsu; Song, Chanwoo; Kim, Siyun; Kim, JuwonPark, S., C. Song, S. Kim, J. Kim, 2024: Parameterization of the Elevated Convection With a Unified Convection Scheme (UNICON) and Its Impacts on the Diurnal Cycle of Precipitation. Journal of Advances in Modeling Earth Systems, 16(3), e2023MS003651. doi: 10.1029/2023MS003651. To improve the simulation of nocturnal precipitation, we develop a parameterization for the elevated convection that is launched from the level of maximum grid-mean moist static energy, when grid-mean vertical flow is upward at the launching interface. The parameterized elevated convection is forced by both cold pool-driven and partially resolved external mesoscale organized flows. Properties of the external mesoscale flow are estimated from grid-mean vertical velocity and three dimensional advection tendencies of temperature and moisture. The new parameterization is implemented into a unified convection scheme (UNICON) and tested for both the single-column case at the Southern Great Plain (SGP) site in US and in global simulations. At the SGP site, the parameterized elevated convection strengthens nocturnal convection, increases nocturnal precipitation, and better simulates the observed diurnal cycle of precipitation. It appears that the elevated and surface-based convections interact with each other by stabilizing the atmospheric column, which affects subsequent convection. Global simulation shows that the elevated convection mostly occurs over the continents during the night, and also over the oceanic mid-latitude warm air advection and storm track regions during summer. Without degrading global mean climate, the elevated convection improves the simulation of nocturnal precipitation in the mid-US but simulates somewhat strong nocturnal precipitation in northeastern Asia. It seems that a key to simulate observed nocturnal precipitation is to appropriately parameterize the impacts of external organized flow on the elevated convection. convection parameterization; diurnal cycle of precipitation; elevated convection
Peng, Liran; Blossey, Peter N.; Hannah, Walter M.; Bretherton, Christopher S.; Terai, Christopher R.; Jenney, Andrea M.; Pritchard, MichaelPeng, L., P. N. Blossey, W. M. Hannah, C. S. Bretherton, C. R. Terai, A. M. Jenney, M. Pritchard, 2024: Improving Stratocumulus Cloud Amounts in a 200-m Resolution Multi-Scale Modeling Framework Through Tuning of Its Interior Physics. Journal of Advances in Modeling Earth Systems, 16(3), e2023MS003632. doi: 10.1029/2023MS003632. High-Resolution Multi-scale Modeling Frameworks (HR)—global climate models that embed separate, convection-resolving models with high enough resolution to resolve boundary layer eddies—have exciting potential for investigating low cloud feedback dynamics due to reduced parameterization and ability for multidecadal throughput on modern computing hardware. However low clouds in past HR have suffered a stubborn problem of over-entrainment due to an uncontrolled source of mixing across the marine subtropical inversion manifesting as stratocumulus dim biases in present-day climate, limiting their scientific utility. We report new results showing that this over-entrainment can be partly offset by using hyperviscosity and cloud droplet sedimentation. Hyperviscosity damps small-scale momentum fluctuations associated with the formulation of the momentum solver of the embedded large eddy simulation. By considering the sedimentation process adjacent to default one-moment microphysics in HR, condensed phase particles can be removed from the entrainment zone, which further reduces entrainment efficiency. The result is an HR that can produce more low clouds with a higher liquid water path and a reduced stratocumulus dim bias. Associated improvements in the explicitly simulated sub-cloud eddy spectrum are observed. We report these sensitivities in multi-week tests and then explore their operational potential alongside microphysical retuning in decadal simulations at operational 1.5° exterior resolution. The result is a new HR having desired improvements in the baseline present-day low cloud climatology, and a reduced global mean bias and root mean squared error of absorbed shortwave radiation. We suggest it should be promising for examining low cloud feedbacks with minimal approximation. superparameterization; climate modeling; cloud physics; atmospheric science; multi-scale modeling
Povea-Pérez, Yoania; Guilyardi, Éric; Fedorov, Alexey V.; Ferster, BradyPovea-Pérez, Y., É. Guilyardi, A. V. Fedorov, B. Ferster, 2024: The central role of the Atlantic meridional overturning circulation in the Bjerknes compensation. Climate Dynamics, 62(1), 575-587. doi: 10.1007/s00382-023-06926-0. Poleward heat (energy) transport plays a major role in shaping the Earth’s climate. Its oceanic and atmospheric components carry heat from low to high latitudes thus reducing the equator-to-pole temperature contrast. In quasi-equilibrium climate states, changes in the top-of-the-atmosphere (TOA) energy fluxes and ocean heat content remain small. In such conditions, anomalies in oceanic and atmospheric heat transport must have the same magnitude but opposite signs. This phenomenon is known as the Bjerknes compensation (BJC). The BJC hypothesis is of high importance in climate, since it imposes a strong constraint on climate variability at sufficiently long timescales (on sub-decadal and shorter timescales TOA flux variations may become comparable to other heat budget terms, interfering with BJC). However, to which extent BJC operates in the climate system and the key mechanisms of the compensation remain poorly understood. Here we analyze BJC in the IPSL-CM6A-LR climate model, focusing on its timescale dependence, its links to the Atlantic Meridional Overturning Circulation (AMOC), and the connection to Intertropical Convergence Zone (ITCZ) shifts. We show that BJC occurs in the model at both multi-decadal and centennial timescales, but is stronger on centennial timescales than decadal. In both cases BJC is initiated by variations in ocean heat transport induced by AMOC variability that are partially or fully compensated by atmospheric heat transport. For decadal timescales, we find two regions of a strong BJC at latitudes associated with the storm track region and the marginal ice zone in the Northern Hemisphere. Finally, on centennial timescales we observe a Bjerknes-like interbasin compensation between the Atlantic and Indo-Pacific heat transports, which is also related to strong centennial AMOC fluctuations and involves Southern Ocean zonal heat transport. Climate variability; Atlantic meridional overturning circulation; Bjerknes compensation; Poleward heat transport
Prajwal, K.; Kottayil, Ajil; Xavier, Prince; Legras, BernardPrajwal, K., A. Kottayil, P. Xavier, B. Legras, 2024: A new insight into monsoon intraseasonal variability as revealed from distinct wind-precipitation regimes over the southwest coast of India. Climate Dynamics. doi: 10.1007/s00382-024-07366-0. This study evaluates the observed non-linearity in the wind-precipitation relationship over India’s southwest coast and maps this non-linearity to monsoon intraseasonal oscillations. The wind-precipitation data is subjected to clustering, and five distinct regimes are identified. The large-scale dynamical and thermodynamical condition that leads to wind-precipitation clustering is explored. It uses novel observations from the Stratosphere–Troposphere wind profiler radar placed over Cochin (10.04° N; 76.33° E) for the period 2019–2021 to derive characteristics of monsoon low-level jets. Out of five wind-precipitation clusters, low wind low precipitation (LWLP) and low wind high precipitation clusters (LWHP) bear signatures of monsoon break conditions over central India. The occurrence of Madden Julian events or monsoon lows in LWHP generates heavy rainfall over the southwest coast. The high wind low precipitation (HWLP) cluster occurs during the weak phase of northward propagating monsoon intraseasonal oscillation (MISO) over the southwest coast, while the high wind high precipitation (HWHP) cluster lies within the strong phase of MISO. The fifth cluster, the high wind extreme precipitation cluster (HWEP), although technically lying within the strong phase of MISO, however has more apparent signatures of northwestward propagating monsoon depressions. The Lagrangian trajectories launched from 500 hPa level for each cluster reveal some intriguing aspects. The dry air intrusion from adjacent regions near the west coast makes the mid-troposphere dry over the southwest coast in LWLP and HWLP clusters. In HWHP and HWEP, strong moisture sources confined over the west coast create mid-troposphere moistening owing to the moisture supply from below 500 hPa. This study highlights that wind-precipitation clustering effectively defines sub-seasonal variability during the monsoon. Clustering; Convection; Intraseasonal oscillation; West coast
Prince, Hamish D.; L’Ecuyer, Tristan S.Prince, H. D., T. S. L’Ecuyer, 2024: Observed Energetic Adjustment of the Arctic and Antarctic in a Warming World. J. Climate, 37(8), 2611-2627. doi: 10.1175/JCLI-D-23-0294.1. Abstract Satellite observations reveal that decreasing surface albedo in both polar regions is increasing the absorption of solar radiation, but the disposition of this absorbed energy is fundamentally different. Fluxes of absorbed solar radiation, emitted thermal radiation, and net energy imbalances are assessed for both polar regions for the last 21 years in the Clouds and Earth’s Radiant Energy System record. Arctic absorbed solar radiation is increasing at 0.98 ± 0.69 W m−2 decade−1, consistent with the anticipated response to sea ice loss. However, Arctic thermal emission is responding at a similar rate of 0.94 ± 0.55 W m−2 decade−1. This is surprising since the radiative impact of ice loss would be expected to favor increasing solar absorption. We find however, that clouds substantially mask trends in Arctic solar absorption relative to clear sky while having only a modest impact on thermal emission trends. As a result, the Arctic net radiation imbalance has not changed over the period. Furthermore, variability of absorbed solar radiation explains two-thirds of the variability in annual thermal emission suggesting that Arctic thermal fluxes rapidly adjust to offset changes in solar absorption and re-establish equilibrium. Conversely, Antarctic thermal emission is not responding to the increasing (although not yet statistically significant) solar absorption of 0.59 ± 0.64 W m−2 decade−1 with less than a third of the annual thermal variability explained by accumulated solar absorption. The Arctic is undergoing rapid adjustment to increasing solar absorption resulting in no change to the net energy deficit, while increasing Antarctic solar absorption represents additional energy input into the Earth system. Significance Statement The polar regions of Earth are undergoing ice loss through ongoing global warming, reducing the ice cover and decreasing solar reflectivity, which would be expected to warm these regions. We use satellite observations to measure the trends in solar absorption and emitted thermal radiation over the Arctic and Antarctic for the last two decades. Arctic thermal emission is increasing at a compensating rate to solar absorption with a close relationship between these processes. Conversely, Antarctic thermal emission is not responding to solar absorption demonstrating that Antarctic surface temperatures are not significantly influenced by the region’s reflectivity. The Arctic is undergoing rapid adjustment to increasing solar absorption through warming, while increasing Antarctic solar absorption represents additional energy input into the Earth system.
Priya, J. S.; Krishnakumar, V.; Baiju, Sona; Sreelekshmi, R. G.; Shoufeer, AfnaPriya, J. S., V. Krishnakumar, S. Baiju, R. G. Sreelekshmi, A. Shoufeer, 2024: Study on the Seasonal and Spatial Variations of Cirrus Parameters, Radiative Characteristics and Precipitation over the Indian Subcontinent. Journal of the Indian Society of Remote Sensing. doi: 10.1007/s12524-024-01926-x. This study investigates the spatiotemporal oscillations of cirrus characteristics over the Indian subcontinent from 2013 to 2021 using Moderate Resolution Imaging Spectroradiometer observations. Analyzing Cirrus Fraction (CiF), Cirrus Reflectance (CiR), and radiative characteristics using the Clouds and the Earth’s Radiant Energy System data, the distinct spatial and seasonal fluctuations with respect to the regional precipitation characteristics is unveiled. Radiative characteristics demonstrate significant seasonal influences on Net Short-Wave Flux, Net Long Wave Flux, and Net Total Flux (NETF). Through linear regression analysis, a strong positive correlation is found between CiF, CiR and precipitation, indicating a robust linear relationship. Seasonal variations in cloud parameters and radiative characteristics are examined, revealing heightened Cloud Optical Thickness and Cloud Effective Radius during the South West monsoon season compared to other seasons. CiR and NETF are notably elevated during the Monsoon. These findings underscore the significant impact of the rain on cloud properties and energy flux dynamics over the Indian subcontinent. Cirrus cloud; Cirrus Fraction; Cirrus Reflectance; Indian subcontinent; MODIS; Precipitation
Raghuraman, Shiv Priyam; Medeiros, Brian; Gettelman, AndrewRaghuraman, S. P., B. Medeiros, A. Gettelman, 2024: Observational Quantification of Tropical High Cloud Changes and Feedbacks. Journal of Geophysical Research: Atmospheres, 129(7), e2023JD039364. doi: 10.1029/2023JD039364. The response of tropical high clouds to surface warming and their radiative feedbacks are uncertain. For example, it is uncertain whether their coverage will contract or expand in response to surface warming and whether such changes entail a stabilizing radiative feedback (iris feedback) or a neutral feedback. Global satellite observations with passive and active remote sensing capabilities over the last two decades can now be used to address such effects that were previously observationally limited. Using these observations, we show that the vertically averaged coverage exhibits no significant contraction or expansion. However, we find a reduction in coverage at the altitude where high clouds peak and are particularly radiatively-relevant. This results in a negative longwave (LW) feedback and a positive shortwave (SW) feedback which cancel to yield a near-zero high-cloud amount feedback, providing observational evidence against an iris feedback. Next, we find that tropical high clouds have risen but have also warmed, leading to a positive, but small, high-cloud altitude feedback dominated by the LW feedback. Finally, we find that high clouds have been thinning, leading to a near-zero high-cloud optical depth feedback from a cancellation between negative LW and positive SW feedbacks. Overall, high clouds lead the total tropical cloud feedback to be small due to the negative LW-positive SW feedback cancellations. clouds; climate sensitivity; feedbacks; high clouds; anvils; satellites
Ren, Zikun; Zhou, TianjunRen, Z., T. Zhou, 2024: Understanding the alleviation of “Double-ITCZ” bias in CMIP6 models from the perspective of atmospheric energy balance. Climate Dynamics. doi: 10.1007/s00382-024-07238-7. The simulation of tropical precipitation has been a challenge to climate models. The multi-model ensemble mean of CMIP6 models only show limited improvement relative to the CMIP3 and CMIP5 models. However, a simple ensemble mean may mask the improvement of individual models. Here we evaluated 20 CMIP6 models and their corresponding earlier version in CMIP5. The results show that the CMIP6 models is significantly improved in the tropical precipitation compared to their counterparts in CMIP5, and the alleviation of bias mainly happened in the top ten model pairs with largest RMSE reduction (TOP10). For the mean of TOP10, the antisymmetric (symmetric) bias mode in CMIP5 is significantly reduced by 55% (78%). Further energetics evaluation shows that, the CMIP5-to-CMIP6 decrease of antisymmetric bias in the bulk of TOP10 models is accompanied by more realistic southward cross-equatorial atmospheric energy transport ($${AET}_{EQ}$$), which is mainly contributed by the better representation of the extra-tropical surface turbulent flux ($$STF$$). On the other hand, the decrease in the symmetric bias of TOP10 models is associated with the enlargement of the negative bias in the seasonal contrast of $${AET}_{EQ}$$, which is caused by the alleviation of the biases in the seasonal contrast of extra-tropical $$STF$$. Our analysis revealed the improvement in the simulation of tropical precipitation in CMIP6, and we pointed out that the improvement is associated with the model-generational changes in the simulated atmospheric energy balances. Atmospheric energy balance; CMIP5,6; Double-ITCZ problem; Model improvement
Restrepo-Coupe, Natalia; Campos, Kleber Silva; Alves, Luciana F.; Longo, Marcos; Wiedemann, Kenia T.; de Oliveira, Raimundo Cosme; Aragao, Luiz E. O. C.; Christoffersen, Bradley O.; Camargo, Plinio B.; Figueira, Adelaine M. e S.; Ferreira, Maurício Lamano; Oliveira, Rafael S.; Penha, Deliane; Prohaska, Neill; da Araujo, Alessandro C.; Daube, Bruce C.; Wofsy, Steven C.; Saleska, Scott R.Restrepo-Coupe, N., K. S. Campos, L. F. Alves, M. Longo, K. T. Wiedemann, R. C. de Oliveira, L. E. O. C. Aragao, B. O. Christoffersen, P. B. Camargo, A. M. e. S. Figueira, M. L. Ferreira, R. S. Oliveira, D. Penha, N. Prohaska, A. C. da Araujo, B. C. Daube, S. C. Wofsy, S. R. Saleska, 2024: Contrasting carbon cycle responses to dry (2015 El Niño) and wet (2008 La Niña) extreme events at an Amazon tropical forest. Agricultural and Forest Meteorology, 353, 110037. doi: 10.1016/j.agrformet.2024.110037. Land surface models diverge in their predictions of the Amazon forest's response to climate change-induced droughts, with some showing a catastrophic collapse of forests, while others simulating resilience. Therefore, observations of tropical ecosystem responses to real-world droughts and other extreme events are needed. We report long-term seasonal dynamics of photosynthesis, respiration, net carbon exchange, phenology, and tree demography and characterize the effect of dry and wet events on ecosystem form and function at the Tapajós National Forest, Brazil, using over two decades of eddy covariance observations that include the 2015–2016 El Niño drought and La Niña 2008–2009 wet periods. We found strong forest responses to both ENSO events: La Niña saw forest net carbon loss from reduced photosynthesis (due to lower incoming radiation from increased cloudiness) even as ecosystem respiration (Reco) was maintained at mean seasonal levels. El Niño induced the opposite short-term effect, net carbon gains, despite significant reductions in photosynthesis (from a drought-induced halving of canopy conductance to CO2 and significant losses of leaf area), because drought suppression of Reco losses was even greater. However, long-term responses to the two climate perturbations were very different: transient during La Niña –the forest returned to its “normal” state as soon as the climate did, and long-lasting during El Niño –leaf area loss and associated declines in photosynthetic capacity (Pc) and canopy conductance were exacerbated and extended by feedbacks from higher temperatures and atmospheric evaporative demand and persisted for ∼3+ years after normal rainfall resumed. These findings indicate that these forests are more vulnerable to drought than to excess rain, because drought drives significant changes in forest structure (e.g., leaf-abscission and mortality) and ecosystem function (e.g. reduced stomatal conductance). As future Amazonian climate change increases frequencies of hydrological extremes, these mechanisms will determine the long-term fate of tropical forests. Amazonia; Carbon; Ecosystem-climate interactions; Eddy covariance; ENSO; Tropical forests; Water and energy flux seasonality
Sanatan, Binisia; Vinoj, V.; Landu, KiranmayiSanatan, B., V. Vinoj, K. Landu, 2024: The atmospheric aerosol spatial distribution and tropical intra-seasonal oscillations over the South Asian region. Atmospheric Pollution Research, 15(9), 102199. doi: 10.1016/j.apr.2024.102199. Intra-seasonal oscillations (ISO) are well known to modulate the weather phenomena which in turn are known to influence the atmospheric aerosol loading. This study investigates how aerosol loading is modulated in ISO spatio-temporal scales over the Indian region using long-term satellite aerosol optical depth data from Moderate Resolution Imaging Spectroradiometer (MODIS) sensor, onboard Terra Satellite. It is shown that Madden-Julian Oscillation (MJO) and Equatorial Rossby waves (ER) have the highest effect (15–20% of the mean) followed by Mixed-Rossby-gravity and Tropical depressions (MT), and Kelvin wave (KE) (5–15%). Further, a dipolar pattern in aerosol loading was observed, with poles over the Arabian Sea and the Bay of Bengal. These variabilities were found to be mainly driven by anomalous winds associated with the ISOs. Similar to aerosol, dipolar signatures in the atmospheric aerosol radiative forcing (ARF) were also observed with clearer patterns. However, the forcing poles are not centered exactly where aerosol poles were observed, indicating the effect of differential properties of aerosols on the aerosol radiative forcing. Quantitatively, at the surface level, modulation in ARF is up to 3 Wm-2 (15%) for MJO and ER, and up to 2 Wm-2 (5%) for KE and MT; in the atmosphere and at the top of the atmosphere, modulation is up to 2 Wm-2 (15%) for MJO and ER, and up to 1 Wm-2 (5%) for KE and MT. Aerosol distribution; Convectively coupled equatorial waves; India; Intra-seasonal oscillations; Pollution
Schneider, Tapio; Leung, L. Ruby; Wills, Robert C. J.Schneider, T., L. R. Leung, R. C. J. Wills, 2024: Opinion: Optimizing climate models with process knowledge, resolution, and artificial intelligence. Atmospheric Chemistry and Physics, 24(12), 7041-7062. doi: 10.5194/acp-24-7041-2024. Accelerated progress in climate modeling is urgently needed for proactive and effective climate change adaptation. The central challenge lies in accurately representing processes that are small in scale yet climatically important, such as turbulence and cloud formation. These processes will not be explicitly resolvable for the foreseeable future, necessitating the use of parameterizations. We propose a balanced approach that leverages the strengths of traditional process-based parameterizations and contemporary artificial intelligence (AI)-based methods to model subgrid-scale processes. This strategy employs AI to derive data-driven closure functions from both observational and simulated data, integrated within parameterizations that encode system knowledge and conservation laws. In addition, increasing the resolution to resolve a larger fraction of small-scale processes can aid progress toward improved and interpretable climate predictions outside the observed climate distribution. However, currently feasible horizontal resolutions are limited to O(10 km) because higher resolutions would impede the creation of the ensembles that are needed for model calibration and uncertainty quantification, for sampling atmospheric and oceanic internal variability, and for broadly exploring and quantifying climate risks. By synergizing decades of scientific development with advanced AI techniques, our approach aims to significantly boost the accuracy, interpretability, and trustworthiness of climate predictions.
Seiler, Christian; Kou-Giesbrecht, Sian; Arora, Vivek K.; Melton, Joe R.Seiler, C., S. Kou-Giesbrecht, V. K. Arora, J. R. Melton, 2024: The Impact of Climate Forcing Biases and the Nitrogen Cycle on Land Carbon Balance Projections. Journal of Advances in Modeling Earth Systems, 16(1), e2023MS003749. doi: 10.1029/2023MS003749. Earth System Models (ESMs) project that the terrestrial carbon sink will continue to grow as atmospheric CO2 increases, but this projection is uncertain due to biases in the simulated climate and how ESMs represent ecosystem processes. In particular, the strength of the CO2-fertilization effect, which is modulated by nutrient cycles, varies substantially across models. This study evaluates land carbon balance uncertainties for the Canadian Earth System Model (CanESM) by conducting simulations where the latest version of CanESM's land surface component is driven offline with raw and bias-adjusted CanESM5 climate forcing data. To quantify the impact of nutrient limitation, we complete simulations where the nitrogen cycle is enabled or disabled. Results show that bias adjustment improves model performance across most ecosystem variables, primarily due to reduced biases in precipitation. Turning the nitrogen cycle on increases the global land carbon sink during the historical period (1995–2014) due to enhanced nitrogen deposition, placing it within the Global Carbon Budget uncertainty range. During the future period (2080–2099), the simulated land carbon sink increases in response to bias adjustment and decreases in response to the dynamic carbon-nitrogen interaction, leading to a net decrease when both factors are acting together. The dominating impact of the nitrogen cycle demonstrates the importance of representing nutrient limitation in ESMs. Such efforts may produce more robust carbon balance projections in support of global climate change mitigation policies such as the 2015 Paris Agreement. climate change; climate forcing bias; land carbon balance; nitrogen cycle
Shan, Yunpeng; Fan, Jiwen; Zhang, Kai; Shpund, Jacob; Terai, Christopher; Zhang, Guang J.; Song, Xiaoliang; Chen, Chih-Chieh-Jack; Lin, Wuyin; Liu, Xiaohong; Shrivastava, Manish; Wang, Hailong; Xie, ShaochengShan, Y., J. Fan, K. Zhang, J. Shpund, C. Terai, G. J. Zhang, X. Song, C. Chen, W. Lin, X. Liu, M. Shrivastava, H. Wang, S. Xie, 2024: Improving Aerosol Radiative Forcing and Climate in E3SM: Impacts of New Cloud Microphysics and Improved Wet Removal Treatments. Journal of Advances in Modeling Earth Systems, 16(8), e2023MS004059. doi: 10.1029/2023MS004059. Numerous Earth system models exhibit excessive aerosol effective forcing at the top of the atmosphere (TOA), including the Department of Energy's Energy Exascale Earth System Model (E3SM). Here, in the context of the E3SM version 3 effort, the predicted particle property (P3) stratiform cloud microphysics scheme and an enhanced deep convection parameterization suite (ZM_plus) are implemented into E3SM. The ZM_plus includes a convective cloud microphysics scheme, a multi-scale coherent structure parameterization for mesoscale convective systems, and a revised cloud base mass flux formulation considering impacts of the large-scale environment. The P3 scheme improved cloud and radiation particularly over the Northern Hemisphere and the frequency of heavy precipitation over the tropics, and the ZM_plus improved clouds in the tropics. P3 decreases aerosol effective forcing by 0.15 W m−2, while the ZM_plus increases it by 0.27 W m−2, resulting from excessive direct (0.31 W m−2) and indirect forcing (−1.79 W m−2). The excessive aerosol forcings are due to aerosol overestimation associated with insufficient aerosol wet removal. By improving the physical treatments in the aerosol wet removal, we effectively mitigate anthropogenic aerosol overestimation and thus attenuate direct (0.09 W m−2) and indirect aerosol forcing (−1.52 W m−2). Adjustment to primary organic matter hygroscopicity reduces direct and indirect forcing to more reasonable values: −0.13 W m−2 and −1.31 W m−2, respectively. On climatology, improved aerosol treatments mitigate overestimation of aerosol optical depth. aerosol radiative forcing; aerosol-cloud interaction; cloud microphysics; convection; Earth system model; wet removal
She, Xiaojun; Li, Yao; Jiao, Wenzhe; Sun, Yuanheng; Ni, Xiangnan; Zuo, Zhenpeng; Knyazikhin, Yuri; Myneni, Ranga B.She, X., Y. Li, W. Jiao, Y. Sun, X. Ni, Z. Zuo, Y. Knyazikhin, R. B. Myneni, 2024: Varied responses of Amazon forests to the 2005, 2010, and 2015/2016 droughts inferred from multi-source satellite data. Agricultural and Forest Meteorology, 353, 110051. doi: 10.1016/j.agrformet.2024.110051. The Amazon forests play an integral role in the global carbon cycle and have a substantial impact on Earth's climate. However, it is increasingly susceptible to the effects of prolonged droughts, exacerbated by climate change and human activities. This vulnerability underscores the importance of understanding the forests’ reaction to such environmental stressors. Despite their significance, comprehensive cross-comparisons of the climate and vegetation responses during the 2005, 2010, and 2015/2016 drought episodes are not well-established. Here we utilize a range of gridded vegetation and climate datasets—including leaf area index (LAI), solar-induced chlorophyll fluorescence (SIF), enhanced vegetation index (EVI), vegetation optical depth (VOD), self-calibrating Palmer drought severity index (scPDSI), precipitation (P), land surface temperature (LST), and photosynthetically active radiation (PAR)—to thoroughly assess the climate and vegetation response to these three drought events. Our findings reveal that the extent of drought inhibition in the Amazon forests was 74.7 % in 2015, increasing to 81.3 % in 2016, a significant escalation from 49.6 % in 2005 and 57.7 % in 2010. The effects of these three droughts on vegetation varied in both physiological and structural aspects. The Amazon forests’ photosynthetic activity, greenness, and leaf area experienced comparable suppression in 2010 and 2015/2016 droughts. However, canopy water content exhibited more extensive and severe impacts during the 2015/2016 drought. Our findings indicate that varying sensitivities to water deficit and solar radiation lead to diverse spatial patterns and intensities of vegetation response, highlighting the complex dynamics of the Amazon forests under drought stress. Amazon forests; Drought; Leaf area; Solar radiation; Solar-induced chlorophyll fluorescence; Vegetation optical depth
Shen, Lixing; Zhao, Chuanfeng; Xu, Changsan; Yan, Yunwei; Chen, Annan; Yang, Yikun; Hang, Rui; Zhu, Yizhi; Zhang, Zhijiang; Song, XiangzhouShen, L., C. Zhao, C. Xu, Y. Yan, A. Chen, Y. Yang, R. Hang, Y. Zhu, Z. Zhang, X. Song, 2024: Effects of Sea Land Breeze on Air-Sea Turbulent Heat Fluxes in Different Seasons Using Platform Observation in East China Sea. Journal of Geophysical Research: Atmospheres, 129(5), e2023JD040001. doi: 10.1029/2023JD040001. Using 2-year platform observations, this study investigates seasonal characteristics of sea land breeze (SLB) and how it influences air-sea turbulent heat fluxes (THFs) in the coastal areas of East China Sea (ECS) in different seasons. Unlike other SLB studies, this study uses hourly observation on a sea platform to explore SLB's effect on both air-sea latent heat and sensible heat transferring. The results show that sea wind (SW) does not have an obvious seasonal variation pattern while land wind (LW) is stronger in autumn and winter. The SLB day number shows a clear seasonal variation pattern, which accounts for 38.04% and 18.23% of summertime and wintertime days, reaching its peak and bottom respectively. The latent heat flux (LHF) and sensible heat flux (SHF) are high in autumn and winter while low in summer. The SLB-contributed LHF and SHF reach peaks in autumn and winter, which are 61.07 and 7.39 W/m2 respectively. The contribution importance of SLB on air-sea sensible/latent heat transferring is highest in summer while lowest in winter. On SLB days, the SHF decreases significantly by at least about 50% while LHF decreases moderately in all seasons, among which spring witnesses an inversion of sensible heat transferring direction. The warming effect of SLB is mainly responsible for the slump of SHF on SLB days. Multiple factors including relative humidity (RH), background wind field and in situ radiation cause the LHF decrease together, whose changing range varies with season. sensible heat flux; East China Sea; latent heat flux; platform observation; sea land breeze; umbrella effect
Shen, Pengke; Zhao, ShuqingShen, P., S. Zhao, 2024: Intensifying urban imprint on land surface warming: Insights from local to global scale. iScience, 27(3), 109110. doi: 10.1016/j.isci.2024.109110. Increasing urbanization exacerbates surface energy balance perturbations and the health risks of climate warming; however, it has not been determined whether urban-induced warming and attributions vary from local, regional, to global scale. Here, the local surface urban heat island (SUHI) is evidenced to manifest with an annual daily mean intensity of 0.99°C–1.10°C during 2003–2018 using satellite observations over 536 cities worldwide. Spatiotemporal patterns and mechanisms of SUHI tightly link with climate-vegetation conditions, with regional warming effect reaching up to 0.015°C–0.138°C (annual average) due to surface energy alterations. Globally, the SUHI footprint of 1,860 cities approximates to 1% of the terrestrial lands, about 1.8–2.9 times far beyond the urban impervious areas, suggesting the enlargements of the imprint of urban warming from local to global scales. With continuous development of urbanization, the implications for SUHI-added warming and scaling effects are considerably important on accelerating global warming. Remote sensing; Climatology; Earth sciences; Global change; Environmental science
Siemes, Christian; van den IJssel, Jose; Visser, PieterSiemes, C., J. van den IJssel, P. Visser, 2024: Uncertainty of thermosphere mass density observations derived from accelerometer and GNSS tracking data. Advances in Space Research. doi: 10.1016/j.asr.2024.02.057. Thermosphere mass density and crosswind can be derived from accelerometer and GNSS tracking data. However, present datasets are often provided without comprehensive uncertainty specifications. We present a newly developed method that propagates measurement noise and errors in the satellite specification, thermosphere models, and radiation flux data to density observations to quantify their uncertainty. We focus specifically on density observations derived only from GNSS tracking data, which are limited in resolution along the orbit due to unavoidable smoothing. While the method can be applied to simulated and real data, making it useful for existing datasets and mission design, we demonstrated it using data from the GRACE B satellite. First, we compare the aerodynamic acceleration derived separately from the accelerometer and GNSS tracking data, highlighting the role of two significant noise sources: noise due to the differentiation of the positions and noise from the evaluation of the gravity vector at a noisy position. Averaging substantially reduces the noise in the aerodynamic acceleration as long as the differentiation noise dominates, which is the case at frequencies higher than the orbital frequency. Below, gravity vector evaluation noise becomes the dominating noise source, and consequently, averaging over longer periods leads to only marginal uncertainty reduction. Further, we investigate the uncertainty in the radiation pressure acceleration and demonstrate that averaging over one orbit substantially reduces the uncertainty in the along-track radiation pressure acceleration. We show that the uncertainty of density observations derived from the accelerometer data is about 4% of the density for data from 2003 when the GRACE B satellite was at 490 km altitude during high solar activity. In 2008, solar activity was very low, and the altitude was still 476 km, resulting in an uncertainty of 5%–20% because GNSS tracking noise and radiation pressure modeling errors play a much larger role as the aerodynamic acceleration becomes smaller. In the case of density observations derived only from GNSS tracking data, the uncertainty is about 5% in 2003 and 20%–50% in 2008 when averaging over one-third orbit. In 2008, GNSS tracking noise explains nearly all uncertainty in the density observation. Averaging over one orbit reduces the uncertainty to 4% and 5% in 2003 and 2008, respectively. Accelerometer; Uncertainty; GNSS tracking; Neutral density
Singh, Vivek; Srivastava, Atul Kumar; Gupta, Anu; Konduru, Rakesh Teja; Singh, Amarendra; Singh, Sumit; Kumar, Arun; Bisht, Deewan Singh; Singh, Abhay KumarSingh, V., A. K. Srivastava, A. Gupta, R. T. Konduru, A. Singh, S. Singh, A. Kumar, D. S. Bisht, A. K. Singh, 2024: Intensification mechanisms and moisture dynamics of super cyclonic storm ‘Amphan’ over the Bay of Bengal: Implications for aerosol re-distribution. Science of The Total Environment, 951, 175501. doi: 10.1016/j.scitotenv.2024.175501. The present research investigates the dynamics and underlying causes contributing to the exceptional intensity of Super Cyclonic Storm (SuCS) Amphan (16th to 21st May 2020) over the Bay of Bengal (BoB), as well as its impact on aerosol redistribution along the four cities of eastern coast and north-eastern India. Notably, the SuCS was formed during the first phase of the COVID-19 lockdown in India, giving it a unique aspect of study and analysis. Our analysis based on 30 years of climatology data from Modern-Era Retrospective Analysis for Research and Applications, Version 2 (MERRA-2) reanalysis reveals ‘positive’ monthly anomalous winds (0.8 to 1.6 m/s) prevailed over the central BoB for May 2020. The present study further found the evolution of ‘barrier layer thickness’(BLT) leading up to landfall, noting a thickening trend from 8 to 3 days before landfall, contributing to maintaining warmer sea surface temperatures near the coast. Additionally, utilizing European Centre for Medium-Range Weather Forecasts (ECMWF), reanalysis version-5 (ERA-5) data, a mean positive sea surface temperature (SST) anomaly of 0.8 to 1 °C was observed ‘before’ cyclone period (10–15 May 2020) near the cyclogenesis point. A detailed examination of Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observations (CALIPSO) vertical cross-section plots during the cyclone's intensification stage reveals the presence of high-altitude clouds composed primarily of ice crystals. Further, analysis also indicates that the cyclone transported Sea-salt PM2.5 aerosols from the ocean, dispersing them in the landfall region.The aerosol optical Depth (AOD) data obtained from the National Aeronautics and Space Administration's (NASA) ‘Clouds and the Earth's Radiant Energy System (CERES)’ mission and MERRA-2 were also analysed, revealing that the cyclone redistributed aerosols over the Bengal basin region (mainly over ‘Kolkata') and three other nearby cities along the track of the cyclone (i.e., Bhubaneswar (Odisha) Agartala (Tripura) and Shillong (Meghalaya) respectively). Aerosol optical depth; Amphan; Barrier layer thickness; COVID-19 lockdown; Sea salt PM; Super cyclonic storm
Song, Chanwoo; Park, SungsuSong, C., S. Park, 2024: A New Comprehensive Cloud Macrophysics Scheme With a Prognostic Dual-Triangular PDF. Journal of Advances in Modeling Earth Systems, 16(4), e2023MS003963. doi: 10.1029/2023MS003963. To improve cloud simulation in a general circulation model, we develop a new cloud macrophysics scheme that treats detrained cumulus generated by convective detrainment process separately from pure stratus; prognoses two symmetric triangular probability density functions of total specific humidity for each detrained cumulus and pure stratus; and diagnoses both cloud fraction and cloud condensate in all liquid, ice, and mixed-phases in a consistent and unified way without any adjustment to remove empty or very dense cloud. Supersaturation is allowed within ice cloud. The new scheme (“NEW”) is compared with the previous model (“OLD”) using single-column simulations for subtropical marine stratocumulus (DYCOMS2) and continental deep convection (ARM97) cases. In DYCOMS2, both NEW and OLD produce vertical profiles of grid-mean cloud condensate similar to large-eddy simulation. In ARM97, compared with OLD, NEW simulates less sporadic vertical profiles of in-cloud condensates, due to consistent diagnosis of cloud fraction and cloud condensate; more continuously-varying detrained cumulus with time, due to prognostic treatment of detrained cumulus; and ice cloud fraction and ice condensate similar to those of OLD, in spite of completely different treatment of ice cloud processes. The global performance of NEW is similar to OLD with improved relative humidity. Compared to OLD, NEW simulates more and improved cloud condensate, but less and degraded cloud fraction, particularly, in the lower troposphere. Detrained cumulus is moister and colder and has a larger moisture variance than pure stratus. Overall, NEW simulates stronger condensation-deposition rates than OLD, due in part to the separate treatment of detrained cumulus and pure stratus. general circulation model; cloud parameterization; cloud macrophysics scheme
Song, Ci; McCoy, Daniel T.; Eidhammer, Trude; Gettelman, Andrew; McCoy, Isabel L.; Watson-Parris, Duncan; Wall, Casey J.; Elsaesser, Gregory; Wood, RobertSong, C., D. T. McCoy, T. Eidhammer, A. Gettelman, I. L. McCoy, D. Watson-Parris, C. J. Wall, G. Elsaesser, R. Wood, 2024: Buffering of Aerosol-Cloud Adjustments by Coupling Between Radiative Susceptibility and Precipitation Efficiency. Geophysical Research Letters, 51(11), e2024GL108663. doi: 10.1029/2024GL108663. Aerosol-cloud interactions (ACI) in warm clouds are the primary source of uncertainty in effective radiative forcing (ERF) during the historical period and, by extension, inferred climate sensitivity. The ERF due to ACI (ERFaci) is composed of the radiative forcing due to changes in cloud microphysics and cloud adjustments to microphysics. Here, we examine the processes that drive ERFaci using a perturbed parameter ensemble (PPE) hosted in CAM6. Observational constraints on the PPE result in substantial constraints in the response of cloud microphysics and macrophysics to anthropogenic aerosol, but only minimal constraint on ERFaci. Examination of cloud and radiation processes in the PPE reveal buffering of ERFaci by the interaction of precipitation efficiency and radiative susceptibility. aerosol-cloud interactions; global climate models
Song, Qianghua; Wang, Chunzai; Yao, Yulong; Fan, HanjieSong, Q., C. Wang, Y. Yao, H. Fan, 2024: Unraveling the Indian monsoon’s role in fueling the unprecedented 2022 Marine Heatwave in the Western North Pacific. npj Climate and Atmospheric Science, 7(1), 1-8. doi: 10.1038/s41612-024-00645-x. An unprecedented marine heatwave (MHW) event occurred in the middle-high latitudes of the western North Pacific during the summer of 2022. We demonstrate that excessive precipitation thousands of kilometers away fuels this extreme MHW event in July 2022. In the upper atmosphere, a persistent atmospheric blocking system, forming over the MHW region, reduces cloud cover and increases shortwave radiation at the ocean surface, leading to high sea surface temperatures. Atmospheric perturbations induced by latent heat release from the extreme precipitation in the Indian summer monsoon region enhance this atmospheric blocking through the propagation of quasi-stationary Rossby waves. Our hypothesis is verified by using a numerical model that is forced with the observed atmospheric anomalous diabatic heating. This study sheds light on how a subtropical extreme event can fuel another extreme event at middle-high latitudes through an atmospheric teleconnection. Atmospheric dynamics; Physical oceanography
Song, Qianqian; Ginoux, Paul; Gonçalves Ageitos, María; Miller, Ron L.; Obiso, Vincenzo; Pérez García-Pando, CarlosSong, Q., P. Ginoux, M. Gonçalves Ageitos, R. L. Miller, V. Obiso, C. Pérez García-Pando, 2024: Modeling impacts of dust mineralogy on fast climate response. Atmospheric Chemistry and Physics, 24(12), 7421-7446. doi: 10.5194/acp-24-7421-2024. Mineralogical composition drives dust impacts on Earth's climate systems. However, most climate models still use homogeneous dust, without accounting for the temporal and spatial variation in mineralogy. To quantify the radiative impact of resolving dust mineralogy on Earth's climate, we implement and simulate the distribution of dust minerals (i.e., illite, kaolinite, smectite, hematite, calcite, feldspar, quartz, and gypsum) from Claquin et al. (1999) (C1999) and activate their interaction with radiation in the GFDL AM4.0 model. Resolving mineralogy reduces dust absorption compared to the homogeneous dust used in the standard GFDL AM4.0 model that assumes a globally uniform hematite volume content of 2.7 % (HD27). The reduction in dust absorption results in improved agreement with observation-based single-scattering albedo (SSA), radiative fluxes from CERES (the Clouds and the Earth's Radiant Energy System), and land surface temperature from the CRU (Climatic Research Unit) compared to the baseline HD27 model version. It also results in distinct radiative impacts on Earth's climate over North Africa. Over the 19-year (from 2001 to 2019) modeled period during JJA (June–July–August), the reduction in dust absorption in AM4.0 leads to a reduction of over 50 % in net downward radiation across the Sahara and approximately 20 % over the Sahel at the top of the atmosphere (TOA) compared to the baseline HD27 model version. The reduced dust absorption weakens the atmospheric warming effect of dust aerosols and leads to an alteration in land surface temperature, resulting in a decrease of 0.66 K over the Sahara and an increase of 0.7 K over the Sahel. The less warming in the atmosphere suppresses ascent and weakens the monsoon inflow from the Gulf of Guinea. This brings less moisture to the Sahel, which combined with decreased ascent induces a reduction of precipitation. To isolate the effect of reduced absorption compared to resolving spatial and temporal mineralogy, we carry out a simulation where the hematite volume content of homogeneous dust is reduced from 2.7 % to 0.9 % (HD09). The dust absorption (e.g., single-scattering albedo) of HD09 is comparable to that of the mineralogically speciated model on a global mean scale, albeit with a lower spatial variation that arises solely from particle size. Comparison of the two models indicates that the spatial inhomogeneity in dust absorption resulting from resolving mineralogy does not have significant impacts on Earth's radiation and climate, provided there is a similar level of dust absorption on a global mean scale before and after resolving dust mineralogy. However, uncertainties related to emission and distribution of minerals may blur the advantages of resolving minerals to study their impact on radiation, cloud properties, ocean biogeochemistry, air quality, and photochemistry. On the other hand, lumping together clay minerals (i.e., illite, kaolinite, and smectite), but excluding externally mixed hematite and gypsum, appears to provide both computational efficiency and relative accuracy. Nevertheless, for specific research, it may be necessary to fully resolve mineralogy to achieve accuracy.
Sorenson, Blake T.; Reid, Jeffrey S.; Zhang, Jianglong; Holz, Robert E.; Smith Sr., William L.; Gumber, AmandaSorenson, B. T., J. S. Reid, J. Zhang, R. E. Holz, W. L. Smith Sr., A. Gumber, 2024: Thermal infrared observations of a western United States biomass burning aerosol plume. Atmospheric Chemistry and Physics, 24(2), 1231-1248. doi: 10.5194/acp-24-1231-2024. Biomass burning smoke particles, due to their submicron particle size in relation to the average thermal infrared (TIR) wavelength, theoretically have negligible signals at the TIR channels. However, nearly instantaneous longwave (LW) signatures of thick smoke plumes can be frequently observed at the TIR channels from remotely sensed data, including at 10.6 µm (IR window), as well as in water-vapor-sensitive wavelengths at 7.3, 6.8, and 6.3 µm (e.g., lower, middle, and upper troposphere). We systematically evaluated multiple hypotheses as to causal factors of these IR signatures of biomass burning smoke using a combination of data from the Aqua MODerate resolution Imaging Spectroradiometer (MODIS), Aqua Cloud and the Earth Radiant Energy System (CERES), Geostationary Operational Environmental Satellite 16/17 (GOES-16/17) Advanced Baseline Imager, and Suomi-NPP Visible Infrared Imaging Radiometer Suite (VIIRS) and Cross-track Infrared Sounder (CrIS). The largely clear transmission of light through wildfire smoke in the near infrared indicates that coarse or giant ash particles are unlikely to be the dominant cause. Rather, clear signals in water vapor and TIR channels suggest that both co-transported water vapor injected to the middle to upper troposphere and surface cooling by the reduction of surface radiation by the plume are more significant, with the surface cooling effect of smoke aloft being the most dominant. Giving consideration of the smoke impacts on TIR and longwave, CERES indicates that large wildfire aerosol plumes are more radiatively neutral. Further, this smoke-induced TIR signal may be used to map very optically thick smoke plumes, where traditional aerosol retrieval methods have difficulties.
Sotiropoulou, Georgia; Lewinschal, Anna; Georgakaki, Paraskevi; Phillips, Vaughan T. J.; Patade, Sachin; Ekman, Annica M. L.; Nenes, AthanasiosSotiropoulou, G., A. Lewinschal, P. Georgakaki, V. T. J. Phillips, S. Patade, A. M. L. Ekman, A. Nenes, 2024: Sensitivity of Arctic Clouds to Ice Microphysical Processes in the NorESM2 Climate Model. doi: 10.1175/JCLI-D-22-0458.1. Ice formation remains one of the most poorly represented microphysical processes in climate models. While primary ice production (PIP) parameterizations are known to have a large influence on the modeled cloud properties, the representation of secondary ice production (SIP) is incomplete and its corresponding impact is therefore largely unquantified. Furthermore, ice aggregation is another important process for the total cloud ice budget, which also remains largely unconstrained. In this study, we examine the impact of PIP, SIP, and ice aggregation on Arctic clouds, using the Norwegian Earth System Model, version 2 (NorESM2). Simulations with both prognostic and diagnostic PIP show that heterogeneous freezing alone cannot reproduce the observed cloud ice content. The implementation of missing SIP mechanisms (collisional breakup, drop shattering, and sublimation breakup) in NorESM2 improves the modeled ice properties, while improvements in liquid content occur only in simulations with prognostic PIP. However, results are sensitive to the description of collisional breakup. This mechanism, which dominates SIP in the examined conditions, is very sensitive to the treatment of the sublimation correction factor, a poorly constrained parameter that is included in the utilized parameterization. Finally, variations in ice aggregation treatment can also significantly impact cloud properties, mainly through their impact on collisional breakup efficiency. Overall, enhancement in ice production through the addition of SIP mechanisms and the reduction in ice aggregation (in line with radar observations of shallow Arctic clouds) result in enhanced cloud cover and decreased TOA radiation biases, compared to satellite measurements, especially during the cold months. Significance Statement Arctic clouds remain a large source of uncertainty in projections of the future climate due to the poor representation of the microphysical processes that govern their life cycle. Ice formation is among the least understood processes. While it is widely recognized that better constraints on primary ice production (PIP) are needed to improve existing parameterizations, we show that secondary ice production (SIP) and ice aggregation can have also a significant impact on ice number concentrations. Constraining ice formation through the addition of missing SIP mechanisms and reducing ice aggregation can improve the representation of the cloud macrophysical properties and enhance total cloud cover in the Arctic region, which in turn contributes to decreased TOA radiation biases in the cold months. Arctic; Climate models; Cloud microphysics; Cloud parameterizations; Clouds; Secondary ice production
Stephens, Graeme L.; Shiro, Kathleen A.; Hakuba, Maria Z.; Takahashi, Hanii; Pilewskie, Juliet A.; Andrews, Timothy; Stubenrauch, Claudia J.; Wu, LongtaoStephens, G. L., K. A. Shiro, M. Z. Hakuba, H. Takahashi, J. A. Pilewskie, T. Andrews, C. J. Stubenrauch, L. Wu, 2024: Tropical Deep Convection, Cloud Feedbacks and Climate Sensitivity. Surveys in Geophysics. doi: 10.1007/s10712-024-09831-1. This paper is concerned with how the diabatically-forced overturning circulations of the atmosphere, established by the deep convection within the tropical trough zone (TTZ), first introduced by Riehl and (Malkus) Simpson, in Contr Atmos Phys 52:287–305 (1979), fundamentally shape the distributions of tropical and subtropical cloudiness and the changes to cloudiness as Earth warms. The study first draws on an analysis of a range of observations to understand the connections between the energetics of the TTZ, convection and clouds. These observations reveal a tight coupling of the two main components of the diabatic heating, the cloud component of radiative heating, shaped mostly by high clouds formed by deep convection, and the latent heating associated with the precipitation. Interannual variability of the TTZ reveals a marked variation that connects the depth of the tropical troposphere, the depth of convection, the thickness of high clouds and the TOA radiative imbalance. The study examines connections between this convective zone and cloud changes further afield in the context of CMIP6 model experiments of climate warming. The warming realized in the CMIP6 SSP5-8.5 scenario multi-model experiments, for example, produces an enhanced Hadley circulation with increased heating in the zone of tropical deep convection and increased radiative cooling and subsidence in the subtropical regions. This impacts low cloud changes and in turn the model warming response through low cloud feedbacks. The pattern of warming produced by models, also influenced by convection in the tropical region, has a profound influence on the projected global warming. Climate change; Cloud feedbacks; Tropical convection
Storto, Andrea; Yang, ChunxueStorto, A., C. Yang, 2024: Acceleration of the ocean warming from 1961 to 2022 unveiled by large-ensemble reanalyses. Nature Communications, 15(1), 545. doi: 10.1038/s41467-024-44749-7. Long-term changes in ocean heat content (OHC) represent a fundamental global warming indicator and are mostly caused by anthropogenic climate-altering gas emissions. OHC increases heavily threaten the marine environment, therefore, reconstructing OHC before the well-instrumented period (i.e., before the Argo floats deployment in the mid-2000s) is crucial to understanding the multi-decadal climate change in the ocean. Here, we shed light on ocean warming and its uncertainty for the 1961-2022 period through a large ensemble reanalysis system that spans the major sources of uncertainties. Results indicate a 62-year warming of 0.43 ± 0.08 W m−2, and a statistically significant acceleration rate equal to 0.15 ± 0.04 W m−2 dec−1, locally peaking at high latitudes. The 11.6% of the global ocean area reaches the maximum yearly OHC in 2022, almost doubling any previous year. At the regional scale, major OHC uncertainty is found in the Tropics; at the global scale, the uncertainty represents about 40% and 15% of the OHC variability, respectively before and after the mid-2000s. The uncertainty of regional trends is mostly affected by observation calibration (especially at high latitudes), and sea surface temperature data uncertainty (especially at low latitudes). Climate and Earth system modelling; Physical oceanography
Stubenrauch, Claudia J.; Kinne, Stefan; Mandorli, Giulio; Rossow, William B.; Winker, David M.; Ackerman, Steven A.; Chepfer, Helene; Di Girolamo, Larry; Garnier, Anne; Heidinger, Andrew; Karlsson, Karl-Göran; Meyer, Kerry; Minnis, Patrick; Platnick, Steven; Stengel, Martin; Sun-Mack, Szedung; Veglio, Paolo; Walther, Andi; Cai, Xia; Young, Alisa H.; Zhao, GuangyuStubenrauch, C. J., S. Kinne, G. Mandorli, W. B. Rossow, D. M. Winker, S. A. Ackerman, H. Chepfer, L. Di Girolamo, A. Garnier, A. Heidinger, K. Karlsson, K. Meyer, P. Minnis, S. Platnick, M. Stengel, S. Sun-Mack, P. Veglio, A. Walther, X. Cai, A. H. Young, G. Zhao, 2024: Lessons Learned from the Updated GEWEX Cloud Assessment Database. Surveys in Geophysics. doi: 10.1007/s10712-024-09824-0. Since the first Global Energy and Water Exchanges cloud assessment a decade ago, existing cloud property retrievals have been revised and new retrievals have been developed. The new global long-term cloud datasets show, in general, similar results to those of the previous assessment. A notable exception is the reduced cloud amount provided by the Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observation (CALIPSO) Science Team, resulting from an improved aerosol–cloud distinction. Height, opacity and thermodynamic phase determine the radiative effect of clouds. Their distributions as well as relative occurrences of cloud types distinguished by height and optical depth are discussed. The similar results of the two assessments indicate that further improvement, in particular on vertical cloud layering, can only be achieved by combining complementary information. We suggest such combination methods to estimate the amount of all clouds within the atmospheric column, including those hidden by clouds aloft. The results compare well with those from CloudSat-CALIPSO radar–lidar geometrical profiles as well as with results from the International Satellite Cloud Climatology Project (ISCCP) corrected by the cloud vertical layer model, which is used for the computation of the ISCCP-derived radiative fluxes. Furthermore, we highlight studies on cloud monitoring using the information from the histograms of the database and give guidelines for: (1) the use of satellite-retrieved cloud properties in climate studies and climate model evaluation and (2) improved retrieval strategies. Cloud cover; Satellite remote sensing; Atmosphere; Cloud height; Cloud radiative properties; Cloud types; Microphysical properties
Sun-Mack, Sunny; Minnis, Patrick; Chen, Yan; Hong, Gang; Smith Jr., William L.Sun-Mack, S., P. Minnis, Y. Chen, G. Hong, W. L. Smith Jr., 2024: Identification of ice-over-water multilayer clouds using multispectral satellite data in an artificial neural network. Atmospheric Measurement Techniques, 17(10), 3323-3346. doi: 10.5194/amt-17-3323-2024. An artificial neural network (ANN) algorithm, employing several Aqua MODerate-resolution Imaging Spectroradiometer (MODIS) channels, the retrieved cloud phase and total cloud visible optical depth, and temperature and humidity vertical profiles is trained to detect multilayer (ML) ice-over-water cloud systems identified by matched 2008 CloudSat and CALIPSO (CC) data. The trained multilayer cloud-detection ANN (MCANN) was applied to 2009 MODIS data resulting in combined ML and single layer detection accuracies of 87 % (89 %) and 86 % (89 %) for snow-free (snow-covered) regions during the day and night, respectively. Overall, it detects 55 % and ∼ 30 % of the CC ML clouds over snow-free and snow-covered surfaces, respectively, and has a relatively low false alarm rate. The net gain in accuracy, which is the difference between the true and false ML fractions, is 7.5 % and ∼ 2.0 % over snow-free and snow/ice-covered surfaces. Overall, the MCANN is more accurate than most currently available methods. When corrected for the viewing-zenith-angle dependence of each parameter, the ML fraction detected is relatively invariant across the swath. Compared to the CC ML variability, the MCANN is robust seasonally and interannually and produces similar distribution patterns over the globe, except in the polar regions. Additional research is needed to conclusively evaluate the viewing zenith angle (VZA) dependence and further improve the MCANN accuracy. This approach should greatly improve the monitoring of cloud vertical structure using operational passive sensors.
Sunil, Sneha; Padmakumari, B.Sunil, S., B. Padmakumari, 2024: Optical and Radiative Characteristics of the Lower Part of Cirrus Clouds Over a Rain Shadow Region in South Peninsular India. Pure and Applied Geophysics, 181(5), 1697-1724. doi: 10.1007/s00024-024-03466-4. Cirrus (Ci) clouds have an important influence on Earth's radiation budget, and they remain one of the most significant uncertainties in predicting Earth's climate. In this study, we use ground-based radiometers along with a sky imager to monitor clouds and retrieve cloud properties (cloud fraction (CF), cloud optical depth (COD) and effective radii (Re)) over a rain shadow region in south peninsular India during September and October months, 2011. Lower part of Ci clouds are identified using the thresholds pertaining to COD and cloud base height (CBH). The optical and radiative properties of Ci clouds showed large variability on temporal and diurnal scales. The CF, COD and Re varied from 7 to 100%, 0.76 to 9.99, and 2.76 to 37.92 μm, respectively. The CBH and Cloud Base Temperature (CBT) are found to vary from 7.24 to 8.99 km and − 31.99 to − 13.75 °C. The Shortwave Cloud Radiative forcing (SWCRF) exerted by the lower part of Ci clouds over the region is observed to vary from − 435 to 148.87 W m−2 on a temporal scale with an average value of − 23.06 W m−2. The relationship between SWCRF and COD revealed radiative cooling effect with increase in COD with a dependency rate of − 18.53 W m−2/τ. SWCRF is found to be more sensitive to COD as compared to other cloud characteristics (CF, CBH and CBT). The case studies depict that the observed lower part of Ci clouds are advected from the ocean indicating the influence of large scale systems. Lower part of Ci optical and radiative properties showed wide variability depending up on the source of formation and evolution. This study also suggests that the high temporal variability of optical and radiative properties of Ci clouds needs to be well considered in climate models to reduce the uncertainty of cirrus radiative effects. Cirrus clouds; Cloud optical depth; Cloud properties; Cloud radiative forcing; SW radiation
Takasuka, Daisuke; Kodama, Chihiro; Suematsu, Tamaki; Ohno, Tomoki; Yamada, Yohei; Seiki, Tatsuya; Yashiro, Hisashi; Nakano, Masuo; Miura, Hiroaki; Noda, Akira T.; Nasuno, Tomoe; Miyakawa, Tomoki; Masunaga, RyusukeTakasuka, D., C. Kodama, T. Suematsu, T. Ohno, Y. Yamada, T. Seiki, H. Yashiro, M. Nakano, H. Miura, A. T. Noda, T. Nasuno, T. Miyakawa, R. Masunaga, 2024: How Can We Improve the Seamless Representation of Climatological Statistics and Weather Toward Reliable Global K-Scale Climate Simulations?. Journal of Advances in Modeling Earth Systems, 16(2), e2023MS003701. doi: 10.1029/2023MS003701. Toward the achievement of reliable global kilometer-scale (k-scale) climate simulations, we improve the Nonhydrostatic ICosahedral Atmospheric Model (NICAM) by focusing on moist physical processes. A goal of the model improvement is to establish a configuration that can simulate realistic fields seamlessly from the daily-scale variability to the climatological statistics. Referring to the two representative configurations of the present NICAM, each of which has been used for climate-scale and sub-seasonal-scale experiments, we try to find the appropriate partitioning of fast/local and slow/global-scale circulations. In a series of sensitivity experiments at 14-km horizontal resolution, we test (a) the tuning of terminal velocities of rain, snow, and cloud ice, (b) the implementation of turbulent diffusion by the Leonard term, and (c) enhanced vertical resolution. These tests yield reasonable convection triggering and convection-induced tropospheric moistening, and result in better performance than in previous NICAM climate simulations. In the mean state, double Intertropical Convergence Zone bias disappears, and the zonal contrast of equatorial precipitation, top-of-atmosphere radiation balance, vertical temperature profile, and position/strength of subtropical jet are reproduced dramatically better. Variability such as equatorial waves and the Madden–Julian oscillation (MJO) is spontaneously realized with appropriate spectral power balance, and the Asian summer monsoon, boreal-summer MJO, and tropical cyclone (TC) activities are more realistically simulated especially around the western Pacific. Meanwhile, biases still exist in the representation of low-cloud fraction, TC intensity, and precipitation diurnal cycle, suggesting that both higher spatial resolutions and further model development are warranted. climate simulation; global convection-resolving model; physics-dynamics coupling
Tan, Chuyan; McCoy, Daniel T.; Elsaesser, Gregory S.Tan, C., D. T. McCoy, G. S. Elsaesser, 2024: Constraints on Southern Ocean Shortwave Cloud Feedback From the Hydrological Cycle. Journal of Geophysical Research: Atmospheres, 129(6), e2023JD040489. doi: 10.1029/2023JD040489. Shifts in Southern Ocean (SO, 40–85°S) shortwave cloud feedback (SWFB) toward more positive values are the dominant contributor to higher effective climate sensitivity (ECS) in Coupled Model Intercomparison Project Phase 6 (CMIP6) models. To provide an observational constraint on the SO SWFB, we use a simplified physical model to connect SO SWFB with the response of column-integrated liquid water mass (LWP) to warming and the susceptibility of albedo to LWP in 50 CMIP5 and CMIP6 GCMs. In turn, we predict the responses of SO LWP using a cloud-controlling factor (CCF) model. The combination of the CCF model and radiative susceptibility explains about 50% of the variance in the GCM-simulated SWFB in the SO. Observations of SW radiation fluxes, LWP, and CCFs from reanalysis are used to constrain the SO SWFB. Observations suggest a SO LWP increase in response to warming and albedo susceptibility to LWP that is on the lower end relative to GCMs. The overall constraint on the contribution of SO to global mean SWFB is −0.168 to +0.051 W m−2 K−1, relative to −0.277 to +0.270 Wm−2 K−1. In summary, observations suggest SO SWFB is less likely to be as extremely positive as predicted by some CMIP6 GCMs, but more likely to range from moderately negative to weakly positive. climate; clouds; Southern Ocean; precipitation; feedback; moisture convergence
Tan, Ivy; Zelinka, Mark D.; Coopman, Quentin; Kahn, Brian H.; Oreopoulos, Lazaros; Tselioudis, George; McCoy, Daniel T.; Li, NinghuiTan, I., M. D. Zelinka, Q. Coopman, B. H. Kahn, L. Oreopoulos, G. Tselioudis, D. T. McCoy, N. Li, 2024: Contributions From Cloud Morphological Changes to the Interannual Shortwave Cloud Feedback Based on MODIS and ISCCP Satellite Observations. Journal of Geophysical Research: Atmospheres, 129(8), e2023JD040540. doi: 10.1029/2023JD040540. Abstract The surface temperature-mediated change in cloud properties, referred to as the cloud feedback, continues to dominate the uncertainty in climate projections. A larger number of contemporary global climate models (GCMs) project a higher degree of warming than the previous generation of GCMs. This greater projected warming has been attributed to a less negative cloud feedback in the Southern Ocean. Here, we apply a novel ?double decomposition method? that employs the ?cloud radiative kernel? and ?cloud regime? concepts, to two data sets of satellite observations to decompose the interannual cloud feedback into contributions arising from changes within and shifts between cloud morphologies. Our results show that contributions from the latter to the cloud feedback are large for certain regimes. We then focus on interpreting how both changes within and between cloud morphologies impact the shortwave cloud optical depth feedback over the Southern Ocean in light of additional observations. Results from the former cloud morphological changes reveal the importance of the wind response to warming increases low- and mid-level cloud optical thickness in the same region. Results from the latter cloud morphological changes reveal that a general shift from thick storm-track clouds to thinner oceanic low-level clouds contributes to a positive feedback over the Southern Ocean that is offset by shifts from thinner broken clouds to thicker mid- and low-level clouds. Our novel analysis can be applied to evaluate GCMs and potentially diagnose shortcomings pertaining to their physical parameterizations of particular cloud morphologies. climate; cloud feedback; MODIS; Southern Ocean; ISCCP; morphology
Tang, Wenjun; He, Junmei; Shao, Changkun; Song, Jun; Yuan, Zongtao; Yan, BowenTang, W., J. He, C. Shao, J. Song, Z. Yuan, B. Yan, 2024: Constructing a long-term global dataset of direct and diffuse radiation (10 km, 3 h, 1983–2018) separating from the satellite-based estimates of global radiation. Remote Sensing of Environment, 311, 114292. doi: 10.1016/j.rse.2024.114292. In addition to global radiation (Rg), direct radiation (Rdir) and diffuse radiation (Rdif) are important fundamental data urgently needed in scientific and industrial fields. However, compared with Rg, Rdir and Rdif have received little attention in the past, either in observations or in satellite retrievals, mainly due to the high cost of their observations and the difficulty of retrieving them effectively from satellites. In this study, a long-term global gridded dataset of Rdir and Rdif was constructed by separating from a high-precision satellite-based product of Rg using the Light Gradient Boosting Machine (LightGBM) model, trained with in-situ observations measured at the Baseline Surface Radiation Network (BSRN). The inputs to construct the dataset are the four variables of Rg, the cloud transmittance for Rg, the ratio of Rdif to Rg under clear sky condition (call the clear diffuse ratio), and the cosine of the solar zenith angle. The developed dataset was validated against in-situ observations and compared with other satellite-based products. Evaluations against the BSRN observations indicated that our proposed method has good generality and outperforms the machine learning-based direct estimation method of Hao et al. (2020). Independent validations were further performed against the observations measured at 17 China Meteorological Administration (CMA) radiation stations and the estimation based on sunshine duration observations at >2400 CMA routine meteorological stations, respectively. It was found that the accuracies of our estimates for both Rdir and Rdif were improved when upscaled to ≥ 30 km. Comparisons with three other satellite-based products indicate that our developed dataset of both Rdir and Rdif was generally more accurate than the global products of the Earth's Radiant Energy System (CERES) and Hao et al. (2020) based on the Deep Space Climate Observatory/Earth Polychromatic Imaging Camera (EPIC) (DSCOVER/EPIC) satellite, and the regional gridded product (JIEA) of Jiang et al. (2020a). The dataset developed in this study will contribute to ecological research and solar engineering applications. Dataset; Diffuse radiation; Direct radiation; Global radiation; Separation method
Thandlam, Venugopal; Kaagita, Venkatramana; Sakirevupalli, Venkatramana ReddyThandlam, V., V. Kaagita, V. R. Sakirevupalli, 2024: Long-term meteorological characteristics and extreme climate indices over Tirupati: a rapidly developing tropical city. Discover Cities, 1(1), 14. doi: 10.1007/s44327-024-00013-7. Tirupati’s climate has undergone significant changes in both temperature and precipitation patterns. While there has been a consistent increase in rainfall during the southwest monsoon, there is a concerning long-term trend of a decrease in total annual precipitation over the last 30 years. The city has experienced a rise in wet days during both the southwest and northeast monsoons, yet a recent decrease over the past three decades. Heavy precipitation events, particularly during the southwest monsoon, have shown a positive trend, whereas there have been no significant changes in heavy rainfall days during the northeast monsoon. Temperature trends reveal that there has been a warming scenario, with a significant positive trend in annual maximum temperatures and a consistent annual rise in mean minimum temperatures. A substantial decrease in cold and very cold days, especially during the last 30 years, suggests a broader warming trend impacting seasonal temperature variations in Tirupati. These findings highlight the complex interplay of monsoons, temperature variations, and changing precipitation patterns in Tirupati's climate over the years. Climate; Cold days; Dry days; Hot days; Monsoons; Precipitation; Temperature; Tirupati; Wet days
Thimsen, ElijahThimsen, E., 2024: Planetary Energy Flow and Entropy Production Rate by Earth from 2002 to 2023. Entropy, 26(5), 350. doi: 10.3390/e26050350. In this work, satellite data from the Clouds and Earth’s Radiant Energy System (CERES) and Moderate Resolution Imaging Spectroradiometer (MODIS) instruments are analyzed to determine how the global absorbed sunlight and global entropy production rates have changed from 2002 to 2023. The data is used to test hypotheses derived from the Maximum Power Principle (MPP) and Maximum Entropy Production Principle (MEP) about the evolution of Earth’s surface and atmosphere. The results indicate that both the rate of absorbed sunlight and global entropy production have increased over the last 20 years, which is consistent with the predictions of both hypotheses. Given the acceptance of the MPP or MEP, some peripheral extensions and nuances are discussed. albedo; ecosystems; entropy generation; evolution; externalities; geoengineering; life; nonequilibrium thermodynamics; social sciences
Tselioudis, George; Rossow, William B.; Bender, Frida; Oreopoulos, Lazaros; Remillard, JasmineTselioudis, G., W. B. Rossow, F. Bender, L. Oreopoulos, J. Remillard, 2024: Oceanic cloud trends during the satellite era and their radiative signatures. Climate Dynamics. doi: 10.1007/s00382-024-07396-8. The present study analyzes zonal mean cloud and radiation trends over the global oceans for the past 35 years from a suite of satellite datasets covering two periods. In the longer period (1984–2018) cloud properties come from the ISCCP-H, CLARA-A3, and PATMOS-x datasets and radiative properties from the ISCCP-FH dataset, while for the shorter period (2000–2018) cloud data from MODIS and CloudSat/CALIPSO and radiative fluxes from CERES-EBAF are added. Zonal mean total cloud cover (TCC) trend plots show an expansion of the subtropical dry zone, a poleward displacement of the midlatitude storm zone and a narrowing of the tropical intertropical convergence zone (ITCZ) region over the 1984–2018 period. This expansion of the ‘low cloud cover curtain’ and the contraction of the ITCZ rearrange the boundaries and extents of all major climate zones, producing a more poleward and narrower midlatitude storm zone and a wider subtropical zone. Zonal mean oceanic cloud cover trends are examined for three latitude zones, two poleward of 50 ° and one bounded within 50oS and 50oN, and show upward or near-zero cloud cover trends in the high latitude zones and consistent downward trends in the low latitude zone. The latter dominate in the global average resulting in TCC decreases that range from 0.72% per decade to 0.17% per decade depending on dataset and period. These contrasting cloud cover changes between the high and low latitude zones produce contrasting low latitude cloud radiative warming and high latitude cloud radiative cooling effects, present in both the ISCCP-FH and CERES-EBAF datasets. The global ocean mean trend of the short wave cloud radiative effect (SWCRE) depends on the balance between these contrasting trends, which in the CERES dataset materializes as a SW cloud radiative warming trend of 0.12 W/m2/decade coming from the dominance of the low-latitude positive SWCRE trends while in the ISCCP-FH dataset it manifests as a 0.3 W/m2/decade SW cloud radiative cooling trend coming from the dominance of the high latitude negative SWCRE trends. The CERES cloud radiative warming trend doubles in magnitude to 0.24 W/m2/decade when the period is extended from 2016 to 2022, implying a strong cloud radiative heating in the past 6 years coming from the low latitude zone. Climate change; Cloud feedbacks; Clouds; Radiation
Uribe, Alejandro; Bender, Frida; Mauritsen, ThorstenUribe, A., F. Bender, T. Mauritsen, 2024: Constraining net long term climate feedback from satellite observed internal variability possible by mid 2030s. EGUsphere, 1-21. doi: 10.5194/egusphere-2024-1559. Abstract. Observing climate feedbacks to long term global warming, crucial climate regulators, is not feasible within the observational record. However, linking them to top-of-the-atmosphere flux variations in response to surface temperature fluctuations (internal variability feedbacks) is a viable approach. Here, we explore the use of this method of relating internal variability to forced climate feedbacks in models and applying the resulting relationship to observations to constrain forced climate feedbacks. Our findings reveal strong longwave and shortwave feedback relationships in models during the 14-year overlap with the CERES observational record. Yet, due to the weaker relationship between internal variability and forced climate longwave feedbacks, the net feedback relationship remains weak, even over longer periods extending beyond the CERES record. However, after about half a century, this relationship strengthens primarily due to a reinforcement of the relationship between internal variability and forced climate shortwave feedbacks. We therefore explore merging the satellite records with reanalysis to establish an extended data record. The resulting constraint suggests a stronger negative forced climate net feedback than the model´s distribution and an equilibrium climate sensitivity of about 2.5 K (2.14 K to 3.07 K, 5–95 % confidence intervals). Nevertheless, for example biogeochemical climate feedbacks, inactive on short time scales, and also not represented in most models, may lead to climate sensitivity being underestimated by this method. Also, continuous satellite observations until at least the mid-2030s are necessary for using purely observed estimate of the net internal variability feedback in constraining net forced climate feedback and, consequently, climate sensitivity.
Urraca, Ruben; Lanconelli, Christian; Gobron, NadineUrraca, R., C. Lanconelli, N. Gobron, 2024: Impact of the Spatio-Temporal Mismatch Between Satellite and In Situ Measurements on Validations of Surface Solar Radiation. Journal of Geophysical Research: Atmospheres, 129(10), e2024JD041007. doi: 10.1029/2024JD041007. Satellite and in situ sensors do not observe exactly the same measurand. This introduces a mismatch between both types of measurements in the spatial or temporal. The mismatch differences can be the dominant component in their comparison, so they have to be removed for an adequate validation of satellite products. With this aim, we propose a methodology to characterize the mismatch between satellite and in situ measurements of surface solar radiation, evaluating the impact of the mismatch on validations. The Surface Solar Radiation Data Set—Heliosat (SARAH-2) and the Baseline Surface Radiation Network are used to characterize the spatial and temporal mismatch, respectively. The mismatch differences in both domains are driven by cloud variability. At least 5 years are needed to characterize the mismatch, which is not constant throughout the year due to seasonal and diurnal cloud cover patterns. Increasing the mismatch can artificially improve the validation metrics under some circumstances, but the mismatch must be always minimized for a correct product assessment. Finally, we test two types of up-scaling methods based on SARAH-2 in the validation of degree-scale products. The fully data-driven correction removes all the mismatch effects (systematic and random) but fully propagates SARAH-2 uncertainty to the corrections. The model-based correction only removes the systematic mismatch difference, but it can correct measurements not covered by the high-resolution data set and depends less SARAH-2 uncertainty. remote sensing; satellite product; solar irradiance; spatial representativeness; validation
Vargas Zeppetello, Lucas R.; Trevino, Aleyda M.; Huybers, PeterVargas Zeppetello, L. R., A. M. Trevino, P. Huybers, 2024: Disentangling contributions to past and future trends in US surface soil moisture. Nature Water, 1-12. doi: 10.1038/s44221-024-00193-x. Climate model simulations and various aridity indices generally indicate that summertime surface soil moisture will decrease in the continental USA as a consequence of anthropogenic climate change. However, soil moisture observations from ground probes and satellites from 2011 to 2020 indicate positive summertime trends across 57% of the continental USA. To evaluate the mechanisms driving these trends, we have developed a two-layer land surface model that predicts surface temperature and soil moisture on the basis of observed variations in precipitation, solar radiation, vapour pressure and snowmelt. Of these four model forcings, we found that internal precipitation variability explains the largest fraction of the observed soil moisture trends from 2011 to 2020. Surface air warming and the response of plants to increasing atmospheric CO2 also influence the soil moisture trends, but these effects are small at decadal timescales and partly compensate for one another. Looking forwards, our results indicate that internal precipitation variability will dictate decadal soil moisture trends and that centennial soil moisture trends will primarily depend on changes in precipitation that are currently highly uncertain. Hydrology; Climate sciences
Wang, Gaofeng; Wang, Tianxing; Yuan, Hongyin; Leng, Wanchun; Letu, Husi; Xian, YuyangWang, G., T. Wang, H. Yuan, W. Leng, H. Letu, Y. Xian, 2024: Surface Shortwave Net Radiation Estimation From Space: Emphasizing the Effects of Aerosol, Solar Zenith Angles, and DEM. IEEE Transactions on Geoscience and Remote Sensing, 62, 1-21. doi: 10.1109/TGRS.2024.3350027. Shortwave net radiation (SWNR) plays an important role in the surface radiation balance and serves as the primary driving force for the exchange of surface and atmospheric materials. Although numerous algorithms exist for estimating SWNR, most of them tend to ignore the influence of aerosols and digital elevation model (DEM) on SWNR. Specifically, the impact of different aerosol types on SWNR can vary significantly, and the SWNR also exhibits considerable variations at different altitudes. It is true that many algorithms demonstrate higher accuracy in low-altitude regions with less polluted rural aerosol (nonabsorbent aerosol) areas. However, their accuracy tends to decrease when applied to high-altitude areas and heavily polluted urban aerosol (absorbent aerosol) regions. In this study, an improved all-sky parameterized algorithm is proposed to estimate SWNR by fully considering solar zenith angle (SZA), DEM, and different aerosol types, and rural and urban aerosol types are distinguished by a random forest (RF) method. The new algorithm is verified versus surface radiation budget network (SURFRAD) and baseline surface radiation network (BSRN) observations and compared with the traditional algorithms (Tang-2006 and Li-1993) and Clouds and the Earth’s Radiant Energy System (CERES) products. The results reveal that the new algorithm exhibits excellent accuracy at both instantaneous and hourly scales. For rural and urban aerosol types under all-sky conditions, the bias and root mean square error (RMSE) of the new algorithm are both less than 3.5 and 106.5 W/m on the instantaneous scale and less than 12 and 77 W/ \textm^2 on hourly scale, respectively. However, the existing algorithms show a significant overestimation (bias > 50 W/ \textm^2 ) for the urban aerosol type under various atmospheres conditions. For the CERES single scanner footprint (SSF) (instantaneous) and CERES SYNergy (CERES SYN, 1-hourly) products, the overestimation phenomenon is also detected under urban aerosol type, with bias greater than 40 and 15 W/ \textm^2 , respectively. Compared with the existing algorithms, the new algorithm demonstrates superior applicability under larger SZA conditions. When the SZA exceeds 70°, the rate of estimated effective value can be increased by up to 14%. In addition, the new algorithm can effectively solve the problem of underestimation in high-altitude areas, which frequently occurs in most existing algorithms (bias < -16 W/ \textm^2 ). The improved accuracy and applicability of the new algorithm, along with its strategy of distinguishing aerosol types, can provide valuable insights for the SWNR estimation from space. Satellites; Atmospheric modeling; Clouds; Spatial resolution; Remote sensing; aerosol optical depth (AOD); Aerosol; Aerosols; top-of-atmosphere (TOA) albedo; digital elevation mode; Geospatial analysis; perceptible water content (PWC); random forest (RF); shortwave net radiation (SWNR); solar zenith angle (SZA)
Wang, Hai; Zheng, Xiao-Tong; Cai, Wenju; Han, Zi-Wen; Xie, Shang-Ping; Kang, Sarah M.; Geng, Yu-Fan; Liu, Fukai; Wang, Chuan-Yang; Wu, Yue; Xiang, Baoqiang; Zhou, LeiWang, H., X. Zheng, W. Cai, Z. Han, S. Xie, S. M. Kang, Y. Geng, F. Liu, C. Wang, Y. Wu, B. Xiang, L. Zhou, 2024: Atmosphere teleconnections from abatement of China aerosol emissions exacerbate Northeast Pacific warm blob events. Proceedings of the National Academy of Sciences, 121(21), e2313797121. doi: 10.1073/pnas.2313797121. During 2010 to 2020, Northeast Pacific (NEP) sea surface temperature (SST) experienced the warmest decade ever recorded, manifested in several extreme marine heatwaves, referred to as “warm blob” events, which severely affect marine ecosystems and extreme weather along the west coast of North America. While year-to-year internal climate variability has been suggested as a cause of individual events, the causes of the continuous dramatic NEP SST warming remain elusive. Here, we show that other than the greenhouse gas (GHG) forcing, rapid aerosol abatement in China over the period likely plays an important role. Anomalous tropospheric warming induced by declining aerosols in China generated atmospheric teleconnections from East Asia to the NEP, featuring an intensified and southward-shifted Aleutian Low. The associated atmospheric circulation anomaly weakens the climatological westerlies in the NEP and warms the SST there by suppressing the evaporative cooling. The aerosol-induced mean warming of the NEP SST, along with internal climate variability and the GHG-induced warming, made the warm blob events more frequent and intense during 2010 to 2020. As anthropogenic aerosol emissions continue to decrease, there is likely to be an increase in NEP warm blob events, disproportionately large beyond the direct radiative effects.
Wang, Jilong; Yu, Guirui; Han, Lang; Yao, Yuan; Sun, Mingyu; Yan, ZhifengWang, J., G. Yu, L. Han, Y. Yao, M. Sun, Z. Yan, 2024: Ecosystem carbon exchange across China's coastal wetlands: Spatial patterns, mechanisms, and magnitudes. Agricultural and Forest Meteorology, 345, 109859. doi: 10.1016/j.agrformet.2023.109859. Coastal wetlands are of great importance for global carbon cycle and climate mitigation because of their strong carbon uptake capacity. However, the national-scale ecosystem carbon exchange dynamics in coastal wetlands, including magnitudes, spatial patterns, and controlling mechanisms, remains poorly understood. In this study, we utilized eddy covariance measurements from China's coastal wetlands to quantify carbon fluxes, assess their spatial patterns, and explore the controlling mechanisms. Integrating climate, vegetation, and soil factors, we constructed a cascaded relationship network to reveal the potential controlling mechanisms of spatial variations in carbon fluxes. The results revealed that gross primary production (GPP) and ecosystem respiration (ER) were 1405 ± 656 (mean ± sd) gC m−2 yr−1and 893 ± 465, respectively. Net ecosystem production (NEP) in coastal wetlands (567 ± 348 gC m−2 yr−1) exceeded China's terrestrial and marine ecosystems by 2–8 times, highlighting their significant carbon sink capacity. The carbon sink capacity in mangroves was significantly higher than salt marsh, exhibiting a twofold difference in NEP. Spatially, carbon fluxes displayed negative correlations with latitude, indicating the influence of climate features. Although tropical climate zone exhibited significantly higher carbon fluxes than temperate zone, no differences were observed between subtropics zone with others due to the distribution of mixed plants and largest area. The structural equation model (SEM) showed that the climate factors, including temperature, precipitation, and net radiation indirectly promoted GPP and ER through regulating the physiological process of mangrove and salt marsh, as well as soil carbon production and consumption. The cascaded relationship of climate-vegetation-soil showed in SEM explained 71–85 % of the spatial variations in GPP and ER, and ultimately accounted for 85 % of NEP. The carbon consumption efficiency (ER/GPP) in coastal vegetations was of 0.6, lower than that of global and China's terrestrial ecosystems, suggesting their strong efficiency in carbon fixation in coastal wetlands. Lastly, the scenario simulation results implied the importance of coastal vegetation restoration on enhancing blue carbon benefits. Blue carbon; Coastal wetlands; Ecosystem carbon fluxes; Spatial patterns
Wang, Jingyu; Lin, Yun; Wang, Xianfeng; Gu, Yu; Yim, Steve Hung-LamWang, J., Y. Lin, X. Wang, Y. Gu, S. H. Yim, 2024: Significant changes in cloud radiative effects over Southwestern United States during the COVID-19 flight reduction period. Science of The Total Environment, 910, 168656. doi: 10.1016/j.scitotenv.2023.168656. Aircraft-induced clouds (AICs) are one of the most visible anthropogenic atmospheric phenomena, which mimic the natural cirrus clouds and perturb global radiation budget by reducing incoming shortwave (SW) radiation and trapping outgoing longwave (LW) radiation. The COVID-19 pandemic has caused a 70 % global decline in flight numbers from mid-March to October 2020, which provided a unique opportunity to examine the climatic impact of AICs. Among various regions, Western Europe and the Contiguous United States experienced the most substantial reduction in air traffic during the COVID-19 pandemic. Interestingly, only the Southwestern United States demonstrated a significant decrease in cirrus clouds, leading to notable changes in shortwave (SW) and longwave (LW) cloud radiative effects. Such changes were likely due to the reduction in AICs. However, further investigations indicated that this region also experienced abnormal high pressure and low relative humidity in the middle and upper atmosphere, resulting in unusual subsidence and dryness that prohibit the formation and maintenance of cirrus cloud. While it remains challenging to quantify the exact climatic impact of reduced AICs, the remarkable anomalies documented in this study provide valuable observational benchmark for future modelling studies of the climatic impact AICs. COVID-19; Cloud radiative effect; Aircraft-induced clouds; Contrail; Flight reduction; Southwestern US
Wang, Meihua; Su, Jing; Han, Xinyi; Deng, Xingzhu; Peng, Nan; Liu, LeiWang, M., J. Su, X. Han, X. Deng, N. Peng, L. Liu, 2024: Changes in Daytime Cirrus Properties From the ISCCP-H Data Set and Their Impacts on the Radiation Energy Budget. Earth and Space Science, 11(9), e2023EA003352. doi: 10.1029/2023EA003352. The change in clouds during the day is critical to the Earth's energy balance and climatic evolution. However, there have been relatively few studies on cloud variations at daily timescales, owing to limitations of ground- and satellite-observations, especially for cirrus clouds. In this study, we examined the daytime cirrus variation (DCV) at the global scales and its associated effects on radiation budgets based on the International Satellite Cloud Climatology Project H data set. The changes in continental cirrus cover are more significant than that over the ocean, reaching a maximum of 17.3% in the afternoon. Over the tropical deep convection regions, cirrus cloud cover and optical depth exhibit large amplitudes during the daytime, closely linked to average properties of cirrus clouds. Using a process-based radiative transfer model, we calculated the variations in daytime cirrus cloud radiative forcing (CRF). After noon, cirrus clouds over both land and ocean generate the strongest shortwave (SW) cooling and longwave (LW) warming effects at the top of the atmosphere (TOA). At the global scale, daytime cirrus clouds cause an average net CRF of 3.6 W/m2 at the TOA. If the DCV is neglected in the model, the SW cooling and LW warming effects are overestimated by 2.5 and 1.8 W/m2 at the TOA, leading to a net radiation bias of 0.7 W/m2. The findings provide key information for targeting specific aspects of the cirrus parameterization scheme in climate models. daytime cirrus variation; ISCCP-H observations; physical properties; radiative effect
Wang, Mengjia; Ciais, Philippe; Fensholt, Rasmus; Brandt, Martin; Tao, Shengli; Li, Wei; Fan, Lei; Frappart, Frédéric; Sun, Rui; Li, Xiaojun; Liu, Xiangzhuo; Wang, Huan; Cui, Tianxiang; Xing, Zanpin; Zhao, Zhe; Wigneron, Jean-PierreWang, M., P. Ciais, R. Fensholt, M. Brandt, S. Tao, W. Li, L. Fan, F. Frappart, R. Sun, X. Li, X. Liu, H. Wang, T. Cui, Z. Xing, Z. Zhao, J. Wigneron, 2024: Satellite observed aboveground carbon dynamics in Africa during 2003–2021. Remote Sensing of Environment, 301, 113927. doi: 10.1016/j.rse.2023.113927. Vegetation dynamics in the African continent play an important role in the global terrestrial carbon cycle. Above-ground biomass carbon (AGC) stocks in Africa are sensitive to drought, fires and anthropogenic disturbances, and can be increased from forest restoration and tree plantation. However, there are large uncertainties in estimating changes that have occurred in AGC stocks in Africa over the past decades. Here, we used a microwave remote sensing-based vegetation index named Vegetation Optical Depth produced from X-band observations by INRAE Bordeaux (IB X-VOD) to describe the AGC dynamics in Africa covering recent decades. From 2003 to 2021, African AGC showed a net increase at a rate of +0.06 [+0.04, +0.07] PgC·yr−1 (the range represents the minimum and maximum AGC changes estimated by four calibrations), resulting from a large carbon gain of +0.55 [+0.46, +0.60] PgC·yr−1 during the first decade of the twenty-first century (period 1: 2003–2010) and a much weaker increase of +0.05 [+0.04, +0.07] PgC·yr−1 over the recent decade (period 2: 2013–2021). AGC gains were mainly found in non-forest woody areas, which contributed the most to the AGC changes during 2003–2021. Rainforests showed a minor AGC loss of −0.02 [−0.03, −0.02] PgC·yr−1, which emphasizes the need for forest conservation in Africa. Relationships between the AGC changes and potential forcing climate or anthropogenic variables suggested that human-induced deforestation and water stress (especially the vapor pressure deficit (VPD)) are the most important variables explaining the spatial and temporal AGC variations, respectively. For areas of rainforests, we identified a strong relationship between AGC and VPD (negative), soil moisture (positive) and radiation (positive). For areas of sparse vegetation (mainly located in drylands), AGC changes are largely dominated by changes in the soil water conditions. This study presents a new dataset for monitoring AGC dynamics at a continental scale over recent decades being independent of optical observations, quantifying the impacts of anthropogenic pressure and water stress on aboveground biomass carbon changes. Aboveground carbon dynamics; African continent; Vegetation optical depth
Wang, Xiaocong; Miao, Hao; Feng, Juan; Liu, YiminWang, X., H. Miao, J. Feng, Y. Liu, 2024: Comparison of Short-Term Cloud Feedbacks at Top of the Atmosphere and the Surface in Observations and AMIP6 Models. Journal of Geophysical Research: Atmospheres, 129(2), e2023JD039936. doi: 10.1029/2023JD039936. We compared short-term cloud feedback, defined at the top of the atmosphere (TOA), the atmospheric column (ATM), and the surface (SFC), between observations and models participating in Atmospheric Model Intercomparison Project Phase 6 (AMIP6) for the period 2000–2014. The globally averaged net cloud feedbacks observed at TOA, ATM, and SFC are −0.06 ± 0.63, −0.17 ± 0.70, and 0.11 ± 0.81 W m−2 K−1, respectively. While most models produced TOA cloud feedbacks that agreed with the observations within uncertainty ranges, the intermodel spread at SFC and within ATM was relatively larger. This demonstrates that models are diverse in how their TOA feedback is distributed between ATM and SFC. Because short-term cloud feedback is mainly driven by El Niño–Southern Oscillation (ENSO), the global-mean cloud feedback was further decomposed into components from the ENSO and non-ENSO regions. Results show that cloud feedback in these two regions tends to be inversely related. Compared to observations, almost all models overestimated the longwave cloud feedback in the ENSO region due to the overestimation of cloud amount changes for high-topped clouds. For these models, it is the offset between deviations in ENSO and non-ENSO regions that leads to the overall agreement of global mean with observations. Sensitivity tests show that the main conclusions still hold when alternative kernels are used in estimating cloud feedback. cloud feedback; climate sensitivity; hydrological sensitivity; cloud radiative kernel; El Niño-Southern Oscillation (ENSO)
Weaver, Clark; Wu, Dong L.; Bhartia, P. K.; Labow, Gordon; Haffner, David P.; Borgia, Lauren; McBride, Laura; Salawitch, RossWeaver, C., D. L. Wu, P. K. Bhartia, G. Labow, D. P. Haffner, L. Borgia, L. McBride, R. Salawitch, 2024: Comparison of Proxy-Shortwave Cloud Albedo from SBUV Observations with CMIP6 Models. doi: 10.1175/JCLI-D-23-0170.1. We construct a long-term record of top of atmosphere (TOA) shortwave (SW) albedo of clouds and aerosols from 340-nm radiances observed by NASA and NOAA satellite instruments from 1980 to 2013. We compare our SW cloud+aerosol albedo with simulated cloud albedo from both AMIP and historical CMIP6 simulations from 47 climate models. While most historical runs did not simulate our observed spatial pattern of the trends in albedo over the Pacific Ocean, four models qualitatively simulate our observed patterns. Those historical models and the AMIP models collectively estimate an equilibrium climate sensitivity (ECS) of ∼3.5°C, with an uncertainty from 2.7° to 5.1°C. Our ECS estimates are sensitive to the instrument calibration, which drives the wide range in ECS uncertainty. We use instrument calibrations that assume a neutral change in reflectivity over the Antarctic ice sheet. Our observations show increasing cloudiness over the eastern equatorial Pacific and off the coast of Peru as well as neutral cloud trends off the coast of Namibia and California. To produce our SW cloud+aerosol albedo, we first retrieve a black-sky cloud albedo (BCA) and empirically correct the sampling bias from diurnal variations. Then, we estimate the broadband proxy albedo using multiple nonlinear regression along with several years of CERES cloud albedo to obtain the regression coefficients. We validate our product against CERES data from the years not used in the regression. Zonal mean trends of our SW cloud+aerosol albedo show reasonable agreement with CERES as well as the Pathfinder Atmospheres–Extended (PATMOS-x) observational dataset. Significance Statement Equilibrium climate sensitivity is a measure of the rise in global temperature over hundreds of years after a doubling of atmospheric CO2 concentration. Current state-of-the-art climate models forecast a wide range of equilibrium climate sensitivities (1.5°–6°C), due mainly to how clouds, aerosols, and sea surface temperatures are simulated within these models. Using data from NASA and NOAA satellite instruments from 1980 to 2013, we first construct a dataset that describes how much sunlight has been reflected by clouds over the 34 years and then we compare this data record to output from 47 climate models. Based on these comparisons, we conclude the best estimate of equilibrium climate sensitivity is about 3.5°C, with an uncertainty range of 2.7°–5.1°C. Climate sensitivity; Cloud radiative effects; Cloud retrieval; Satellite observations
Wen, Qi; Liu, Kang; Li, Yan; Li, Xu; Song, WenjunWen, Q., K. Liu, Y. Li, X. Li, W. Song, 2024: Climatic characteristics and meteorology-sensitivity of surface solar radiation in reanalysis products compared to observations and satellite data over China. Atmospheric Environment, 334, 120713. doi: 10.1016/j.atmosenv.2024.120713. Due to the significant role of the surface solar radiation (SSR) in climate, hydrological, and biogeochemical cycles, this study evaluates the climatology, annual cycle, and interannual variability and meteorological sensitivity (total cloud cover (TCC), aerosol optical depth (AOD), and precipitable water (PW)) of six reanalysis SSR datasets (GLDAS, ERA5, NCEP1, NCEP2, JRA55, and MERRA2) using a satellite dataset (CERES SYN), and 130 radiation stations in China during 2001–2020. The results show that the climatology (R = 0.88–0.93) and annual cycle (R = 0.92–0.98) of the SSR datasets exhibit better spatial characteristics in these products compared to interannual variability (EOF1: R = 0.03–0.88; EOF2: R = 0.27–0.83). The GLDAS has relatively small estimation SSR error in the climatology but is limited to reproduce interannual variability (EOF1: R = 0.08). As the concentration of meteorological elements increases, the sensitivity of most SSRs errors to TCC increases, while the trend of sensitivity to AOD and PW decreases due to the mitigating effect of the corresponding tendency of TCC error reduction. The importance of PW for estimating SSRs increased significantly in high altitude, ranging from 29.5 to 53%. Overall, ERA5 is the most consistent in quality of the three time-scales and high-meteorological variability.
Wu, Wan; Liu, Xu; Yang, Qiguang; Currey, Jon Chris; Bartle, Aron D.; Thurston, Adam; Smith, Natividad M.; Shea, Yolanda L.; Bhatt, RajendraWu, W., X. Liu, Q. Yang, J. C. Currey, A. D. Bartle, A. Thurston, N. M. Smith, Y. L. Shea, R. Bhatt, 2024: The Angular Correction Algorithm for the Intercalibration of Satellite Instruments Using CLARREO Pathfinder as a Reference. IEEE Transactions on Geoscience and Remote Sensing, 62, 1-11. doi: 10.1109/TGRS.2024.3359972. The Climate Absolute Radiance and Refractivity (CLARREO) Pathfinder (CPF) mission will take Système Internationale (SI)-traceable spectral reflectance measurements of Earth at an unprecedented accuracy of 0.3% ( k = 1). CPF will also take measurements to support intercalibration of other satellite-based sensors. To achieve the desired intercalibration methodology uncertainty of 0.3% ( k = 1), the CPF intercalibration measurements need to closely match those from target sensors in time, space, angles, and wavelength. This article introduces an innovative angular correction method to significantly reduce errors due to angular mismatches between CPF and target sensor measurements. The method leverages the spectral correlations among the reflected solar (RS) radiances from the same surface target at two adjacent angles. Our studies have shown that the spectral radiance or reflectance difference measured at angles slightly deviating from the CPF observation angles can be accurately predicted based on the hyperspectral CPF measurements. The method will serve as part of the operational algorithms to support the core mission goal of conducting intercalibration analysis with measurements from the shortwave channel of the Clouds and the Earth’s Radiance Energy System (CERES) and the reflective solar bands of the Visible Infrared Imaging Radiometer Suite (VIIRS); however, it can also be extended for other reference-target intercalibration applications. Calibration; Sensors; Databases; Training; intercalibration; Wavelength measurement; Uncertainty; Angular correction; Climate Absolute Radiance and Refractivity (CLARREO) Pathfinder (CPF); climate benchmarking; Geometry; Système Internationale (SI)-traceable
Wu, Yuqing; Gao, Jing; Zhao, AibinWu, Y., J. Gao, A. Zhao, 2024: Cloud properties and dynamics over the Tibetan Plateau – A review. Earth-Science Reviews, 248, 104633. doi: 10.1016/j.earscirev.2023.104633. Cloud properties over the Tibetan Plateau (TP) and their underlying dynamics play a crucial role in the energy balance and regional water cycle of the climate system. In this review, we assess the progress in observational methods and model simulations of cloud macro- and micro-physical properties over the TP since the 1960s. We summarize the spatiotemporal patterns of cloud distribution and the main drivers, discussing the difficulties posed by cloud dynamics and their feedback into climate change on the TP. In short, we found that while the TP is warming and wetting, total cloud cover has decreased over the TP from 1960 to 2021 and from the southeast to the northwest, which typically exhibits the largest proportion of high cloud cover (HCC) and mid-high cloud cover. Meteorological elements (such as air temperature, precipitation), topography, and atmospheric circulation are the main factors influencing cloud formation. During the warm season (May–October), the intensification and northward shift of the South–Asian High and the South Asian monsoon lead to an uneven distribution of precipitation over the TP, while the Indian monsoon promotes the formation of low cloud cover. During the cold season (November–April), the northward expansion of the Hadley circulation inhibits the formation of HCC and middle cloud cover. The amount of cloud cover also affects climatic warming on the TP by radiative forcing. We end the review with a discussion of future research challenges, and propose to focus on improving the accuracy of model parameterizations to facilitate a deeper understanding of the effects of climate change on the TP and the associated water cycle processes. Tibetan plateau; Cloud properties; Cloud dynamics; Model development; Observational methods
Xing, Yuxuan; Chen, Yang; Yan, Shirui; Cao, Xiaoyi; Zhou, Yong; Zhang, Xueying; Shi, Tenglong; Niu, Xiaoying; Wu, Dongyou; Cui, Jiecan; Zhou, Yue; Wang, Xin; Pu, WeiXing, Y., Y. Chen, S. Yan, X. Cao, Y. Zhou, X. Zhang, T. Shi, X. Niu, D. Wu, J. Cui, Y. Zhou, X. Wang, W. Pu, 2024: Dust storms from the Taklamakan Desert significantly darken snow surface on surrounding mountains. Atmospheric Chemistry and Physics, 24(9), 5199-5219. doi: 10.5194/acp-24-5199-2024. The Taklamakan Desert (TD) is a major source of mineral dust emissions into the atmosphere. These dust particles have the ability to darken the surface of snow on the surrounding high mountains after deposition, significantly impacting the regional radiation balance. However, previous field measurements have been unable to capture the effects of severe dust storms accurately, and their representation on regional scales has been inadequate. In this study, we propose a modified remote-sensing approach that combines data from the Moderate Resolution Imaging Spectroradiometer (MODIS) satellite and simulations from the Snow, Ice, and Aerosol Radiative (SNICAR) model. This approach allows us to detect and analyze the substantial snow darkening resulting from dust storm deposition. We focus on three typical dust events originating from the Taklamakan Desert and observe significant snow darkening over an area of ∼ 2160, ∼ 610, and ∼ 640 km2 in the Tien Shan, Kunlun, and Qilian mountains, respectively. Our findings reveal that the impact of dust storms extends beyond the local high mountains, reaching mountains located approximately 1000 km away from the source. Furthermore, we observe that dust storms not only darken the snowpack during the spring but also in the summer and autumn seasons, leading to increased absorption of solar radiation. Specifically, the snow albedo reduction (radiative forcing) triggered by severe dust deposition is up to 0.028–0.079 (11–31.5 W m−2), 0.088–0.136 (31–49 W m−2), and 0.092–0.153 (22–38 W m−2) across the Tien Shan, Kunlun, and Qilian mountains, respectively. This further contributes to the aging of the snow, as evidenced by the growth of snow grain size. Comparatively, the impact of persistent but relatively slow dust deposition over several months during non-event periods is significantly lower than that of individual dust events. This highlights the necessity of giving more attention to the influence of extreme events on the regional radiation balance. This study provides a deeper understanding of how a single dust event can affect the extensive snowpack and demonstrates the potential of employing satellite remote sensing to monitor large-scale snow darkening.
Xu, Ri; Zhao, Jun; Bao, Shanhu; Shang, Huazhe; Bao, Fangling; Tana, Gegen; Wei, LesiXu, R., J. Zhao, S. Bao, H. Shang, F. Bao, G. Tana, L. Wei, 2024: Estimation of Top-of-Atmosphere Longwave Cloud Radiative Forcing Using FengYun-4A Geostationary Satellite Data. Remote Sensing, 16(8), 1415. doi: 10.3390/rs16081415. The distribution and variation of top-of-atmosphere longwave cloud radiative forcing (LCRFTOA) has drawn a significant amount of attention due to its importance in understanding the energy budget. Advancements in sensor and data processing technology, as well as a new generation of geostationary satellites, such as the FengYun-4A (FY-4A), allow for high spatiotemporal resolutions that are crucial for real-time radiation monitoring. Nevertheless, there is a distinct lack of official top-of-atmosphere outgoing longwave radiation products under clear-sky conditions (OLRclear). Consequently, this study addresses the challenge of constructing LCRFTOA data with high spatiotemporal resolution over the full disk region of FY-4A. After simulating the influence of atmospheric parameters on OLRclear based on the SBDART radiation transfer model (RTM), we developed a model for estimating OLRclear using infrared channels from the advanced geosynchronous radiation imager (AGRI) onboard the FY-4A satellite. The OLRclear results showed an RMSE of 5.05 W/m2 and MBE of 1.59 W/m2 compared to ERA5. The corresponding RMSE and MBE value compared to CERES was 6.52 W/m2 and 2.39 W/m2. Additionally, the calculated LCRFTOA results were validated against instantaneous, daily average, and monthly average ERA5 and CERES LCRFTOA products, supporting the validity of the algorithm proposed in this paper. Finally, the changes in LCRFTOA due to varied cloud heights (high, medium, and low cloud) were analyzed. This study provides the basis for comprehensive studies on the characteristics of top-of atmosphere radiation. The results suggest that high-height clouds exert a greater degree of radiative forcing more frequently, while low-height clouds are more frequently found in the lower forcing range. outgoing longwave radiation; cloud radiative forcing; satellite remote sensing; top-of-atmosphere; clear-sky; FengYun-4A
Xu, Xiaoqi; Heng, Zhiwei; Li, Yueqing; Wang, Shunjiu; Li, Jian; Wang, Yuan; Chen, Jinghua; Zhang, Peiwen; Lu, ChunsongXu, X., Z. Heng, Y. Li, S. Wang, J. Li, Y. Wang, J. Chen, P. Zhang, C. Lu, 2024: Improvement of cloud microphysical parameterization and its advantages in simulating precipitation along the Sichuan-Xizang Railway. Science China Earth Sciences, 67(3), 856-873. doi: 10.1007/s11430-023-1247-2. The Sichuan-Xizang Railway is an important part of the railway network in China, and geological disasters, such as mountain floods and landslides, frequently occur in this region. Precipitation is an important cause of these disasters; therefore, accurate simulation of the precipitation in this region is highly important. In this study, the descriptions for uncertain processes in the cloud microphysics scheme are improved; these processes include cloud droplet activation, cloud-rain autoconversion, rain accretion by cloud droplets, and the entrainment-mixing process. In the default scheme, the cloud water content of different sizes corresponds to the same cloud droplet concentration, which is inconsistent with the actual content; this results in excessive cloud droplet size, unreasonable related conversion rates of microphysical process (such as cloud-rain autoconversion), and an overestimation of precipitation. Our new scheme overcomes the problem of excessive cloud droplet size. The processes of cloudrain autoconversion and rain accretion by cloud droplets are similar to the stochastic collection equation, and the mixing mechanism of cloud droplets is more consistent with that occurred during the actual physical process in the cloud. Based on the new and old schemes, multiple precipitation processes in the flood season of 2021 along the Sichuan-Xizang Railway are simulated, and the results are evaluated using ground observations and satellite data. Compared to the default scheme, the new scheme is more suitable for the simulation of cloud physics, reducing the simulation deviation of the liquid water path and droplet radius from 2 times to less than 1 time and significantly alleviating the overestimation of precipitation intensity and range of precipitation center. The average root-mean-square error is reduced by 22%. Our results can provide a scientific reference for improving precipitation forecasting and disaster prevention in this region. Precipitation; Cloud microphysics; Model improvement; The Sichuan-Xizang Railway
Xue, Wenhao; Zhang, Jing; Deng, Xiaoqing; Tian, YuluXue, W., J. Zhang, X. Deng, Y. Tian, 2024: Responses of vegetation photosynthetic processes to aerosol-induced direct radiative effect in China. Atmospheric Environment, 329, 120557. doi: 10.1016/j.atmosenv.2024.120557. Aerosols play an essential role in the energy cycle of land-atmosphere systems through interactions with radiation and clouds. Aerosol-induced direct radiative effect (ADRE) has a large effect on the photosynthetic processes of vegetation in terrestrial ecosystems. We used the Fu-Liou radiation transfer model integrated with the Community Land Model (CLM) to quantify ADRE and the responses of vegetation photosynthetic processes to ADRE in China from 2001 to 2014. The aerosols exhibited a positive effect on the diffuse fraction and it increased at first and decreased later. Positive impacts of ADRE on the leaf area index (LAI) of both sun (LAISUN) and shaded leaves (LAISHA) were captured in most areas of China, with increases of 0.01 and 0.09, respectively. The changes in LAI caused by ADRE were consistent with aerosol loading in northern and eastern China. In addition, due to the large decrease in total radiation caused by aerosols, ADRE reduced the photosynthetic rate of sun leaves. However, when the aerosol optical depth (AOD) ranged from 0.50 to 0.57, ADRE had positive effects on the photosynthetic rate of shaded leaves, and the AOD interval for positive impacts on the photosynthetic rate was different in each subregion of China. Mechanistic analysis found that ADRE could reduce the ribulose 1,5-bisphosphate (RuBP) carboxylase-limited rate of carboxylation and enhance the light-limited rate. When the AOD was around 0.47, the positive impacts of ADRE on the light-limited rate peaked throughout China (∼0.149 μmol m−2 s−1). China; Aerosol-induced direct radiative effect; Community land model; Fu-liou model; Leaf area index; Photosynthesis
Yamauchi, Akira; Suzuki, Kentaroh; Oikawa, Eiji; Sekiguchi, Miho; Nagao, Takashi; Ishida, HarumaYamauchi, A., K. Suzuki, E. Oikawa, M. Sekiguchi, T. Nagao, H. Ishida, 2024: Description and validation of the Japanese algorithm for radiative flux and heating rate products with all four EarthCARE instruments: Pre-launch test with A-Train. Atmospheric Measurement Techniques Discussions, 1-24. doi: 10.5194/amt-2024-78. Abstract. This study developed the Level 2 (L2) atmospheric radiation flux and heating rate product by a Japanese team for Earth Clouds, Aerosols, and Radiation Explorer (EarthCARE). This product offers vertical profiles of downward and upward longwave (LW) and shortwave (SW) radiative fluxes and their atmospheric heating rates. This paper describes the algorithm developed for generating products, including the atmospheric radiative transfer model and input datasets, and its validation against measurement data of radiative fluxes. In the testing phase before the EarthCARE launch, we utilized A-Train data that provided input and output variables analogous to EarthCARE, so that the developed algorithm could be directly applied to EarthCARE after its launch. The results include comparisons of radiative fluxes between radiative transfer simulations and satellite/ground-based observations that quantify errors in computed radiative fluxes at the top of the atmosphere against Clouds and Earth's Radiant Energy System (CERES) observations and their dependence on cloud type with varying thermodynamic phases. For SW fluxes, the bias was 24.4 Wm-2, and the root mean square error (RMSE) was 36.3 Wm-2 relative to the CERES observations at spatial and temporal scales of 5° and 1 month, respectively. On the other hand, LW exhibits a bias of -10.7 Wm-2 and an RMSE of 14.2 Wm-2. When considering different cloud phases, the SW water cloud exhibited a bias of -11.7 Wm-2 and an RMSE of 46.2 Wm-2, while the LW showed a bias of 0.8 Wm-2 and an RMSE of 6.0 Wm-2. When ice clouds were included, the SW bias ranged from 58.7 to 81.5 Wm-2 and the RMSE from 72.8 to 91.6 Wm-2 depending on the ice-containing cloud types, while the corresponding LW bias ranged from -8.8 to -28.4 Wm-2 and the RMSE from 25.9 to 31.8 Wm-2, indicating that the primary source of error was ice-containing clouds. The comparisons were further extended to various spatiotemporal scales to investigate the scale dependency of the flux errors. The SW component of this product exhibited an RMSE of approximately 30 Wm-2 at spatial and temporal scales of 40° and 40 days, respectively, whereas the LW component did not show a significant decrease in RMSE with increasing spatiotemporal scale. Radiative transfer simulations were also compared with ground-based observations of the surface downward SW and LW radiative fluxes at selected locations. The results show that the bias and RMSE for SW are -17.6 Wm-2 and 172.0 Wm-2, respectively, which are larger than those for LW that are -5.6 Wm-2 and 19.0 Wm-2, respectively.
Yamazaki, K.; Miura, H.Yamazaki, K., H. Miura, 2024: Reproducibility of Equatorial Kelvin Waves in a Superparameterized MIROC: 1. Implementation and Verification of Blockwise-Coupled SP-MIROC. Journal of Advances in Modeling Earth Systems, 16(5), e2023MS003836. doi: 10.1029/2023MS003836. The potential scope of superparameterization (SP) was extended to higher resolutions of the global climate model (GCM) component by devising a technique called blockwise coupling. In this method, a horizontal average of multiple GCM columns, instead of one, is coupled to a cloud-resolving model (CRM) domain. This enables SP-GCMs to reduce the computational cost drastically, enabling higher-resolution GCMs to be superparameterized. A blockwise-coupled SP-GCM called SP-MIROC was implemented by coupling the climate model MIROC6 to the CRM SCALE-RM. The 4 × 4-bundled SP-MIROC successfully reproduced horizontal patterns and frequency distributions of precipitation and realistic amplitudes of equatorial Kelvin waves (EKWs), which were underestimated in the standard MIROC6. As discussed in Yamazaki and Miura (2024b, https://doi.org/10.1029/2023MS003837) of this study, the amplitude boost of EKWs was enabled by a top-heavy heating in SP-MIROC. Comparison of power spectra between the 4 × 4-bundled SP-MIROC and nonbundled SP-MIROC indicated that the effective resolution of dynamic variables was not degraded by the blockwise technique. Rather, spectra in the 4 × 4-bundled SP-MIROC were more realistic than those in the nonbundled SP-MIROC. Although the 4 × 4-bundling limits convective coupling in the smallest GCM scale, it could offer the best match of resolutions between the GCM-handled dynamics and SP-derived physics because the effective resolution of the dynamics is lower than the nominal grid spacing. superparameterization; global model
Yang, Kai; Chen, Jinghua; Wu, Xiaoqing; Yin, Yan; Zhao, Tianliang; Lu, Chunsong; Deng, Liping; Ding, HuiYang, K., J. Chen, X. Wu, Y. Yin, T. Zhao, C. Lu, L. Deng, H. Ding, 2024: Effects of the Indian summer monsoon on the cloud characteristics over the Eastern Tibetan Plateau: a simulation study. Climate Dynamics. doi: 10.1007/s00382-024-07219-w. As one of important large-scale systems in south Asia, the Indian summer monsoon (ISM) can affect the moisture budget and cloud processes over the Tibetan Plateau (TP). The influneces of ISM on cloud and precipitation of the Eastern TP (ETP) are discussed via a cloud-resolving model. The outbreak of ISM can activate the moisture transport between TP and the southern ocean in May, which reaches its annual most active period in July. The simulation results show that, compared to a normal ISM year, the moisture transport is intensified in pre-summer and is weakened in a strong ISM year, leading to more pre-summer deep clouds and rainfall. However, a weak ISM year exhibits weak pre-summer moisture transport and active summer moisture transport, resulting in few pre-summer deep clouds and rainfall. The summer moderate cloud cells are reduced in the strong ISM year while are promoted in the weak ISM year, taking responsibility for the summer precipitation variations. The ETP daily maximum precipitation appears at around 21:00 LST and increases after mid-April, reaches its maximum in summer. The model also suggests that the ETP warm season precipitation variation in the strong ISM year is closely related to deep convective cloud (DCC) properties (e.g. frequency and cloud water content). However, deep clouds (cloud depth > 4.0 km) rather than DCC contribute more to the precipitation diurnal variations during June and July in the weak ISM year. Cloud and precipitation; Indian summer monsoon; The Tibetan Plateau
Yarger, Drew; Wagman, Benjamin Moore; Chowdhary, Kenny; Shand, LyndsayYarger, D., B. M. Wagman, K. Chowdhary, L. Shand, 2024: Autocalibration of the E3SM Version 2 Atmosphere Model Using a PCA-Based Surrogate for Spatial Fields. Journal of Advances in Modeling Earth Systems, 16(4), e2023MS003961. doi: 10.1029/2023MS003961. Global Climate Model tuning (calibration) is a tedious and time-consuming process, with high-dimensional input and output fields. Experts typically tune by iteratively running climate simulations with hand-picked values of tuning parameters. Many, in both the statistical and climate literature, have proposed alternative calibration methods, but most are impractical or difficult to implement. We present a practical, robust, and rigorous calibration approach on the atmosphere-only model of the Department of Energy's Energy Exascale Earth System Model (E3SM) version 2. Our approach can be summarized into two main parts: (a) the training of a surrogate that predicts E3SM output in a fraction of the time compared to running E3SM, and (b) gradient-based parameter optimization. To train the surrogate, we generate a set of designed ensemble runs that span our input parameter space and use polynomial chaos expansions on a reduced output space to fit the E3SM output. We use this surrogate in an optimization scheme to identify values of the input parameters for which our model best matches gridded spatial fields of climate observations. To validate our choice of parameters, we run E3SMv2 with the optimal parameter values and compare prediction results to expertly-tuned simulations across 45 different output fields. This flexible, robust, and automated approach is straightforward to implement, and we demonstrate that the resulting model output matches present day climate observations as well or better than the corresponding output from expert tuned parameter values, while considering high-dimensional output and operating in a fraction of the time. climate; machine learning; calibration; tuning
Ye, Hanlin; Guo, Huadong; Liu, Guang; Huang, Jing; Liang, DongYe, H., H. Guo, G. Liu, J. Huang, D. Liang, 2024: Disk-Integrated Earth’s Outgoing Longwave Radiation Viewed From a Moon-Based Platform: Model Simulations. Journal of Geophysical Research: Atmospheres, 129(5), e2023JD038908. doi: 10.1029/2023JD038908. A Moon-based sensor can observe the Earth as a single point and achieve disk-integrated measurements of outgoing longwave radiation (OLR), which significantly differs from low orbital, geostationary, and Sun–Earth L1 point platforms. In this study, a scheme of determining the disk-integrated Earth’s OLR based on a Moon-based platform is proposed. The observational solid angle was theoretically derived based on the Earth’s ellipsoid model and the disk-integrated observational anisotropic factor was estimated to eliminate the effects of the Earth’s radiant anisotropy. The simulated disk-integrated Earth's OLR obtained from a Moon-based platform varies periodically, due to changes in the observation geometry and Earth's scene distribution within the observed Earth’s disk. Clouds, meteorological parameters, and the land cover distribution notably affect the disk-integrated Earth’s OLR. By analyzing the disk-integrated Earth’s OLR from a Moon-based platform, significant variabilities were investigated. Additionally, the Earth’s shape and radiant anisotropy that affecting the disk-integrated Earth’s OLR were estimated. In conclusion, a more realistic Earth’s shape, the latest version of the angular distribution model (ADM), and accurate land cover and meteorological datasets are needed when determining the disk-integrated Earth’s OLR. It is expected the unique variability captured by this platform and its ability to complement traditional satellite data make it a valuable tool for studying Earth’s radiation budget and energy cycle, and contributing to diagnostic of the climate General Circulation Models (GCM) performance. outgoing longwave radiation (OLR); disk-integrated measurement; Earth’s ellipsoid model; Earth’s radiant anisotropy; Moon-based platform
Yu, Lan; Zhang, Ming; Wang, Lunche; Li, Huaping; Li, JunliYu, L., M. Zhang, L. Wang, H. Li, J. Li, 2024: Characteristics of Aerosols and Clouds and Their Role in Earth’s Energy Budget. J. Climate, 37(3), 995-1014. doi: 10.1175/JCLI-D-23-0414.1. Abstract Clouds and aerosols provide the greatest uncertainty in estimating and interpreting Earth’s energy budget. This study not only focuses on surface brightening/dimming, but also explores Earth’s energy balance. The validation results of the CERES-SYN, ISCCP-FH, and GEWEX-SRB datasets with Baseline Surface Radiation Network (BSRN), Surface Radiation Budget Network (SURFRAD), and CMA observations show that CERES data have the highest accuracy and the longest temporal coverage. The role of clouds and aerosols in Earth’s energy budget was explained using CERES and MERRA-2 products. The results show that Earth’s energy increases at a rate of 0.63 W m−2 decade−1 in 2000–21. The global surface brightens at a rate of 0.57 W m−2 decade−1, with surface energy decreasing at a rate of 0.19 W m−2 decade−1. Brightening was found over Australia, central Asia, and southern Africa, mainly associated with cloud reduction, with aerosol emissions reductions contributing to the East Asian surface brightening. The surface brightening in South America and Southeast Asia is also due to the reduction of clouds. The increase of aerosols in South Asia is the main factor for its surface dimming, while we infer that the climatic effect from the increase of black carbon (BC) aerosols in South Asia is the inducing factor for the dimming in southern China. The surface darkening in West Asia is the result of the combined effect of clouds and aerosols, while in northern Africa it may be related to the increase of clouds caused by the decrease of dust aerosols. Surface energy increases only in Southeast Asia, South America, and Europe. Significance Statement Clouds and aerosols provide the greatest uncertainty in estimating and interpreting Earth’s changing energy budget. Moreover, the relative importance of clouds and aerosols is variable, depending on the regions and time scales of studies. This study shows that the energy inflow to the Earth system is greater than the energy outflow in 2000–21, with radiation on Earth increasing at a rate of 0.63 W m−2 decade−1 with the surface energy decreases at a rate of 0.19 W m−2 decade−1. Brightening was found over Southeast Asia, South America, Australia, and southern Africa, with the areas of surface darkening occurring mainly in Asia and northern Africa.
Yuan, Chang; Zhang, Hua; Jing, Xianwen; Zhao, Shuyun; Li, XiaohanYuan, C., H. Zhang, X. Jing, S. Zhao, X. Li, 2024: Impact of a New Radiation Scheme on Simulated Climate in the Global–Regional Integrated SysTem Model under Varying Physical Parameterization Schemes. Atmosphere, 15(4), 501. doi: 10.3390/atmos15040501. In this study, the radiation scheme BCC-RAD (Beijing Climate Center RADiative transfer model) developed for global climate models is implemented into the Global–Regional Integrated SysTem (GRIST) model as an alternative to the default RRTMG (general circulation model (GCM) version of the Rapid Radiative Transfer Model) scheme. Its impact on the simulated climate is comprehensively evaluated under different physics parametrization packages, in comparison with both the CERES (partly from ERA5 reanalysis) observations and multi-model results from CMIP6. The results indicate that under the default physics parameterization package of GRIST (PhysC), BCC-RAD improved the simulated global mean cloud cover by ~3% and the clear-sky outgoing longwave radiation by ~5.6 W/m2. Upon the inclusion of the PhysCN parameterization package, BCC-RAD exhibited further improvement in simulated cloud cover and radiative forcing (particularly longwave radiative forcing, the bias of which decreases from −9.2 W/m2 to −1.8 W/m2), leading it to be closer to observations than RRTMG. Additionally, BCC-RAD improved the simulation of atmospheric temperature and hence notably diminished the apparent overestimation of atmospheric humidity seen in RRTMG. This study demonstrates the advantages of BCC-RAD over RRTMG in certain aspects of the GRIST-simulated climate, verifying its capability for the climate-oriented configuration of GRIST. climate simulation; BCC-RAD; GRIST; radiation scheme evaluation
Yuan, Tianle; Song, Hua; Oreopoulos, Lazaros; Wood, Robert; Bian, Huisheng; Breen, Katherine; Chin, Mian; Yu, Hongbin; Barahona, Donifan; Meyer, Kerry; Platnick, StevenYuan, T., H. Song, L. Oreopoulos, R. Wood, H. Bian, K. Breen, M. Chin, H. Yu, D. Barahona, K. Meyer, S. Platnick, 2024: Abrupt reduction in shipping emission as an inadvertent geoengineering termination shock produces substantial radiative warming. Communications Earth & Environment, 5(1), 1-8. doi: 10.1038/s43247-024-01442-3. Human activities affect the Earth’s climate through modifying the composition of the atmosphere, which then creates radiative forcing that drives climate change. The warming effect of anthropogenic greenhouse gases has been partially balanced by the cooling effect of anthropogenic aerosols. In 2020, fuel regulations abruptly reduced the emission of sulfur dioxide from international shipping by about 80% and created an inadvertent geoengineering termination shock with global impact. Here we estimate the regulation leads to a radiative forcing of $$+0.2\pm 0.11$$Wm−2 averaged over the global ocean. The amount of radiative forcing could lead to a doubling (or more) of the warming rate in the 2020 s compared with the rate since 1980 with strong spatiotemporal heterogeneity. The warming effect is consistent with the recent observed strong warming in 2023 and expected to make the 2020 s anomalously warm. The forcing is equivalent in magnitude to 80% of the measured increase in planetary heat uptake since 2020. The radiative forcing also has strong hemispheric contrast, which has important implications for precipitation pattern changes. Our result suggests marine cloud brightening may be a viable geoengineering method in temporarily cooling the climate that has its unique challenges due to inherent spatiotemporal heterogeneity. Climate and Earth system modelling; Atmospheric chemistry
Yun, Misun; Kang, Jae-Joong; Jeong, Yubeen; Jo, Young-Heon; Sun, Jun; Lee, Sang-HeonYun, M., J. Kang, Y. Jeong, Y. Jo, J. Sun, S. Lee, 2024: Experimental Assessment of Ultraviolet Radiation Impact on the Primary Production of Phytoplankton in the East/Japan Sea. Journal of Marine Science and Engineering, 12(8), 1258. doi: 10.3390/jmse12081258. Solar radiation, particularly ultraviolet radiation (UVR, 280–400 nm), is known to play a significant role in driving primary production in marine ecosystems. However, our understanding of the specific effects of UVR on the primary production of natural phytoplankton communities is still limited. We utilized the 13C stable isotope to quantify primary production and conducted experiments using different types of incubation bottles (polycarbonate and quartz bottles) to compare the primary production in the absence and presence of UVR. Although we observed a weak inhibitory effect at the surface of the water column, UVR exposure resulted in an approximately 1.5-fold increase in primary production over the euphotic zone. The enhanced primary production during the study period can be attributed to the combined effect of low UVB (280–320 nm) dose and abundant nutrient conditions. Notably, our size-fractionated measurements revealed that UVR exposure led to a two-fold increase in primary production in large cells (>2 μm) compared to the exposure of solely photosynthetically active radiation (PAR). In contrast, there was no significant difference in the primary production of small cells ( phytoplankton; ultraviolet radiation; cell size; polycarbonate bottle; primary production; quartz bottle
Zhang, Bosong; Donner, Leo J.; Zhao, Ming; Tan, ZhihongZhang, B., L. J. Donner, M. Zhao, Z. Tan, 2024: Improved Precipitation Diurnal Cycle in GFDL Climate Models With Non-Equilibrium Convection. Journal of Advances in Modeling Earth Systems, 16(9), e2024MS004315. doi: 10.1029/2024MS004315. Most global climate models with convective parameterization have trouble in simulating the observed diurnal cycle of convection. Maximum precipitation usually happens too early during summertime, especially over land. Observational analyses indicate that deep convection over land cannot keep pace with rapid variations in convective available potential energy, which is largely controlled by boundary-layer forcing. In this study, a new convective closure in which shallow and deep convection interact strongly, out of equilibrium, is implemented in atmosphere-only and ocean-atmosphere coupled models. The diurnal cycles of convection in both simulations are significantly improved with small changes to their mean states. The new closure shifts maximum precipitation over land later by about three hours. Compared to satellite observations, the diurnal phase biases are reduced by half. Shallow convection to some extent equilibrates rapid changes in the boundary layer at subdiurnal time scales. Relaxed quasi-equilibrium for convective available potential energy holds in significant measure as a result. Future model improvement will focus on the remaining biases in the diurnal cycle, which may be further reduced by including stochastic entrainment and cold pools. deep convection; diurnal cycle of precipitation; shallow convection
Zhang, Chunyan; Wang, Donghai; Yao, Lebao; Wu, Zhenzhen; Ma, Qianhui; Li, Yongsheng; Wang, PeidongZhang, C., D. Wang, L. Yao, Z. Wu, Q. Ma, Y. Li, P. Wang, 2024: Contrasts of Large-Scale Moisture and Heat Budgets between Different Sea Areas of the South China Sea and the Adjacent Land. J. Appl. Meteor. Climatol., 63(1), 105-124. doi: 10.1175/JAMC-D-23-0084.1. Abstract This study investigates and compares large-scale moisture and heat budgets over the eastern rainy sea area around Dongsha, the western rainless sea area around Xisha, and the northern coastland of the South China Sea. Ten-year (2011–20) surface, balloon-sounding, satellite measurements, and ERA5 reanalysis are merged into the physically consistent data to study annual and vertical variations of the budgets. It shows that the surface and column-integrated heat and moisture budgets have the smallest annual evolution over the coastland. The latent heat as a key heat contributor in summer is mainly offset by total cold advection and partially offset by net radiative cooling. The horizontal moisture advection below 700 hPa presents moistening over the sea whereas drying over the coastland during rainy months, in which the vertical moisture advection presents moistening up to 250 hPa for all three subregions. The horizontal temperature advection is weak throughout the year over the sea but displays strong top warming and bottom cooling in summer and nearly the opposite in winter over the coastland. The diabatic cooling with a peak at ∼700 hPa in winter is largely due to the enhanced radiative cooling and latent cooling. While the diabatic heating with a peak at ∼500 hPa in summer is largely due to the enhanced latent heating. The earliest atmospheric heating and moistening occur in spring over the coastland, inducing the earliest precipitation increase. The enhanced heating and moistening over Xisha have a 1-month lag relative to Dongsha, resulting in lagging precipitation.
Zhang, Chunyan; Wang, Donghai; Zhang, Kaifeng; He, Wanwen; Zheng, Yanping; Xu, YanZhang, C., D. Wang, K. Zhang, W. He, Y. Zheng, Y. Xu, 2024: Differences in Precipitation and Related Wind Dynamics and Moisture and Heat Features in Separate Areas of the South China Sea before and after Summer Monsoon Onset. Advances in Atmospheric Sciences, 41(8), 1643-1660. doi: 10.1007/s00376-023-3141-3. Using surface and balloon-sounding measurements, satellite retrievals, and ERA5 reanalysis during 2011–20, this study compares the precipitation and related wind dynamics, moisture and heat features in different areas of the South China Sea (SCS) before and after SCS summer monsoon onset (SCSSMO). The rainy sea around Dongsha (hereafter simply referred to as Dongsha) near the north coast, and the rainless sea around Xisha (hereafter simply referred to as Xisha) in the western SCS, are selected as two typical research subregions. It is found that Dongsha, rather than Xisha, has an earlier and greater increase in precipitation after SCSSMO under the combined effect of strong low-level southwesterly winds, coastal terrain blocking and lifting, and northern cold air. When the 950-hPa southwesterly winds enhance and advance northward, accompanied by strengthened moisture flux, there is a strong convergence of wind and moisture in Dongsha due to a sudden deceleration and rear-end collision of wind by coastal terrain blocking. Moist and warm advection over Dongsha enhances early and deepens up to 200 hPa in association with the strengthened upward motion after SCSSMO, thereby providing ample moisture and heat to form strong precipitation. However, when the 950-hPa southwesterly winds weaken and retreat southward, Xisha is located in a wind-break area where strong convergence and upward motion centers move in. The vertical moistening and heating by advection in Xisha enhance later and appear far weaker compared to that in Dongsha, consistent with later and weaker precipitation. Dongsha; heat; moisture; precipitation; South China Sea summer monsoon onset; wind dynamics; Xisha; 东沙; 南海夏季风爆发; 水汽; 热量; 西沙; 降水; 风动
Zhang, Chunyan; Wang, Donghai; Zhou, Qinqiang; Yang, Yuhong; Hou, Ling; Yang, KunlinZhang, C., D. Wang, Q. Zhou, Y. Yang, L. Hou, K. Yang, 2024: Diabatic heating structures varying with convective and rainfall intensities in different areas of the pan-South China Sea region. Atmospheric Research, 306, 107474. doi: 10.1016/j.atmosres.2024.107474. This study investigates and compares diabatic heating structures related to vertical velocity, cloud types, and rainfall intensities in the northeast rainy sea subregion named Dongsha, the west rainless sea subregion named Xisha, and the north rainy land subregion named Coastland in the pan-SCS region. The diabatic heating rate of >2 K hr−1 over Dongsha and Coastland has a higher frequency and a deeper distribution than over Xisha where it requires stronger upward motion to achieve the same heating rate, indicating more frequent and deeper convection over the north coastal sea and land areas than the west sea area of the pan-SCS region. The deep convective Q1 profiles show a stronger peak at ∼500 hPa and a weaker peak at ∼700 hPa over two sea subregions while a single peak at ∼500 hPa over Coastland. The nimbostratus Q1 profile has a weakened heating peak at 350–550 hPa over Dongsha, 500–600 hPa over Xisha, and 425–575 hPa over Coastland. The shallow cumulus Q1 profile of Dongsha shows weak heating in the mid-to-lower troposphere while that of Xisha and Coastland has hardly heating. Latent heating and vertical turbulence significantly affect the diabatic heating structure related to deep convective clouds and nimbostratus but hardly affect that related to shallow cumulus. Despite cloud types, Dongsha has the strongest diabatic heating among the three subregions due to its geographical advantages. The no-rainfall Q1 profiles over three subregions have a similar shape with a weak cooling peak at ∼700 hPa due to boundary-layer evaporation and eddies. But the small-rainfall Q1 profiles present upper heating and lower cooling over sea subregions whereas the opposite over Coastland possibly due to stronger surface sensible heating on the land. From moderate to heavy rainfall, the Q1 profiles over three subregions are similar with a heating maximum at ∼500 hPa associated with deep convection, except for heating intensity which is much stronger over Xisha than the other two subregions. This suggests that Xisha presents stronger convection to achieve the same rainfall intensity as Dongsha and Coastland, which is closely due to a positive effect of coastal terrain blocking and uplifting on precipitation for Dongsha and Coastland whereas a negative effect of the Annam Mountains for Xisha. Cloud types; Diabatic heating; pan-SCS region; Profiles; Rainfall intensities
Zhang, Haipeng; Zheng, Youtong; Li, ZhanqingZhang, H., Y. Zheng, Z. Li, 2024: Improving Low-Cloud Fraction Prediction Through Machine Learning. Geophysical Research Letters, 51(15), e2024GL109735. doi: 10.1029/2024GL109735. In this study, we evaluated the performance of machine learning (ML) models (XGBoost) in predicting low-cloud fraction (LCF), compared to two generations of the community atmospheric model (CAM5 and CAM6) and ERA5 reanalysis data, each having a different cloud scheme. ML models show a substantial enhancement in predicting LCF regarding root mean squared errors and correlation coefficients. The good performance is consistent across the full spectrums of atmospheric stability and large-scale vertical velocity. Employing an explainable ML approach, we revealed the importance of including the amount of available moisture in ML models for representing spatiotemporal variations in LCF in the midlatitudes. Also, ML models demonstrated marked improvement in capturing the LCF variations during the stratocumulus-to-cumulus transition (SCT). This study suggests ML models' great potential to address the longstanding issues of “too few” low clouds and “too rapid” SCT in global climate models. cloud parameterization scheme; low-cloud fraction; machine learning; stratocumulus-to-cumulus transition
Zhang, Haipeng; Zheng, Youtong; Li, ZhanqingZhang, H., Y. Zheng, Z. Li, 2024: Evaluation of Stratocumulus Evolution Under Contrasting Temperature Advections in CESM2 Through a Lagrangian Framework. Geophysical Research Letters, 51(4), e2023GL106856. doi: 10.1029/2023GL106856. This study leveraged a Lagrangian framework to examine the evolution of stratocumulus clouds under cold and warm advections (CADV and WADV) in the Community Earth System Model 2 (CESM2) against observations. We found that CESM2 simulates a too rapid decline in low-cloud fraction (LCF) and cloud liquid water path (CLWP) under CADV conditions, while it better aligns closely with observed LCF under WADV conditions but overestimates the increase in CLWP. Employing an explainable machine learning approach, we found that too rapid decreases in LCF and CLWP under CADV conditions are related to overestimated drying effects induced by sea surface temperature, whereas the substantial increase in CLWP under WADV conditions is associated with the overestimated moistening effects due to free-tropospheric moisture and surface winds. Our findings suggest that overestimated drying effects of sea surface temperature on cloud properties might be one of crucial causes for the high equilibrium climate sensitivity in CESM2. equilibrium climate sensitivity; cloud simulation; explainable machine learning approach; horizontal temperature advection; stratocumulus evolution
Zhang, Haotian; Zhao, Chuanfeng; Xia, Yan; Chen, Annan; Yang, Yikun; Yang, Jie; Zhao, Xin; Chi, Yulei; Xu, Hongtao; Zhong, ShouyiZhang, H., C. Zhao, Y. Xia, A. Chen, Y. Yang, J. Yang, X. Zhao, Y. Chi, H. Xu, S. Zhong, 2024: Cloud Radiative Effects Slow Sea Ice Changes During Summer Arctic Dipole Anomaly. Geophysical Research Letters, 51(16), e2024GL111205. doi: 10.1029/2024GL111205. Over the past 30 years, the Arctic Dipole Anomaly (DA) has repeatedly led to record lows in summer sea ice extent, with cloud radiative effects (CRE) playing a crucial regulatory role. Here, we reveal the CRE variations between positive and negative DA events and elucidate the slowing impacts of CRE on sea ice thickness (SIT) changes. The DA triggers robust meridional winds and transpolar drift, markedly reducing SIT in the Beaufort Sea (BeS), Chukchi Sea (CS), and East Siberian Sea (ESS), while increasing it in the Greenland Sea (GS). CRE significantly slow SIT changes, contributing +14.4, +4.4, +16.4, and −26.7 cm to changes from June to August, against total changes of −55.9, −29.4, −39.8, and +42.8 cm in September over BeS, CS, ESS, and GS, respectively. This study underscores the key impacts of CRE on sea ice variation, emphasizing their significance in the polar climate system. Arctic dipole anomaly; cloud radiative effect; cloud variation; sea ice thickness
Zhang, Qian; Wang, Tijian; Wu, Hao; Qu, Yawei; Xie, Min; Li, Shu; Zhuang, Bingliang; Li, Mengmeng; Kilifarska, Natalya AndreevaZhang, Q., T. Wang, H. Wu, Y. Qu, M. Xie, S. Li, B. Zhuang, M. Li, N. A. Kilifarska, 2024: Radiative and Chemical Effects of Non-Homogeneous Methane on Terrestrial Carbon Fluxes in Asia. Journal of Geophysical Research: Atmospheres, 129(8), e2023JD040204. doi: 10.1029/2023JD040204. Methane (CH4) plays a crucial role in shaping terrestrial ecosystems due to its radiative effect and atmospheric photochemical reactions. In this study, we employed an enhanced regional climate-chemistry-ecosystem model (RegCM-Chem-YIBs) to comprehensively evaluate the impacts of both radiative and chemical effects of CH4 on terrestrial carbon fluxes across the East, South, and Southeast Asia (EA, SA, SEA) during the year 2010. Our findings showed that the radiative effects of CH4 yielded a positive influence on carbon fluxes. Specifically, the EA region experienced a significant increase in the gross primary production (GPP), reaching up to 0.515 Pg C Yr−1. In comparison, the SEA region exhibited a decrease in the net ecosystem exchange (NEE) of approximately −0.066 Pg C Yr−1. Further analysis revealed that alterations in radiation and vapor pressure deficit (VPD) were dominant drivers. Conversely, the chemical effects of CH4 lead to heightened regional surface ozone (O3) concentrations (2.704–3.115 ppb) and generate a negative response in carbon fluxes. Within the SEA region, GPP observed a decrease of up to −0.144 Pg C Yr−1, while NEE displayed a significant increase of 0.022 Pg C Yr−1. Taken together, the combined radiative and chemical effects of CH4 indicated a positive impact on regional carbon fluxes, with GPP increasing by 0.632 Pg C Yr−1 and NEE decreasing by −0.09 Pg C Yr−1. This holistic perspective is crucial for comprehending the intricate interactions linking climate change, atmospheric pollution, and the global carbon cycle.
Zhang, Taiping; Stackhouse, Paul W.; Macpherson, Bradley; Colleen Mikovitz, J.Zhang, T., P. W. Stackhouse, B. Macpherson, J. Colleen Mikovitz, 2024: A CERES-based dataset of hourly DNI, DHI and global tilted irradiance (GTI) on equatorward tilted surfaces: Derivation and comparison with the ground-based BSRN data. Solar Energy, 274, 112538. doi: 10.1016/j.solener.2024.112538. The NASA CERES SYN1deg(Ed4.1) satellite-based products include hourly global horizontal irradiance (GHI), diffuse horizontal irradiance (DHI) and direct horizontal irradiance (DirHI) as well as hourly solar zenith angle (SZA), and the direct normal irradiance (DNI) can thus be calculated by dividing the DirHI by cos(SZA). The spatial resolution of the dataset is 1° latitude by 1° longitude, and the time span is from March 2000 to near present (October 2023 as of this writing). While the GHI of the dataset agrees well with the ground-based Baseline Surface Radiation Network (BSRN) data, the DHI and DirHI, and thus DNI, show appreciable biases against the BSRN data. Nevertheless, the uncertainty of the DHI and DNI, as exhibited in the standard deviations of their differences from the BSRN data, are smaller than results from the DirIndex model, a global-to-beam model, applied to the CERES data, albeit the model is one of the two best out of 140 models according to a study. This means that the original CERES hourly DNI, though biased, renders the spatiotemporal variability better than does the DirIndex model. For this reason, we decided to perform a bias correction on the hourly DHI and DNI. With the corrected hourly DHI and DNI, we are able to use the isotropic model to calculate the global tilted irradiance (GTI) and the global tracker irradiance (GTrI) on an hourly basis. The BSRN DHI and DNI, on the other hand, are available on near-instantaneous time scales (1-, 2-, 3, or 5-minute intervals) and thus are more conducive to the isotropic model, and for the first time, we use the BSRN data to validate the GTI and GTrI, as opposed to GHI and DHI that have previously been used for validation purpose. For comparison and validation, we also use the monthly-mean-based LJCR method, an independent method as used by RETScreen®, which requires monthly mean GHI and DHI, to directly calculate the monthly mean DNI, GTI and, to extend the model, GTrI, and the results agree well with the BSRN data, which proves the LJCR method itself and corroborates the corrected DHI and DNI as well as the derived GTI and GTrI. The monthly mean DHI and DNI from the Whitlock Method, also monthly-mean-based, are evaluated as well, and we find that minor modification can dramatically improve the method. BSRN; POWER; CERES SYN1deg; DHI; DNI; Global tilted irradiance; GTI
Zhang, Tianyu; Letu, Husi; Dai, Tie; Shi, Chong; Lei, Yonghui; Peng, Yiran; Lin, Yanluan; Chen, Liangfu; Shi, Jiancheng; Tian, Wei; Shi, GuangyuZhang, T., H. Letu, T. Dai, C. Shi, Y. Lei, Y. Peng, Y. Lin, L. Chen, J. Shi, W. Tian, G. Shi, 2024: Estimating hourly surface shortwave radiation over northeast of the Tibetan Plateau by assimilating Himawari-8 cloud optical thickness. Geoscience Letters, 11(1), 1. doi: 10.1186/s40562-023-00312-8. To reduce the uncertainty estimation of clouds and improve the forecast of surface shortwave radiation (SSR) over the Tibetan Plateau, a new cloud assimilation system is proposed which is the first attempt to directly apply the four-dimensional local ensemble transform Kalman filter method to assimilate the cloud optical thickness (COT). The high-resolution spatial and temporal data assimilated from the next-generation geostationary satellite Himawari-8, with the high-assimilation frequency, realized an accurate estimation of the clouds and radiation forecasting. The COT and SSR were significantly improved after the assimilation by independent verification. The correlation coefficient (CORR) of the SSR was increased by 11.3%, and the root-mean-square error (RMSE) and mean bias error (MBE) were decreased by 28.5% and 58.9%, respectively. The 2-h cycle assimilation forecast results show that the overestimation of SSR has been effectively reduced using the assimilation system. These findings demonstrate the high potential of this assimilation technique in forecasting of SSR in numerical weather prediction. The ultimate goal that to improve the model forecast through the assimilation of cloud properties requires further studies to achieve.
Zhang, Wei; Chen, Yongzhe; Ji, Qinghua; Fan, Yuying; Zhang, Gong; Lu, Xi; Hu, Chengzhi; Liu, Huijuan; Qu, JiuhuiZhang, W., Y. Chen, Q. Ji, Y. Fan, G. Zhang, X. Lu, C. Hu, H. Liu, J. Qu, 2024: Assessing global drinking water potential from electricity-free solar water evaporation device. Nature Communications, 15(1), 6784. doi: 10.1038/s41467-024-51115-0. Universal and equitable access to affordable safely managed drinking water (SMDW) is a significant challenge and is highlighted by the United Nations’ Sustainable Development Goals-6.1. However, SMDW coverage by 2030 is estimated to reach only 81% of the global population. Solar water evaporation (SWE) represents one potential method to ensure decentralized water purification, but its potential for addressing the global SMDW challenge remains unclear. We use a condensation-enhanced strategy and develop a physics-guided machine learning model for assessing the global potential of SWE technology to meet SMDW demand for unserved populations without external electricity input. We find that a condensation-enhanced SWE device (1 m2) can supply enough drinking water (2.5 L day−1) to 95.8% of the population lacking SMDW. SWE can help fulfill universal SMDW coverage by 2030 with an annual cost of 10.4 billion U.S. dollars, saving 66.7% of the current investment and fulfilling the SDG-6.1 goal.
Zhang, Yanqing; Gao, Yi; Xu, Liren; Guan, Xu; Gong, Anbao; Zhang, MeigenZhang, Y., Y. Gao, L. Xu, X. Guan, A. Gong, M. Zhang, 2024: Assessment of future solar energy potential changes under the shared socio-economic pathways scenario 2–4.5 with WRF-chem: The roles of meteorology and emission. Atmospheric Environment, 318, 120232. doi: 10.1016/j.atmosenv.2023.120232. The 26th United Nations Climate Change Conference (COP26) proposes to limit global warming to WRF-Chem; Future emission reductions; Future meteorological conditions; Solar energy potential; SSP2–4.5 scenario
Zhang, Zhanjie; Wang, Yong; Zhang, Guang J.; Xing, Cheng; Xia, Wenwen; Yang, MengmiaoZhang, Z., Y. Wang, G. J. Zhang, C. Xing, W. Xia, M. Yang, 2024: Light rain exacerbates extreme humid heat. Nature Communications, 15(1), 7326. doi: 10.1038/s41467-024-51778-9. Humid heat waves pose significant risks to human health and the ecosystem. Intuitively, rainfall often alleviates extreme humid heat. However, here we show that light rain often accompanies extreme humid heat, exacerbating its frequency and intensity, especially over arid and semi-arid regions compared to no rain and moderate-to-heavy rain cases. This is because light rain does not dramatically reduce solar radiation but increases near-surface humidity through enhanced surface evaporation. The water replenishment from light rain as well as a shallower planetary boundary layer is crucial for consecutive extremes where there are commonly sporadic drizzle days amidst several rain-free days. These extremes last longer than rain-free extremes. Current global climate models (GCMs) overestimate light rain. After reducing this bias in a GCM, underestimations of humid heat waves in energy-limited regions and overestimations in water-limited regions are largely alleviated. These findings underscore the underappreciated impact of light rain on extreme humid heat. Atmospheric science; Hydrology
Zhang, Zhiding; Yue, Xu; Zhou, Hao; Zhu, Jun; Lei, Yadong; Tian, ChenguangZhang, Z., X. Yue, H. Zhou, J. Zhu, Y. Lei, C. Tian, 2024: Simulation of the Ecosystem Productivity Responses to Aerosol Diffuse Radiation Fertilization Effects over the Pan-Arctic during 2001–19. Advances in Atmospheric Sciences, 41(1), 84-96. doi: 10.1007/s00376-023-2329-x. The pan-Arctic is confronted with air pollution transported from lower latitudes. Observations have shown that aerosols help increase plant photosynthesis through the diffuse radiation fertilization effects (DRFEs). While such DRFEs have been explored at low to middle latitudes, the aerosol impacts on pan-Arctic ecosystems and the contributions by anthropogenic and natural emission sources remain less quantified. Here, we perform regional simulations at 0.2°×0.2° using a well-validated vegetation model (Yale Interactive terrestrial Biosphere, YIBs) in combination with multi-source of observations to quantify the impacts of aerosol DRFEs on the net primary productivity (NPP) in the pan-Arctic during 2001–19. Results show that aerosol DRFEs increase pan-Arctic NPP by 2.19 Pg C (12.8%) yr−1 under clear-sky conditions, in which natural and anthropogenic sources contribute to 8.9% and 3.9%, respectively. Under all-sky conditions, such DRFEs are largely dampened by cloud to only 0.26 Pg C (1.24%) yr−1, with contributions of 0.65% by natural and 0.59% by anthropogenic species. Natural aerosols cause a positive NPP trend of 0.022% yr−1 following the increased fire activities in the pan-Arctic. In contrast, anthropogenic aerosols induce a negative trend of −0.01% yr−1 due to reduced emissions from the middle latitudes. Such trends in aerosol DRFEs show a turning point in the year of 2007 with more positive NPP trends by natural aerosols but negative NPP trends by anthropogenic aerosols thereafter. Though affected by modeling uncertainties, this study suggests a likely increasing impact of aerosols on terrestrial ecosystems in the pan-Arctic under global warming. anthropogenic aerosols; diffuse radiation fertilization effects; natural aerosols; net primary productivity; pan-Arctic; 人为气溶胶; 净初级生产力; 散射辐射施肥效应; 泛北极; 自然气溶胶
Zhao, MingZhao, M., 2024: Cloud Radiative Effects Associated With Daily Weather Regimes. Geophysical Research Letters, 51(10), e2024GL109090. doi: 10.1029/2024GL109090. Using high temporal resolution satellite observations and reanalysis data, we classify daily weather into distinct regimes and quantify their associated cloud radiative effect (CRE) to better understand the roles of various weather systems in affecting Earth's top-of-atmosphere radiation budget. These regimes include non-precipitation, drizzle, wet non-storm, and storm days, which encompass atmospheric rivers (AR), tropical storms (TS), and mesoscale convection systems (MCS). We find that precipitation (wet) days account for roughly 80% (60%) of global longwave (LW) and shortwave (SW) CREs due to their large frequency and high intensity in CRE. Despite being rare globally (13%), AR, TS, and MCS days together account for 32% of global LW CRE and 27% of SW CRE due to their higher intensity in LW and SW CRE. These results enhance our understanding of how various weather systems, particularly severe storms, influence Earth's radiative balance, and will help to better constrain climate models. atmospheric rivers; cloud radiative effects; mesoscale convective systems; precipitation; tropical storms; weather regimes
Zheng, Mengzhe; Wu, Tongwen; Xin, Xiaoge; Liu, Xiangwen; Lu, Yixiong; Jie, Weihua; Xie, Chengjun; Zhou, YumengZheng, M., T. Wu, X. Xin, X. Liu, Y. Lu, W. Jie, C. Xie, Y. Zhou, 2024: Simulation of MJO with improved deep convection scheme in different resolutions of BCC-CSM2 models. Climate Dynamics, 62(3), 2161-2185. doi: 10.1007/s00382-023-07015-y. This study investigates the impacts of modifying the deep convection scheme on the ability to simulate the Madden–Julian Oscillation (MJO) in the Beijing Climate Center Climate System Model version 2 with a medium resolution (BCC-CSM2-T159) and a high resolution (BCC-CSM2-T382). On the basis of the original deep convection scheme, a modified scheme is suggested, which involves the transport processes of deep convective cloud water. The liquid cloud water that is detrained is transferred horizontally to its neighboring grids, and a portion of the cloud water that is horizontally transported is allowed to be transported downward into the lower troposphere. Both BCC-CSM2-T159 and BCC-CSM2-T382 with the modified deep convection scheme perform better than that used the original deep convection scheme in reproducing the major features of the MJO, such as its spectrum, period, intensity, eastward propagation and life cycle. Further analysis shows that those pronounced improvements in the MJO features in both BCC-CSM2-T159 and BCC-CSM2-T382 with the modified scheme are caused by transport processes of deep convective cloud water. The modified deep convection scheme enhances moisture and energy exchange from the lower troposphere to the upper troposphere around convective cloud, and promotes the convergence of moisture in the lower troposphere to the east of the MJO convection center, and then induces eastward propagation of the MJO. The comparisons between the coupled experiments and their corresponding experiments following Atmospheric Model Intercomparison Project (AMIP) simulations indicated that atmosphere–ocean interactions are also important to improve MJO simulations in the models. MJO; BCC-CSM2; Deep convection scheme; Improvement; MJO simulation
Zheng, Yueming; He, Tao; Liang, Shunlin; Ma, YichuanZheng, Y., T. He, S. Liang, Y. Ma, 2024: Deriving High Resolution Estimation of TOA Net Shortwave Radiation Over Global Land Using Data from Multiple-Geostationary Satellites. IEEE Transactions on Geoscience and Remote Sensing, 1-1. doi: 10.1109/TGRS.2024.3440329. Estimation of net shortwave radiation at the top-of-the atmosphere (Rns,TOA) at high spatial and temporal resolutions is essential for studying the Earth’s energy budget and its associated radiative forcing of natural or anthropogenic events on global or regional scales. Existing products typically use broadband sensors with coarse spatial resolution for the estimation. While narrowband sensors offer higher spatial resolution, they have a limited number of daily observations. Traditional estimation methods often necessitate atmospheric products as inputs, while inaccurate cloud and aerosol information can result in substantial estimation errors. Furthermore, geostationary satellites-based products are often developed for specific regions, with limited spatial coverage and varying accuracy due to the diverse range of satellites and algorithms used. To overcome these challenges and obtain global Rns,TOA with improved spatiotemporal resolution and accuracy, a universal approach was proposed in this study to derive hourly 3-km global Rns,TOA, which takes the advantages from radiative transfer model, machine learning algorithm, and dense observations from five geostationary satellites. Our Rns,TOA estimation shows reasonably good agreement with the Earth’s Radiant Energy System (CERES) product, with root mean square errors (RMSE) ranging from 53.43 W/m2 to 75.67 W/m2 and bias ranging from -12.78 W/m2 to -2.01 W/m2 on instantaneous scales, and the RMSE on daily scale improved by up to 6.7 W/m2 compared to those of the sinusoidal-integrated values. Our generated 3-km daily Rns,TOA exhibits highly consistency of spatial pattern with 1° CERES product at multiple temporal conditions, while providing much more spatial details. Furthermore, we find the diurnal patterns at 3km resolution differ significantly from the sinusoidal patterns at 1°, exhibiting greater variability. The difference in daytime Rns,TOA estimation between the two reaches up to 86W/m2. This significant difference reflects the unreliability of relying solely on sinusoidal pattern and the necessity of high frequency observations to estimate daily values at high spatial resolution. However, increasing the observation frequency beyond a certain point (120-min) yields only limited improvements in the accuracy of daily radiation estimates. Overall, the algorithms proposed in this study are reliable, and can be easily applied to any satellite equipped with MSG (Meteosat Second Generation)-like or more bands. This study demonstrates the feasibility of jointly using multiple geostationary satellites for, Rns,TOA estimation with high spatial and temporal resolutions. Accuracy; Atmospheric modeling; CERES; Estimation; geostationary satellite; Geostationary satellites; machine learning algorithm; Net shortwave radiation at TOA; radiative transfer model; Satellite broadcasting; Sensors; Spatial resolution
Zhong, Xiang; Dong, Xiquan; Xi, Baike; Brendecke, Jordann; Pilewskie, PeterZhong, X., X. Dong, B. Xi, J. Brendecke, P. Pilewskie, 2024: Tracing the physical signatures among the calculated global clear-sky spectral shortwave radiative flux distribution. Journal of Quantitative Spectroscopy and Radiative Transfer, 328, 109167. doi: 10.1016/j.jqsrt.2024.109167. This study utilized the high-spectral resolution radiative transfer model (MODerate resolution atmospheric TRANsmission, MODTRAN6.0.2.5) to compute global clear-sky shortwave (SW) radiative flux and compared it with NASA’s Clouds and the Earth’s Radiant Energy System (CERES) Synoptic Radiative Fluxes and Clouds (SYN1deg) product. The comparison revealed that the global distributions of clear-sky downwelling SW fluxes at the surface from the M6.0 calculations and SYN1 results are similar, with annual means of 246.51 Wm-2 and 242.42 Wm-2, respectively. Analysis further showed that most of the M6.0 calculations are slightly higher from low to mid-latitudes, particularly in the Northern Hemisphere (NH), but lower in higher latitudes compared to SYN1 results. However, these differences mostly fall within the CERES estimated uncertainty (6 Wm-2) of monthly mean clear-sky downwelling SW flux at the surface. The sensitivity of clear-sky SW/μ0 fluxes to changes in Precipitable Water Vapor (PWV), represented by the clear-sky water vapor radiative kernel, is about -0.7 Wm-2/(kgm-2) over oceans for both M6.0 and CERES SYN1 products, except for SYN1 results over the Southern Hemisphere (SH) ocean. Additionally, the zonal means of land coverage and SW/VIS/NIR albedos from M6.0 calculations indicate that VIS albedos are highest in polar regions (>60°), followed by SW and NIR albedos, while NIR albedos become highest from low to mid-latitudes ( Clear-sky shortwave flux at the surface; MODTRAN radiative transfer modeling; Water vapor radiative kernels
Ziar, HesanZiar, H., 2024: A global statistical assessment of designing silicon-based solar cells for geographical markets. Joule. doi: 10.1016/j.joule.2024.02.023. Here, we first visualize the achievable global efficiency for single-junction crystalline silicon cells and demonstrate how different regional markets have radically varied requirements for Si wafer thickness and injection level. Our findings showed that 219 g/kW of polysilicon can be conserved while producing slightly more electricity when c- Si cells are manufactured based on the global geographical market instead of standard test conditions. Then, we investigate the bifacial silicon cell and show that its optimal wafer thickness should be 1.67–2.89 times thicker than its monofacial counterpart, depending on the geographical region. Further, we study a double-junction two-terminal Si-based cell, reevaluate its theoretical limit as 42.8%, and illustrate that globally, tandem cells’ efficiency will only be slightly decreased when significantly reducing the bottom cell Si wafer thickness (−0.3%/mm). The outcomes of this study offer a blueprint to strategically design solar cells for target geographic markets, ensuring the conservation of substantial polysilicon volumes. bifacial; efficiency limit; global map; outdoor working condition; perovskite on silicon; polysilicon consumption; PV; silicon wafer thickness; single- and double-junction cells; solar photovoltaics
Akkermans, Tom; Clerbaux, NicolasAkkermans, T., N. Clerbaux, 2023: Validation of the CLARA-A3 Top-of-Atmosphere Radiative Fluxes Climate Data Record. J. Atmos. Oceanic Technol., 40(11), 1523-1539. doi: 10.1175/JTECH-D-23-0065.1. Abstract The third edition of the CM SAF Cloud, Albedo and Surface Radiation dataset from AVHRR data (CLARA-A3) contains for the first time the top-of-atmosphere products reflected solar flux (RSF) and outgoing longwave radiation (OLR), which are presented and validated using CERES, HIRS, and ERA5 reference data. The products feature an unprecedented resolution (0.25°) and time span (4 decades) and offer synergy and compatibility with other CLARA-A3 products. The RSF is relatively stable; its bias with respect to (w.r.t.) ERA5 remains mostly within ±2 W m−2. Deviations are predominantly caused by absence of either morning or afternoon satellite, mostly during the first decade. The radiative impact of the Pinatubo volcanic eruption is estimated at 3 W m−2. The OLR is stable w.r.t. ERA5 and HIRS, except during 1979–80. OLR regional uncertainty w.r.t. HIRS is quantified by the mean absolute bias (MAB) and correlates with observation density and time (satellite orbital configuration), which is optimal during 2002–16, with monthly and daily MAB of approximately 1.5 and 3.5 W m−2, respectively. Daily OLR uncertainty is higher (MAB +40%) during periods with only morning or only afternoon observations (1979–87). During the CERES era (2000–20), the OLR uncertainties w.r.t. CERES-EBAF, CERES-SYN, and HIRS are very similar. The RSF uncertainty achieves optimal results during 2002–16 with a monthly MAB w.r.t. CERES-EBAF of ∼2 W m−2 and a daily MAB w.r.t. CERES-SYN of ∼5 W m−2, and it is more sensitive to orbital configuration than is OLR. Overall, validation results are satisfactory for this first release of TOA flux products in the CLARA-A3 portfolio.
Amma, Michinari; Hayasaka, TadahiroAmma, M., T. Hayasaka, 2023: Interannual Variation in Top-of-Atmosphere Upward Shortwave Flux over the Arctic Related to Sea Ice, Snow Cover, and Land Cloud Cover in Spring and Summer. J. Climate, 36(15), 5163-5178. doi: 10.1175/JCLI-D-22-0440.1. Abstract We investigated the interannual variations in the annual mean and seasonal cycle of upward shortwave radiation at the top of the atmosphere (TOA SW↑) over the Arctic using the Clouds and the Earth’s Radiant Energy System (CERES) observation data during 2001–20. The annual mean TOA SW↑ over the Arctic showed a decreasing trend from 2001 to 2012 (−2.5 W m−2 decade−1) and had a large interannual variability after 2012. The standard deviation of detrended TOA SW↑ increased from 0.4 W m−2 in 2001–12 to 1.1 W m−2 in 2012–20. Over land, TOA SW↑ variation was related to snow cover in May; snow cover, cloud fraction, and cloud optical depth (COD) in June; and cloud fraction and COD in July. Over ocean, TOA SW↑ variation in June and July was linked to sea ice cover. TOA SW↑ variation over ocean in June and July after 2012 was highly related to the North Atlantic Oscillation (NAO). This study suggests that changes in the large annual mean TOA SW↑ variability after 2012 are explained by the timing of land snow and sea ice melt in spring and summer and cloud variability over land in summer.
Andersen, Hendrik; Cermak, Jan; Douglas, Alyson; Myers, Timothy A.; Nowack, Peer; Stier, Philip; Wall, Casey J.; Wilson Kemsley, SarahAndersen, H., J. Cermak, A. Douglas, T. A. Myers, P. Nowack, P. Stier, C. J. Wall, S. Wilson Kemsley, 2023: Sensitivities of cloud radiative effects to large-scale meteorology and aerosols from global observations. Atmospheric Chemistry and Physics, 23(18), 10775-10794. doi: 10.5194/acp-23-10775-2023. The radiative effects of clouds make a large contribution to the Earth's energy balance, and changes in clouds constitute the dominant source of uncertainty in the global warming response to carbon dioxide forcing. To characterize and constrain this uncertainty, cloud-controlling factor (CCF) analyses have been suggested that estimate sensitivities of clouds to large-scale environmental changes, typically in cloud-regime-specific multiple linear regression frameworks. Here, local sensitivities of cloud radiative effects to a large number of controlling factors are estimated in a regime-independent framework from 20 years (2001–2020) of near-global (60∘ N–60∘ S) satellite observations and reanalysis data using statistical learning. A regularized linear regression (ridge regression) is shown to skillfully predict anomalies of shortwave (R2=0.63) and longwave cloud radiative effects (CREs) (R2=0.72) in independent test data on the basis of 28 CCFs, including aerosol proxies. The sensitivity of CREs to selected CCFs is quantified and analyzed. CRE sensitivities to sea surface temperature and estimated inversion strength are particularly pronounced in low-cloud regions and generally in agreement with previous studies. The analysis of CRE sensitivities to three-dimensional wind field anomalies reflects the fact that CREs in tropical ascent regions are mainly driven by variability of large-scale vertical velocity in the upper troposphere. In the subtropics, CRE is sensitive to free-tropospheric zonal and meridional wind anomalies, which are likely to encapsulate information on synoptic variability that influences subtropical cloud systems by modifying wind shear and thus turbulence and dry-air entrainment in stratocumulus clouds, as well as variability related to midlatitude cyclones. Different proxies for aerosols are analyzed as CCFs, with satellite-derived aerosol proxies showing a larger CRE sensitivity than a proxy from an aerosol reanalysis, likely pointing to satellite aerosol retrieval biases close to clouds, leading to overestimated aerosol sensitivities. Sensitivities of shortwave CREs to all aerosol proxies indicate a pronounced cooling effect from aerosols in stratocumulus regions that is counteracted to a varying degree by a longwave warming effect. The analysis may guide the selection of CCFs in future sensitivity analyses aimed at constraining cloud feedback and climate forcings from aerosol–cloud interactions using data from both observations and global climate models.
Arsego, Vivian Bauce Machado; de Gonçalves, Luis Gustavo Gonçalves; Arsego, Diogo Alessandro; Figueroa, Silvio Nilo; Kubota, Paulo Yoshio; de Souza, Carlos RenatoArsego, V. B. M., L. G. G. de Gonçalves, D. A. Arsego, S. N. Figueroa, P. Y. Kubota, C. R. de Souza, 2023: Impact of Soil Moisture in the Monsoon Region of South America during Transition Season. Atmosphere, 14(5), 804. doi: 10.3390/atmos14050804. The land surface is an important component of numerical weather and climate forecast models due to their effect on energy–water balances and fluxes, and it is essential for forecasts on a seasonal scale. The present study aimed to understand the effects of land surface processes on initialization of seasonal forecasts in the austral spring, in particular soil moisture. We built forecasts with the Brazilian global Atmospheric Model hindcast from 2000 to 2010, with a configuration similar to those used in the operational environment. To improve it, we developed a new initial condition of the land surface using the Land Information System over South America and the Global Land Data Assimilation System for the rest of the globe and used it as the input in the forecast model. The results demonstrated that the model is sensitive to changes in soil moisture and that the new high–resolution soil moisture dataset can be used in model initialization, which resulted in an increase in the correlation of precipitation over part of South America. We also noticed an improvement in the representation of surface fluxes and an increase in soil moisture content and specific humidity at medium and low levels of the atmosphere. The analysis of the coupling between the land surface and the atmosphere showed that, for Central Brazil, the states of the continental surface define the surface fluxes. For the Amazon and La Plata Basins, the model did not correctly represent the coupling because it underestimated the soil moisture content. soil moisture; land surface; Brazilian global Atmospheric Model; initialization; seasonal forecast
Athulya, K.; Girishkumar, M. S.; McPhaden, M. J.; Kolukula, S. S.Athulya, K., M. S. Girishkumar, M. J. McPhaden, S. S. Kolukula, 2023: Seasonal Variation of the Land Breeze System in the Southwestern Bay of Bengal and Its Influence on Air-Sea Interactions. Journal of Geophysical Research: Oceans, 128(2), e2022JC019477. doi: 10.1029/2022JC019477. This study examines the seasonal variability of the Land Breeze System (LBS) in the Bay of Bengal (BoB) using hourly moored buoy data, coastal radar data, atmospheric reanalysis data, and 6-hourly satellite-based Cross-Calibrated Multi-Platform (CCMP) wind velocity data. We first provide an overview of the LBS for the entire BoB, then focus on the pronounced LBS in southwestern BoB and its impact on the near-surface current field and latent heat flux (LHF). We show that the LBS in the southwestern BoB exhibits a maximum diurnal wind speed amplitude of ∼2 m s−1 with seaward nearshore winds best developed in the morning hours. The geographical coverage is maximum in July and August and minimum in December and January. During its peak phase in July–August, the signature of the LBS in the southwestern BoB extends up to 600 km offshore, occupies ∼20% of the basin, and accounts for approximately 15% of the seasonal mean wind speed variance. The near-surface current field shows a rapid response to the diurnal wind speed variations, with an eastward current observed between 1000–1800 IST, a westward current between 1800–0800 IST, and a diurnal range of 12 cm s−1. LHF shows well-defined diurnal variability in response to diurnal LBS wind speed variability, with a morning maximum, evening minimum, and a diurnal range of 35 W m−2. We also find that the large-scale seasonal winds are the main factor in determining the annual variability in strength and geographical coverage of the LBS in the southwestern BoB. air-sea interaction; Bay of Bengal; land-sea breeze system; sub-daily variability
Ayyagari, Deepthi; Datta, Soumen; Das, Saurabh; Datta, AbhirupAyyagari, D., S. Datta, S. Das, A. Datta, 2023: Ionospheric response during Tropical Cyclones - A Brief Review on Amphan and Nisarga. Advances in Space Research, 71(6), 2799-2817. doi: 10.1016/j.asr.2022.11.026. Here, we explore the different characteristics of a possible coupling between tropospheric and ionospheric activities during the impact of tropical cyclones (TC) like Amphan and Nisarga in the Indian subcontinent. We have analyzed the effect of TCs Amphan and Nisarga on the low latitude ionosphere using the measurements from several IGS stations around India and a GPS + NavIC station in Indore, India. For the first time, this study assesses the impact of tropical cyclones on the equatorial ionosphere using both GPS and NavIC. After the landfall of TC Amphan, the VTEC analysis shows a significant drop from nominal values in both NavIC as well in GPS by 5.1 TECU and 3.6 TECU, respectively. In contrast to TC Amphan, Nisarga showed a rise in VTEC which ranged from 0.9 TECU in GPS to 1.7 - 5 TECU in NavIC satellites except for PRN6. The paper examines Outgoing Longwave Radiation as a proxy to the convective activity which may be responsible for the ionospheric variation through the generation of gravity waves. In addition, the horizontal neutral wind observations at the location of TC landfall confirm the presence of ionospheric disturbances. VTEC perturbation analysis using a band-pass filter reveals a variation in differential TEC values between ±0.4 and ±0.8 based on the IGS station measurements. This indicates that the gravity wave is one of the responsible mechanisms for the lower–upper atmospheric coupling during both cyclones. Gravity waves; Tropical cyclones; VTEC
Banerjee, Argha; Sarangi, Chandan; Rashid, Irfan; Vijay, Saurabh; Najar, Nadeem Ahmad; Chandel, Amit SinghBanerjee, A., C. Sarangi, I. Rashid, S. Vijay, N. A. Najar, A. S. Chandel, 2023: A Scaling Relation for Cryoconite Holes. Geophysical Research Letters, 50(22), e2023GL104942. doi: 10.1029/2023GL104942. Tiny cryoconite holes are commonly found on glacier surfaces. Despite a long history of research on them, their influence on glacier-scale mass balance and runoff are not well understood. We model the absorption of solar radiation at the bottom of cylindrical cryoconite holes, incorporating the three-dimensional geometry. The simulated holes achieve a limiting steady-state depth, where the daily melt rate at the bottom of the holes matches that at the glacier surface. This implies a feedback loop restricting the excess ice melt due to the presence of dark supraglacial impurities. The modeled steady-state depth scales approximately linearly with the radius, consistent with in situ observations at several glaciers across the world. Given the areal coverage and radius distribution of cryoconite holes on a glacier, this scaling yields first-order estimates of their melt contribution. cryoconite holes; glacier mass balance; glacier runoff; numerical modeling
Basso, Luana S.; Wilson, Chris; Chipperfield, Martyn P.; Tejada, Graciela; Cassol, Henrique L. G.; Arai, Egídio; Williams, Mathew; Smallman, T. Luke; Peters, Wouter; Naus, Stijn; Miller, John B.; Gloor, ManuelBasso, L. S., C. Wilson, M. P. Chipperfield, G. Tejada, H. L. G. Cassol, E. Arai, M. Williams, T. L. Smallman, W. Peters, S. Naus, J. B. Miller, M. Gloor, 2023: Atmospheric CO2 inversion reveals the Amazon as a minor carbon source caused by fire emissions, with forest uptake offsetting about half of these emissions. Atmospheric Chemistry and Physics, 23(17), 9685-9723. doi: 10.5194/acp-23-9685-2023. Tropical forests such as the Amazonian rainforests play an important role for climate, are large carbon stores and are a treasure of biodiversity. Amazonian forests have been exposed to large-scale deforestation and degradation for many decades. Deforestation declined between 2005 and 2012 but more recently has again increased with similar rates as in 2007–2008. The resulting forest fragments are exposed to substantially elevated temperatures in an already warming world. These temperature and land cover changes are expected to affect the forests, and an important diagnostic of their health and sensitivity to climate variation is their carbon balance. In a recent study based on CO2 atmospheric vertical profile observations between 2010 and 2018, and an air column budgeting technique used to estimate fluxes, we reported the Amazon region as a carbon source to the atmosphere, mainly due to fire emissions. Instead of an air column budgeting technique, we use an inverse of the global atmospheric transport model, TOMCAT, to assimilate CO2 observations from Amazon vertical profiles and global flask measurements. We thus estimate inter- and intra-annual variability in the carbon fluxes, trends over time and controls for the period of 2010–2018. This is the longest period covered by a Bayesian inversion of these atmospheric CO2 profile observations to date. Our analyses indicate that the Amazon is a small net source of carbon to the atmosphere (mean 2010–2018 = 0.13 ± 0.17 Pg C yr−1, where 0.17 is the 1σ uncertainty), with the majority of the emissions coming from the eastern region (77 % of total Amazon emissions). Fire is the primary driver of the Amazonian source (0.26 ± 0.13 Pg C yr−1), while forest carbon uptake removes around half of the fire emissions to the atmosphere (−0.13 ± 0.20 Pg C yr−1). The largest net carbon sink was observed in the western-central Amazon region (72 % of the fire emissions). We find larger carbon emissions during the extreme drought years (such as 2010, 2015 and 2016), correlated with increases in temperature, cumulative water deficit and burned area. Despite the increase in total carbon emissions during drought years, we do not observe a significant trend over time in our carbon total, fire and net biome exchange estimates between 2010 and 2018. Our analysis thus cannot provide clear evidence for a weakening of the carbon uptake by Amazonian tropical forests.
Bauer, Michael; Glenn, Tasha; Achtyes, Eric D.; Alda, Martin; Agaoglu, Esen; Altınbaş, Kürsat; Andreassen, Ole A.; Angelopoulos, Elias; Ardau, Raffaella; Aydin, Memduha; Ayhan, Yavuz; Baethge, Christopher; Bauer, Rita; Baune, Bernhard T.; Balaban, Ceylan; Becerra-Palars, Claudia; Behere, Aniruddh P.; Behere, Prakash B.; Belete, Habte; Belete, Tilahun; Belizario, Gabriel Okawa; Bellivier, Frank; Belmaker, Robert H.; Benedetti, Francesco; Berk, Michael; Bersudsky, Yuly; Bicakci, Şule; Birabwa-Oketcho, Harriet; Bjella, Thomas D.; Brady, Conan; Cabrera, Jorge; Cappucciati, Marco; Castro, Angela Marianne Paredes; Chen, Wei-Ling; Cheung, Eric Y. W.; Chiesa, Silvia; Crowe, Marie; Cuomo, Alessandro; Dallaspezia, Sara; Del Zompo, Maria; Desai, Pratikkumar; Dodd, Seetal; Etain, Bruno; Fagiolini, Andrea; Fellendorf, Frederike T.; Ferensztajn-Rochowiak, Ewa; Fiedorowicz, Jess G.; Fountoulakis, Kostas N.; Frye, Mark A.; Geoffroy, Pierre A.; Gitlin, Michael J.; Gonzalez-Pinto, Ana; Gottlieb, John F.; Grof, Paul; Haarman, Bartholomeus C. M.; Harima, Hirohiko; Hasse-Sousa, Mathias; Henry, Chantal; Hoffding, Lone; Houenou, Josselin; Imbesi, Massimiliano; Isometsä, Erkki T.; Ivkovic, Maja; Janno, Sven; Johnsen, Simon; Kapczinski, Flávio; Karakatsoulis, Gregory N.; Kardell, Mathias; Kessing, Lars Vedel; Kim, Seong Jae; König, Barbara; Kot, Timur L.; Koval, Michael; Kunz, Mauricio; Lafer, Beny; Landén, Mikael; Larsen, Erik R.; Lenger, Melanie; Licht, Rasmus W.; Lopez-Jaramillo, Carlos; MBauer, M., T. Glenn, E. D. Achtyes, M. Alda, E. Agaoglu, K. Altınbaş, O. A. Andreassen, E. Angelopoulos, R. Ardau, M. Aydin, Y. Ayhan, C. Baethge, R. Bauer, B. T. Baune, C. Balaban, C. Becerra-Palars, A. P. Behere, P. B. Behere, H. Belete, T. Belete, G. O. Belizario, F. Bellivier, R. H. Belmaker, F. Benedetti, M. Berk, Y. Bersudsky, Ş. Bicakci, H. Birabwa-Oketcho, T. D. Bjella, C. Brady, J. Cabrera, M. Cappucciati, A. M. P. Castro, W. Chen, E. Y. W. Cheung, S. Chiesa, M. Crowe, A. Cuomo, S. Dallaspezia, M. Del Zompo, P. Desai, S. Dodd, B. Etain, A. Fagiolini, F. T. Fellendorf, E. Ferensztajn-Rochowiak, J. G. Fiedorowicz, K. N. Fountoulakis, M. A. Frye, P. A. Geoffroy, M. J. Gitlin, A. Gonzalez-Pinto, J. F. Gottlieb, P. Grof, B. C. M. Haarman, H. Harima, M. Hasse-Sousa, C. Henry, L. Hoffding, J. Houenou, M. Imbesi, E. T. Isometsä, M. Ivkovic, S. Janno, S. Johnsen, F. Kapczinski, G. N. Karakatsoulis, M. Kardell, L. V. Kessing, S. J. Kim, B. König, T. L. Kot, M. Koval, M. Kunz, B. Lafer, M. Landén, E. R. Larsen, M. Lenger, R. W. Licht, C. Lopez-Jaramillo, . M, 2023: Exploratory study of ultraviolet B (UVB) radiation and age of onset of bipolar disorder. International Journal of Bipolar Disorders, 11(1), 22. doi: 10.1186/s40345-023-00303-w. Sunlight contains ultraviolet B (UVB) radiation that triggers the production of vitamin D by skin. Vitamin D has widespread effects on brain function in both developing and adult brains. However, many people live at latitudes (about > 40 N or S) that do not receive enough UVB in winter to produce vitamin D. This exploratory study investigated the association between the age of onset of bipolar I disorder and the threshold for UVB sufficient for vitamin D production in a large global sample.
Bazo, Elena; Granados-Muñoz, María J.; Román, Roberto; Bravo-Aranda, Juan Antonio; Cazorla, Alberto; Valenzuela, Antonio; González, Ramiro; Olmo, Francisco José; Alados-Arboledas, LucasBazo, E., M. J. Granados-Muñoz, R. Román, J. A. Bravo-Aranda, A. Cazorla, A. Valenzuela, R. González, F. J. Olmo, L. Alados-Arboledas, 2023: Evaluation of the vertically-resolved aerosol radiative effect on shortwave and longwave ranges using sun-sky photometer and ceilometer measurements. Atmospheric Research, 282, 106517. doi: 10.1016/j.atmosres.2022.106517. The aerosol radiative effect (ARE) is one of the atmospheric components still affected by large uncertainty. One of the causes is related to the fact that the longwave (LW) component is usually neglected, even though it is necessary for an accurate quantification of the ARE together with the shortwave component (SW). In this study we have developed a methodology based on the GAME (Global Atmospheric Model) radiative transfer model (RTM) that allows to obtain the radiative effect of the atmospheric aerosol for both spectral ranges in an automated way. The microphysical and optical properties necessary to feed the RTM have been obtained through the GRASP (Generalized Retrieval of Aerosol and Surface Properties) algorithm, with the combination of ceilometer and sun-sky photometer data. Data measured in Granada (Spain) during 2017 have been used for the evaluation and implementation of this methodology. According to the results, the ARE in the SW spectral range (ARESW) varies between 0 and − 50 Wm−2 for most of the data, whereas the ARE in the LW range (ARELW) varies between 0 and 5 Wm−2, at heights near the surface. In general, the obtained results agree with those found in the literature, with negative values in the SW range (cooling effect) and positive values in the LW (heating effect). The seasonal analysis shows that, for both components, the ARE is more important during the spring and summer seasons, when the aerosol load is greater, as expected. The analysis of the aerosol heating rate (AHR) shows positive values in the SW and negative values in the LW range. The majority of the AHRSW data varies between 0 and 1 Kd−1 during the year whereas the AHRLW does it between 0 and − 0.15 Kd−1. The seasonal analysis of the AHR shows that the greater monthly average values are found during spring, however there is not much variability along the year, with the exception of February, under the effects of an extreme dust intrusion. The mineral dust particles in this event cause an ARESW of −130 Wm−2 and an ARELW of 23 Wm−2 (ARELW/ARESW = 17%), thus pointing out that the LW component should not be neglected for coarse mode particles. Additionally, it is observed that the vertical distribution of the aerosol layers strongly influences the ARE and the AHR obtained profiles, affecting the way the atmospheric cooling/heating occurs in the vertical coordinate. Aerosol radiative properties; Ceilometer; GAME; GRASP; Longwave radiative effect; Sun-sky photometer
Braghiere, R. K.; Wang, Y.; Gagné-Landmann, A.; Brodrick, P. G.; Bloom, A. A.; Norton, A. J.; Ma, S.; Levine, P.; Longo, M.; Deck, K.; Gentine, P.; Worden, J. R.; Frankenberg, C.; Schneider, T.Braghiere, R. K., Y. Wang, A. Gagné-Landmann, P. G. Brodrick, A. A. Bloom, A. J. Norton, S. Ma, P. Levine, M. Longo, K. Deck, P. Gentine, J. R. Worden, C. Frankenberg, T. Schneider, 2023: The Importance of Hyperspectral Soil Albedo Information for Improving Earth System Model Projections. AGU Advances, 4(4), e2023AV000910. doi: 10.1029/2023AV000910. Earth system models (ESMs) typically simplify the representation of land surface spectral albedo to two values, which correspond to the photosynthetically active radiation (PAR, 400–700 nm) and the near infrared (NIR, 700–2,500 nm) spectral bands. However, the availability of hyperspectral observations now allows for a more direct retrieval of ecological parameters and reduction of uncertainty in surface reflectance. To investigate sensitivity and quantify biases of incorporating hyperspectral albedo information into ESMs, we examine how shortwave soil albedo affects surface radiative forcing and simulations of the carbon and water cycles. Results reveal that the use of two broadband values to represent soil albedo can introduce systematic radiative-forcing differences compared to a hyperspectral representation. Specifically, we estimate soil albedo biases of ±0.2 over desert areas, which can result in spectrally integrated radiative forcing divergences of up to 30 W m−2, primarily due to discrepancies in the blue (404–504 nm) and far-red (702–747 nm) regions. Furthermore, coupled land-atmosphere simulations indicate a significant difference in net solar flux at the top of the atmosphere (>3.3 W m−2), which can impact global energy fluxes, rainfall, temperature, and photosynthesis. Finally, simulations show that considering the hyperspectrally resolved soil reflectance leads to increased maximum daily temperatures under current and future CO2 concentrations. carbon cycle; Earth system models; radiative forcing; energy cycle; hyperspectral data; soil albedo
Cesana, Grégory V.; Ackerman, Andrew S.; de Guélis, Thibault Vaillant; Henderson, David S.Cesana, G. V., A. S. Ackerman, T. V. de Guélis, D. S. Henderson, 2023: Cloud-Radiation Interactions and Cloud-Climate Feedbacks From an Active-Sensor Satellite Perspective. Clouds and Their Climatic Impacts, 87-102. Clouds are ubiquitous in the troposphere. Their interactions with radiation may result in either a warming or a cooling of the Earth system and generate diverse climate feedbacks. The vertical structure of the radiative effects of clouds as well as the response of clouds to global warming (i.e., the cloud feedbacks) are inadequately constrained within the diversity of current climate models, which limits our ability to project the magnitude of future warming. In this chapter, we show how relatively recent active-sensor space-borne observations have narrowed constraints on cloud feedbacks. The value added beyond what can be retrieved from passive sensors is only just beginning to be exploited. climate sensitivity; climate models; radiation; cloud feedbacks; CloudSat-CALIPSO satellites
Cheng, Anning; Yang, FanglinCheng, A., F. Yang, 2023: Direct Radiative Effects of Aerosols on Numerical Weather Forecasts—A Comparison of Two Aerosol Datasets in the NCEP GFS. Wea. Forecasting, 38(5), 753-772. doi: 10.1175/WAF-D-22-0060.1. Abstract This study compares aerosol direct radiative effects on numerical weather forecasts made by the NCEP Global Forecast System (GFS) with two different aerosol datasets, the Optical Properties of Aerosols and Clouds (OPAC) and MERRA-2 aerosol climatologies. The underestimation of aerosol optical depth (AOD) by OPAC over northwest Africa, central to East Africa, the Arabian Peninsula, Southeast Asia, and the Indo-Gangetic Plain, and overestimation in the storm-track regions in both hemispheres are reduced by MERRA-2. Surface downward shortwave (SW) and longwave (LW) fluxes and the top-of-the-atmosphere SW and outgoing LW fluxes from model forecasts are compared with CERES satellite observations. Forecasts made with OPAC aerosols have large radiative flux biases, especially in northwest Africa and the storm-track regions. These biases are also reduced in the forecasts made with MERRA-2 aerosols. The improvements from MERRA-2 are most noticeable in the surface downward SW fluxes. GFS medium-range weather forecasts made with the MERRA-2 aerosols demonstrated slightly improved forecast accuracy of sea level pressure and precipitation over the Indian and East Asian summer monsoon region. A stronger Africa easterly jet is produced, associated with a low pressure over the east Atlantic Ocean and west of northwest Africa. Impacts on large-scale skill scores such as 500-hPa geopotential height anomaly correlation are generally positive in the Northern Hemisphere and the Pacific and North American regions in both the winter and summer seasons.
Christensen, Matthew W.; Ma, Po-Lun; Wu, Peng; Varble, Adam C.; Mülmenstädt, Johannes; Fast, Jerome D.Christensen, M. W., P. Ma, P. Wu, A. C. Varble, J. Mülmenstädt, J. D. Fast, 2023: Evaluation of aerosol–cloud interactions in E3SM using a Lagrangian framework. Atmospheric Chemistry and Physics, 23(4), 2789-2812. doi: 10.5194/acp-23-2789-2023. A Lagrangian framework is used to evaluate aerosol–cloud interactions in the U.S. Department of Energy's Energy Exascale Earth System Model (E3SM) version 1 (E3SMv1) for measurements taken at Graciosa Island in the Azores where a U.S. Department of Energy Atmosphere Radiation Measurement (ARM) site is located. This framework uses direct measurements of cloud condensation nuclei (CCN) concentration (instead of relying on satellite retrievals of aerosol optical depth) and incorporates a suite of ground-based ARM measurements, satellite retrievals, and meteorological reanalysis products that when applied to over a 1500 trajectories provides key insights into the evolution of low-level clouds and aerosol radiative forcing that is not feasible from a traditional Eulerian analysis framework. Significantly lower concentrations (40 %) of surface CCN concentration are measured when precipitation rates in 48 h back trajectories average above 1.2 mm d−1 in the Integrated Multi-satellitE Retrievals for Global Precipitation Measurement (IMERG) product. The depletion of CCN concentration when precipitation rates are elevated is nearly twice as large in the ARM observations compared to E3SMv1 simulations. The model CCN concentration bias remains significant despite modifying the autoconversion and accretion rates in warm clouds. As the clouds in trajectories associated with larger surface-based CCN concentration advect away from Graciosa Island, they maintain higher values of droplet number concentrations (Nd) over multiple days in observations and E3SM simulations compared to trajectories that start with lower CCN concentrations. The response remains robust even after controlling for meteorological factors such as lower troposphere stability, the degree of cloud coupling with the surface, and island wake effects. E3SMv1 simulates a multi-day aerosol effect on clouds and a Twomey radiative effect that is within 30 % of the ARM and satellite observations. However, the mean cloud droplet concentration is more than 2–3 times larger than in the observations. While Twomey radiative effects are similar amongst autoconversion and accretion sensitivity experiments, the liquid water path and cloud fraction adjustments are positive when using a regression model as opposed to negative when using the present-day minus pre-industrial aerosol emissions approach. This result suggests that tuning the autoconversion and accretion alone is unlikely to produce the desired aerosol susceptibilities in E3SMv1.
Chu, Wenchao; Lin, YanluanChu, W., Y. Lin, 2023: Description and Evaluation of a New Deep Convective Cloud Model Considering In-Cloud Inhomogeneity. Journal of Advances in Modeling Earth Systems, 15(2), e2022MS003119. doi: 10.1029/2022MS003119. Convections still need to be parameterized in general circulation models (GCMs) in the coming decades. Performances of GCMs are significantly influenced by the convection schemes used. In contrast to most conventional cloud models that ignore in-cloud inhomogeneities, a new convective cloud model explicitly considering in-cloud inhomogeneities is developed. The new model adopts a single bulk plume approach, but divides the plume into a series of interacting sub-plumes in order to mimic the transition from the plume core to its edges. We implemented the new cloud model in NCAR Community Atmosphere Model version 5.0 (CAM5) and evaluated its performance. Single-column tests show a stronger mass flux profile and low-level detrainment with the new model. In global simulations, the long-lasting wet bias in the tropical free troposphere of CAM5 is alleviated. Spatial pattern and intensity distribution of precipitation is improved, but the global hydrological cycle is over-enhanced. The diurnal cycle of tropical precipitation is also better captured though the precipitation peak still occurs earlier than the observations and the amplitude of the cycle tends to weaken. MJO simulation is slightly improved with the new scheme. In addition, the new cloud model generated more tropical cyclones, in better agreement with observations. CAM5; convection scheme; cloud inhomogeneity
Cordero, Raúl R.; Feron, Sarah; Damiani, Alessandro; Sepúlveda, Edgardo; Jorquera, Jose; Redondas, Alberto; Seckmeyer, Gunther; Carrasco, Jorge; Rowe, Penny; Ouyang, ZutaoCordero, R. R., S. Feron, A. Damiani, E. Sepúlveda, J. Jorquera, A. Redondas, G. Seckmeyer, J. Carrasco, P. Rowe, Z. Ouyang, 2023: Surface Solar Extremes in the Most Irradiated Region on Earth, Altiplano. Bull. Amer. Meteor. Soc., 104(6), E1206-E1221. doi: 10.1175/BAMS-D-22-0215.1. Abstract Satellites have consistently pointed to the Altiplano of the Atacama Desert as the place on Earth where the world’s highest surface irradiance occurs. This region, near the Tropic of Capricorn, is characterized by its high elevation, prevalent cloudless conditions, and relatively low concentrations of ozone, aerosols, and precipitable water. Aimed at studying the variability of the surface solar irradiance and detecting atmospheric composition changes in the Altiplano, an atmospheric observatory was set up in 2016 at the northwestern border of the Chajnantor Plateau (5,148 m MSL, 22.95°S, 67.78°W, Chile). Here, we report on the first 5 years of measurements at this observatory that establish the Altiplano as the region that receives the highest-known irradiation on Earth and illuminate the unique features of surface solar extremes at high-altitude locations. We found that the global horizontal shortwave (SW) irradiance on the plateau is on average 308 W m−2 (equivalent to an annual irradiation of 2.7 MWh m−2 yr−1, the highest worldwide). We also found that forward scattering by broken clouds often leads to intense bursts of SW irradiance; a record of 2,177 W m−2 was measured, equivalent to the extraterrestrial SW irradiance expected at approximately 0.79 astronomical units (AU) from the Sun. These cloud-driven surface solar extremes occur on the Chajnantor Plateau at a frequency, intensity, and duration not previously seen anywhere in the world, making the site an ideal location for studying the response of photovoltaic (PV) power plants to periods of enhanced SW variability.
Coss, Stephen; Durand, Michael T.; Shum, C. K.; Yi, Yuchan; Yang, Xiao; Pavelsky, Tamlin; Getirana, Augusto; Yamazaki, DaiCoss, S., M. T. Durand, C. K. Shum, Y. Yi, X. Yang, T. Pavelsky, A. Getirana, D. Yamazaki, 2023: Channel Water Storage Anomaly: A New Remotely Sensed Quantity for Global River Analysis. Geophysical Research Letters, 50(1), e2022GL100185. doi: 10.1029/2022GL100185. River channels store large volumes of water globally, critically impacting ecological and biogeochemical processes. Despite the importance of river channel storage, there is not yet an observational constraint on this quantity. We introduce a 26-year record of entirely remotely sensed volumetric channel water storage (CWS) change on 26 major world rivers. We find mainstem volumetric CWS climatology amplitude (CA) represents an appreciable amount of basin-wide terrestrial water storage variability (median 2.78%, range 0.04%–12.54% across world rivers), despite mainstem rivers themselves represent an average of just 0.2% of basin area. We find that two global river routing schemes coupled with land surface models reasonably approximate CA (within ±50%) in only 11.5% (CaMa-Flood) and 30.7% (HyMap) of rivers considered. These findings demonstrate volumetric CWS is a useful quantity for assessing global hydrological model performance, and for advancing understanding of spatial patterns in global hydrology. GRACE; hydrology; altimetery; river; storage; SWOT
Črnivec, Nina; Cesana, Grégory; Pincus, RobertČrnivec, N., G. Cesana, R. Pincus, 2023: Evaluating the Representation of Tropical Stratocumulus and Shallow Cumulus Clouds As Well As Their Radiative Effects in CMIP6 Models Using Satellite Observations. Journal of Geophysical Research: Atmospheres, 128(23), e2022JD038437. doi: 10.1029/2022JD038437. Low clouds over tropical oceans reflect a great proportion of solar radiation back to space and thereby cool the Earth, yet this phenomenon has been poorly simulated in several previous generations of climate models. The principal aim of the present study is to employ satellite observations to evaluate the representation of marine tropical low clouds and their radiative effect at the top of the atmosphere in a subset of latest climate models participating in CMIP6. We strive for regime-oriented model validation and hence introduce a qualitative approach to discriminate stratocumulus (Sc) from shallow cumulus (Cu). The novel Sc-Cu categorization has a conceptual advantage of being based on cloud properties, rather than relying on a model response to a cloud-controlling factor. We find that CMIP6 models underestimate low-cloud cover in both Sc-regions and Cu-regions of tropical oceans. A more detailed investigation of cloud biases reveals that most CMIP6 models underestimate the relative frequency of occurrence (RFO) of Sc and overestimate RFO of Cu. We further demonstrate that tropical low cloudiness in CMIP6 models remains too bright. The regime-oriented validation represents the basis for improving parameterizations of physical processes that determine the cloud cover and radiative impact of Sc and Cu, which are still misrepresented in current climate models. radiative effects; satellite observations; stratocumulus; climate model validation; marine tropical low clouds; shallow cumulus
Crueger, Traute; Schmidt, Hauke; Stevens, BjornCrueger, T., H. Schmidt, B. Stevens, 2023: Hemispheric Albedo Asymmetries across Three Phases of CMIP. J. Climate, 36(15), 5267-5280. doi: 10.1175/JCLI-D-22-0923.1. Abstract Earth’s planetary albedo shows a remarkable hemispheric symmetry. We assess to what extent CMIP models symmetrize the hemispheric clear-sky albedo asymmetry and what the role of clouds is for this. Following Voigt et al., we calculate a reference TOA reflected solar radiation considering the masking of clear-sky asymmetry by symmetric cloud contributions. We use the simple radiation model of Donohoe and Battisti to estimate this benchmark and to separate surface, aerosol, and cloud contributions to the compensation of this benchmark. In CERES, tropical clouds enhance the reference asymmetry while extratropical cloud asymmetries balance the reference asymmetry and the additional asymmetry introduced by tropical clouds. CMIP multimodel means show similar results as CERES. Clouds compensate reference asymmetries by 85% (CMIP3), 65% (CMIP5), and 78% (CMIP6) as compared with 98% for CERES. Spatial distributions of hemispheric differences indicate clear improvements across the CMIP phases. Remaining all-sky reflection asymmetries predominantly result from too-small, partly compensating cloud asymmetries: a too-weak enhancement of the reference asymmetry in the tropical Atlantic and eastern Pacific Oceans is accompanied by a too-weak compensation by extratropical clouds. Thus, tropical clouds and extratropical storm track regions are largely responsible for the compensation of hemispheric clear-sky asymmetries in CERES and CMIP, and for remaining biases in the GCMs. An unexpected result is the magnitude of model biases in the clear-sky asymmetries, which potentially condition systematic cloud biases. Experiments testing cloud-controlling factors influencing hemispheric asymmetry could help us to understand what drives hemispheric cloud differences.
Curasi, Salvatore R.; Melton, Joe R.; Humphreys, Elyn R.; Wang, Libo; Seiler, Christian; Cannon, Alex J.; Chan, Ed; Qu, BoCurasi, S. R., J. R. Melton, E. R. Humphreys, L. Wang, C. Seiler, A. J. Cannon, E. Chan, B. Qu, 2023: Evaluating the Performance of the Canadian Land Surface Scheme Including Biogeochemical Cycles (CLASSIC) Tailored to the Pan-Canadian Domain. Journal of Advances in Modeling Earth Systems, 15(4), e2022MS003480. doi: 10.1029/2022MS003480. Canada's boreal forests and tundra ecosystems are responding to unprecedented climate change with implications for the global carbon (C) cycle and global climate. However, our ability to model the response of Canada's terrestrial ecosystems to climate change is limited and there has been no comprehensive, process-based assessment of Canada's terrestrial C cycle. We tailor the Canadian Land Surface Scheme Including Biogeochemical Cycles (CLASSIC) to Canada and evaluate its C cycling performance against independent reference data. We utilize skill scores to assess model performance against reference data alongside benchmark scores that quantify the level of agreement between the reference data sets to aid in interpretation. Our results demonstrate CLASSIC's sensitivity to prescribed vegetation cover. They also show that the addition of five region-specific Plant functional types (PFTs) improves CLASSIC's skill at simulating the Canadian C cycle. CLASSIC performs well when tailored to Canada, falls within the range of the reference data sets, and meets or exceeds the benchmark scores for most C cycling processes. New region-specific land cover products, well-informed PFT parameterizations, and more detailed reference data sets will facilitate improvements to the representation of the terrestrial C cycle in regional and global land surface models. Incorporating a parameterization for boreal disturbance processes and explicitly representing peatlands and permafrost soils will improve CLASSIC's future performance in Canada and other boreal regions. This is an important step toward a comprehensive process-based assessment of Canada's terrestrial C cycle and evaluating Canada's net C balance under climate change. Arctic; boreal; Canada; carbon cycle; CLASSIC; land surface model
Das, Ripan; Chaturvedi, Rajiv Kumar; Roy, Adrija; Karmakar, Subhankar; Ghosh, SubimalDas, R., R. K. Chaturvedi, A. Roy, S. Karmakar, S. Ghosh, 2023: Warming inhibits increases in vegetation net primary productivity despite greening in India. Scientific Reports, 13(1), 21309. doi: 10.1038/s41598-023-48614-3. India is the second-highest contributor to the post-2000 global greening. However, with satellite data, here we show that this 18.51% increase in Leaf Area Index (LAI) during 2001–2019 fails to translate into increased carbon uptake due to warming constraints. Our analysis further shows 6.19% decrease in Net Primary Productivity (NPP) during 2001–2019 over the temporally consistent forests in India despite 6.75% increase in LAI. We identify hotspots of statistically significant decreasing trends in NPP over the key forested regions of Northeast India, Peninsular India, and the Western Ghats. Together, these areas contribute to more than 31% of the NPP of India (1274.8 TgC.year−1). These three regions are also the warming hotspots in India. Granger Causality analysis confirms that temperature causes the changes in net-photosynthesis of vegetation. Decreasing photosynthesis and stable respiration, above a threshold temperature, over these regions, as seen in observations, are the key reasons behind the declining NPP. Our analysis shows that warming has already started affecting carbon uptake in Indian forests and calls for improved climate resilient forest management practices in a warming world. Climate sciences; Ecology
de Ávila, Álvaro Vasconcellos Araujo; de Gonçalves, Luis Gustavo Gonçalves; Souza, Vanessa de Arruda; Alves, Laurizio Emanuel Ribeiro; Galetti, Giovanna Deponte; Maske, Bianca Muss; Getirana, Augusto; Ruhoff, Anderson; Biudes, Marcelo Sacardi; Machado, Nadja Gomes; Roberti, Débora Reginade Ávila, Á. V. A., L. G. G. de Gonçalves, V. d. A. Souza, L. E. R. Alves, G. D. Galetti, B. M. Maske, A. Getirana, A. Ruhoff, M. S. Biudes, N. G. Machado, D. R. Roberti, 2023: Assessing the Performance of the South American Land Data Assimilation System Version 2 (SALDAS-2) Energy Balance across Diverse Biomes. Atmosphere, 14(6), 959. doi: 10.3390/atmos14060959. Understanding the exchange of energy between the surface and the atmosphere is important in view of the climate scenario. However, it becomes a challenging task due to a sparse network of observations. This study aims to improve the energy balance estimates for the Amazon, Cerrado, and Pampa biomes located in South America using the radiation and precipitation forcing obtained from the Clouds and the Earth’s Radiant Energy System (CERES) and the precipitation CPTEC/MERGE datasets. We employed three surface models—Noah-MP, Community Land Model (CLSM), and Integrated Biosphere Simulator (IBIS)—and conducted modeling experiments, termed South America Land Data Assimilation System (SALDAS-2). The results showed that SALDAS-2 radiation estimates had the smallest errors. Moreover, SALDAS-2 precipitation estimates were better than the Global Land Data Assimilation System (GLDAS) in the Cerrado (MBE = −0.16) and Pampa (MBE = −0.19). Noah-MP presented improvements compared with CLSM and IBIS in 100% of towers located in the Amazon. CLSM tends to overestimate the latent heat flux and underestimate the sensible heat flux in the Amazon. Noah-MP and Ensemble outperformed GLDAS in terms latent and sensible heat fluxes. The potential of SALDAS-2 should be emphasized to provide more accurate estimates of surface energy balance. energy; modeling; surface; precipitation; balance
Devaliya, Sandeep; Bhate, Jyoti N.; Sunder Raman, Ramya; Muduchuru, Kaushik; Sharma, Arushi; Singh, Vikas; Kesarkar, Amit P.; Venkataraman, ChandraDevaliya, S., J. N. Bhate, R. Sunder Raman, K. Muduchuru, A. Sharma, V. Singh, A. P. Kesarkar, C. Venkataraman, 2023: Assessment of the impact of atmospheric aerosols and meteorological data assimilation on simulation of the weather over India during summer 2015. Atmospheric Environment, 297, 119586. doi: 10.1016/j.atmosenv.2023.119586. This study investigates the sensitivity of climate model-predicted surface radiation and surface meteorological parameters to atmospheric aerosols and meteorological data assimilation (meteorological initial and boundary conditions) utilizing the Weather Research and Forecasting model coupled with Chemistry (WRF-Chem). For this purpose, three sets of simulations including WRFChemCntrl (WRFChem without meteorological data assimilation), WRFChemDA (WRFChem with meteorological data assimilation) and WRFDA (WRF only with meteorological data assimilation) were performed over the South Asian domain. A 12-hourly cyclic 3-dimensional variational (3DVAR) meteorological data assimilation (DA) of in-situ meteorological observations was used to generate WRFChemDA and WRFDA reanalyses, during summer (March–May) 2015. The Carbon Bond Mechanism-Z (CBMZ) gas-phase chemistry with Model for Simulating Aerosol Interactions and Chemistry (MOSAIC) was selected for the chemistry simulations. A reduction in incoming shortwave radiation (∼10–60 W/m2) over the Indian landmass and a slight increase (∼10–20 W/m2) over the surrounding oceanic region due to the influence of aerosols in WRF-Chem simulations was observed, suggesting that aerosols effects, were simulated by the model successfully. These effects of aerosols were further evident in the model output of other parameters such as outgoing longwave radiation at the surface, 2-m temperature (T2), 2-m relative humidity (RH2), and planetary boundary layer height (PBLH). Our results also show that the inclusion of aerosols in the WRFDA simulations (i.e WRFChemDA) improved the prediction of incoming shortwave radiation but deteriorated some of the meteorological parameters. However, an improved agreement between model simulated radiation, T2, RH2 and PBLH and observations was evident in WRFChemDA output compared to WRFChemCntrl output, reinforcing DA induced improvements in meteorological parameters for a given model set-up. India; 3-Dimensional variational data assimilation (3DVAR); Aerosol-meteorology interactions; COALESCE project; WRF-Chem with CBMZ-MOSAIC
Devika, M. V.; Kottayil, Ajil; Koovekkallu, Prajwal; Xavier, Prince; John, VijuDevika, M. V., A. Kottayil, P. Koovekkallu, P. Xavier, V. John, 2023: Influence of monsoon extreme rainfall on the distribution of upper tropospheric humidity. International Journal of Climatology, 43(16), 7633-7645. doi: 10.1002/joc.8284. This study focuses on the changes in the upper tropospheric humidity (UTH) associated with two different extreme precipitation conditions for the period 2000–2019 over the Indian summer monsoon region. The analysis embodies UTH datasets derived from microwave sounders on-board NOAA and MetOp-A polar-orbiting satellites. The circulation characteristics in the upper troposphere are studied using the high-resolution ERA5 reanalysis data. The analysis of UTH variability over the Indian region shows a unique positive (negative) UTH anomaly patch extending from northwestern regions of India to the northern Arabian Sea for the enhanced (deficient) rainfall days over central India during the southwest monsoon period. The investigation reveals that deep convection alone does not impact the UTH variability. Rather the circulation in the upper troposphere also plays a crucial role in UTH distribution. The dynamics in the upper troposphere cause large-scale dispersal of both wet and dry air in the upper troposphere, which is linked to the strengthening/weakening of Asian monsoon anticyclone. The study indicates that monsoon extremes exhibit a distinct moisture distribution pattern in the upper troposphere, influenced by upper-level dynamics, which are associated with the intensity of the Asian monsoon anticyclone. Indian summer monsoon; extreme rainfall; Asian monsoon anticyclone; UTH
Diamond, Michael S.Diamond, M. S., 2023: Detection of large-scale cloud microphysical changes within a major shipping corridor after implementation of the International Maritime Organization 2020 fuel sulfur regulations. Atmospheric Chemistry and Physics, 23(14), 8259-8269. doi: 10.5194/acp-23-8259-2023. New regulations from the International Maritime Organization (IMO) limiting sulfur emissions from the shipping industry are expected to have large benefits in terms of public health but may come with an undesired side effect: acceleration of global warming as the climate-cooling effects of ship pollution on marine clouds are diminished. Previous work has found a substantial decrease in the detection of ship tracks in clouds after the IMO 2020 regulations went into effect, but changes in large-scale cloud properties have been more equivocal. Using a statistical technique that estimates counterfactual fields of what large-scale cloud and radiative properties within an isolated shipping corridor in the southeastern Atlantic would have been in the absence of shipping, we confidently detect a reduction in the magnitude of cloud droplet effective radius decreases within the shipping corridor and find evidence for a reduction in the magnitude of cloud brightening as well. The instantaneous radiative forcing due to aerosol–cloud interactions from the IMO 2020 regulations is estimated as O(1 W m−2) within the shipping corridor, lending credence to global estimates of O(0.1 W m−2). In addition to their geophysical significance, our results also provide independent evidence for general compliance with the IMO 2020 regulations.
Ding, Jiachen; Yang, Ping; Wang, Lifan; Oran, Elaine; Loeb, Norman G.; Smith Jr., William L.; Minnis, PatrickDing, J., P. Yang, L. Wang, E. Oran, N. G. Loeb, W. L. Smith Jr., P. Minnis, 2023: Quantification of Global Cloud Properties With Use of Spherical Harmonic Functions. Earth and Space Science, 10(3), e2022EA002718. doi: 10.1029/2022EA002718. Spherical harmonic (SH) expansion is a useful tool to study any variable that has valid values at all latitudes and longitudes. The variable can be quantified as a sum of different spherical harmonic components, which are the spherical harmonic functions multiplied by their expansion coefficients. We find that the SH components of cloud radiative effect (CRE) have correlations with El Niño-Southern Oscillation (ENSO) and the Hadley Circulation (HC). In particular, the expansion degree 2 () SH power spectrum component anomaly of CRE is strongly correlated with ENSO. The two dipole patterns appearing in the SH component anomaly map can be reasonably explained by a known mechanism of ENSO's impact on cloud properties. The and SH power spectrum components are correlated with HC intensity, whereas the and components are correlated with HC latitudinal widths. In ENSO warm and cold phases, the HC-correlated SH components have opposite anomalies, which suggests the impact of ENSO on HC. This study illustrates that the SH expansion technique provides a different perspective to study the impacts of large-scale atmospheric circulation on global cloud properties and radiative effects. cloud; cloud radiative effect; radiative transfer; spherical harmonic functions
Dommo, A.; Klutse, Nana Ama Browne; Fiedler, Stephanie; Koffi, Hubert Azoda; Vondou, Derbetini A.Dommo, A., N. A. B. Klutse, S. Fiedler, H. A. Koffi, D. A. Vondou, 2023: The seasonal cycle of cloud radiative effects over Congo Basin based on CERES observation and comparison to CMIP6 models. Atmospheric Research, 291, 106820. doi: 10.1016/j.atmosres.2023.106820. This study investigates the seasonal variability of the cloud radiative effects (CREs) over Congo Basin (CB) using 15-year observations from Clouds and the Earth's Radiant Energy System (CERES) Energy Budget and Filled (EBAF) Ed4.1 level 3b dataset involving CERES and Moderate Resolution Imaging Spectroradiometer (MODIS) instruments on board Terra and Aqua satellites. The relationships between CREs and cloud properties such as total cloud fraction (TCF), cloud top height (CTH), cloud top temperature (CTT) and cloud optical thickness (COT) are checked. An evaluation of Coupled Model Intercomparison Project (CMIP) Phase 6 in capturing the seasonal cycle of CREs as well as the magnitudes of the CREs along the seasonal cycle is also performed. This study shows a net cloud cooling effect of −8.4 W/m2 and − 43.9 W/m2 respectively at the top of the atmosphere (TOA) and at the surface, leading to a net warming effect of 35.67 W/m2 in the atmosphere. This value implies a large energy source over the Central Africa (CA) atmospheric column. The associated relationships between CREs and cloud properties show that the shortwave CRE is more sensitive to TCF and optical thickness whereas its longwave counterparts is more sensitive to CTH, CTT and COT at the TOA and in the atmosphere. All of the four CMIP6 models used in this study can capture the spatial pattern of CREs as well as their seasonal cycle but misrepresent intensity of CREs. Results also show that a better-simulated TCF considerably reduces the intensity of the annual mean underestimation in both longwave and shortwave CRE for some CMIP6 models, but not for models with overestimated shortwave CRE. Central Africa; CERES; Cloud radiative effect; CMIP6
Dong, Xiquan; Minnis, PatrickDong, X., P. Minnis, 2023: Stratus, Stratocumulus, and Remote Sensing. Fast Processes in Large-Scale Atmospheric Models, 141-199. Stratus and stratocumulus clouds comprise a critical component of the atmospheric system and have long been the subject of research from many perspectives. Observations from the surface, air, and space have provided the data necessary to quantify their occurrence, properties, and interactions with radiation, dynamics, and other atmospheric components. Such data have served to develop and improve parameterizations for characterizing these clouds in climate and weather prediction models. This chapter provides an overview of this cloud type and its role in climate with a focus upon what we have learned from ground-based and satellite remote sensing. The processes that determine the variations in these low-level cloud properties and govern where and when they occur are discussed along with factors, such as aerosols, radiation, and humidity, that influence their characteristics. Retrieval methods used to infer the properties of these stratiform clouds from satellite-based and ground-based sensors are also reviewed. Remote sensing is a critical means to further our understanding of these clouds and the processes involving them, as well as, for monitoring and predicting their role in a changing climate. Aerosol-cloud Interactions; Diurnal Variations; Remote Sensing; Stratus and Stratpcumulus clouds; Their macrophysical and Microphysical Properties
Dong, Zixiang; Ge, Jinming; Gao, Ang; Zhu, Zeen; Yan, Jialin; Mu, Qingyu; Su, Jing; Yang, Xuan; Hu, XiaoyuDong, Z., J. Ge, A. Gao, Z. Zhu, J. Yan, Q. Mu, J. Su, X. Yang, X. Hu, 2023: Comparisons of cirrus clouds and their linkages to meteorology at the SACOL and the SGP sites. Atmospheric Research, 281, 106467. doi: 10.1016/j.atmosres.2022.106467. Three-year of continuous observations collected by Ka-band zenith radars (KAZRs) at the Semi-Arid Climate and Environment Observatory of Lanzhou University (SACOL) and the Atmospheric Radiation Measurement (ARM) Program Southern Great Plains (SGP) sites are used to explore and compare the midlatitude cirrus cloud macro-physical properties at distinct locations. Cirrus clouds over the two sites exhibit prominent differences of seasonal and diurnal variations with higher occurrence frequency and larger thickness over the SACOL than over the SGP. The linkages between the cirrus properties (e.g., frequency, thickness, height, and radiative effect) and the meteorological parameters in the upper troposphere are also examined. Cirrus clouds at the two sites have qualitatively similar relations with the meteorological factors. Large cirrus frequency and thickness are associated with large relative humidity, strong upward motion, low stability, cold temperature and positive vorticity advection in the upper troposphere. However, cirrus over the SACOL occurs more frequently than that over the SGP for a given constant meteorological condition, implying cirrus formation may be affected by different formation pathways. To explore the joint impact of atmospheric conditions on cirrus macrophysics, we combine four meteorological variables in the upper troposphere into a single factor that represents the largest atmospheric variability corresponding to the cirrus cloud development based on the principal component analysis (PCA) method. Most cirrus properties show better relations with the leading principal component (PC1) than any single meteorological indicator alone, and the changes of PC1 can well explain the annual and diurnal variations of cirrus occurrence. Meteorology; Cirrus cloud; Physical properties; Linkages；KAZR; Midlatitude sites
Du, Yihan; Wang, Tianxing; Zhou, Yu; Li, Dahui; Wang, Shiyao; Xian, YuyangDu, Y., T. Wang, Y. Zhou, D. Li, S. Wang, Y. Xian, 2023: Upscaling of longwave downward radiation from instantaneous to any temporal scale: Algorithms, validation, and comparison. International Journal of Applied Earth Observation and Geoinformation, 117, 103196. doi: 10.1016/j.jag.2023.103196. Surface longwave downward radiation (LWDR) is a key factor affecting the surface energy balance. The daily LWDR and the diurnal variations of LWDR are of great significance for studies of climate change and surface processes. How to obtain LWDR at an averaged temporal scale from instantaneous LWDR is one of the long-standing problems in the field of radiation budget from remote sensing. In this paper, two temporal upscaling methods are introduced, namely, a method based on the diurnal variations of LWDR (diurnal variation based, DVB) and a method based on random forest regression (RFR). The results reveal that: (1) The DVB method has a global hourly and daily LWDR root-mean-square error (RMSE) of less than 21 W/m2 and 15 W/m2, respectively, and the RMSE of the daily LWDR based on RFR is less than 7 W/m2; (2) When compared with four existing statistical interpolation methods, the DVB method can not only ensure the accuracy, but also can overcome the problem of missing samples and/or an abnormal samples during upscaling; (3) Except for directly predict daily LWDR, the DVB methods can also obtain more accurate LWDR diurnal variations such as hourly, half-hourly etc. The RFR method enables high-efficiency and accurate estimation of daily averaged LWDR from instantaneous measurements. Compared with existing methods and products, the proposed methods are not only efficient, but also have a superior applicability and reliable accuracy. The proposed strategies provide new ideas for the community in estimating LWDR at continuous temporal scales from remotely sensed measurements. Diurnal variation; Longwave downward radiation; Random forest regression; Statistical interpolation; Temporal upscaling
Duda, David P.; Smith Jr., William L.; Bedka, Sarah; Spangenberg, Douglas; Chee, Thad; Minnis, PatrickDuda, D. P., W. L. Smith Jr., S. Bedka, D. Spangenberg, T. Chee, P. Minnis, 2023: Impact of COVID-19-Related Air Traffic Reductions on the Coverage and Radiative Effects of Linear Persistent Contrails Over Conterminous United States and Surrounding Oceanic Routes. Journal of Geophysical Research: Atmospheres, 128(6), e2022JD037554. doi: 10.1029/2022JD037554. The radiative effects of the large-scale air traffic slowdown during April and May 2020 due to the international response to the COVID-19 pandemic are estimated by comparing the coverage (CC), optical properties, and radiative forcing of persistent linear contrails over the conterminous United States and two surrounding oceanic air corridors during the slowdown period and a similar baseline period during 2018 and 2019 when air traffic was unrestricted. The detected CC during the slowdown period decreased by an area-averaged mean of 41% for the three analysis boxes. The retrieved contrail optical properties were mostly similar for both periods. Total shortwave contrail radiative forcings (CRFs) during the slowdown were 34% and 42% smaller for Terra and Aqua, respectively. The corresponding differences for longwave CRF were 33% for Terra and 40% for Aqua. To account for the impact of any changes in the atmospheric environment between baseline and slowdown periods on detected CC amounts, the contrail formation potential (CFP) was computed from reanalysis data. In addition, a filtered CFP (fCFP) was also developed to account for factors that may affect contrail formation and visibility of persistent contrails in satellite imagery. The CFP and fCFP were combined with air traffic data to create empirical models that estimated CC during the baseline and slowdown periods and were compared to the detected CC. The models confirm that decreases in CC and radiative forcing during the slowdown period were mostly due to the reduction in air traffic, and partly due to environmental changes. contrail; COVID pandemic; radiative effects
Duffey, Alistair; Irvine, Peter; Tsamados, Michel; Stroeve, JulienneDuffey, A., P. Irvine, M. Tsamados, J. Stroeve, 2023: Solar Geoengineering in the Polar Regions: A Review. Earth's Future, 11(6), e2023EF003679. doi: 10.1029/2023EF003679. Solar geoengineering refers to proposals, including stratospheric aerosol injection (SAI), to slow or reverse climate change by reflecting away incoming sunlight. The rapid changes ongoing in the Arctic and Antarctic, and the risk of exceeding tipping points in the cryosphere within decades, make limiting such changes a plausible objective of solar geoengineering. Here, we review the impacts of SAI on polar climate and cryosphere, including the dependence of these impacts on the latitude(s) of injection, and make recommendations for future research directions. SAI would cool the polar regions and reduce many changes in polar climate under future warming scenarios. Some under-cooling of the polar regions relative to the global mean is expected under SAI without high latitude injection, due to latitudinal variation in insolation and CO2 forcing, the forcing dependence of the polar lapse rate feedback, and altered atmospheric dynamics. There are also potential limitations in the effectiveness of SAI to arrest changes in winter-time polar climate and to prevent sea-level rise from the Antarctic ice sheet. Finally, we also review the prospects for three other solar geoengineering proposals targeting the poles: marine cloud brightening, cirrus cloud thinning, and sea-ice albedo modification. Sea-ice albedo modification appears unlikely to be viable on pan-Arctic or Antarctic scales. Whether marine cloud brightening or cirrus cloud thinning would be effective in the polar regions remains uncertain. Solar geoengineering is an increasingly prominent proposal and a robust understanding of its consequences in the polar regions is needed to inform climate policy in the coming decades. climate change; polar climate; sea ice; solar geoengineering; solar radiation modification; stratospheric aerosol injection
Dunn, Robert J. H.; Miller, John B.; Willett, Kate M.; Gobron, Nadine; Ades, Melanie; Adler, Robert; Alexe, Mihai; Allan, Richard P.; Anderson, John; Anneville, Orlane; Aono, Yasuyuki; Arguez, Anthony; Arosio, Carlo; Augustine, John A.; Azorin-Molina, Cesar; Barichivich, Jonathan; Barnes, John E.; Beck, Hylke E.; Bellouin, Nicolas; Benedetti, Angela; Blagrave, Kevin; Blenkinsop, Stephen; Bock, Olivier; Bodin, Xavier; Bosilovich, Michael; Boucher, Olivier; Buechler, Dennis; Buehler, Stefan A.; Campos, Diego; Carrea, Laura; Chang, Kai-Lan; Christiansen, Hanne H.; Christy, John R.; Chung, Eui-Seok; Ciasto, Laura M.; Clingan, Scott; Coldewey-Egbers, Melanie; Cooper, Owen R.; Cornes, Richard C.; Covey, Curt; Créatux, Jean-François; Crimmins, Theresa; Cropper, Thomas; Crotwell, Molly; Culpepper, Joshua; Cusicanqui, Diego; Davis, Sean M.; Jeu, Richard A. M. de; Degenstein, Doug; Delaloye, Reynald; Dokulil, Martin T.; Donat, Markus G.; Dorigo, Wouter A.; Dugan, Hilary A.; Durre, Imke; Dutton, Geoff; Duveiller, Gregory; Estilow, Thomas W.; Estrella, Nicole; Fereday, David; Fioletov, Vitali E.; Flemming, Johannes; Foster, Michael J.; Franz, Bryan; Frith, Stacey M.; Froidevaux, Lucien; Füllekrug, Martin; Garforth, Judith; Garg, Jay; Gibbes, Badin; Goodman, Steven; Goto, Atsushi; Gruber, Alexander; Gu, Guojun; Hahn, Sebastian; Haimberger, Leopold; Hall, Bradley D.; Harris, Ian; Hemming, Deborah L.; Hirschi, Martin; Ho, Shu-peng (Ben); Holzworth, Robert; Hrbáček, Filip; Hu, Guojie; HDunn, R. J. H., J. B. Miller, K. M. Willett, N. Gobron, M. Ades, R. Adler, M. Alexe, R. P. Allan, J. Anderson, O. Anneville, Y. Aono, A. Arguez, C. Arosio, J. A. Augustine, C. Azorin-Molina, J. Barichivich, J. E. Barnes, H. E. Beck, N. Bellouin, A. Benedetti, K. Blagrave, S. Blenkinsop, O. Bock, X. Bodin, M. Bosilovich, O. Boucher, D. Buechler, S. A. Buehler, D. Campos, L. Carrea, K. Chang, H. H. Christiansen, J. R. Christy, E. Chung, L. M. Ciasto, S. Clingan, M. Coldewey-Egbers, O. R. Cooper, R. C. Cornes, C. Covey, J. Créatux, T. Crimmins, T. Cropper, M. Crotwell, J. Culpepper, D. Cusicanqui, S. M. Davis, R. A. M. d. Jeu, D. Degenstein, R. Delaloye, M. T. Dokulil, M. G. Donat, W. A. Dorigo, H. A. Dugan, I. Durre, G. Dutton, G. Duveiller, T. W. Estilow, N. Estrella, D. Fereday, V. E. Fioletov, J. Flemming, M. J. Foster, B. Franz, S. M. Frith, L. Froidevaux, M. Füllekrug, J. Garforth, J. Garg, B. Gibbes, S. Goodman, A. Goto, A. Gruber, G. Gu, S. Hahn, L. Haimberger, B. D. Hall, I. Harris, D. L. Hemming, M. Hirschi, S. Ho, R. Holzworth, F. Hrbáček, G. Hu, . H, 2023: Global Climate. Bull. Amer. Meteor. Soc., 104(9), S11-S145. doi: 10.1175/BAMS-D-23-0090.1. "Global Climate" published on 06 Sep 2023 by American Meteorological Society.
Ekman, Annica M. L.; Nygren, Eva; Pérez, Alejandro Baró; Schwarz, Matthias; Svensson, Gunilla; Bellouin, NicolasEkman, A. M. L., E. Nygren, A. B. Pérez, M. Schwarz, G. Svensson, N. Bellouin, 2023: Influence of horizontal resolution and complexity of aerosol–cloud interactions on marine stratocumulus and stratocumulus-to-cumulus transition in HadGEM3-GC3.1. Quarterly Journal of the Royal Meteorological Society, 149(755), 2049-2066. doi: 10.1002/qj.4494. Stratocumulus (Sc) clouds and stratocumulus-to-cumulus transitions (SCTs) are challenging to represent in global models and they contribute to a large spread in modeled subtropical cloud feedbacks. We evaluate the impact of increasing the horizontal model resolution (∼135, 60 and 25 km, respectively) and increasing the complexity of the aerosol–cloud interaction parameterization (interactive versus non-interactive at medium resolution) on springtime subtropical marine Sc properties and SCTs in the atmosphere-only version of HadGEM3-GC3.1. No significant impact on the spatial location of the SCT could be found between the different model versions. Increasing horizontal resolution led to small but significant increases in liquid water content and a stronger (more negative) shortwave (SW) cloud radiative effect (CRE), in particular over the southern-hemisphere Sc regions. However, for two out of the four studied regions, the stronger SW CRE also brought the model outside the range of satellite-derived values of the SW CRE. Applying non-interactive aerosols instead of interactive aerosols also led to significantly higher liquid water content and a stronger SW CRE over the southern-hemisphere Sc regions, while over the northern-hemisphere Sc regions, a competition between a substantial increase in the cloud droplet number concentration and small changes in the liquid water content resulted in a weaker SW CRE or non-significant changes. In general, using interactive instead of non-interactive aerosol–cloud interactions brought the model closer to satellite-retrieved mean values of the SW CRE. Our results suggest that increasing the horizontal resolution or the complexity of the aerosol–cloud parameterization has a small but statistically significant effect on the SW CRE of marine Sc, in particular over regions with high liquid water content. For these regions, the effect of introducing non-interactive versus interactive aerosol–cloud interactions is about as large as increasing the horizontal resolution from medium to high. general circulation model; stratocumulus; aerosol–cloud interaction; stratocumulus-to-cumulus transition
Fasullo, John; Golaz, Jean-Christophe; Caron, Julie; Rosenbloom, Nan; Meehl, Gerald; Strand, Warren; Glanville, Sasha; Stevenson, Samantha; Molina, Maria; Shields, Christine; Zhang, Chengzhu; Benedict, James; Bartoletti, TonyFasullo, J., J. Golaz, J. Caron, N. Rosenbloom, G. Meehl, W. Strand, S. Glanville, S. Stevenson, M. Molina, C. Shields, C. Zhang, J. Benedict, T. Bartoletti, 2023: An Overview of the E3SM version 2 Large Ensemble and Comparison to other E3SM and CESM Large Ensembles. EGUsphere, 1-32. doi: 10.5194/egusphere-2023-2310. Abstract. This work assesses a recently produced 21-member climate model large ensemble (LE) based on the U.S. Department of Energy’s Energy Exascale Earth System Model (E3SM) version 2 (E3SM2). The ensemble spans the historical era (1850 to 2014) and 21st Century (2015 to 2100), using the SSP370 pathway, allowing for an evaluation of the model’s forced response (FR). A companion 500-year preindustrial control simulation is used to initialize the ensemble and estimate drift. Characteristics of the LE are documented and compared against other recently produced ensembles using the E3SM version 1 (E3SM1) and Community Earth System Model (CESM) versions 1 and 2. Simulation drift is found to be smaller, and model agreement with observations is higher, in versions 2 of E3SM and CESM versus their version 1 counterparts. Shortcomings in E3SM2 include a lack of warming from the mid to late 20th Century likely due to excessive cooling influence of anthropogenic sulfate aerosols, an issue also evident in E3SM1. Associated impacts on the water cycle and energy budgets are also identified. Considerable model dependence in the FR associated with both aerosol and greenhouse gas responses is documented and E3SM2’s sensitivity to variable prescribed biomass burning emissions is demonstrated. Various E3SM2 and CESM2 model benchmarks are found to be on par with the highest performing recent generation of climate models, establishing the E3SM2 LE as an important resource for estimating climate variability and responses, though with various caveats as discussed herein. As an illustration of the usefulness of LEs in estimating the potential influence of internal variability, the observed CERES-era trend in net top-of-atmosphere flux is compared to simulated trends and found to be much larger than the FR in all LEs, with only a few members exhibiting trends as large as observed, thus motivating further study.
Feng, Taichen; Yuan, Tiangang; Cao, Jiahui; Wang, Zhikuan; Zhi, Rong; Hu, Zhiyuan; Huang, JianpingFeng, T., T. Yuan, J. Cao, Z. Wang, R. Zhi, Z. Hu, J. Huang, 2023: The influence of dust on extreme precipitation at a large city in North China. Science of The Total Environment, 901, 165890. doi: 10.1016/j.scitotenv.2023.165890. In recent decades, the Beijing-Tianjin-Hebei city cluster is experiencing rapid urbanization along with economic booming. Meanwhile, these cities are suffering the influence of extreme precipitation and dust storms. In this study, the impact of dust aerosol on extreme precipitation that occurred in Beijing during 19–21 July 2016 is investigated using both satellite retrievals and Weather Research and Forecasting model coupled to Chemistry (WRF-Chem) model simulations. Results reveal that the dust particles can increase extreme precipitation by promoting the formation of ice clouds and enhancing convections. The dust is lifted into the upper troposphere (>10 km) via strong convection and affects the physical process of precipitation after long-range transport. It further transforms the supercooled water into the middle and high levels of ice nuclei (IN). These promote the formation of ice clouds according to the decreased effective radius of IN and increased ice water path, respectively. Along with sufficient water vapor transport and strong convergence, the formation of IN could release more latent heat and further strengthen convection development. Thus, the precipitation amount in southern Beijing is almost enhanced by 40 % (>80 mm). This study will provide a deep insight into understanding the causes of urban extreme precipitation. WRF-Chem; Dust aerosol; Extreme precipitation; Urbanization
Fernández-Soler, Alejandro; González-Bárcena, David; Torralbo-Gimeno, Ignacio; Pérez-Grande, IsabelFernández-Soler, A., D. González-Bárcena, I. Torralbo-Gimeno, I. Pérez-Grande, 2023: Ascent phase convective heat transfer of a stratospheric-balloon-borne payload. Advances in Space Research. doi: 10.1016/j.asr.2023.04.010. Stratospheric ballooning flights are becoming more relevant due to these platforms can place payloads to an altitude above almost 99% of the atmosphere, where the environmental conditions are very similar to the space ones. From the thermal point of view, during the ascent phase convection is very relevant and, despite what a priori may be thought, depending on the element considered, convection may not be negligible at the float phase. With this in mind, the Thermal Analysis Support and Environment Characterization Laboratory (TASEC-Lab) was born. It is an experiment based on COTS, which consists in a 3U CubeSat-like experiment, that was launched onboard a stratospheric balloon in León (Spain) on 16th, July 2021. The upper unit of the 3U box contains a heated plate, with the aim of quantifying the relevance of convection during the flight. In this paper, the relevance of convection during the ascent phase is described, the correlation of in-flight temperature measurements with those provided by the thermal mathematical model developed in ESATAN-TMS is performed, using the air mass flow inside the cavity as a fitting parameter with a fitting error lower than 5°C during the ascent phase. ascent phase; Ballooning; convection; correlation; ESATAN-TMS; thermal control; thermal modelling
Field, Paul R.; Hill, Adrian; Shipway, Ben; Furtado, Kalli; Wilkinson, Jonathan; Miltenberger, Annette; Gordon, Hamish; Grosvenor, Daniel P.; Stevens, Robin; Van Weverberg, KwintenField, P. R., A. Hill, B. Shipway, K. Furtado, J. Wilkinson, A. Miltenberger, H. Gordon, D. P. Grosvenor, R. Stevens, K. Van Weverberg, 2023: Implementation of a double moment cloud microphysics scheme in the UK met office regional numerical weather prediction model. Quarterly Journal of the Royal Meteorological Society, n/a(n/a). doi: 10.1002/qj.4414. Cloud microphysics parametrizations control the transfer of water between phases and hydrometeor species in numerical weather prediction and climate models. As a fundamental component of weather modelling systems cloud microphysics can determine the intensity and timing of precipitation, the extent and longevity of cloud cover and its impact on radiative balance, and directly influence near surface weather metrics such as temperature and wind. In this paper we introduce and demonstrate the performance of a double moment cloud microphysical scheme (CASIM: Cloud AeroSol Interacting Microphysics) in both midlatitude and tropical settings using the same model configuration. Comparisons are made against a control configuration using the current operational single moment cloud microphysics, and CASIM configurations that use fixed in-cloud droplet number or compute cloud droplet number concentration from the aerosol environment. We demonstrate that configuring CASIM as a single moment scheme results in precipitation rate histograms that match the operational single moment microphysics. In the midlatitude setting, results indicate that CASIM performs as well as the single moment microphysics configuration, but improves certain aspects of the surface precipitation field such as greater extent of light ( CASIM; double moment microphysics; NWP
Flores, Hauke; Veyssière, Gaëlle; Castellani, Giulia; Wilkinson, Jeremy; Hoppmann, Mario; Karcher, Michael; Valcic, Lovro; Cornils, Astrid; Geoffroy, Maxime; Nicolaus, Marcel; Niehoff, Barbara; Priou, Pierre; Schmidt, Katrin; Stroeve, JulienneFlores, H., G. Veyssière, G. Castellani, J. Wilkinson, M. Hoppmann, M. Karcher, L. Valcic, A. Cornils, M. Geoffroy, M. Nicolaus, B. Niehoff, P. Priou, K. Schmidt, J. Stroeve, 2023: Sea-ice decline could keep zooplankton deeper for longer. Nature Climate Change, 1-9. doi: 10.1038/s41558-023-01779-1. As Arctic sea ice deteriorates, more light enters the ocean, causing largely unknown effects on the ecosystem. Using an autonomous biophysical observatory, we recorded zooplankton vertical distribution under Arctic sea ice from dusk to dawn of the polar night. Here we show that zooplankton ascend into the under-ice habitat during autumn twilight, following an isolume of 2.4 × 10−4 W m−2. We applied this trigger isolume to CMIP6 model outputs accounting for incoming radiation after sunset and before sunrise of the polar night. The models project that, in about three decades, the total time spent by zooplankton in the under-ice habitat could be reduced by up to one month, depending on geographic region. This will impact zooplankton winter survival, the Arctic foodweb, and carbon and nutrient fluxes. These findings highlight the importance of biological processes during the twilight periods for predicting change in high-latitude ecosystems. Cryospheric science; Phenology; Biooceanography; Marine biology
Fonseca, Ricardo; Francis, Diana; Nelli, Narendra; Cherif, CharfeddineFonseca, R., D. Francis, N. Nelli, C. Cherif, 2023: Regional atmospheric circulation patterns driving consecutive fog events in the United Arab Emirates. Atmospheric Research, 282, 106506. doi: 10.1016/j.atmosres.2022.106506. In this study, the link between the occurrence of consecutive fog days in the United Arab Emirates (UAE) and the associated synoptic-scale circulation is investigated. This is particularly pertinent, as such a link may provide an important predictive skill for a phenomenon that has a pronounced impact on road and air traffic but is still poorly simulated by numerical models. A cluster analysis of all consecutive fog days from January 1983 to December 2021 indicated that the positive phase of the East Atlantic/Western Russia teleconnection pattern, Eastern Pacific La Nina events, and the circumglobal wavenumber 5 pattern promote the occurrence of multiple fog days in the UAE. The fog's radiative impacts, as estimated from satellite data, revealed that the fog in the UAE is more optically thick than that observed elsewhere. A trend analysis over the period 1983 to 2021 revealed that consecutive fog events have become more frequent and longer-lasting but less intense (i.e., associated with higher values of visibility). The fog's spatial extent over the UAE at its mature stage has also decreased over time. An analysis of the trends in the surface and top of atmosphere (TOA) radiative fluxes indicated that over the period 2000–2021, the fog clouds have likely become less reflective, with a statistically significant decrease in the surface downward shortwave and TOA upward longwave radiation fluxes. Long-term measurements of fog microphysics in the region are needed to better understand the variability in the properties of the fog cloud droplets. Atmospheric circulation; Trends; Boreal winter; Fog; Radiative impact; Teleconnections
Francis, Diana; Fonseca, Ricardo; Nelli, Narendra; Bozkurt, Deniz; Cuesta, Juan; Bosc, EmmanuelFrancis, D., R. Fonseca, N. Nelli, D. Bozkurt, J. Cuesta, E. Bosc, 2023: On the Middle East's severe dust storms in spring 2022: Triggers and impacts. Atmospheric Environment, 296, 119539. doi: 10.1016/j.atmosenv.2022.119539. Large amounts of dust in the air can disrupt daily activities and pose a threat to human health. In May 2022, consecutive major dust storms occurred over the Middle East resulting in severe environmental, social and health impacts. In this study, we investigate the exceptional factors driving these storms and the effects of the dust clouds. Using a combination of satellite, in-situ and reanalysis datasets, we identify the atmospheric triggers for the occurrence of these severe dust storms, characterize their three-dimensional structure and evaluate the dust radiative impact. The dust emission was promoted by density currents emanating from deep convection over Turkey. The convective systems were triggered by cut-off lows from mid-latitudes fed by moisture from African atmospheric rivers. Data from the Infrared Atmospheric Sounding Interferometer (IASI) showed that the dust clouds were transported southward at 4 km in altitudes but sunk to ground levels when they reached the southern Arabian Peninsula due to strong subsidence. At a station in coastal UAE, the dust caused a 350 W m−2 drop in the surface downward shortwave flux and a 70 W m−2 increase in the longwave one during the dust episodes. This contributed to a 9 °C increase in nighttime temperatures which exacerbated the effects of the heat for the population. The newly highlighted mechanism for dust emission in the Middle East, in which a cut-off low interacts with an atmospheric river, as well as direct observations of the dust impact on the radiative budget can contribute to reducing associated uncertainties in climate models. Atmospheric rivers; Cut-off low; Density currents; Drylands; Dust storms; IASI
Franzke, Christian L. E.; Harnik, NiliFranzke, C. L. E., N. Harnik, 2023: Long-Term Trends of the Atmospheric Circulation and Moist Static Energy Budget in the JRA-55 Reanalysis. J. Climate, 36(9), 2959-2984. doi: 10.1175/JCLI-D-21-0724.1. Abstract The atmospheric circulation response to global warming is an important problem that is theoretically still not well understood. This is a particular issue since climate model simulations provide uncertain, and at times contradictory, projections of future climate. In particular, it is still unclear how a warmer and moister atmosphere will affect midlatitude eddies and their associated poleward transport of heat and moisture. Here we perform a trend analysis of three main components of the global circulation—the zonal-mean state, eddies, and the net energy input into the atmosphere—and examine how they relate in terms of a moist static energy budget for the JRA-55 reanalysis data. A particular emphasis is made on understanding the contribution of moisture to circulation trends. The observed trends are very different between the hemispheres. In the Southern Hemisphere there is an overall strengthening and during boreal summer, also a poleward shifting, of the jet stream, the eddies, and the meridional diabatic heating gradients. Correspondingly, we find an overall strengthening of the meridional gradients of the net atmospheric energy input. In the Northern Hemisphere, the trend patterns are more complex, with the dominant signal being a clear boreal winter Arctic amplification of positive trends in lower-tropospheric temperature and moisture, as well as a significant weakening of both bandpass and low-pass eddy heat and moisture fluxes. Consistently, surface latent and sensible heat fluxes, upward and downward longwave radiation, and longwave cloud radiative fluxes at high latitudes show significant trends. However, radiative fluxes and eddy fluxes are inconsistent, suggesting data assimilation procedures need to be improved. Significance Statement We use a long-term reanalysis dataset to get an overall view of the changes in the global circulation and its role in transporting moist static energy from the equator to the poles. We do this by examining the trends in its three main components—the zonal means, the eddies, and the net energy input into the atmosphere. We find that in the Southern Hemisphere, there is an overall strengthening of the eddies, their poleward energy fluxes, and correspondingly the meridional gradients of the net atmospheric energy input. In the Northern Hemisphere, though the pattern is more complex, there is an overall weakening of the eddies and poleward eddy fluxes, and of the meridional gradients of the net atmospheric energy input, consistent with Arctic warming.
Furtado, K.; Tsushima, Y.; Field, P. R.; Rostron, J.; Sexton, D.Furtado, K., Y. Tsushima, P. R. Field, J. Rostron, D. Sexton, 2023: The Relationship Between the Present-Day Seasonal Cycles of Clouds in the Mid-Latitudes and Cloud-Radiative Feedback. Geophysical Research Letters, 50(15), e2023GL103902. doi: 10.1029/2023GL103902. We show that the seasonal cycles of clouds over the mid-latitude oceans in the Northern Hemisphere are predictors of the responses of clouds to increasing sea-surface temperatures globally. These regions are therefore “natural laboratories” in which the processes responsible for low-cloud feedbacks on global scales are observed as seasonal changes in local cloud properties. We use an ensemble of configurations of a global-climate model to show that the sensitivities of cloud-radiative anomalies to surface temperature and lower-tropospheric stability in the “laboratory” regions predict the models' global cloud-radiative feedbacks. Models with greater changes in low-clouds between seasons are shown to have stronger negative feedbacks in the mid-latitudes, and stronger positive feedbacks from the subtropical stratocumulus. The biases in the simulated seasonal cycles, compared to observations, imply that both feedbacks are too weak in the model. The consequences of this for configuring our model to have a lower climate sensitivity are discussed.
Gao, Lu; Huang, Qian; Yao, Suxiang; Sun, TianleGao, L., Q. Huang, S. Yao, T. Sun, 2023: Numerical study of the precipitation diurnal variation and its relationship with cloud radiative heating during the Meiyu period in 2020. Meteorology and Atmospheric Physics, 136(1), 3. doi: 10.1007/s00703-023-01000-0. Based on hourly rain gauge observation, cloud amount, and radiative fluxes data from the Clouds and the Earth’s Radiant Energy System (CERES) and ECMWF Reanalysis v5 (ERA5) dataset, the precipitation process during the Meiyu period in the middle and lower reaches of the Yangtze River in 2020 was simulated in WRF to reveal the influence of cloud radiative heating process on the diurnal variation of precipitation using multiple cloud microphysical schemes. The statistical evaluation of three microphysical parameterization schemes shows that the two-moment scheme WDM6 is more reasonable than the other two schemes in simulating the precipitation distribution, central intensity, and cloud characteristic distribution. There are significant bimodal characteristics in the diurnal variation of precipitation during the Meiyu period by analyzing the observation data. The numerical experiment accurately simulated the time and magnitude of the early morning peak in the heavy rain area but failed to reproduce the peak in the late afternoon, resulting in a false weak rainfall accumulation. The comparison of simulation results with the observed cloud macroscale and microscale characteristics revealed that the reason for the deviation of precipitation simulation was closely related to the inaccurate description of cloud microphysical quantities. The lack of ice phase cloud droplets led to excessively strong radiative heating rate at 200–500 hPa, resulting in anomalous warming in the mid-upper troposphere. Meanwhile, the cold advection at 850 hPa led to anomalous cooling in the lower troposphere, increasing atmospheric stability and further inhibiting the development of the afternoon thermal convection process.
Gautam, Ritesh; Patel, Piyushkumar N.; Singh, Manoj K.; Liu, Tianjia; Mickley, Loretta J.; Jethva, Hiren; DeFries, Ruth S.Gautam, R., P. N. Patel, M. K. Singh, T. Liu, L. J. Mickley, H. Jethva, R. S. DeFries, 2023: Extreme Smog Challenge of India Intensified by Increasing Lower Tropospheric Stability. Geophysical Research Letters, 50(11), e2023GL103105. doi: 10.1029/2023GL103105. Extreme smog in India widely impacts air quality in late autumn and winter months. While the links between emissions, air quality and health impacts are well-recognized, the association of smog and its intensification with climatic trends in the lower troposphere, where aerosol pollution and its radiative effects manifest, are not understood well. Here we use long-term satellite data to show a significant increase in aerosol exceedances over northern India, resulting in sustained atmospheric warming and surface cooling trends over the last two decades. We find several lines of evidence suggesting these aerosol radiative effects have induced a multidecadal (1980–2019) strengthening of lower tropospheric stability and increase in relative humidity, leading to over fivefold increase in poor visibility days. Given this crucial aerosol-radiation-meteorological feedback driving the smog intensification, results from this study would help inform mitigation strategies supporting stronger region-wide measures, which are critical for solving the smog challenge in India. aerosols; India; meteorology; satellite data; smog
Gavrouzou, Maria; Hatzianastassiou, Nikos; Korras-Carraca, Marios-Bruno; Stamatis, Michalis; Lolis, Christos; Matsoukas, Christos; Michalopoulos, Nikos; Vardavas, IliasGavrouzou, M., N. Hatzianastassiou, M. Korras-Carraca, M. Stamatis, C. Lolis, C. Matsoukas, N. Michalopoulos, I. Vardavas, 2023: Three-Dimensional Distributions of the Direct Effect of anExtended and Intense Dust Aerosol Episode (16–18 June 2016) over the Mediterranean Basin on Regional Shortwave Radiation, Atmospheric Thermal Structure, and Dynamics. Applied Sciences, 13(12), 6878. doi: 10.3390/app13126878. In the present study, we used the FORTH deterministic spectral Radiation Transfer Model (RTM) to estimate detailed three-dimensional distributions of the Direct Radiative Effects (DREs) and their consequent modification of the thermal structure of the regional atmosphere during an intense dust episode that took place from 16 to 18 June 2016 over the Mediterranean Basin (MB). The RTM operated on a 3-hourly temporal and 0.5 × 0.625° spatial resolution, using 3-D aerosol optical properties (i.e., aerosol optical depth, single scattering albedo, and asymmetry parameter) and other surface and atmospheric properties from the MERRA-2 reanalysis and cloud properties (i.e., cloud amount, cloud optical depth, and cloud top height) from the ISCCP-H dataset. The model ran with and without dust aerosols, yielding the upwelling and downwelling solar fluxes at the top of the atmosphere, in the atmosphere, and at the Earth’s surface as well as at 50 levels in the atmosphere. The dust direct radiative effect (DDRE) was estimated as the difference between the two (one taking into account all aerosol types and one taking into account all except for dust aerosols) flux outputs. The atmospheric heating rates and subsequent convection induced by dust radiative absorption were calculated at 50 levels to determine how the DDRE affects the thermal structure and dynamics of the atmosphere. The results showed that such a great and intense dust transport event significantly reduces the net surface solar radiation over the MB (by up to 62 W/m2 on a daily mean basis, and up to 200 W/m2 on an hourly basis, at 12:00 UTC) while increasing the atmospheric solar absorption (by up to 72 W/m2 daily and 187 W/m2 hourly, at 12:00 UTC). At the top of the atmosphere, both heating (over desert areas) and cooling (over oceanic and other continental areas) are observed due to the significantly different surface albedos. Transported dust causes considerable heating of the region’s atmosphere, which becomes maximum at altitudes where the dust loadings are highest (0.14 K/3 h on 17 June 2016, 12:00 UTC, at 3–5 km above sea level). The dust solar absorption and heating induce a buoyancy as strong as 0.014 m/s2, resulting in considerable changes in vertical air motions and possibly contributing to the formation of middle- and high-level clouds over the Mediterranean Basin. radiative forcing; heating rates; buoyancy; dust episodes; Mediterranean Basin
Ge, Jun; Huang, Xin; Zan, Beilei; Qiu, Bo; Cao, Yipeng; Guo, WeidongGe, J., X. Huang, B. Zan, B. Qiu, Y. Cao, W. Guo, 2023: Local surface cooling from afforestation amplified by lower aerosol pollution. Nature Geoscience, 16(9), 781-788. doi: 10.1038/s41561-023-01251-x. Afforestation can play a key role in local climate mitigation by influencing local temperature through changes in land surface properties. Afforestation impacts depend strongly on the background climate, with contrasting effects observed across geographical locations, seasons and levels of greenhouse gas-induced warming. Meanwhile, atmospheric aerosols, which are a critical factor influencing regional climate, have varied substantially in recent decades and will continue to change. However, the impacts of aerosol changes on the local effects of afforestation remain unknown. Here, using multiple emissions scenario-based simulations, we show that lower anthropogenic emissions can modulate the local effects of afforestation through modifications in the surface energy balance. If current anthropogenic emissions are reduced to preindustrial levels, afforestation can produce additional cooling effects of up to 0.4 °C. The cooling effects of afforestation are projected to be most strongly affected in China if strict control measures on air pollution are adopted in the future. Our results demonstrate that the enhanced cooling effects of afforestation could partially counteract the warming effect of air quality control, with implications for countries that face the dual challenges of clean air and climate mitigation. Climate change; Environmental impact; Climate-change mitigation; Atmospheric chemistry
Ghausi, Sarosh Alam; Tian, Yinglin; Zehe, Erwin; Kleidon, AxelGhausi, S. A., Y. Tian, E. Zehe, A. Kleidon, 2023: Radiative controls by clouds and thermodynamics shape surface temperatures and turbulent fluxes over land. Proceedings of the National Academy of Sciences, 120(29), e2220400120. doi: 10.1073/pnas.2220400120. Land surface temperatures (LSTs) are strongly shaped by radiation but are modulated by turbulent fluxes and hydrologic cycling as the presence of water vapor in the atmosphere (clouds) and at the surface (evaporation) affects temperatures across regions. Here, we used a thermodynamic systems framework forced with independent observations to show that the climatological variations in LSTs across dry and humid regions are mainly mediated through radiative effects. We first show that the turbulent fluxes of sensible and latent heat are constrained by thermodynamics and the local radiative conditions. This constraint arises from the ability of radiative heating at the surface to perform work to maintain turbulent fluxes and sustain vertical mixing within the convective boundary layer. This implies that reduced evaporative cooling in dry regions is then compensated for by an increased sensible heat flux and buoyancy, which is consistent with observations. We show that the mean temperature variation across dry and humid regions is mainly controlled by clouds that reduce surface heating by solar radiation. Using satellite observations for cloudy and clear-sky conditions, we show that clouds cool the land surface over humid regions by up to 7 K, while in arid regions, this effect is absent due to the lack of clouds. We conclude that radiation and thermodynamic limits are the primary controls on LSTs and turbulent flux exchange which leads to an emergent simplicity in the observed climatological patterns within the complex climate system.
Ghosh, Sushovan; Kumar, Alok; Ganguly, Dilip; Dey, SagnikGhosh, S., A. Kumar, D. Ganguly, S. Dey, 2023: India's Photovoltaic Potential amidst Air Pollution and Land Constraints. iScience, 107856. doi: 10.1016/j.isci.2023.107856. India aims for ambitious solar energy goal to fulfil its climate commitment but limited studies on solar resource assessment considering both environmental and land availability constraints. Present work attempts to address this issue using satellite-derived air pollution, radiation, and land use data over the Indian region. Surface insolation over India has been decreasing at a rate of -0.29±0.19 Wm-2 y-1 between 2001 to 2018. Solar resources over nearly 98%, 40%, and 39% of the Indian landmass are significantly impacted by aerosols, clouds, and both aerosols and clouds respectively. Only 29.3% of the Indian landmass is presently suitable for effective solar photovoltaic harnessing, but this is further declining by -0.21% annually, causing a presumptive loss of 50 GW solar potential, translating 75 TWh power generation. Lowering two decades of aerosol burden can make 8% additional landmass apt for photovoltaic use. Alleviating aerosol-induced dimming can fast-track India's solar energy expansion. India; Global dimming and brightening; Global Human Settlement Layer (GHSL); Normalized Difference Vegetation Index (NDVI); Solar energy resources; Solar photovoltaic (SPV)
Goodwin, Philip; Williams, Richard G.Goodwin, P., R. G. Williams, 2023: On the Arctic Amplification of surface warming in a conceptual climate model. Physica D: Nonlinear Phenomena, 454, 133880. doi: 10.1016/j.physd.2023.133880. Over the last century Earth’s surface temperatures have warmed by order 1 K as a global average, but with significant variation in latitude: there has been most surface warming at high Northern latitudes, around 3 times more than in low latitude regions (termed Arctic Amplification), while there has been least warming over the Southern Ocean. Many contributing processes have been suggested to explain this asymmetrical latitudinal warming pattern, but quantification of the contributing factors responsible remains elusive. Complex general circulation climate models can reproduce similar asymmetrical patterns of warming, but it can be difficult to interpret the contributing processes. Meanwhile, idealised conceptual energy balance climate models have been able to reproduce a general polar amplification of warming whose origins can be interpreted, but this warming is often symmetrical across both hemispheres and may not be responsible for the real-world pattern. Here, we use a conceptual Energy Balance Model, with imposed closures for initial horizontal diffusivity and cloudiness drawing upon observational constraints and including temperature-dependent diffusivity and a sub-surface ocean heat reservoir, to show that the magnitude of present-day Arctic Amplification may arise through relatively simple thermodynamic (Clausius–Clapeyron) and radiative (climate feedback) processes. The current asymmetry between hemispheric warming may arise due to the transient heat transport up through the base of the surface ocean mixed layer from the slow-responding deep ocean to the fast-responding surface ocean being dominated by upwelling in the Southern Ocean. It should be noted that the processes identified here are not a unique in offering a potential solution, and so significant, or dominant, roles for dynamical processes remain plausible explanations for Arctic Amplification. Arctic amplification; Conceptual climate modelling; Energy balance climate models; Polar amplification
Gristey, Jake J.; Schmidt, K. Sebastian; Chen, Hong; Feldman, Daniel R.; Kindel, Bruce C.; Mauss, Joshua; van den Heever, Mathew; Hakuba, Maria Z.; Pilewskie, PeterGristey, J. J., K. S. Schmidt, H. Chen, D. R. Feldman, B. C. Kindel, J. Mauss, M. van den Heever, M. Z. Hakuba, P. Pilewskie, 2023: Angular sampling of a monochromatic, wide-field-of-view camera to augment next-generation Earth radiation budget satellite observations. Atmospheric Measurement Techniques, 16(15), 3609-3630. doi: 10.5194/amt-16-3609-2023. Earth radiation budget (ERB) satellite observations require conversion of the measured radiance, which is a remotely sensed quantity, to a derived irradiance, which is the relevant energy balance quantity routinely used in modeling and analysis of the climate system. The state-of-the-art approach for radiance-to-irradiance conversion taken by the Clouds and the Earth's Radiant Energy System (CERES) benefits from the exhaustive sampling of radiance anisotropy by multiple CERES instruments across many years. Unfortunately, the CERES approach is not easily extended to new ERB spectral channels that lack previous sampling, such as the “split-shortwave” planned to be part of the next-generation ERB mission Libera. As an alternative approach, the capability of a monochromatic, wide-field-of-view camera to provide dense angular sampling in a much shorter time frame is assessed. We present a general concept for how this can be achieved and quantify the proficiency of a camera to provide rapid angular distribution model (ADM) generation for the new Libera ultraviolet and visible (VIS) sub-band. A single mid-visible camera wavelength (555 nm) is shown to be ideal for representing the VIS sub-band, requiring only basic scene stratification for 555 nm to VIS conversion. Synthetic camera sampling with realistic operating constraints also demonstrates that the angular radiance field of various scenes can be well populated within a single day of sampling, a notable advance over existing approaches. These results provide a path for generating observationally based VIS ADMs with minimal lag time following Libera's launch. Coupled with efforts to utilize a camera for scene identification, this may also pave the way for future ERB satellite systems to develop stand-alone irradiance products for arbitrary sets of spectral channels, opening up new measurement and science possibilities.
Gupta, Mayank; Wild, Martin; Ghosh, SubimalGupta, M., M. Wild, S. Ghosh, 2023: Analytical framework based on thermodynamics to estimate spatially distributed surface energy fluxes from remotely sensed radiations. Remote Sensing of Environment, 295, 113659. doi: 10.1016/j.rse.2023.113659. The Limited surface observations of turbulent heat fluxes result in incomplete knowledge about the surface energy balance that drives the climate system. The highly parameterized surface energy balance models suffer from significant uncertainties. Remote sensing information of incoming and outgoing radiation fluxes are important input variables for turbulent heat flux models, though analytical solutions of surface energy budget from these variables are yet to be derived. Here, we developed a novel, purely physics-based analytical method grounded on the thermodynamic principle of maximum power. The approach derives the total turbulent heat flux only from the four inputs of incoming and outgoing longwave and shortwave radiations at the land surface, which are available from remotely sensed satellite data. The proposed approach does not use any parameterization, unlike the existing surface energy balance models, and hence does not suffer from uncertainty due to the same. We validated our methodology with 102 eddy covariance observation stations around the globe with different land use land covers from FLUXNET2015 and available urban datasets. Based on monthly averages of the total turbulent flux estimates for the eddy covariance sites, we observed root-mean-square error (RMSE) of 23.2 ± 10.9 Wm−2, a mean bias error (MBE) of 11.9 ± 13.1 Wm−2 and R2 value of 0.86 ± 0.15. Using the satellite observations of radiation fluxes from CERES at a spatial resolution of 10, we obtained the global flux field of total turbulent flux (QJ) and land surface heat storage (ΔQs) fluxes. On validation of QJ with FLUXNET sites for six grids for different land use land cover, we found RMSE of 20.1 ± 7 Wm−2, MBE of 14.4 ± 9 Wm−2 and R2 value of 0.96 ± 0.02. Further, from the evaporative stress factor of GLEAM, which is based on microwave remotely sensed vegetation optical depth and root zone soil moisture, we have obtained spatially distributed global estimates of Sensible(H) and latent heat (LE). In addition, our analytical estimates address the distribution of residual energy associated with the surface energy balance closure problem driven by the land use land cover. The theoretical estimates of all surface energy balance components from remote sensing based observations will improve our understanding of surface warming for different land use land covers across the globe. Radiation balance; Satellite based radiation; Surface eneregy balance; Thermodynamics
Hadas, Or; Datseris, George; Blanco, Joaquin; Bony, Sandrine; Caballero, Rodrigo; Stevens, Bjorn; Kaspi, YohaiHadas, O., G. Datseris, J. Blanco, S. Bony, R. Caballero, B. Stevens, Y. Kaspi, 2023: The role of baroclinic activity in controlling Earth’s albedo in the present and future climates. Proceedings of the National Academy of Sciences, 120(5), e2208778120. doi: 10.1073/pnas.2208778120. Clouds are one of the most influential components of Earth’s climate system. Specifically, the midlatitude clouds play a vital role in shaping Earth’s albedo. This study investigates the connection between baroclinic activity, which dominates the midlatitude climate, and cloud-albedo and how it relates to Earth’s existing hemispheric albedo symmetry. We show that baroclinic activity and cloud-albedo are highly correlated. By using Lagrangian tracking of cyclones and anticyclones and analyzing their individual cloud properties at different vertical levels, we explain why their cloud-albedo increases monotonically with intensity. We find that while for anticyclones, the relation between strength and cloudiness is mostly linear, for cyclones, in which clouds are more prevalent, the relation saturates with strength. Using the cloud-albedo strength relationships and the climatology of baroclinic activity, we demonstrate that the observed hemispheric difference in cloud-albedo is well explained by the difference in the population of cyclones and anticyclones, which counter-balances the difference in clear-sky albedo. Finally, we discuss the robustness of the hemispheric albedo symmetry in the future climate. Seemingly, the symmetry should break, as the northern hemisphere’s storm track response differs from that of the southern hemisphere due to Arctic amplification. However, we show that the saturation of the cloud response to storm intensity implies that the increase in the skewness of the southern hemisphere storm distribution toward strong storms will decrease future cloud-albedo in the southern hemisphere. This complex response explains how albedo symmetry might persist even with the predicted asymmetric hemispheric change in baroclinicity under climate change.
Hakuba, Maria Z.; Reynerson, Charles M.; Quadrelli, Marco B.; Wiese, David N.; Mccullough, Christopher; Landerer, Felix W.; Stephens, Graeme L.Hakuba, M. Z., C. M. Reynerson, M. B. Quadrelli, D. N. Wiese, C. Mccullough, F. W. Landerer, G. L. Stephens, 2023: Measuring Earth's Energy Imbalance via Radiation Pressure Accelerations Experienced in Orbit: Initial Simulations for “Space Balls”. 2023 IEEE Aerospace Conference, 1-10. doi: 10.1109/AERO55745.2023.10115678. The direct measurement of Earth's radiative Energy Imbalance (EEI) from space is a challenge for state-of-the-art radiometric observing systems. Current spaceborne radiometers measure the individual shortwave (Solar incoming and Earth reflected solar radiation) and longwave (Earth emitted thermal radiation) components of Earth's energy balance with unprecedented stability, but with calibration errors that are too large to determine the absolute magnitude of global mean EEI or net radiative flux, respectively, as the components' residual. Best estimates of multi-year (2005–2020) EEI are derived from temporal changes in planetary heat content, predominantly ocean heat content, and amount to 0.9 Wm−2. To monitor EEI directly from space, we propose an independent approach based on accelerometry that measures non-gravitational radial accelerations induced by radiation pressure. To provide requirements for a near-spherical “Space Balls” spacecraft and mission design, we develop a simulation environment using JPL's Mission Analysis, Operations, and Navigation Toolkit Environment (MONTE) software libraries and present-day radiative fluxes from the Clouds and Earth's Radiant Energy System (CERES). At its current initial stage, the toolset allows us to simulate accelerations acting on a spherical spacecraft due to solar radiation pressure, Earth's reflected shortwave (albedo) and emitted longwave radiation, as well as due to aerodynamic force. Induced accelerations as well as their sensitivity to mean orbit altitude and spacecraft absorptivity agree well with back-of the-envelope calculations and previous simulations that assess the role of radiation pressure accelerations for orbital drift. Future investigations will expand the MONTE-based simulation environment with additional shape and confounding force models. Preliminary simulations with an integrated spacecraft dynamics model suggest that the main confounding accelerations for a non-perfect, faceted sphere are related to Yarkovsky, aerodynamic force and relativistic effects, which will have to be mitigated to facilitate a high-accuracy EEI measurement from space. Earth; Extraterrestrial measurements; Sea measurements; Space vehicles; Energy measurement; Accelerometers; Force
Hao, Dalei; Bisht, Gautam; Gu, Yu; Leung, L. RubyHao, D., G. Bisht, Y. Gu, L. R. Leung, 2023: Regional and Teleconnected Impacts of Solar Radiation-Topography Interaction Over the Tibetan Plateau. Geophysical Research Letters, 50(23), e2023GL106293. doi: 10.1029/2023GL106293. Solar radiation-topography interaction plays an important role in surface energy balance over the Tibetan Plateau (TP). However, the impacts of such interaction over the TP on climate locally and in the Asian regions remain unclear. This study uses the Energy Exascale Earth System Model (E3SM) to evaluate the regional and teleconnected impacts of solar radiation-topography interaction over the TP. Land-atmosphere coupled experiments show that topography regulates the surface energy balance, snow processes, and surface climate over the TP across seasons. Accounting for solar radiation-topography interaction improves E3SM simulation of surface climate. The winter cold bias in air temperature decreases from −4.57 to −3.79 K, and the wet bias in summer precipitation is mitigated in southern TP. The TP's solar radiation-topography interaction further reduces the South and East Asian summer precipitation biases. Our results demonstrate the topographic roles in regional climate over the TP and highlight its teleconnected climate impacts. Tibetan Plateau; E3SM; East Asian summer monsoon; surface energy balance; radiation-topography interaction; teleconnected impacts
Heim, Christoph; Leutwyler, David; Schär, ChristophHeim, C., D. Leutwyler, C. Schär, 2023: Application of the Pseudo-Global Warming Approach in a Kilometer-Resolution Climate Simulation of the Tropics. Journal of Geophysical Research: Atmospheres, 128(5), e2022JD037958. doi: 10.1029/2022JD037958. Clouds over tropical oceans are an important factor in the Earth's response to increased greenhouse gas concentrations, but their representation in climate models is challenging due to the small-scale nature of the involved convective processes. We perform two 4-year-long simulations at kilometer-resolution (3.3 km horizontal grid spacing) with the limited-area model COSMO over the tropical Atlantic on a 9,000 × 7,000 km2 domain: A control simulation under current climate conditions driven by the ERA5 reanalysis, and a climate change scenario simulation using the Pseudo-Global Warming approach. We compare these results to the changes projected in the CMIP6 scenario ensemble. Validation shows a good representation of the annual cycle of albedo, in particular for trade-wind clouds, even compared to the ERA5 reanalysis. Also, the vertical structure and annual cycle of the intertropical convergence zone (ITCZ) is accurately simulated, and the simulation does not suffer from the double ITCZ problem commonly present in global climate models (GCMs). The response to global warming differs between the COSMO simulation and the analyzed GCMs. While both exhibit an overall weakening of the Hadley circulation, the narrowing of the ITCZ (known as the deep-tropics squeeze) is not so pronounced in the kilometer-resolution simulation, likely due to the absence of a double ITCZ bias. Also, there is a more pronounced intensification of the ITCZ at the equator in the kilometer-resolution COSMO simulation, and a stronger associated increase in the anvil cloud fraction. ITCZ; climate simulation; tropical clouds; Hadley cell; kilometer-resolution model; tropical low clouds
Hill, P. G.; Holloway, C. E.; Byrne, M. P.; Lambert, F. H.; Webb, M. J.Hill, P. G., C. E. Holloway, M. P. Byrne, F. H. Lambert, M. J. Webb, 2023: Climate Models Underestimate Dynamic Cloud Feedbacks in the Tropics. Geophysical Research Letters, 50(15), e2023GL104573. doi: 10.1029/2023GL104573. Cloud feedbacks are the leading cause of uncertainty in climate sensitivity. The complex coupling between clouds and the large-scale circulation in the tropics contributes to this uncertainty. To address this problem, the coupling between clouds and circulation in the latest generation of climate models is compared to observations. Significant biases are identified in the models. The implications of these biases are assessed by combining observations of the present day with future changes predicted by models to calculate observationally constrained feedbacks. For the dynamic cloud feedback (i.e., due to changes in circulation), the observationally constrained values are consistently larger than the model-only values. This is due to models failing to capture a nonlinear minimum in cloud brightness for weakly descending regimes. Consequently, while the models consistently predict that these regimes increase in frequency in association with a weakening tropical circulation, they underestimate the positive cloud feedback associated with this increase.
Horner, George; Gryspeerdt, EdwardHorner, G., E. Gryspeerdt, 2023: The evolution of deep convective systems and their associated cirrus outflows. Atmospheric Chemistry and Physics, 23(22), 14239-14253. doi: 10.5194/acp-23-14239-2023. Tropical deep convective clouds, particularly their large cirrus outflows, play an important role in modulating the energy balance of the Earth's atmosphere. Whilst the cores of these deep convective clouds have a significant short-wave (SW) cooling effect, they dissipate quickly. Conversely, the thin cirrus that flow from these cores can persist for days after the core has dissipated, reaching hundreds of kilometres in extent. These thin cirrus have a potential for large warming in the tropics. Understanding the evolution of air parcels from deep convection, clouds along these trajectories, and how they change in response to anthropogenic emissions is therefore important to understand past and future climate change. This work uses a novel approach to investigate the evolution of tropical convective clouds by introducing the concept of “time since convection” (TSC). This is used to build a composite picture of the lifecycle of air parcels from deep convection. Cloud properties are a strong function of TSC, showing decreases in the optical thickness, cloud-top height, and cloud fraction over time, thereby driving the latitudinal structure of cloudiness. After an initial dissipation of the convective core, changes in thin cirrus cloud amount were seen beyond 200 h from convection. Changes in cloud are shown to be a strong function of TSC and not simply reflective of latitudinal changes as air moves from the tropics to the extratropics. Finally, in the initial stages of convection there was a large net negative cloud radiative effect (CRE). However, once the convective core had dissipated, the sign of the CRE flipped and there was a sustained net warming CRE beyond 120 h from the convective event. Changes are present in the cloud properties long after the main convective activities have dissipated, signalling the need to continue further analysis at longer timescales than previously studied.
Horvath, Sean; Boisvert, Linette; Parker, Chelsea; Webster, Melinda; Taylor, Patrick; Boeke, Robyn; Fons, Steven; Stewart, J. ScottHorvath, S., L. Boisvert, C. Parker, M. Webster, P. Taylor, R. Boeke, S. Fons, J. S. Stewart, 2023: Database of daily Lagrangian Arctic sea ice parcel drift tracks with coincident ice and atmospheric conditions. Scientific Data, 10(1), 73. doi: 10.1038/s41597-023-01987-6. Since the early 2000s, sea ice has experienced an increased rate of decline in thickness, extent and age. This new regime, coined the ‘New Arctic’, is accompanied by a reshuffling of energy flows at the surface. Understanding of the magnitude and nature of this reshuffling and the feedbacks therein remains limited. A novel database is presented that combines satellite observations, model output, and reanalysis data with sea ice parcel drift tracks in a Lagrangian framework. This dataset consists of daily time series of sea ice parcel locations, sea ice and snow conditions, and atmospheric states, including remotely sensed surface energy budget terms. Additionally, flags indicate when sea ice parcels travel within cyclones, recording cyclone intensity and distance from the cyclone center. The quality of the ice parcel database was evaluated by comparison with sea ice mass balance buoys and correlations are high, which highlights the reliability of this database in capturing the seasonal changes and evolution of sea ice. This database has multiple applications for the scientific community; it can be used to study the processes that influence individual sea ice parcel time series, or to explore generalized summary statistics and trends across the Arctic. Cryospheric science; Physics
Hsu, Wei-Ching; Kooperman, Gabriel J.; Hannah, Walter M.; Reed, Kevin A.; Akinsanola, Akintomide A.; Pendergrass, Angeline G.Hsu, W., G. J. Kooperman, W. M. Hannah, K. A. Reed, A. A. Akinsanola, A. G. Pendergrass, 2023: Evaluating Mesoscale Convective Systems Over the US in Conventional and Multiscale Modeling Framework Configurations of E3SMv1. Journal of Geophysical Research: Atmospheres, 128(23), e2023JD038740. doi: 10.1029/2023JD038740. Organized mesoscale convective systems (MCSs) contribute a significant amount of precipitation in the Central and Eastern US during spring and summer, which impacts the availability of freshwater and flooding events. However, current global Earth system models cannot capture MCSs well and misrepresent the statistics of precipitation in the region. In this study, we investigate the representation of MCSs in three configurations of the Energy Exascale Earth System Model (E3SMv1) by tracking individual storms based on outgoing longwave radiation using a new application of TempestExtremes. Our results indicate that conventional parameterizations of convection, implemented in both low (LR; ∼150 km) and high (HR; ∼25 km) resolution configurations, fail to capture almost all MCS-like events, in-part because they underestimate high-level cloud ice associated with deep convection. On the other hand, the multiscale modeling framework (MMF; cloud-resolving models embedded in each grid-column of ∼150 km resolution E3SMv1) configuration represents MCSs and their annual cycle better. Nevertheless, relative to observations, the E3SMv1-MMF spatial distribution of MCSs and associated precipitation is shifted eastward, and the diurnal timing is lagged. A comparison between the large-scale environment in E3SMv1-MMF and ERA5 reanalysis suggests that the biases during the summer in E3SMv1-MMF are associated with biases in low-level humidity and meridional moisture transport within the low-level jet. The fact that conventional parameterizations of convection, even with high-resolution, cannot capture MCSs over the US suggests that methods with explicit representation of kilometer-scale convective organization, such as the MMF, may be necessary for improving the simulation of these convective systems. multiscale modeling framework; E3SMv1; mesoscale convection systems
Hu, Liang; Ritchie, Elizabeth A.; Scott Tyo, J.Hu, L., E. A. Ritchie, J. Scott Tyo, 2023: Quantifying the cooling effect of tropical cyclone clouds on the climate system. npj Climate and Atmospheric Science, 6(1), 1-10. doi: 10.1038/s41612-023-00433-z. The net effect on the upwelling radiation caused by tropical cyclone clouds is calculated over a 20-year global data set, and the corresponding contribution to the earth energy balance is analyzed. Tropical cyclone clouds are shown on average to increase the upwelling radiation at the top of the atmosphere compared with the background non-tropical-cyclone-cloud climatology. This increase in upwelling radiation provides an overall cooling effect on the climate system because the increased reflected shortwave radiation (cooling) outweighs the decreased emitted longwave radiation (warming). While the effect neglects the (likely considerable) contribution due to tropical cyclone drying, the amount of cooling by clouds alone represents a considerable fraction of the excess warming energy in the climate system. Thus, any future change in tropical cyclone activity has the potential to impact the overall energy balance if it substantially alters this total. The seasonal and geographic distribution of warming and cooling effects, and the diurnal dynamics that impact whether any particular cyclone is net cooling or net warming are discussed in this study. Climate change; Atmospheric dynamics
Hu, Wenting; Duan, Anmin; Wu, Guoxiong; Mao, Jiangyu; He, BianHu, W., A. Duan, G. Wu, J. Mao, B. He, 2023: Quasi-Biweekly Oscillation of Surface Sensible Heating over the Central-Eastern Tibetan Plateau and Its Relationship with Spring Rainfall in China. J. Climate, 36(19), 6917-6936. doi: 10.1175/JCLI-D-22-0892.1. Abstract This study examines the characteristics and phase evolution of the quasi-biweekly oscillation of surface sensible heating (SH) over the central-eastern Tibetan Plateau (CETP) during spring. The mechanism connecting CETP SH to spring rainfall in China on the quasi-biweekly time scale is further investigated. Results show that the dominant mode of quasi-biweekly CETP SH presents a monopole pattern, in which the peak leads the maximum of the quasi-biweekly rainfall in the middle and lower reaches of the Yangtze River (MLYR) and South China by approximately 5 and 7 days, respectively. As an upper-level Rossby wave train propagates eastward, an anomalous center of convergence moves to the CETP, which leads to a strong downdraft and reduced cloud cover. The resultant elevated shortwave radiation input and drier soil conditions are favorable for the CETP SH quasi-biweekly oscillation to enter a positive phase. When reaching its peak, the CETP SH efficiently heats the lower atmosphere, resulting in a local updraft. Due to the “SH-driven air pump” effect, abundant water vapor is transported from the oceans to China. A lower-layer southerly anomaly on the east side of the TP develops into an anomalous cyclonic circulation via the effect of topographic friction, which leads to the expansion of the positive potential vorticity anomaly and the maximum of the quasi-biweekly rainfall in the MLYR. Further southeastward propagation of the wave train leads to a shift in the rainfall anomaly center to South China. These findings suggest that the CETP monopole SH warming could be a good indicator for predicting intraseasonal variations in spring rainfall over China.
Huang, Han; Huang, YiHuang, H., Y. Huang, 2023: Diagnosing the Radiation Biases in Global Climate Models Using Radiative Kernels. Geophysical Research Letters, 50(13), e2023GL103723. doi: 10.1029/2023GL103723. Radiation energy balance at the top of the atmosphere (TOA) is a critical boundary condition for the Earth climate. It is essential to validate it in the global climate models (GCM) on both global and regional scales. However, the comparison of overall radiation field is known to conceal compensating errors. Here we use a new set of radiative kernels to diagnose the radiation biases caused by different geophysical variables in the GCMs of the Coupled Model Intercomparison Project. We find although clouds remain a primary cause of radiation biases, the radiation biases caused by non-cloud variables are of comparable magnitudes. Many GCMs have a cold air temperature bias and a moist tropospheric humidity bias, which lead to considerable biases in TOA radiation budget but are compensated by cloud biases. These findings signify the importance of validating the GCM simulations in terms of both the overall and component radiation biases. CMIP6; energy budget; radiation biases
Hulsman, P.; Keune, J.; Koppa, A.; Schellekens, J.; Miralles, D. G.Hulsman, P., J. Keune, A. Koppa, J. Schellekens, D. G. Miralles, 2023: Incorporating Plant Access to Groundwater in Existing Global, Satellite-Based Evaporation Estimates. Water Resources Research, 59(8), e2022WR033731. doi: 10.1029/2022WR033731. Groundwater is an important water source for evaporation, especially during dry conditions. Despite this recognition, plant access to groundwater is often neglected in global evaporation models. This study proposes a new, conceptual approach to incorporate plant access to groundwater in existing global evaporation models, and analyses the groundwater contribution to evaporation globally. To this end, the Global Land Evaporation Amsterdam Model (GLEAM) is used. The new GLEAM-Hydro model relies on the linear reservoir assumption for modeling groundwater flow, and introduces a transpiration partitioning approach to estimate groundwater contributions. Model estimates are validated globally against field observations of evaporation, soil moisture, discharge and groundwater level for the time period 2015–2021, and compared to a regional groundwater model. Representing groundwater access influences evaporation in 22% of the continental surface. Globally averaged, evaporation increases by 2.5 mm year−1 (0.5% of terrestrial evaporation), but locally, evaporation can increase up to 245.2 mm year−1 (149.7%). The groundwater contribution to transpiration is highest for tall vegetation under dry conditions due to more frequent groundwater access. The temporal dynamics of the simulated evaporation improve across 75% of the stations where groundwater is a relevant water source. The skill of the model for variables such as soil moisture and runoff remains similar to GLEAM v3. The proposed approach enables a more realistic process representation of evaporation under water-limited conditions in satellite-data driven models such as GLEAM, and sets the ground to assimilate satellite gravimetry data in the future. satellite observations; evaporation; GLEAM; groundwater
Ibrahim, Hamed D.; Sun, YunfangIbrahim, H. D., Y. Sun, 2023: Sea Surface Cooling by Rainfall Modulates Earth’s Heat Energy Flow. J. Climate, 36(15), 5125-5141. doi: 10.1175/JCLI-D-22-0735.1. Abstract Characterizing the physical processes that modulate the continuous partitioning of heat between the ocean and overlying atmosphere is important for monitoring the subsequent flow of the heat accumulating in the ocean because of anthropogenic climate change. Oceanic rainfall sensible heat flux (Qp), whereby rainwater cools the sea surface, is computed and compared to the sea surface heat energy balance in the 60°N–60°S region. Contrary to popular belief, the results show that Qp is large at both short and long time scales, accounting for up to 22.5% of sea surface net heat flux around the 5.8°N line of latitude, 10.1% in the tropical 20°N–20°S region, and 5.7% in the global 60°N–60°S region. In the mixed layer of these same regions, area-average temperature change owing to a 10-yr accumulated Qp is up to −2.6° and −1.4°C, respectively. Further analysis reveals a previously unspecified rainfall–evaporation negative feedback between successive evaporation–rainfall cycles at the sea surface. The Qp depresses sea surface temperature and thus inhibits evaporation (latent heat flux), which in turn inhibits rainfall owing to decrease in water vapor supply to the atmosphere. The decrease in sea surface temperature also inhibits heat conduction from the ocean to the atmosphere (sensible heat flux). To compensate for the weaker latent and sensible heat fluxes, sea surface upward longwave radiation flux strengthens. We conclude that Qp acts like a modulator of Earth’s heat energy flow by controlling the partition of upper-ocean heat energy and the cycle of heat flow in the ocean and between the ocean and the atmosphere. Significance Statement Upper-ocean heat energy is partitioned between the ocean and the overlying atmosphere. Characterizing the physical processes that modulate this continuous partitioning is important for monitoring the subsequent flow of the heat energy accumulating in the ocean because of anthropogenic climate change. Here, we identify sea surface cooling by rainwater (oceanic rainfall sensible heat flux) as a modulator of this partition: this cooling depresses sea surface temperature and thus inhibits evaporation (latent heat flux), which in turn inhibits rainfall owing to the decrease in water vapor supply to the atmosphere; depressing sea surface temperature also inhibits heat conduction from the ocean to the atmosphere (sensible heat flux). To compensate for the weaker latent and sensible heat fluxes, sea surface upward longwave radiation flux strengthens.
Ivanova, I. Yu.; Shakirov, V. A.; Khalgaeva, N. A.Ivanova, I. Y., V. A. Shakirov, N. A. Khalgaeva, 2023: Accuracy Analysis of Estimates of Total Solar Radiation in Databases and Regression Models for Eastern Russia. Geography and Natural Resources, 44(3), 278-283. doi: 10.1134/S1875372823030058. The efficient use of solar energy requires an accurate assessment of the incoming solar radiation. The study involves comparing the accuracy of monthly means of the global solar radiation flux from the ERA5 reanalysis database, the SYN1deg satellite-based observation database, climate reference data, and data of regression models for seven settlements in the east of Russia. The study employs two well-known regression models, including parameters of extraterrestrial solar radiation, total cloudiness, air humidity, minimum and maximum air temperature, atmospheric pressure, and a new regression model, which additionally includes parameters of low-level cloudiness and sun elevation angle. The accuracy of databases and regression models is evaluated by comparing their data with ground measurements of weather stations. The indices of the mean absolute error, root-mean-square error, and mean bias error are calculated. The comparison shows that the data of climate reference books for the period from 1937–1957 to 1980 have the smallest deviation from the estimates of the monthly mean flux of global solar radiation for 2006–2020 at most of the points discussed. The ERA5 monthly mean estimates of the global solar radiation flux are more accurate than the SYN1deg data at five of the seven points considered. The new regression model proposed in the study makes it possible to provide greater accuracy of monthly estimates of the global solar radiation flux compared to the data of SYN1deg and ERA5 for most of the points considered. satellite data; reanalysis; solar radiation; accuracy comparison; regression model
Jenkins, Matthew T.; Dai, Aiguo; Deser, ClaraJenkins, M. T., A. Dai, C. Deser, 2023: Seasonal Variations and Spatial Patterns of Arctic Cloud Changes in Association with Sea Ice Loss during 1950–2019 in ERA5. J. Climate, 37(2), 735-754. doi: 10.1175/JCLI-D-23-0117.1. Abstract The dynamic and thermodynamic mechanisms that link retreating sea ice to increased Arctic cloud amount and cloud water content are unclear. Using the fifth generation of the ECMWF Reanalysis (ERA5), the long-term changes between years 1950–79 and 1990–2019 in Arctic clouds are estimated along with their relationship to sea ice loss. A comparison of ERA5 to CERES satellite cloud fractions reveals that ERA5 simulates the seasonal cycle, variations, and changes of cloud fraction well over water surfaces during 2001–20. This suggests that ERA5 may reliably represent the cloud response to sea ice loss because melting sea ice exposes more water surfaces in the Arctic. Increases in ERA5 Arctic cloud fraction and water content are largest during October–March from ∼950 to 700 hPa over areas with significant (≥15%) sea ice loss. Further, regions with significant sea ice loss experience higher convective available potential energy (∼2–2.75 J kg−1), planetary boundary layer height (∼120–200 m), and near-surface specific humidity (∼0.25–0.40 g kg−1) and a greater reduction of the lower-tropospheric temperature inversion (∼3°–4°C) than regions with small (
Jiang, Xianan; Su, Hui; Jiang, Jonathan H.; Neelin, J. David; Wu, Longtao; Tsushima, Yoko; Elsaesser, GregoryJiang, X., H. Su, J. H. Jiang, J. D. Neelin, L. Wu, Y. Tsushima, G. Elsaesser, 2023: Muted extratropical low cloud seasonal cycle is closely linked to underestimated climate sensitivity in models. Nature Communications, 14(1), 5586. doi: 10.1038/s41467-023-41360-0. A large spread in model estimates of the equilibrium climate sensitivity (ECS), defined as the global mean near-surface air-temperature increase following a doubling of atmospheric CO2 concentration, leaves us greatly disadvantaged in guiding policy-making for climate change adaptation and mitigation. In this study, we show that the projected ECS in the latest generation of climate models is highly related to seasonal variations of extratropical low-cloud fraction (LCF) in historical simulations. Marked reduction of extratropical LCF from winter to summer is found in models with ECS > 4.75 K, in accordance with the significant reduction of extratropical LCF under a warming climate in these models. In contrast, a pronounced seasonal cycle of extratropical LCF, as supported by satellite observations, is largely absent in models with ECS Projection and prediction; Climate and Earth system modelling
Jiang, Xiaoyu; Wu, Chenglai; Chen, Bing; Wang, Weiyi; Liu, Xiaohong; Lin, Zhaohui; Han, ZhenyuJiang, X., C. Wu, B. Chen, W. Wang, X. Liu, Z. Lin, Z. Han, 2023: Exploring a variable-resolution approach for simulating the regional climate in Southwest China using VR-CESM. Atmospheric Research, 292, 106851. doi: 10.1016/j.atmosres.2023.106851. The complex terrain of Southwest China (SWC) leads to large spatial variations in its climate, which are challenging for climate models to accurately simulate. In this study, we perform a high-resolution simulation (∼0.125°) using the Variable-Resolution Community Earth System Model (VR-CESM) for SWC and evaluate the model's ability to simulate the spatiotemporal variations of precipitation and temperature in SWC. The VR-CESM results are compared with observations, as well as the simulation of the standard version of CESM at a quasi-uniform ∼1° resolution. We find that the high-resolution VR-CESM model better portrays the fine distribution of precipitation and temperature than the coarse resolution CESM model (∼1°). VR-CESM also shows some improvements in the seasonal variations of precipitation in SWC. VR-CESM reduces the overestimulation of precipitation in the Hengduan Mountains and surrounding areas. For heavy precipitation (daily precipitation >25 mm), VR-CESM better simulates its frequency than CESM (∼1°). Overall, VR-CESM has good simulation capabilities for the spatiotemporal evolution of precipitation and the occurrence frequency of extreme precipitation in SWC. Therefore, the VR-CESM model is a useful tool for understanding the mechanism driving the climate changes in SWC in the past and for projecting future climate changes in the region. High-resolution simulation; Precipitation; Southwest China; VR-CESM
Jiang, Yun; Tang, Bo-Hui; Zhang, HuanyuJiang, Y., B. Tang, H. Zhang, 2023: Estimation of downwelling surface longwave radiation for all-weather skies from FengYun-4A geostationary satellite data. International Journal of Remote Sensing, 1-14. doi: 10.1080/01431161.2023.2170194. Fengyun-4A (FY-4A) is the latest generation of China’s geostationary satellite. The Advanced Geosynchronous Radiation Imager (AGRI) onboard FY-4A can provide high-precision, high-frequency observation data, which makes a new possibility for estimating the downwelling surface longwave radiation (DSLR) with high spatial and temporal resolution. This work presents a new method for estimating DSLRs under all-sky conditions using a genetic algorithm–artificial neural network (GA-ANN) algorithm based on brightness temperature (BT) from the FY-4A AGRI infrared channels and near-surface air temperature and dew point temperature from ERA5 reanalysis data. Based on the verification results of two independent observation sites, it is shown that the bias and RMSE are - 4.31 W/m2 and 35.28 W/m2, respectively. Compared the CERES SYN all-sky DSLR product with the DSLR estimated by the new method, the bias and RMSE are 0.86 W/m2 and 26.87 W/m2, respectively, and the new method has a higher spatial resolution (4 km), which can display more details of spatial variation. all-sky; Downwelling surface longwave radiation; ERA5; FY-4A
Jin, Daeho; Kim, Daehyun; Son, Seok-Woo; Oreopoulos, LazarosJin, D., D. Kim, S. Son, L. Oreopoulos, 2023: QBO deepens MJO convection. Nature Communications, 14(1), 4088. doi: 10.1038/s41467-023-39465-7. The underlying mechanism that couples the Quasi-Biennial Oscillation (QBO) and the Madden-Julian oscillation (MJO) has remained elusive, challenging our understanding of both phenomena. A popular hypothesis about the QBO-MJO connection is that the vertical extent of MJO convection is strongly modulated by the QBO. However, this hypothesis has not been verified observationally. Here we show that the cloud-top pressure and brightness temperature of deep convection and anvil clouds are systematically lower in the easterly QBO (EQBO) winters than in the westerly QBO (WQBO) winters, indicating that the vertical growth of deep convective systems within MJO envelopes is facilitated by the EQBO mean state. Moreover, the deeper clouds during EQBO winters are more effective at reducing longwave radiation escaping to space and thereby enhancing longwave cloud-radiative feedback within MJO envelopes. Our results provide robust observational evidence of the enhanced MJO activity during EQBO winters by mean state changes induced by the QBO. Atmospheric dynamics; Climate and Earth system modelling
Jin, Daeho; Kramer, Ryan J.; Oreopoulos, Lazaros; Lee, DongminJin, D., R. J. Kramer, L. Oreopoulos, D. Lee, 2023: ENSO Disrupts Boreal Winter CRE Feedback. J. Climate, 37(2), 585-603. doi: 10.1175/JCLI-D-23-0282.1. Abstract Twenty years of satellite-based cloud and radiation observations allow us to examine the observed cloud radiative effect (CRE) feedback (i.e., CRE change per unit change in global mean surface temperature). By employing a decomposition method to separate the contribution of “internal changes” and “relative-frequency-of-occurrence (RFO) changes” of distinct cloud regime (CR) groups, notable seasonal contrasts of CRE feedback characteristics emerge. Boreal winter CRE feedback is dominated by the positive shortwave CRE (SWCRE) feedback of oceanic low-thick clouds, due to their decreasing RFO as temperature rises. This signal is most likely due to El Niño–Southern Oscillation (ENSO) activity. When ENSO signals are excluded, boreal winter CRE feedback becomes qualitatively similar to the boreal summer feedback, where several CR groups contribute to the total CRE feedback more evenly. Most CR groups’ CRE feedbacks largely come from changing RFO (e.g., the predominant transition from oceanic cumulus to broken clouds and more occurrences of higher convective clouds with warming temperature). At the same time, low-thick and broken clouds experience optical thinning and decreasing cloud fraction, and these features are more prominent in boreal summer than winter. Overall, the seasonally asymmetric patterns of CRE feedback, primarily due to ENSO, introduce complexity in assessments of CRE feedback.
Jin, Yubin; Hu, Shijie; Ziegler, Alan D.; Gibson, Luke; Campbell, J. Elliott; Xu, Rongrong; Chen, Deliang; Zhu, Kai; Zheng, Yan; Ye, Bin; Ye, Fan; Zeng, ZhenzhongJin, Y., S. Hu, A. D. Ziegler, L. Gibson, J. E. Campbell, R. Xu, D. Chen, K. Zhu, Y. Zheng, B. Ye, F. Ye, Z. Zeng, 2023: Energy production and water savings from floating solar photovoltaics on global reservoirs. Nature Sustainability, 1-10. doi: 10.1038/s41893-023-01089-6. Growing global energy use and the adoption of sustainability goals to limit carbon emissions from fossil fuel burning are increasing the demand for clean energy, including solar. Floating photovoltaic (FPV) systems on reservoirs are advantageous over traditional ground-mounted solar systems in terms of land conservation, efficiency improvement and water loss reduction. Here, based on multiple reservoir databases and a realistic climate-driven photovoltaic system simulation, we estimate the practical potential electricity generation for FPV systems with a 30% coverage on 114,555 global reservoirs is 9,434 ± 29 TWh yr−1. Considering the proximity of most reservoirs to population centres and the potential to develop dedicated local power systems, we find that 6,256 communities and/or cities in 124 countries, including 154 metropolises, could be self-sufficient with local FPV plants. Also beneficial to FPV worldwide is that the reduced annual evaporation could conserve 106 ± 1 km3 of water. Our analysis points to the huge potential of FPV systems on reservoirs, but additional studies are needed to assess the potential long-term consequences of large systems. Hydrology; Solar energy; Water resources
Johnson, G. C.; Lumpkin, R.; Atkinson, C.; Biló, Tiago; Boyer, Tim; Bringas, Francis; Carter, Brendan R.; Cetinić, Ivona; Chambers, Don P.; Chan, Duo; Cheng, Lijing; Chomiak, Leah; Cronin, Meghan F.; Dong, Shenfu; Feely, Richard A.; Franz, Bryan A.; Gao, Meng; Garg, Jay; Gilson, John; Goni, Gustavo; Hamlington, Benjamin D.; Hobbs, W.; Hu, Zeng-Zhen; Huang, Boyin; Ishii, Masayoshi; Jevrejeva, Svetlana; Johns, W.; Landschützer, Peter; Lankhorst, Matthias; Leuliette, Eric; Locarnini, Ricardo; Lyman, John M.; McPhaden, Michael J.; Merrifield, Mark A.; Mishonov, Alexey; Mitchum, Gary T.; Moat, Ben I.; Mrekaj, Ivan; Nerem, R. Steven; Purkey, Sarah G.; Qiu, Bo; Reagan, James; Sato, Katsunari; Schmid, Claudia; Sharp, Jonathan D.; Siegel, David A.; Smeed, David A.; Stackhouse, Paul W.; Sweet, William; Thompson, Philip R.; Triñanes, Joaquin A.; Volkov, Denis L.; Wanninkhof, Rik; Wen, Caihong; Westberry, Toby K.; Widlansky, Matthew J.; Willis, J.; Xie, Ping-Ping; Yin, Xungang; Zhang, Huai-min; Zhang, Li; Allen, Jessicca; Camper, Amy V.; Haley, Bridgette O.; Hammer, Gregory; Love-Brotak, S. Elizabeth; Ohlmann, Laura; Noguchi, Lukas; Riddle, Deborah B.; Veasey, Sara W.Johnson, G. C., R. Lumpkin, C. Atkinson, T. Biló, T. Boyer, F. Bringas, B. R. Carter, I. Cetinić, D. P. Chambers, D. Chan, L. Cheng, L. Chomiak, M. F. Cronin, S. Dong, R. A. Feely, B. A. Franz, M. Gao, J. Garg, J. Gilson, G. Goni, B. D. Hamlington, W. Hobbs, Z. Hu, B. Huang, M. Ishii, S. Jevrejeva, W. Johns, P. Landschützer, M. Lankhorst, E. Leuliette, R. Locarnini, J. M. Lyman, M. J. McPhaden, M. A. Merrifield, A. Mishonov, G. T. Mitchum, B. I. Moat, I. Mrekaj, R. S. Nerem, S. G. Purkey, B. Qiu, J. Reagan, K. Sato, C. Schmid, J. D. Sharp, D. A. Siegel, D. A. Smeed, P. W. Stackhouse, W. Sweet, P. R. Thompson, J. A. Triñanes, D. L. Volkov, R. Wanninkhof, C. Wen, T. K. Westberry, M. J. Widlansky, J. Willis, P. Xie, X. Yin, H. Zhang, L. Zhang, J. Allen, A. V. Camper, B. O. Haley, G. Hammer, S. E. Love-Brotak, L. Ohlmann, L. Noguchi, D. B. Riddle, S. W. Veasey, 2023: Global Oceans. Bull. Amer. Meteor. Soc., 104(9), S146-S206. doi: 10.1175/BAMS-D-23-0076.2. "Global Oceans" published on 06 Sep 2023 by American Meteorological Society.
Johnson, Gregory C.; Landerer, Felix W.; Loeb, Norman G.; Lyman, John M.; Mayer, Michael; Swann, Abigail L. S.; Zhang, JinlunJohnson, G. C., F. W. Landerer, N. G. Loeb, J. M. Lyman, M. Mayer, A. L. S. Swann, J. Zhang, 2023: Closure of Earth’s Global Seasonal Cycle of Energy Storage. Surveys in Geophysics. doi: 10.1007/s10712-023-09797-6. The global seasonal cycle of energy in Earth’s climate system is quantified using observations and reanalyses. After removing long-term trends, net energy entering and exiting the climate system at the top of the atmosphere (TOA) should agree with the sum of energy entering and exiting the ocean, atmosphere, land, and ice over the course of an average year. Achieving such a balanced budget with observations has been challenging. Disagreements have been attributed previously to sparse observations in the high-latitude oceans. However, limiting the local vertical integration of new global ocean heat content estimates to the depth to which seasonal heat energy is stored, rather than integrating to 2000 m everywhere as done previously, allows closure of the global seasonal energy budget within statistical uncertainties. The seasonal cycle of energy storage is largest in the ocean, peaking in April because ocean area is largest in the Southern Hemisphere and the ocean’s thermal inertia causes a lag with respect to the austral summer solstice. Seasonal cycles in energy storage in the atmosphere and land are smaller, but peak in July and September, respectively, because there is more land in the Northern Hemisphere, and the land has more thermal inertia than the atmosphere. Global seasonal energy storage by ice is small, so the atmosphere and land partially offset ocean energy storage in the global integral, with their sum matching time-integrated net global TOA energy fluxes over the seasonal cycle within uncertainties, and both peaking in April. Earth; Seasonal cycle; Climate; Global energy
Johnson, Richard H.; Szoeke, Simon P. de; Ciesielski, Paul E.; Brewer, W. AlanJohnson, R. H., S. P. d. Szoeke, P. E. Ciesielski, W. A. Brewer, 2023: The Atmospheric Boundary Layer and the Initiation of the MJO. J. Climate, 36(22), 7893-7903. doi: 10.1175/JCLI-D-23-0210.1. Abstract The Indian Ocean is a frequent site for the initiation of the Madden–Julian oscillation (MJO). The evolution of convection during MJO initiation is intimately linked to the subcloud atmospheric mixed layer (ML). Much of the air entering developing cumulus clouds passes through the cloud base; hence, the properties of the ML are critical in determining the nature of cloud development. The properties and depth of the ML are influenced by horizontal advection, precipitation-driven cold pools, and vertical motion. To address ML behavior during the initiation of the MJO, data from the 2011/12 Dynamics of the MJO Experiment (DYNAMO) are utilized. Observations from the research vessel Revelle are used to document the ML and its modification during the time leading up to the onset phase of the October MJO. The mixed layer depth increased from ∼500 to ∼700 m during the 1–12 October suppressed period, allowing a greater proportion of boundary layer thermals to reach the lifting condensation level and hence promote cloud growth. The ML heat budget defines an equilibrium mixed layer depth that accurately diagnoses the mixed layer depth over the DYNAMO convectively suppressed period, provided that horizontal advection is included. The advection at the Revelle is significantly influenced by low-level convective outflows from the southern ITCZ. The findings also demonstrate a connection between cirrus clouds and their remote impact on ML depth and convective development through a reduction in the ML radiative cooling rate. The emergent behavior of the equilibrium mixed layer has implications for simulating the MJO with models with parameterized cloud and turbulent-scale motions.
Karlowska, Eliza; Matthews, Adrian J.; Webber, Benjamin G. M.; Graham, Tim; Xavier, PrinceKarlowska, E., A. J. Matthews, B. G. M. Webber, T. Graham, P. Xavier, 2023: The effect of diurnal warming of sea-surface temperatures on the propagation speed of the Madden–Julian oscillation. Quarterly Journal of the Royal Meteorological Society, 150(758), 334-354. doi: 10.1002/qj.4599. The diurnal warm layer in the upper ocean develops during low surface winds and high incoming solar radiation conditions, often increasing sea-surface temperatures (SSTs) by up to 1°C. The suppressed phase of the Madden–Julian Oscillation (MJO) favours the formation of such a layer. Here, we analyse the coupled ocean–atmosphere and atmosphere-only numerical weather prediction systems of the UK Met Office to reveal that important differences arise from the representation of the diurnal warm layer in the coupled model. Though both models are skilful in predicting the MJO to at least a 7-day lead time, the coupled model predicts approximately 12% faster MJO RMM phase speed propagation than the atmosphere-only model due to the ability to resolve diurnal warming in the upper ocean that rectifies onto MJO-associated SST anomalies. The diurnal warming of SST (dSST) in the coupled model leads to an increase in daily mean SST compared with the atmosphere-only model persisted foundation SST. The strength of the dSST in the coupled model is modulated by MJO conditions. During suppressed MJO conditions on lead day 1, the dSST is enhanced, leading to 0.2°C warmer daily mean MJO-associated SST anomalies and increased convection in the coupled model by lead day 7. During active MJO convection, the dSST is suppressed, leading to 0.1°C colder MJO-associated SST anomalies in the coupled model and reduced convection by lead day 7. This variability in dSST further amplifies the MJO propagation speed, underlining the importance of the two-way feedback between the MJO and the diurnal cycle of SST and the need to accurately represent this process in coupled models. convection; diurnal warm layer; Madden–Julian Oscillation; ocean–atmosphere coupling
Kashtan Sundararaman, Harish Kumar; Shanmugam, Palanisamy; Nagamani, Pullaiahgari VenkataKashtan Sundararaman, H. K., P. Shanmugam, P. V. Nagamani, 2023: Robust extension of the simple sea-surface irradiance model to handle cloudy conditions for the global ocean using satellite remote sensing data. Advances in Space Research, 71(3), 1486-1509. doi: 10.1016/j.asr.2022.10.009. Sea-surface solar radiation (abbreviated as photosynthetically available radiation, PAR) in the visible wavelength (400–700 nm) is an essential parameter to estimate marine primary productivity and understanding phytoplankton dynamics, upper ocean physics and biogeochemical processes. Although many remote-sensing models were developed to estimate daily PAR (DPAR) from ocean colour data, these models often produce biases in the DPAR products under cloudy-sky and complex atmospheric conditions due to the lack of parameterization to deal with the cloud cover conditions and insufficient in-situ DPAR data. This study presents an Extended Sea-surface Solar Irradiance Model (ESSIM) for estimating DPAR over the global ocean. The ESSIM uses the direct and diffuse components from the Simple sea-surface Solar Irradiance Model (SSIM) along with a new parameter to handle cloudy conditions. The ESSIM produced DPAR products with greater accuracy under both clear and cloudy conditions. Its performance was tested on the time-series MODIS-Aqua images and compared with the concurrent in-situ data and the results from two global models. Results showed that the DPAR values produced by ESSIM agree with in-situ data better than the global models for all-sky conditions (with a mean relative error of 11.267 %; a root mean square error of 5.563 Em−2day−1; and a mean net bias of 2.917 Em−2day−1). The ESSIM performed slightly better than the SSIM for clear conditions and the Frouin's Operational Algorithm (FOA) for all-sky conditions. As the new parameterization accounts for cloudy conditions, the ESSIM produced more accurate results for cloud cover conditions across latitudes (up to 60°). The time-series Level-3 binned MODIS-Aqua data (global gridded) also demonstrated that the ESSIM improved the accuracy of DPAR products and produced spatially and temporally consistent DPAR products over the global ocean regardless of the seasons and sky conditions. Satellite observation; Cloudy condition; DPAR; ESSIM; Global Ocean; MODIS-Aqua
Kotsuki, Shunji; Terasaki, Koji; Satoh, Masaki; Miyoshi, TakemasaKotsuki, S., K. Terasaki, M. Satoh, T. Miyoshi, 2023: Ensemble-Based Data Assimilation of GPM DPR Reflectivity: Cloud Microphysics Parameter Estimation With the Nonhydrostatic Icosahedral Atmospheric Model (NICAM). Journal of Geophysical Research: Atmospheres, 128(5), e2022JD037447. doi: 10.1029/2022JD037447. Direct assimilation of Dual-frequency Precipitation Radar (DPR) data of the Global Precipitation Measurement (GPM) core satellite is challenging mainly due to its long revisiting intervals relative to the time scale of precipitation, and precipitation location errors. This study explores a method for improving precipitation forecasts using GPM DPR through model parameter estimation. We developed a 28 km mesh global atmospheric data assimilation system that integrates the Nonhydrostatic ICosahedral Atmospheric Model (NICAM) and Local Ensemble Transform Kalman Filter (LETKF) coupled with a satellite radar simulator. Using the NICAM-LETKF and GPM DPR observations, this study estimates a model cloud physics parameter corresponding to snowfall terminal velocity. To overcome the difficulties of long revisiting intervals and precipitation location errors, we propose a parameter estimation method based on a two-dimensional histogram known as the contoured frequency by temperature diagram (CFTD). Parameter estimation effectively mitigated the gap between simulated and observed CFTD, resulting in improved 6 hr precipitation forecasts. cloud microphysics; data assimilation; parameter estimation; GPM DPR; radar reflectivity
Kuma, Peter; Bender, Frida A.-M.; Schuddeboom, Alex; McDonald, Adrian J.; Seland, ØyvindKuma, P., F. A. Bender, A. Schuddeboom, A. J. McDonald, Ø. Seland, 2023: Machine learning of cloud types in satellite observations and climate models. Atmospheric Chemistry and Physics, 23(1), 523-549. doi: 10.5194/acp-23-523-2023. Uncertainty in cloud feedbacks in climate models is a major limitation in projections of future climate. Therefore, evaluation and improvement of cloud simulation are essential to ensure the accuracy of climate models. We analyse cloud biases and cloud change with respect to global mean near-surface temperature (GMST) in climate models relative to satellite observations and relate them to equilibrium climate sensitivity, transient climate response and cloud feedback. For this purpose, we develop a supervised deep convolutional artificial neural network for determination of cloud types from low-resolution (2.5∘×2.5∘) daily mean top-of-atmosphere shortwave and longwave radiation fields, corresponding to the World Meteorological Organization (WMO) cloud genera recorded by human observers in the Global Telecommunication System (GTS). We train this network on top-of-atmosphere radiation retrieved by the Clouds and the Earth’s Radiant Energy System (CERES) and GTS and apply it to the Coupled Model Intercomparison Project Phase 5 and 6 (CMIP5 and CMIP6) model output and the European Centre for Medium-Range Weather Forecasts (ECMWF) Reanalysis version 5 (ERA5) and the Modern-Era Retrospective Analysis for Research and Applications version 2 (MERRA-2) reanalyses. We compare the cloud types between models and satellite observations. We link biases to climate sensitivity and identify a negative linear relationship between the root mean square error of cloud type occurrence derived from the neural network and model equilibrium climate sensitivity (ECS), transient climate response (TCR) and cloud feedback. This statistical relationship in the model ensemble favours models with higher ECS, TCR and cloud feedback. However, this relationship could be due to the relatively small size of the ensemble used or decoupling between present-day biases and future projected cloud change. Using the abrupt-4×CO2 CMIP5 and CMIP6 experiments, we show that models simulating decreasing stratiform and increasing cumuliform clouds tend to have higher ECS than models simulating increasing stratiform and decreasing cumuliform clouds, and this could also partially explain the association between the model cloud type occurrence error and model ECS.
Leng, Wanchun; Wang, Tianxing; Wang, Gaofeng; Letu, Husi; Wang, Shiyao; Xian, Yuyang; Yan, Xuewei; Zhang, ZiqianLeng, W., T. Wang, G. Wang, H. Letu, S. Wang, Y. Xian, X. Yan, Z. Zhang, 2023: All-sky surface and top-of-atmosphere shortwave radiation components estimation: Surface shortwave radiation, PAR, UV radiation, and TOA albedo. Remote Sensing of Environment, 298, 113830. doi: 10.1016/j.rse.2023.113830. Surface and top-of-atmosphere (TOA) shortwave radiation components are key parameters in the energy budget of the Earth-atmosphere system, which influence the global climate, ecology, hydrology, etc. However, except for total surface shortwave downward radiation (SWDR), only a few satellite missions consistently release other radiation components such as solar direct/diffuse radiation, photosynthetically active radiation (PAR), ultraviolet radiation-A/B (UVA/UVB), as well as TOA albedo, although they are indispensable for many land and ocean applications. In this study, a unified framework by combining multi-band LUT inversion and classification of the atmospheric condition is proposed, which enables the simultaneous derivation of nine surface and TOA radiation variables and emphasizes the separation of direct and diffuse components. The estimated radiation variables include total and direct components of SWDR, PAR, UVA, UVB, as well as TOA albedo. The proposed method is easy-to-use with only a few inputs and works well with reasonable accuracy. Using Moderate Resolution Imaging Spectroradiometer (MODIS) raw resolution images as test data, the surface radiation variables are validated by 80 global sites from BSRN, SURFRAD, and FLUXNET, and the instantaneous RMSEs (biases) of SWDR, SWDRdir, PAR, PARdiff, and UVB are 103.6 (0.1), 114 (−1.7), 47.8 (6.8), 32.9 (5.7), and 0.14 (0.003) W/m2, respectively, demonstrating comparable or even better accuracy compared with existing products. In particular, the estimated SWDR behaves more accurate than CERES in polar regions. Due to the lack of in-situ measurements, TOA albedo is compared with CERES TOA products and shows good agreement with R2 of 0.9 and RMSE (bias) of 0.055 (−0.003). The unified framework reveals obvious advantages over existing studies in generating almost all physically consistent shortwave components in the same manner with simple inputs, implying the great potentials in globally mapping spatio-temporally continuous multiple components of shortwave radiation with a unified scheme. TOA albedo; Photosynthetically active radiation; Look-up table; Shortwave downward radiation; Ultraviolet radiation
Letu, Husi; Ma, Run; Nakajima, Takashi Y.; Shi, Chong; Hashimoto, Makiko; Nagao, Takashi M.; Baran, Anthony J.; Nakajima, Teruyuki; Xu, Jian; Wang, Tianxing; Tana, Gegen; Bilige, Sude; Shang, Huazhe; Chen, Liangfu; Ji, Dabin; Lei, Yonghui; Wei, Lesi; Zhang, Peng; Li, Jun; Li, Lei; Zheng, Yu; Khatri, Pradeep; Shi, JianchengLetu, H., R. Ma, T. Y. Nakajima, C. Shi, M. Hashimoto, T. M. Nagao, A. J. Baran, T. Nakajima, J. Xu, T. Wang, G. Tana, S. Bilige, H. Shang, L. Chen, D. Ji, Y. Lei, L. Wei, P. Zhang, J. Li, L. Li, Y. Zheng, P. Khatri, J. Shi, 2023: Surface Solar Radiation Compositions Observed from Himawari-8/9 and Fengyun-4 Series. Bull. Amer. Meteor. Soc., 104(10), E1772-E1789. doi: 10.1175/BAMS-D-22-0154.1. Abstract Surface downward solar radiation compositions (SSRC), including photosynthetically active radiation (PAR), ultraviolet-A (UVA), ultraviolet-B (UVB), and shortwave radiation (SWR), with high spatial–temporal resolutions and precision are essential for applications including solar power, vegetation photosynthesis, and environmental health. In this study, an optimal algorithm was developed to calculate SSRC, including their direct and diffuse components. Key features of the algorithm include combining the radiative transfer model with machine learning techniques, including full consideration of the effects of aerosol types, cloud phases, and gas components. A near-real-time monitoring system was developed based on this algorithm, with SSRC products generated from Himawari-8/9 and Fengyun-4 series data. Validation with ground-based data shows that the accuracy of the SWR and PAR compositions (daily mean RMSEs of 19.7 and 9.2 W m−2, respectively) are significantly better than those of state-of-the-art products from CERES, ERA5, and GLASS. The accuracy of UVA and UVB measurements is comparable with CERES. Characteristics of aerosols, clouds, gases, and their impacts on SSRC are investigated before, during, and post COVID-19; in particular, significant SSRC variations due to the reduction of aerosols and increase of ozone are identified in the Chinese central and eastern areas during that period. The spatial–temporal resolution of data products [up to 0.05° (10 min)−1 for the full-disk region] is one of the most important advantages. Data for the East Asia–Pacific region during 2016–20 is available from the CARE home page (www.slrss.cn/care/sp/pc/).
Li, Donghao; Folini, Doris; Wild, MartinLi, D., D. Folini, M. Wild, 2023: Assessment of Top of Atmosphere, Atmospheric and Surface Energy Budgets in CMIP6 Models on Regional Scales. Earth and Space Science, 10(4), e2022EA002758. doi: 10.1029/2022EA002758. We examine top of atmosphere (TOA), atmospheric, and surface energy budget components of 53 CMIP6 models for the period 2000–2009 on regional scales with respect to two reference data sets: the NASA Energy and Water cycle Study (NEWS), from which we adopt the regional decomposition, and the Clouds and the Earth's Radiant Energy System (CERES) Energy Balanced and Filled (EBAF). Focusing on regional scale, CMIP6 models tend to have more energy entering or less energy leaving the climate systems at TOA over the Northern Hemisphere land, Southern Hemisphere ocean and the polar regions compared to CERES EBAF, while the contrary applies in other regions. Atmospheric net shortwave and longwave fluxes both tend to be underestimated in CMIP6 models as compared to EBAF, with substantial regional differences. Regional surface radiative fluxes as reported by NEWS and EBAF can differ substantially. Nevertheless, robust regional biases exist in CMIP6. Surface upward shortwave radiation is overestimated by 43 (81%) models over Eurasia. For almost all surface radiative flux components over the North Atlantic and Indian Ocean, there are at least 21 (40%) models which fall outside the NEWS uncertainty range. Latent heat flux is overestimated over most of the land and ocean regions while firm conclusions for sensible heat flux remain elusive due to discrepancies between different reference data sets. Compared to CMIP5, there is an overall improvement in CMIP6 on regional scale. Still, substantial deficiencies and spreads on regional scale remain, which are potentially translated into an inadequate simulation of atmospheric dynamics or hydrological cycle.
Li, Jiandong; Geen, Ruth; Mao, Jiangyu; Song, Yajuan; Vallis, Geoffrey K.; Wu, GuoxiongLi, J., R. Geen, J. Mao, Y. Song, G. K. Vallis, G. Wu, 2023: Mechanical and Thermal Forcings of Asian Large-Scale Orography on Spring Cloud Amount and Atmospheric Radiation Budget over East Asia. J. Climate, 36(15), 5215-5232. doi: 10.1175/JCLI-D-22-0797.1. Abstract Asian large-scale orography profoundly influences circulation in the North Hemisphere. Considerable spring top-of-the-atmosphere (TOA) radiative cooling over Southeast China (SEC) is very likely related to upstream orography forcing. Here we investigate the mechanical and thermal forcings of Asian large-scale orography, particularly the Tibetan Plateau (TP), on downstream East Asian cloud amount and atmospheric radiation budget during March–April using the Global Monsoons Model Intercomparison Project simulations. The thermal forcing drives significant surface heating and a low-level cyclone over the TP, pumping low-level air to the middle troposphere. Ascent and water vapor convergence triggered by the thermal forcing favor air condensation, low–middle clouds, and resultant strong spring cloud radiative cooling over SEC. Moreover, the thermal forcing moves the position of cloud radiative cooling westward toward the TP. The TP’s blocking role weakens low-level westerlies over SEC, but its deflecting role increases downstream high-level westerlies, dynamically favoring cloud formation over SEC and the eastward ocean. In addition, the TP can force ascent and increase cloud amounts over the western and central TP. The thermal forcing contributes to 57.1% of total cloud amount and 47.6% of TOA cloud radiative cooling induced by the combined orography forcing over SEC while the mechanical one accounts for 79.4% and 95.8% of the counterparts over the ocean to the east of SEC. Our results indicate that Asian large-scale orography shapes the contemporary geographical distribution of spring East Asian cloud amount and atmospheric radiation budget to a large extent. Significance Statement Clouds tied to large-scale topography and circulation exhibit some remarkable geographical distributions. The global strongest cloud radiative cooling, with an intensity of up to −90 W m−2, occurs over Southeast China (SEC) during March–April. The primary purpose of this study is to understand the influences of Asian large-scale orography, particularly the Tibetan Plateau (TP), on this unique climatic phenomenon using the latest climate model simulations. Our results show that Asian large-scale orography forcing significantly increases ascent, low–middle cloud formation, and resultant strong spring cloud radiative cooling over SEC and downstream ocean. The sensible-heat-driven air pump induced by the TP’s thermal forcing maintains strong cloud radiative cooling over SEC. This study provides valuable insights that link Asian large-scale orography forcing to downstream cloud–radiation characteristics.
Li, Jiandong; Guo, Zhun; Chen, Guoxing; Zi, PengLi, J., Z. Guo, G. Chen, P. Zi, 2023: Seasonal and interannual characteristics of atmospheric cloud radiative effect over South China and neighbouring ocean regions. International Journal of Climatology, 43(15), 7412-7427. doi: 10.1002/joc.8271. Atmospheric cloud radiative effect (ACRE) is a critical heat source in the atmosphere, with pronounced regional distributions. Here, we investigate seasonal and interannual characteristics of ACRE over South China (SC) and neighbouring ocean regions using 2001–2020 satellite and reanalysis data. Annual mean net ACRE shows a warming role over most of SC, its eastern ocean (ESCO), and the South China Sea and western North Pacific (SWNP), with domain-mean values of 6.0, 14.9, and 32.8 W m−2, respectively. Over SC, the shortwave ACRE warming dominates annual mean net ACRE, and considerable low-middle clouds with small particle size and large water content reflect shortwave radiation and enhance shortwave absorption, especially in spring. Notably, winter longwave ACRE over SC, with a cooling role, strongly offsets its summer counterpart's warming role. In contrast, longwave ACRE mainly accounts for net ACRE over ESCO and SWNP, especially the latter where high clouds prevail. The Asian summer monsoon enhances summer high clouds and longwave (net) ACRE. Cloud types and complex vertical distribution associated with continental environments and the Tibetan Plateau's topography forcing enable seasonal behaviours of ACRE over SC to be different from the other two regions. Longwave ACRE dominates the interannual variation of net ACRE, with a larger interannual variability over SWNP, while a larger annual variability of shortwave ACRE occurs over SC. There are no significant interannual trends of ACRE except for annual and spring mean longwave (net) ACRE over SC. Moreover, the interannual variation of longwave (net) ACRE relates well to 500-hPa vertical velocity, indicating the strong influence of large-scale circulation on regional ACRE. cloud; interannual variation; seasonal variation; atmospheric radiative effect cloud; South China
Li, Na; Zhao, PingLi, N., P. Zhao, 2023: A Daily Land Surface Heat Flux Dataset in Tibetan Plateau During 2001–2016 Based on the Maximum Entropy Production Model and Multi-Source Datasets. doi: 10.2139/ssrn.4414712. The daily long-term land surface sensible (SH) and latent (LE) heat fluxes is important for understanding of energy and water cycle processes in the Tibetan Plateau (TP). In this study, the daily SH and LE at the horizontal resolution of 1° are first estimated using the maximum entropy production (MEP) model (hereinafter SHMEP and LEMEP) in the entire TP during 2001–2016. The MEP model is built on physical and statistical principles to simulate surface heat fluxes. The surface net radiation, soil moisture (SM), and land surface temperature (LST) are the main driving variables for MEP model. In order to select the relatively accurate MEP inputs, the merged surface net radiation (Rn–merged) under all-sky conditions are generated from CERES, ISCCP-FH, and ERA5 using the Bayesian Model Averaging scheme in the TP. Besides, the TP SM and LST from various sources are evaluated using the in-situ observations. Based on the daily Rn–merged, the ERA5 SM, and the CERES LST, the daily SH and LE are estimated in the entire TP. The results show that daily SHMEP and LEMEP perform well at all the TP measurement sites, with the correlation coefficient above 0.73, the root-mean-square error of less than 20.9 W m–2, and the absolute value of bias below 8.9 W m–2. The results are superior to the SH and LE in ERA5, ERA-Interim, and MERRA-2 reanalysis datasets and previous studies, especially for LE. Based on this new dataset, the spatial and temporal varying characteristics of SH and LE in the TP are analyzed. The annual SHMEP is high (small) in the western TP, the Qaidam Basin in the northern TP, and the Himalaya ranges (southeastern TP). The annual LEMEP has the minimum (maximum) value in the western TP and the Qaidam Basin (the southeastern TP). Meanwhile, the annual SHMEP and LEMEP over the entire TP are 35.76 W m–2 and 20.48 W m–2, with the increasing trends of 0.75 and 0.10 W m–2 decade–1 during the study period, respectively. Latent heat flux; Maximum entropy production model; Multi-Source datasets; Sensible heat flux; Tibetan Plateau
Li, Peizhen; Zhong, Lei; Ma, Yaoming; Fu, Yunfei; Cheng, Meilin; Wang, Xian; Qi, Yuting; Wang, ZixinLi, P., L. Zhong, Y. Ma, Y. Fu, M. Cheng, X. Wang, Y. Qi, Z. Wang, 2023: Estimation of 1 km downwelling shortwave radiation over the Tibetan Plateau under all-sky conditions. Atmospheric Chemistry and Physics, 23(16), 9265-9285. doi: 10.5194/acp-23-9265-2023. Downwelling shortwave radiation (DSR) is the basic driving force for the energy and water cycles of the Earth's climate system. Called the Third Pole of the Earth, the Tibetan Plateau (TP) absorbs a large amount of shortwave radiation and exerts important impacts on global weather and climate change. However, due to coarse spatial resolution and insufficient consideration of factors influencing radiative transfer processes, DSR parameterization schemes still need to be improved when applied to the TP. Based on satellite datasets and meteorological forcing data, all-sky DSR over the TP at a spatial resolution of 1 km was derived using an improved parameterization scheme. The influence of topography and different radiative attenuations were comprehensively taken into account. Specifically, the introduction of cloud multiscattering and topography factors further improves the DSR estimation accuracy. The validation results indicated that the developed parameterization scheme showed reasonable accuracy. By comparing with current, widely used DSR products based on the same in situ observations, the derived DSR performed much better on different spatial and temporal scales. On instantaneous, 10 d and monthly timescales, the root-mean-square errors (RMSEs) of the derived DSR are 132.8–158.2, 70.8–76.5 and 61.3–67.5 W m−2, respectively, which are much smaller than those of current DSR products. The derived DSR not only captured the temporal-variation characteristics that are more consistent with the in situ measurements, but also provided reasonable spatial patterns. Meanwhile, the proposed parameterization scheme demonstrated its superiority in characterizing more details and high dynamics of the spatial pattern of DSR due to its terrain correction and high resolution. Moreover, this parameterization scheme does not need any local correction in advance and has the potential to be extended to other regions in the world.
Li, Ruohan; Wang, Dongdong; Liang, ShunlinLi, R., D. Wang, S. Liang, 2023: Comparison between deep learning architectures for the 1 km, 10/15-min estimation of downward shortwave radiation from AHI and ABI. Remote Sensing of Environment, 295, 113697. doi: 10.1016/j.rse.2023.113697. The retrieval of downward shortwave radiation (DSR) with high spatiotemporal resolution and short latency is critical. It is the fundamental driving force of surface energy, carbon, and hydrological circulations, and a key energy source for photovoltaic electricity. However, existing methods face significant challenges owing to cloud heterogeneity and their reliance on other satellite-derived products, which hinder the retrieval of accurate and timely DSR with high spatiotemporal resolution. In addition to the spectral features used in traditional approaches, deep learning (DL) can incorporate the spatial and temporal features of satellite data. This study developed and compared three DL methods, namely the DenseNet, the bidirectional gated recurrent unit without surface albedo as inputs (BiGRUnor), and the convolutional neural network with gated recurrent unit without surface albedo as inputs (CNNGRUnor). These methods were used to estimate DSR at 1 km and 10/15 min resolutions directly from top-of-atmosphere reflectance over the Advanced Himawari Imager (AHI) onboard Himawari-8 and the Advanced Baseline Imager (ABI) onboard GOES-16 coverage, achieving high accuracies. The instantaneous root mean square error (RMSE) and relative RMSE for the three models were 68.4 (16.1%), 69.4 (16.3%), and 67.1 (15.7%) W/m2, respectively, which are lower than the baseline machine learning method, the multilayer perceptron model (MLP), with RMSE at 76.8 W/m2 (18.0%). Hourly accuracies for the three DL methods were 58.6 (14.1%), 57.8 (14.0%), and 57.3 (13.8%) W/m2, which are within the DSR RMSEs that we estimated for existing datasets of the Earth's Radiant Energy System (CERES) (88.8 W/m2, 21.4%) and GeoNEX (77.8 W/m2, 18.8%). The study illustrates that DL models that incorporate temporal information can eliminate the need for surface albedo as an input, which is crucial for timely monitoring and nowcasting of DSR. Incorporating spatial information can enhance retrieval accuracy in overcast conditions, and incorporating infrared bands can further improve the accuracy of DSR estimation. Solar radiation; Deep learning; Solar energy; AHI; Shortwave radiation; Geostationary; ABI; CNN; DeNET; GRU
Li, Xia; Tan, Zhihong; Zheng, Youtong; Bushuk, Mitchell; Donner, Leo J.Li, X., Z. Tan, Y. Zheng, M. Bushuk, L. J. Donner, 2023: Open Water in Sea Ice Causes High Bias in Polar Low-Level Clouds in GFDL CM4. Geophysical Research Letters, 50(24), e2023GL106322. doi: 10.1029/2023GL106322. Global climate models (GCMs) struggle to simulate polar clouds, especially low-level clouds that contain supercooled liquid and closely interact with both the underlying surface and large-scale atmosphere. Here we focus on GFDL's latest coupled GCM–CM4–and find that polar low-level clouds are biased high compared to observations. The CM4 bias is largely due to moisture fluxes that occur within partially ice-covered grid cells, which enhance low cloud formation in non-summer seasons. In simulations where these fluxes are suppressed, it is found that open water with an areal fraction less than 5% dominates the formation of low-level clouds and contributes to more than 50% of the total low-level cloud response to open water within sea ice. These findings emphasize the importance of accurately modeling open water processes (e.g., sea ice lead-atmosphere interactions) in the polar regions in GCMs.
Li, Zhengpeng; Bi, Jianrong; Hu, Zhiyuan; Ma, Junyang; Li, BowenLi, Z., J. Bi, Z. Hu, J. Ma, B. Li, 2023: Regional transportation and influence of atmospheric aerosols triggered by Tonga volcanic eruption. Environmental Pollution, 121429. doi: 10.1016/j.envpol.2023.121429. A cataclysmic submarine volcano at Hunga Tonga-HungaHa'apai (HTHH) near Tonga, erupted violently on 15 January 2022, which injected a plume of ash cloud soaring into the upper atmosphere. In this study, we examined the regional transportation and potential influence of atmospheric aerosols triggered by HTHH volcano, based on active and passive satellite products, ground-based observations, multi-source reanalysis datasets and radiation transfer model. The results indicated that about 0.7 Tg (1 Tg = 109 kg) sulfur dioxide (SO2) gas were emitted into stratosphere from the HTHH volcano, and were lifted to an altitude of 30 km. The regional averaged SO2 columnar content over western Tonga increased by 10–36 Dobson Units (DU), the mean aerosol optical thickness (AOT) retrieved from satellite products increased to 0.25–0.34. The stratospheric AOT values caused by HTHH emissions increased to 0.03, 0.20, and 0.23 on 16, 17, and 19 January, respectively, accounting for 1.5%, 21.9%, and 31.1% of total AOT. Ground-based observations also showed an AOT increase of 0.25–0.43, with the maximum daily average of 0.46–0.71 appeared on 17 January. The volcanic aerosols were remarkably dominated by fine-mode particles and posed strong light-scattering and hygroscopic abilities. Consequently, the mean downward surface net shortwave radiative flux was reduced by 2.45–11.9 Wm-2 on different regional scales, the surface temperature decreased by 0.16–0.42 K. The maximum aerosol extinction coefficient was 0.51 km−1 appeared at 27 km, which resulted in an instantaneous shortwave heating rate of 1.80 Khour−1. The volcanic materials were injected into the stratosphere and completed a circle around the earth in 15 days. This would exert a profound influence on the energy budget, water vapor and ozone exchange in the stratosphere, which deserves to be further studied. Volcanic aerosol; Shortwave heating rate; Tonga volcano
Liang, Hui; Jiang, Bo; Peng, Jianghai; Li, Shaopeng; Han, Jiakun; Yin, XiuwanLiang, H., B. Jiang, J. Peng, S. Li, J. Han, X. Yin, 2023: Estimating daily surface downward shortwave radiation over rugged terrain without bright surface at 30 m on clear-sky days using CERES data. International Journal of Digital Earth, 16(2), 4317-4345. doi: 10.1080/17538947.2023.2263421. In this study, the authors propose a model, called the Daily Downward Shortwave Radiation Random Forest Model over Rugged Terrain (DSRMT), to accurately calculate the downward shortwave radiation over a terrain without bright surface on clear days at a daily scale (DSRdaily−rugged). It was built by using the random forest method based on the comprehensive samples from CERES4_SYN1deg_Ed4A within 17 typical mountainous regions. DSRMT could directly estimate DSRdaily-rugged from the instantaneous direct and diffuse solar radiation on a flat surface during 10:30–14:30hrs on each day by comparing with the terrain factors from a digital elevation model, broadband albedo from the Global Land Surface Satellite, and ancillary information. The in-situ validation results showed that it generally delivered superior performance in estimating DSRdaily-rugged at any time during 10:30–14:30hrs, especially at noon, yielding a validated root mean-squared error (RMSE) of 24.90–29.22 Wm−2 and mean absolute error (MAE) of 19.16–22.94 Wm−2, and the average weighted DSRdaily-rugged were usually more accurate with the RMSE and MAE of 21.63 and 17.14 Wm−2. Overall, DSRMT was found to deliver satisfactory performance because of its high accuracy, robustness, ease of implementation, and efficiency, so it has the strong potential to be widely used in practice. remote sensing; modeling; CERES4; Daily downward shortwave radiation; DSRMT; estimation; rugged terrain
Liang, Kaixin; Wang, Jinfei; Luo, Hao; Yang, QinghuaLiang, K., J. Wang, H. Luo, Q. Yang, 2023: The Role of Atmospheric Rivers in Antarctic Sea Ice Variations. Geophysical Research Letters, 50(8), e2022GL102588. doi: 10.1029/2022GL102588. Antarctic sea ice variations are affected by moisture and heat from low- and mid-latitudes, more than 90% of which are transported by atmospheric rivers (ARs). This study employs the ERA5 reanalysis and satellite observations to detect all the ARs over the Antarctic sea ice and analyze the general contributions of ARs on sea ice changes from 1979 to 2020. Though AR frequency is low in all seasons, ARs give rise to intense sea ice reduction at a rate of more than 10%/day in marginal ice zone. Thermodynamic processes of sea ice dominate the AR-induced variations, associated with anomalous atmospheric conditions during ARs. Warm, moist and cloudy weather causes considerable melting by enhancing sensible heat flux in cold seasons but has restrictive influences in summer due to blocked solar radiation. Heavy precipitation during ARs is also nonnegligible, especially during the summer melt. sea ice; Antarctic; atmospheric river
Liang, Lusheng; Su, Wenying; Sejas, Sergio; Eitzen, Zachary A.; Loeb, Norman G.Liang, L., W. Su, S. Sejas, Z. A. Eitzen, N. G. Loeb, 2023: Next-generation radiance unfiltering process for the Clouds and Earth’s Radiant Energy System instrument. EGUsphere, 1-25. doi: 10.5194/egusphere-2023-1670. Abstract. The filtered radiances measured by the Clouds and the Earth’s Radiant Energy System (CERES) instruments are converted to shortwave (SW), longwave (LW), and window unfiltered radiances based on regressions developed from theoretical radiative transfer simulations to relate filtered and unfiltered radiances. This paper describes an update to the existing Edition 4 CERES unfiltering algorithm (Loeb et al., 2001), incorporating the most recent developments in radiative transfer modeling, ancillary input datasets, and increased computational and storage capabilities during the past 20 years. Simulations are performed with MODTRAN 5.4. Over land and snow, the surface Bidirectional Reflectance Distribution Function (BRDF) is characterized by a kernel-based representation in the simulations, instead of the Lambertian surface used in the Edition 4 unfiltering process. Radiance unfiltering is explicitly separated into 4 seasonally dependent land surface groups based on the spectral radiation similarities of different surface types (defined by International Geosphere-Biosphere Programme); over snow, it is separated into fresh snow, permanent snow, and sea ice. It contrasts to the Edition 4 unfiltering process that one set of regressions for land and snow, respectively. The instantaneous unfiltering errors are estimated with independent test cases generated from radiative transfer simulations in which the ‘true’ unfiltered radiances from radiative transfer simulations are compared with the unfiltered radiances calculated from the regressions. Overall, the relative errors are mostly within ±0.5 % for SW, within ±0.2 % for daytime LW, and within ±0.1 % for nighttime LW for both CERES Terra Flight Model 1 (FM1) and Aqua FM3 instruments. The unfiltered radiances are converted to fluxes and compared to CERES Edition 4 fluxes. The global mean instantaneous fluxes for Aqua FM3 are reduced by less than 0.42 Wm-2 for SW and increased by less than 0.47 Wm-2 for daytime LW; for Terra FM1, they are reduced by less than 0.31 Wm-2 for SW and increased by less than 0.29 Wm-2 for daytime LW, though regional differences can be as large as 2.0 Wm-2. Nighttime LW flux differences are nearly negligible for both instruments.
Liang, Mingjie; Han, Zhiwei; Li, Jiawei; Sun, Yele; Liang, Lin; Li, YueLiang, M., Z. Han, J. Li, Y. Sun, L. Liang, Y. Li, 2023: Radiative effects and feedbacks of anthropogenic aerosols on boundary layer meteorology and fine particulate matter during the COVID-19 lockdown over China. Science of The Total Environment, 862, 160767. doi: 10.1016/j.scitotenv.2022.160767. The COVID-19 epidemic has exerted significant impacts on human health, social and economic activities, air quality and atmospheric chemistry, and potentially on climate change. In this study, an online coupled regional climate–chemistry–aerosol model (RIEMS-Chem) was applied to explore the direct, indirect, and feedback effects of anthropogenic aerosols on radiation, boundary layer meteorology, and fine particulate matter during the COVID-19 lockdown period from 23 January to 8 April 2020 over China. Model performance was validated against a variety of observations for meteorological variables, PM2.5 and its chemical components, aerosol optical properties, as well as shortwave radiation flux, which demonstrated that RIEMS-Chem was able to reproduce the spatial distribution and temporal variation of the above variables reasonably well. During the study period, direct radiative effect (DRE) of anthropogenic aerosols was stronger than indirect radiative effect (IRE) in most regions north of the Yangtze River, whereas IRE dominated over DRE in the Yangtze River regions and South China. In North China, DRE induced larger changes in meteorology and PM2.5 than those induced by IRE, whereas in South China, the changes by IRE were remarkably larger than those by DRE. Emission reduction alone during the COVID-19 lockdown reduced PM2.5 concentration by approximately 32 % on average over East China. As a result, DRE at the surface was weakened by 15 %, whereas IRE changed little over East China, leading to a decrease in total radiative effect (TRE) by approximately 7 % in terms of domain average. The DRE-induced changes in meteorology and PM2.5 were weakened due to emission reduction, whereas the IRE-induced changes were almost the same between the cases with and without emission reductions. By aerosol radiative and feedback effects, the COVID-19 emission reductions resulted in 0.06 °C and 0.04 °C surface warming, 1.6 and 4.0 μg m−3 PM2.5 decrease, 0.4 and 1.3 mm precipitation increase during the lockdown period in 2020 in terms of domain average over North China and South China, respectively, whereas the lockdown caused negligible changes on average over East Asia. COVID-19; Indirect effect; Feedback; Anthropogenic aerosols; Boundary layer meteorology; Direct radiative effect
Liang, Yuanxin; Gui, Ke; Che, Huizheng; Li, Lei; Zheng, Yu; Zhang, Xutao; Zhang, Xindan; Zhang, Peng; Zhang, XiaoyeLiang, Y., K. Gui, H. Che, L. Li, Y. Zheng, X. Zhang, X. Zhang, P. Zhang, X. Zhang, 2023: Changes in aerosol loading before, during and after the COVID-19 pandemic outbreak in China: Effects of anthropogenic and natural aerosol. Science of The Total Environment, 857, 159435. doi: 10.1016/j.scitotenv.2022.159435. Anthropogenic emissions reduced sharply in the short-term during the coronavirus disease pandemic (COVID-19). As COVID-19 is still ongoing, changes in atmospheric aerosol loading over China and the factors of their variations remain unclear. In this study, we used multi-source satellite observations and reanalysis datasets to synergistically analyze the spring (February–May) evolution of aerosol optical depth (AOD) for multiple aerosol types over Eastern China (EC) before, during and after the COVID-19 lockdown period. Regional meteorological effects and the radiative response were also quantitatively assessed. Compared to the same period before COVID-19 (i.e., in 2019), a total decrease of −14.6 % in tropospheric TROPOMI nitrogen dioxide (NO2) and a decrease of −6.8 % in MODIS AOD were observed over EC during the lockdown period (i.e., in 2020). After the lockdown period (i.e., in 2021), anthropogenic emissions returned to previous levels and there was a slight increase (+2.3 %) in AOD over EC. Moreover, changes in aerosol loading have spatial differences. AOD decreased significantly in the North China Plain (−14.0 %, NCP) and Yangtze River Delta (−9.4 %) regions, where anthropogenic aerosol dominated the aerosol loading. Impacted by strong wildfires in Southeast Asia during the lockdown period, carbonaceous AOD increased by +9.1 % in South China, which partially offset the emission reductions. Extreme dust storms swept through the northern region in the period after COVID-19, with an increase of +23.5 % in NCP and + 42.9 % in Northeast China (NEC) for dust AOD. However, unfavorable meteorological conditions overwhelmed the benefits of emission reductions, resulting in a +20.1 % increase in AOD in NEC during the lockdown period. Furthermore, the downward shortwave radiative flux showed a positive anomaly due to the reduced aerosol loading in the atmosphere during the lockdown period. This study highlights that we can benefit from short-term controls for the improvement of air pollution, but we also need to seriously considered the cross-regional transport of natural aerosol and meteorological drivers. Aerosol optical depth; Anthropogenic aerosol; COVID-19 impacts over China; Meteorological drivers; Natural aerosol; Radiative flux
Lin, Lin; Liu, Xiaohong; Fu, Qiang; Shan, YunpengLin, L., X. Liu, Q. Fu, Y. Shan, 2023: Climate Impacts of Convective Cloud Microphysics in NCAR CAM5. J. Climate, 36(10), 3183-3202. doi: 10.1175/JCLI-D-22-0136.1. Abstract We improved the treatments of convective cloud microphysics in the NCAR Community Atmosphere Model version 5.3 (CAM5.3) by 1) implementing new terminal velocity parameterizations for convective ice and snow particles, 2) adding graupel microphysics, 3) considering convective snow detrainment, and 4) enhancing rain initiation and generation rate in warm clouds. We evaluated the impacts of improved microphysics on simulated global climate, focusing on simulated cloud radiative forcing, graupel microphysics, convective cloud ice amount, and tropical precipitation. Compared to CAM5.3 with the default convective microphysics, the too-strong cloud shortwave radiative forcing due primarily to excessive convective cloud liquid is largely alleviated over the tropics and midlatitudes after rain initiation and generation rate is enhanced, in better agreement with the CERES-EBAF estimates. Geographic distributions of graupel occurrence are reasonably simulated over continents; whereas the graupel occurrence remains highly uncertain over the oceanic storm-track regions. When evaluated against the CloudSat–CALIPSO estimates, the overestimation of convective ice mass is alleviated with the improved convective ice microphysics, among which adding graupel microphysics and the accompanying increase in hydrometeor fall speed play the most important role. The probability distribution function (PDF) of rainfall intensity is sensitive to warm rain processes in convective clouds, and enhancement in warm rain production shifts the PDF toward heavier precipitation, which agrees better with the TRMM observations. Common biases of overestimating the light rain frequency and underestimating the heavy rain frequency in GCMs are mitigated.
Liu, Huizeng; Li, Qingquan; Huang, Shaopeng; Qiu, Hong; Jiang, Huiping; Yang, Chao; Zhu, PingLiu, H., Q. Li, S. Huang, H. Qiu, H. Jiang, C. Yang, P. Zhu, 2023: Estimating the Angular Distribution of the Earth’s Longwave Radiation from Radiative Fluxes. IEEE Transactions on Geoscience and Remote Sensing, 1-1. doi: 10.1109/TGRS.2023.3269431. In recent years, several novel satellite platforms and sensors have been proposed for the Earth Radiation Budget (ERB). Simulating the sensor-measured signals could be helpful for optimizing the settings of sensors and exploring their potential in ERB. The anisotropic factor, depicting the anisotropy of Earth’s radiation, is essential in the simulation. However, developing angular distribution models involves complex procedures of data preparation, processing, and modeling. This study, targeting at simplifying the procedure of simulating the signals of ERB sensors, proposed a suit of models for estimating the longwave anisotropic factors directly from the Earth’s radiative fluxes. The models were developed with CERES/Terra data sensed in rotating azimuth plane (RAP) mode during 2000-2005 and the artificial neural network (ANN) algorithm, and tested with 12 monthly of CERES/Terra data collected in RAP and cross-track mode during 2021-2022, respectively. Models were developed for 10 scene types based on Earth’s surface types, and compared with the operational ANN ADMs. Results showed that the longwave anisotropic factors were accurately estimated with the correlation coefficient (r) varying between 0.84 and 0.98 and MAPE within 1.20% for the test dataset, and the approach proposed in this study had comparable performance with the ANN ADMs. With the estimated anisotropic factors, the sensor-measured radiances were accurately retrieved with r=1.00 and MAPE=0.53%. Therefore, the proposed approach is promising in accurate and efficient simulations of novel ERB platforms and sensors like the Moon-based Earth Radiation. CERES; Angular distribution models; Anisotropic factor; Artificial neural networks; Data models; Earth; Earth’s radiative budget; Extraterrestrial measurements; Instruments; Satellite broadcasting; Satellites; Top-of-atmosphere
Liu, Xue; Diao, Yina; Sun, Ruipeng; Gong, QinglongLiu, X., Y. Diao, R. Sun, Q. Gong, 2023: Impacts of Cyclones on Arctic Clouds during Autumn in the Early 21st Century. Atmosphere, 14(4), 689. doi: 10.3390/atmos14040689. Our study shows that, during 2001–2017, when the sea ice was melting rapidly, cyclone days accounted for more than 50% of the total autumn days at the sounding stations in the Arctic marginal seas north of the Eurasian continent and almost 50% of the total autumn days at the sounding station on the northern coast of Canada. It is necessary to investigate the influence of Arctic cyclones on the cloud fraction in autumn when the sea ice refreezes from its summer minimum and the infrared cloud radiative effect becomes increasingly important. Cyclones at the selected stations are characterized by a narrow maximum rising zone with vertically consistent high relative humidity (RH) and a broad region outside the high RH zone with low RH air from the middle troposphere covering the low troposphere’s high relative humidity air. Consequently, on approximately 40% of the cyclone days, the cloud formation condition was improved from the near surface to the upper troposphere due to the cooling of strong rising warm humid air. Therefore, cyclones lead to middle cloud increases and sometimes high cloud increases, since the climatological Arctic autumn clouds are mainly low clouds. On approximately 60% of the cyclone days, only low cloud formed, but the low cloud formation condition was suppressed due to the mixing ratio decrease induced by cold dry air sinking. As a result, cyclones generally lead to a decrease in low clouds. However, the correlation between the cyclones and low clouds is complex and varies with surface ice conditions. Arctic autumn clouds; Arctic cyclones; cloud change
Liu, Yawen; Wang, Minghuai; Yue, Man; Qian, YunLiu, Y., M. Wang, M. Yue, Y. Qian, 2023: Distinct Seasonality in Aerosol Responses to Emission Control Over Northern China. Journal of Geophysical Research: Atmospheres, 128(11), e2022JD038377. doi: 10.1029/2022JD038377. Despite intensive research exploring how aerosols respond to emission control over Northern China, efforts mostly focus on the environmental benefit, especially in winter. Here we found that unlike the most substantial PM2.5 concentration reduction in winter, aerosol optical depth (AOD) declines more than 2 times faster in summer, causing an increase in aerosol radiative effects of 1.2 (5.7)Wm−2 on all-sky (clear-sky) conditions over 2013–2019 and largely shaping the climate impact. Low-level aerosols are shown to be the prime contributor under the synergetic effects of aerosol composition and ambient relative humidity (RH). The dominance of the highly hygroscopic sulfate combined with high RH enables a strong extinction efficiency of the reduced summertime aerosols, while the insignificant AOD decline in wintertime result from the dominance of organic aerosols with weak hygroscopicity, and is further offset by the increased frequencies of extremely high RH. We show the environmental and climatic responses of aerosols to emission control exhibit distinctively different seasonality. aerosol response; climate effect; emission reduction; seasonality
Lu, Lu; Ma, QianLu, L., Q. Ma, 2023: Diurnal Cycle in Surface Incident Solar Radiation Characterized by CERES Satellite Retrieval. Remote Sensing, 15(13), 3217. doi: 10.3390/rs15133217. Surface incident solar radiation (Rs) plays an important role in climate change on Earth. Recently, the use of satellite-retrieved datasets to obtain global-scale Rs with high spatial and temporal resolutions has become an indispensable tool for research in related fields. Many studies were carried out for Rs evaluation based on the monthly satellite retrievals; however, few evaluations have been performed on their diurnal variation in Rs. This study used independently widely distributed ground-based data from the Baseline Surface Radiation Network (BSRN) to evaluate hourly Rs from the Clouds and the Earth’s Radiant Energy System Synoptic (CERES) SYN1deg–1Hour product through a detrended standardization process. Furthermore, we explored the influence of cloud cover and aerosols on the diurnal variation in Rs. We found that CERES-retrieved Rs performs better at midday than at 7:00–9:00 and 15:00–17:00. For spatial distribution, CERES-retrieved Rs performs better over the continent than over the island/coast and polar regions. The Bias, MAB and RMSE in CERES-retrieved Rs under clear-sky conditions are rather small, although the correlation coefficients are slightly lower than those under overcast-sky conditions from 9:00 to 15:00. In addition, the range in Rs bias caused by cloud cover is 1.97–5.38%, which is significantly larger than 0.31–2.52% by AOD. CERES; diurnal variation; BSRN; solar radiation
Luccini, Eduardo; Orte, Facundo; Lell, Julián; Nollas, Fernando; Carbajal, Gerardo; Wolfram, EliánLuccini, E., F. Orte, J. Lell, F. Nollas, G. Carbajal, E. Wolfram, 2023: The UV Index color palette revisited. Journal of Photochemistry and Photobiology, 15, 100180. doi: 10.1016/j.jpap.2023.100180. The UV Index (UVI), standardized by the World Health Organization (WHO) in 2002, is an internationally accepted reference for disseminating information on solar UV radiation levels with the purpose of preventing the harmful effects on human health by sun overexposure. The UVI is the erythemal irradiance expressed in a dimensionless unit, with numerical values adapted to a risk scale that considers the “Extreme” level from a UVI value equal to 11 upwards. This scale is linked to a color palette by health risk ranges, and to a graded color palette by units of UVI for more details. Both the numerical scale and its associated risk levels were universally adopted by the scientific community and by global information systems to the population. However, inconsistencies and limitations persist between both UVI color palettes, making their interpretation and application difficult. In the present work all these aspects are addressed, proposing a revised color palette for unit UVI values that resolves each of them. Based on the WHO risk-ranges UVI color palette, the new color palette for unit UVI values gives coherence to both color charts, allowing reliable identification of the risk level bands and of each unit UVI level within them, and solves the need to distinguish between units for numerical values of UVI higher than 11 that are registered daily in many regions of the world. Color codes; Color palettes; Public health; Risk scale; Solar radiation; UV Index
Luo, Hao; Quaas, Johannes; Han, YongLuo, H., J. Quaas, Y. Han, 2023: Examining cloud vertical structure and radiative effects from satellite retrievals and evaluation of CMIP6 scenarios. Atmospheric Chemistry and Physics, 23(14), 8169-8186. doi: 10.5194/acp-23-8169-2023. Clouds exhibit a wide range of vertical morphologies that are regulated by distinct atmospheric dynamics and thermodynamics and are related to a diversity of microphysical properties and radiative effects. In this study, the new CERES-CloudSat-CALIPSO-MODIS (CCCM) RelD1 dataset is used to investigate the morphology and spatial distribution of different cloud vertical structure (CVS) types during 2007–2010. The combined active and passive satellites provide a more precise CVS than those only based on passive imagers or microwave radiometers. We group the clouds into 12 CVS classes based on how they are located or overlapping in three standard atmospheric layers with pressure thresholds of 440 and 680 hPa. For each of the 12 CVS types, the global average cloud radiative effects (CREs) at the top of the atmosphere, within the atmosphere and at the surface, as well as the cloud heating rate (CHR) profiles are examined. The observations are subsequently used to evaluate the variations in total, high-, middle- and low-level cloud fractions in CMIP6 models. The “historical” experiment during 1850–2014 and two scenarios (ssp245 and ssp585) during 2015–2100 are analyzed. The observational results show a substantial difference in the spatial pattern among different CVS types, with the greatest contrast between high and low clouds. Single-layer cloud fraction is almost 4 times larger on average than multi-layer cloud fraction, with significant geographic differences associated with clearly distinguishable regimes, showing that overlapping clouds are regionally confined. The global average CREs reveal that four types of CVSs warm the planet, while eight of them cool it. The longwave component drives the net CHR profile, and the CHR profiles of multi-layer clouds are more curved and intricate than those of single-layer clouds, resulting in complex thermal stratifications. According to the long-term analysis from CMIP6, the projected total cloud fraction decreases faster over land than over the ocean. The high clouds over the ocean increase significantly, but other types of clouds over land and the ocean continue to decrease, helping to offset the decrease in oceanic total cloud fraction. Moreover, it is concluded that the spatial pattern of CVS types may not be significantly altered by climate change, and only the cloud fraction is influenced. Our findings suggest that long-term observed CVS should be emphasized in the future to better understand CVS responses to anthropogenic forcing and climate change.
Luo, Rui; Ding, Qinghua; Baxter, Ian; Chen, Xianyao; Wu, Zhiwei; Bushuk, Mitchell; Wang, HailongLuo, R., Q. Ding, I. Baxter, X. Chen, Z. Wu, M. Bushuk, H. Wang, 2023: Uncertain role of clouds in shaping summertime atmosphere-sea ice connections in reanalyses and CMIP6 models. Climate Dynamics. doi: 10.1007/s00382-023-06785-9. Downwelling longwave radiation (DLR) driven by the atmospheric and cloud conditions in the troposphere is suggested to be a dominant factor to determine the summertime net surface energy budget over the Arctic Ocean and thus plays a key role to shape the September sea ice. We use reanalyses and the self-organizing map (SOM) method to distinguish CMIP6 model performance in replicating the observed strong atmosphere-DLR connection. We find all models can reasonably simulate the linkage between key atmosphere variables and the clear sky DLR but behave differently in replicating the atmosphere-DLR connection due to cloud forcing. In ERA5 and strongly coupled models, tropospheric high pressure is associated with decreased clouds in the mid- and high-levels and increased clouds near the surface. This out-of-phase structure indicates that DLR cloud forcing is nearly neutral, making the clear sky DLR more important to bridge JJA circulation to late-summer sea ice. In MERRA-2 and weakly coupled models, tropospheric clouds display a vertically homogeneous reduction; the cloud DLR is thus strongly reduced due to the cooling effect, which partially cancels out the clear sky DLR and makes the total DLR less efficient to translate circulation forcing to sea ice. The differences of cloud vertical distribution in CMIP6 appear to be differentiated by circulation related relative humidity. Therefore, a better understanding of the discrepancy of different reanalyses and remote sensing products is critical to comprehensively evaluate simulated interactions among circulation, clouds, sea ice and energy budget at the surface in summer. CMIP6; Atmosphere-Sea ice connection; Clear-sky; Cloud; DLR
Luo, Run; Liu, Yuzhi; Luo, Min; Li, Dan; Tan, Ziyuan; Shao, Tianbin; Alam, KhanLuo, R., Y. Liu, M. Luo, D. Li, Z. Tan, T. Shao, K. Alam, 2023: Dust effects on mixed-phase clouds and precipitation during a super dust storm over northern China. Atmospheric Environment, 313, 120081. doi: 10.1016/j.atmosenv.2023.120081. Dust aerosols have been generally regarded as efficient ice nuclei (IN), but their influences on mixed-phase clouds and precipitation are poorly quantified. In this study, combining satellite observations, reanalysis data and the Weather Research and Forecasting (WRF) model, we investigate the impacts of dust aerosols on mixed-phase clouds and precipitation during a super dust storm over northern China. The Suomi National Polar-Orbiting Partnership (S-NPP) satellite observed a super dust storm from March 15–19, 2021 in northern China, followed by heavy precipitation between March 17 and 19. The results showed that the occurrence of super dust storms may play an important role in cloud formation and precipitation processes. Furthermore, numerical modeling revealed that dust aerosols can increase the ice crystal number concentration (QNi) and decrease the cloud droplet number concentration (QNc) in mixed-phase clouds through the Wegener–Bergeron–Findeisen (WBF) process, in which the maximum increase in QNi can reach 21%. Simultaneously, the mass mixing ratios of rain, graupel and snow increased due to dust aerosols. Consequently, precipitation could increase by up to 9.8% in northern China. This study could provide evidence for understanding the mechanisms of dust effects on mixed-phase clouds over northern China. Precipitation; Satellite observations; WRF model; Dust aerosols; Mixed-phase clouds
Lyapustin, Alexei; Wang, Yujie; Choi, Myungje; Xiong, Xiaoxiong; Angal, Amit; Wu, Aisheng; Doelling, David R.; Bhatt, Rajendra; Go, Sujung; Korkin, Sergey; Franz, Bryan; Meister, Gerhardt; Sayer, Andrew M.; Roman, Miguel; Holz, Robert E.; Meyer, Kerry; Gleason, James; Levy, RobertLyapustin, A., Y. Wang, M. Choi, X. Xiong, A. Angal, A. Wu, D. R. Doelling, R. Bhatt, S. Go, S. Korkin, B. Franz, G. Meister, A. M. Sayer, M. Roman, R. E. Holz, K. Meyer, J. Gleason, R. Levy, 2023: Calibration of the SNPP and NOAA 20 VIIRS sensors for continuity of the MODIS climate data records. Remote Sensing of Environment, 295, 113717. doi: 10.1016/j.rse.2023.113717. Accurate long-term sensor calibration and periodic re-processing to ensure consistency and continuity of atmospheric, land and ocean geophysical retrievals from space within the mission period and across different missions is a major requirement of climate data records. In this work, we applied the Multi-Angle Implementation of Atmospheric Correction (MAIAC)-based vicarious calibration technique over Libya-4 desert site to perform calibration analysis of Visible Infrared Imaging Radiometer Suite (VIIRS) on Suomi National Polar-orbiting Partnership (SNPP) and NOAA-20 satellites. For both VIIRS sensors we characterized residual linear calibration trends and cross-calibrated both sensors to MODerate resolution Imaging Spectroradiometer (MODIS) Aqua regarded as a calibration standard. The relative spectral response (RSR) differences were accounted for using the German Aerospace Center (DLR) Earth Sensing Imaging Spectrometer (DESIS) hyperspectral surface reflectance data. Our results agree with independent vicarious calibration results of both the MODIS/VIIRS Characterization Support Team as well as the CERES Imager and Geostationary Calibration Group within estimated uncertainty of 1–2%. Analysis of MAIAC geophysical products with the new calibration shows a high level of agreement of MAIAC aerosol, surface reflectance and NDVI records between MODIS and VIIRS. Excluding high aerosol optical depth (AOD), all three sensors agree in AOD with mean difference (MD) less than 0.01 and residual mean squared difference rmsd ∼ 0.04. Spectral geometrically normalized surface reflectance agrees within rmsd of 0.003–0.005 in the visible and 0.01–0.012 at longer wavelengths. The residual surface reflectance differences are fully explained by differences in spectral filter functions. Finally, difference in NDVI is characterized by rmsd ∼ 0.02 and MD less than 0.003 for NDVI based on VIIRS imagery bands I1/I2 and less than 0.01 for NDVI based on VIIRS radiometric bands M5/M7. In practical sense, these numbers indicate consistency and continuity in MAIAC records ensuring the smooth transition from MODIS to VIIRS. Calibration; MODIS; VIIRS; NDVI; MAIAC; Surface reflectance
Lyman, John M.; Johnson, Gregory C.Lyman, J. M., G. C. Johnson, 2023: Global High-Resolution Random Forest Regression Maps of Ocean Heat Content Anomalies Using In Situ and Satellite Data. J. Atmos. Oceanic Technol., 40(5), 575-586. doi: 10.1175/JTECH-D-22-0058.1. Abstract The ocean, with its low albedo and vast thermal inertia, plays key roles in the climate system, including absorbing massive amounts of heat as atmospheric greenhouse gas concentrations rise. While the Argo array of profiling floats has vastly improved sampling of ocean temperature in the upper half of the global ocean volume since the mid-2000s, they are not sufficient in number to resolve eddy scales in the oceans. However, satellite sea surface temperature (SST) and sea surface height (SSH) measurements do resolve these scales. Here we use random forest regressions to map ocean heat content anomalies (OHCA) using in situ training data from Argo and other sources on a 7-day × 1/4° × 1/4° grid with latitude, longitude, time, SSH, and SST as predictors. The maps display substantial patterns on eddy scales, resolving variations of ocean currents and fronts. During the well-sampled Argo period, global integrals of these maps reduce noise relative to estimates based on objective mapping of in situ data alone by roughly a factor of 3 when compared to time series of CERES (satellite data) top-of-the-atmosphere energy flux measurements and improve correlations of anomalies with CERES on annual time scales. Prior to and early on in the Argo period, when in situ data were sparser, global integrals of these maps retain low variance, and do not relax back to a climatological mean, avoiding potential deficiencies of various methods for infilling data-sparse regions with objective maps by exploiting temporal and spatial patterns of OHCA and its correlations with SST and SSH. Significance Statement We use a simple machine learning technique to improve maps of subsurface ocean warming by exploiting the relationships between subsurface ocean temperature both sea surface temperature and sea level. Mapping ocean warming is important because it contributes to sea level rise through thermal expansion; impacts marine life through marine heatwaves and changes in mixing, oxygen, and carbon dioxide levels; increases energy available to tropical cyclones; and stores most of the energy building up in Earth’s climate system owing to the accumulation of anthropogenic greenhouse gases in the atmosphere. Our new estimates generally have lower noise energy and higher correlations than other products when compared with global energy fluxes at the top of the atmosphere measured by satellite.
Ma, Qianrong; Sun, Yingxiao; Wan, Shiquan; Gu, Yu; Bai, Yang; Mu, JiayiMa, Q., Y. Sun, S. Wan, Y. Gu, Y. Bai, J. Mu, 2023: An ENSO Prediction Model Based on Backtracking Multiple Initial Values: Ordinary Differential Equations–Memory Kernel Function. Remote Sensing, 15(15), 3767. doi: 10.3390/rs15153767. This article presents a new prediction model, the ordinary differential equations–memory kernel function (ODE–MKF), constructed from multiple backtracking initial values (MBIV). The model is similar to a simplified numerical model after spatial dimension reduction and has both nonlinear characteristics and the low-cost advantage of a time series model. The ODE–MKF focuses on utilizing more temporal information and includes machine learning to solve complex mathematical inverse problems to establish a predictive model. This study first validates the feasibility of the ODE–MKF via experiments using the Lorenz system. The results demonstrate that the ODE–MKF prediction model could describe the nonlinear characteristics of complex systems and exhibited ideal predictive robustness. The prediction of the El Niño-Southern Oscillation (ENSO) index further demonstrates its effectiveness, as it achieved 24-month lead predictions and effectively improved nonlinear problems. Furthermore, the reliability of the model was also tested, and approximately 18 months of prediction were achieved, which was verified with the Clouds and the Earth’s Radiant Energy System (CERES) Energy Balanced and Filled (EBAF) radiation fluxes. The short-term memory index Southern Oscillation (SO) was further used to examine the applicability of ODE–MKF. A six-month lead prediction of the SO trend was achieved, indicating that the predictability of complex systems is related to their inherent memory scales. ENSO 3; multiple backtracking initial values 2; ordinary differential equations–memory kernel function 1; prediction 4
Mace, Gerald G.; Benson, Sally; Humphries, Ruhi; Gombert, Peter M.; Sterner, ElizabethMace, G. G., S. Benson, R. Humphries, P. M. Gombert, E. Sterner, 2023: Natural marine cloud brightening in the Southern Ocean. Atmospheric Chemistry and Physics, 23(2), 1677-1685. doi: 10.5194/acp-23-1677-2023. The number of cloud droplets per unit volume (Nd) is a fundamentally important property of marine boundary layer (MBL) liquid clouds that, at constant liquid water path, exerts considerable controls on albedo. Past work has shown that regional Nd has a direct correlation to marine primary productivity (PP) because of the role of seasonally varying, biogenically derived precursor gases in modulating secondary aerosol properties. These linkages are thought to be observable over the high-latitude oceans, where strong seasonal variability in aerosol and meteorology covary in mostly pristine environments. Here, we examine Nd variability derived from 5 years of MODIS Level 2-derived cloud properties in a broad region of the summer eastern Southern Ocean and adjacent marginal seas. We demonstrate latitudinal, longitudinal and temporal gradients in Nd that are strongly correlated with the passage of air masses over high-PP waters that are mostly concentrated along the Antarctic Shelf poleward of 60∘ S. We find that the albedo of MBL clouds in the latitudes south of 60∘ S is significantly higher than similar liquid water path (LWP) clouds north of this latitude.
Mall, Ankita; Singh, SachchidanandMall, A., S. Singh, 2023: Effects of Atmospheric Aerosol Types on Ultraviolet Flux at Different Stations in the Indo-Gangetic Plain. Environmental Sciences Proceedings, 27(1), 33. doi: 10.3390/ecas2023-15118. Atmospheric aerosols play a crucial role in the scattering and absorption of solar radiation, directly influencing the UV flux reaching the Earth’s surface. This study investigates the impact of different atmospheric aerosol types on the ultraviolet (UV) flux at four stations over the Indo-Gangetic plain (IGP). For this study, high-resolution 1° × 1° UVA and UVB data were obtained from Clouds and the Earth’s Radiant Energy System (CERES). Various aerosol types present in the atmosphere were categorized based upon their optical properties and their quantitative influence on UVA and UVB flux was examined. Ground-level aerosol products were obtained from the NASA-based Aerosol Robotic Network (AERONET) at four stations in the IGP. Based on the optical properties of aerosols (fine mode fraction, single scattering albedo, aerosol optical depth and angstrom exponent), four distinct atmospheric aerosol types were inferred, namely dust-dominant (DT), polluted-continental-dominant (PCD), black-carbon-dominant (BCD), and organic-carbon-dominant (OCD). It is observed that the AOD of different aerosol types when separated do not seem to have made significant effects on UVA/B radiation (except at Kanpur), possibly due to the statistically smaller data set. For the entire combined AOD, the effects on UVA/B became quite significant at all the stations, which shows that a unit rise in AOD leads to a reduction of 5–7 Wm−2 in UVA and 0.14–0.23 Wm−2 in UVB. CERES; AERONET; UVA; UVB; aerosol types
Masunaga, HirohikoMasunaga, H., 2023: The Edge Intensification of Eastern Pacific ITCZ Convection. J. Climate, 36(10), 3469-3480. doi: 10.1175/JCLI-D-22-0382.1. Abstract Tropical precipitation is climatologically most intense at the heart of the intertropical convergence zone (ITCZ), but this is not always true in instantaneous snapshots. Precipitation is amplified along the ITCZ edge rather than at its center from time to time. In this study, satellite observations of column water vapor, precipitation, and radiation as well as the thermodynamic field from reanalysis data are analyzed to investigate the behavior of ITCZ convection in light of the local atmospheric energy imbalance. The analysis is focused on the eastern Pacific ITCZ, defined as the areas where column water vapor exceeds 50 mm over a specified width (typically 400–600 km) in the domain of 20°S–20°N, 180°–90°W. The events with a precipitation maximum at the southern and northern edges of the ITCZ are each averaged into composite statistics and are contrasted against the reference case with peak precipitation at the ITCZ center. The key findings are as follows. When precipitation peaks at the ITCZ center, suppressed radiative cooling forms a prominent positive peak in the diabatic forcing to the atmosphere, counteracted by an export of moist static energy (MSE) owing to a deep vertical advection and a large horizontal export of MSE. When convection develops at the ITCZ edges, to the contrary, a positive peak of the diabatic forcing is only barely present. An import of MSE owing to a shallow ascent on the ITCZ edges presumably allows an edge intensification to occur despite the weak diabatic forcing.
Matsui, Toshi; Wolff, David B.; Lang, Stephen; Mohr, Karen; Zhang, Minghua; Xie, Shaocheng; Tang, Shuaiqi; Saleeby, Stephen M.; Posselt, Derek J.; Braun, Scott A.; Chern, Jiun-Dar; Dolan, Brenda; Pippitt, Jason L.; Loftus, Adrian M.Matsui, T., D. B. Wolff, S. Lang, K. Mohr, M. Zhang, S. Xie, S. Tang, S. M. Saleeby, D. J. Posselt, S. A. Braun, J. Chern, B. Dolan, J. L. Pippitt, A. M. Loftus, 2023: Systematic Validation of Ensemble Cloud-Process Simulations Using Polarimetric Radar Observations and Simulator Over the NASA Wallops Flight Facility. Journal of Geophysical Research: Atmospheres, 128(16), e2022JD038134. doi: 10.1029/2022JD038134. The BiLateral Operational Storm-Scale Observation and Modeling (BLOSSOM) project was initiated to establish a long-term supersite to improve understanding of cloud physical states and processes as well as to support satellite and climate model programs over the Wallops Flight Facility site via a bilateral approach of storm-scale observations and process modeling. This study highlights a noble systematic validation framework of the BLOSSOM ensemble cloud-process simulations through mixed-phase, light-rain, and deep-convective precipitation cases. The framework consists of creating a domain-shifted ensemble of large-scale forcing data sets, and configuring and performing cloud-process simulations with three different bulk microphysics schemes. Validation uses NASA S-band dual-POLarimetric radar observations in the form of statistical composites and skill scores via a polarimetric radar simulator and newly developed CfRad Data tool (CfRAD). While the simulations capture the overall structures of the reflectivity composites, polarimetric signals are still poorly simulated, mainly due to a lack of representation of ice microphysics diversity in shapes, orientation distributions, and their complex mixtures. Despite the limitation, this new ensemble-based validation framework demonstrates that (a) no particular forcing or microphysics scheme outperforms the rest and (b) the skill scores of coarse- and fine-resolution ensemble simulations with different domain-shifted forcing and microphysics schemes are highly correlated with each other with no clear improvement. On the other hand, this suggests that coarse-resolution ensemble simulations are relevant for selecting the best meteorological forcing and microphysics scheme before conducting computationally demanding large eddy simulations in support of aircraft and satellite instrument development as well as cloud-precipitation-convection parameterizations. validation; cloud-process model; ensemble simulations; polarimetric radar; radar simulator; Wallops Flight Facility
McCloskey, Kevin; Chen, Sixing; Meijer, Vincent R.; Ng, Joe Yue-Hei; Davis, Geoff; Elkin, Carl; Van Arsdale, Christopher; Geraedts, ScottMcCloskey, K., S. Chen, V. R. Meijer, J. Y. Ng, G. Davis, C. Elkin, C. Van Arsdale, S. Geraedts, 2023: Estimates of broadband upwelling irradiance from GOES-16 ABI. Remote Sensing of Environment, 285, 113376. doi: 10.1016/j.rse.2022.113376. Satellite-derived estimates of the Earth’s radiation budget are crucial for understanding and predicting the weather and climate. However, existing satellite products measuring broadband outgoing longwave radiation (OLR) and reflected shortwave radiation (RSR) have spatio-temporal resolutions that are too coarse to evaluate important radiative forcers like aircraft condensation trails. We present a neural network which estimates OLR and RSR based on narrowband radiances, using collocated Cloud and Earth’s Radiant Energy System (CERES) and GOES-16 Advanced Baseline Imager (ABI) data. The resulting estimates feature strong agreement with the CERES data products (R2 = 0.977 for OLR and 0.974 for RSR on CERES Level 2 footprints), and we provide open access to the collocated satellite data and model outputs on all available GOES-16 ABI data for the 4 years from 2018–2021. CERES; Artificial neural networks; Spatial resolution; OLR; Temporal resolution; GOES-16 ABI; RSR; Top of atmosphere flux
McCoy, Isabel L.; McCoy, Daniel T.; Wood, Robert; Zuidema, Paquita; Bender, Frida A.-M.McCoy, I. L., D. T. McCoy, R. Wood, P. Zuidema, F. A. Bender, 2023: The Role of Mesoscale Cloud Morphology in the Shortwave Cloud Feedback. Geophysical Research Letters, 50(2), e2022GL101042. doi: 10.1029/2022GL101042. A supervised neural network algorithm is used to categorize near-global satellite retrievals into three mesoscale cellular convective (MCC) cloud morphology patterns. At constant cloud amount, morphology patterns differ in brightness associated with the amount of optically thin cloud features. Environmentally driven transitions from closed MCC to other morphology patterns, typically accompanied by more optically thin cloud features, are used as a framework to quantify the morphology contribution to the optical depth component of the shortwave cloud feedback. A marine heat wave is used as an out-of-sample test of closed MCC occurrence predictions. Morphology shifts in optical depth between 65°S and 65°N under projected environmental changes (i.e., from an abrupt quadrupling of CO2) assuming constant cloud cover contributes between 0.04 and 0.07 W m−2 K−1 (aggregate of 0.06) to the global mean cloud feedback. climate change; cloud heterogeneity; boundary layer clouds; cloud organization; mesoscale cloud morphology; shortwave cloud feedback
Medeiros, Brian; Shaw, Jonah; Kay, Jennifer E.; Davis, IsaacMedeiros, B., J. Shaw, J. E. Kay, I. Davis, 2023: Assessing Clouds Using Satellite Observations Through Three Generations of Global Atmosphere Models. Earth and Space Science, 10(7), e2023EA002918. doi: 10.1029/2023EA002918. Clouds are parameterized in climate models using quantities on the model grid-scale to approximate the cloud cover and impact on radiation. Because of the complexity of processes involved with clouds, these parameterizations are one of the key challenges in climate modeling. Differences in parameterizations of clouds are among the main contributors to the spread in climate sensitivity across models. In this work, the clouds in three generations of an atmosphere model lineage are evaluated against satellite observations. Satellite simulators are used within the model to provide an appropriate comparison with individual satellite products. In some respects, especially the top-of-atmosphere cloud radiative effect, the models show generational improvements. The most recent generation, represented by two distinct branches of development, exhibits some regional regressions in the cloud representation; in particular the southern ocean shows a positive bias in cloud cover. The two branches of model development show how choices during model development, both structural and parametric, lead to different cloud climatologies. Several evaluation strategies are used to quantify the spatial errors in terms of the large-scale circulation and the cloud structure. The Earth mover's distance is proposed as a useful error metric for the passive satellite data products that provide cloud-top pressure-optical depth histograms. The cloud errors identified here may contribute to the high climate sensitivity in the Community Earth System Model, version 2 and in the Energy Exascale Earth System Model, version 1.
Meng, Xia; Hang, Yun; Lin, Xiuran; Li, Tiantian; Wang, Tijian; Cao, Junji; Fu, Qingyan; Dey, Sagnik; Huang, Kan; Liang, Fengchao; Kan, Haidong; Shi, Xiaoming; Liu, YangMeng, X., Y. Hang, X. Lin, T. Li, T. Wang, J. Cao, Q. Fu, S. Dey, K. Huang, F. Liang, H. Kan, X. Shi, Y. Liu, 2023: A satellite-driven model to estimate long-term particulate sulfate levels and attributable mortality burden in China. Environment International, 171, 107740. doi: 10.1016/j.envint.2023.107740. Ambient fine particulate matter (PM2.5) pollution is a major environmental and public health challenge in China. In the recent decade, the PM2.5 level has decreased mainly driven by reductions in particulate sulfate as a result of large-scale desulfurization efforts in coal-fired power plants and industrial facilities. Emerging evidence also points to the differential toxicity of particulate sulfate affecting human health. However, estimating the long-term spatiotemporal trend of sulfate is difficult because a ground monitoring network of PM2.5 constituents has not been established in China. Spaceborne sensors such as the Multi-angle Imaging SpectroRadiometer (MISR) instrument can provide complementary information on aerosol size and type. With the help of state-of-the-art machine learning techniques, we developed a sulfate prediction model under support from available ground measurements, MISR-retrieved aerosol microphysical properties, and atmospheric reanalysis data at a spatial resolution of 0.1°. Our sulfate model performed well with an out-of-bag cross-validationR2 of 0.68 at the daily level and 0.93 at the monthly level. We found that the national mean population-weighted sulfate concentration was relatively stable before the Air Pollution Prevention and Control Action Plan was enforced in 2013, ranging from 10.4 to 11.5 µg m−3. But the sulfate level dramatically decreased to 7.7 µg m−3 in 2018, with a change rate of −28.7 % from 2013 to 2018. Correspondingly, the annual mean total non-accidental and cardiopulmonary deaths attributed to sulfate decreased by 40.7 % and 42.3 %, respectively. The long-term, full-coverage sulfate level estimates will support future studies on evaluating air quality policies and understanding the adverse health effect of particulate sulfate. Air pollution; Machine learning; Atmospheric big data; Health impact assessment; Particulate sulfate; Spatiotemporal distribution
Meyssignac, Benoit; Ablain, Michael; Guérou, Adrien; Prandi, Pierre; Barnoud, Anne; Blazquez, Alejandro; Fourest, Sébastien; Rousseau, Victor; Bonnefond, Pascal; Cazenave, Anny; Chenal, Jonathan; Dibarboure, Gerald; Donlon, Craig; Benveniste, Jérôme; Sylvestre-Baron, Annick; Vinogradova, NadyaMeyssignac, B., M. Ablain, A. Guérou, P. Prandi, A. Barnoud, A. Blazquez, S. Fourest, V. Rousseau, P. Bonnefond, A. Cazenave, J. Chenal, G. Dibarboure, C. Donlon, J. Benveniste, A. Sylvestre-Baron, N. Vinogradova, 2023: How accurate is accurate enough for measuring sea-level rise and variability. Nature Climate Change, 13(8), 796-803. doi: 10.1038/s41558-023-01735-z. Sea-level measurements from radar satellite altimetry have reached a high level of accuracy and precision, which enables detection of global mean sea-level rise and attribution of most of the rate of rise to greenhouse gas emissions. This achievement is far beyond the original objectives of satellite altimetry missions. However, recent research shows that there is still room for improving the performance of satellite altimetry. Reduced uncertainties would enable regionalization of the detection and attribution of the anthropogenic signal in sea-level rise and provide new observational constraints on the water–energy cycle response to greenhouse gas emissions by improving the estimate of the ocean heat uptake and the Earth energy imbalance. Projection and prediction; Attribution; Physical oceanography
Minière, Audrey; von Schuckmann, Karina; Sallée, Jean-Baptiste; Vogt, LinusMinière, A., K. von Schuckmann, J. Sallée, L. Vogt, 2023: Robust acceleration of Earth system heating observed over the past six decades. Scientific Reports, 13(1), 22975. doi: 10.1038/s41598-023-49353-1. Global heating of the Earth system is unequivocal. However, detecting an acceleration of Earth heating has remained elusive to date, despite suggestive evidence of a potential increase in heating rates. In this study, we demonstrate that since 1960, the warming of the world ocean has accelerated at a relatively consistent pace of 0.15 ± 0.05 (W/m2)/decade, while the land, cryosphere, and atmosphere have exhibited an accelerated pace of 0.013 ± 0.003 (W/m2)/decade. This has led to a substantial increase in ocean warming, with a magnitude of 0.91 ± 0.80 W/m2 between the decades 1960–1970 and 2010–2020, which overlies substantial decadal-scale variability in ocean warming of up to 0.6 W/m2. Our findings withstand a wide range of sensitivity analyses and are consistent across different observation-based datasets. The long-term acceleration of Earth warming aligns qualitatively with the rise in CO2 concentrations and the decline in aerosol concentration during the same period, but further investigations are necessary to properly attribute these changes. Climate change; Climate sciences; Physical oceanography; Ocean sciences
Minnis, Patrick; Sun-Mack, Sunny; Smith, William L.; Trepte, Qing Z.; Hong, Gang; Chen, Yan; Yost, Christopher R.; Chang, Fu-Lung; Smith, Rita A.; Heck, Patrick W.; Yang, PingMinnis, P., S. Sun-Mack, W. L. Smith, Q. Z. Trepte, G. Hong, Y. Chen, C. R. Yost, F. Chang, R. A. Smith, P. W. Heck, P. Yang, 2023: VIIRS Edition 1 Cloud Properties for CERES, Part 1: Algorithm Adjustments and Results. Remote Sensing, 15(3), 578. doi: 10.3390/rs15030578. Cloud properties are essential for the Clouds and the Earth’s Radiant Energy System (CERES) Project, enabling accurate interpretation of measured broadband radiances, providing a means to understand global cloud-radiation interactions, and constituting an important climate record. Producing consistent cloud retrievals across multiple platforms is critical for generating a multidecadal cloud and radiation record. Techniques used by CERES for retrievals from measurements by the MODerate-Resolution Imaging Spectroradiometer (MODIS) on Terra and Aqua platforms are adapted for the application to radiances from the Visible Infrared Imaging Radiometer Suite (VIIRS) on the Suomi National Polar-orbiting Partnership to continue the CERES record beyond the MODIS era. The algorithm adjustments account for spectral and channel differences, use revised reflectance models, and set new thresholds for detecting thin cirrus clouds at night. Cloud amounts from VIIRS are less than their MODIS counterparts by 0.016 during the day and 0.026 at night, but trend consistently over the 2012–2020 period. The VIIRS mean liquid water cloud fraction differs by ~0.01 from the MODIS amount. The average cloud heights from VIIRS differ from the MODIS heights by less than 0.2 km, except the VIIRS daytime ice cloud heights, which are 0.4 km higher. The mean VIIRS nonpolar optical depths are 17% (1%) larger (smaller) than those from MODIS for liquid (ice) clouds. The VIIRS cloud hydrometeor sizes are generally smaller than their MODIS counterparts. Discrepancies between the MODIS and VIIRS properties stem from spectral and spatial resolution differences, new tests at night, calibration inconsistencies, and new reflectance models. Many of those differences will be addressed in future editions. cloud; cloud height; cloud optical depth; cloud phase; cloud remote sensing; Clouds and the Earth’s Radiant Energy System (CERES); Visible Infrared Imaging Radiometer Suite (VIIRS); cloud amount; SNPP; Suomi National Polar-orbiting Partnership
Miyamoto, Ayumu; Nakamura, Hisashi; Xie, Shang-Ping; Miyasaka, Takafumi; Kosaka, YuMiyamoto, A., H. Nakamura, S. Xie, T. Miyasaka, Y. Kosaka, 2023: Radiative Impacts of Californian Marine Low Clouds on North Pacific Climate in a Global Climate Model. J. Climate, 36(24), 8443-8459. doi: 10.1175/JCLI-D-23-0153.1. Abstract The northeastern Pacific climate system features an extensive low-cloud deck off California on the southeastern flank of the subtropical high that accompanies intense northeasterly trades and relatively low sea surface temperatures (SSTs). This study assesses climatological impacts of the low-cloud deck and their seasonal differences by regionally turning on and off the low-cloud radiative effect in a fully coupled atmosphere–ocean model. The simulations demonstrate that the cloud radiative effect causes a local SST decrease of up to 3°C on an annual average with the response extending southwestward with intensified trade winds, indicative of the wind–evaporation–SST (WES) feedback. This nonlocal wind response is strong in summer, when the SST decrease peaks due to increased shortwave cooling, and persists into autumn. In these seasons when the background SST is high, the lowered SST suppresses deep-convective precipitation that would otherwise occur in the absence of the low-cloud deck. The resultant anomalous diabatic cooling induces a surface anticyclonic response with the intensified trades that promote the WES feedback. Such seasonal enhancement of the atmospheric response does not occur without air–sea couplings. The enhanced trades accompany intensified upper-tropospheric westerlies, strengthening the vertical wind shear that, together with the lowered SST, acts to shield Hawaii from powerful hurricanes. On the basin scale, the anticyclonic surface wind response accelerates the North Pacific subtropical ocean gyre to speed up the Kuroshio by as much as 30%. SST thereby increases along the Kuroshio and its extension, intensifying upward turbulent heat fluxes from the ocean to increase precipitation.
Mohamed, Marwa S.; Abdel Wahab, M. M.; El‐Metwally, Mossad; El-Nobi, Eman F.Mohamed, M. S., M. M. Abdel Wahab, M. El‐Metwally, E. F. El-Nobi, 2023: Validation of UV-Index retrieved from three satellites against Ground-Based measurements at different climates in Egypt. The Egyptian Journal of Remote Sensing and Space Science, 26(2), 361-367. doi: 10.1016/j.ejrs.2023.04.006. The UV Index is a useful tool to alert people with possible risks of exposure to solar UV radiation in Egypt. Ground UV-Index observation is a primary source to monitor solar UV levels, however the spatial coverage of the ground station is quite limited. The validation of available measurements were used frequently to define the possibility of using satellite data when measurements are not available, this was carried out for (leave area index and temperatures) for example (Ganguly et al., 2012) and (Laraby and Schott, 2018). In order to test the validity of the UV-index satellite products against ground observations, three satellite instruments (OMI, Terra + Aqua, and Terra + Npp) was performed at noontime in all sky conditions in the period 2012–2017 at three sites; Aswan, Cairo, and Matruh. The aforementioned sites were selected to represent different climates in Egypt. Annual intercomparison highlighted higher relative bias (rbias) at OMI (6.4 %) than both Terra + Aqua (2.3%) and Terra + Npp (2.8%). Also, Mean Absolute Percentage Error (MAPE), shows that OMI (10.6%) is relatively higher than both Terra + Aqua and Terra + Npp. (8.5 %). Based on these results, both Terra + Aqua and Terra + Npp have a better performance with respect to ground observations than OMI. This was due to OMI being more sensitive to dust and cloud than, Terra + Aqua and Terra + Npp. OMI/OMI/AURA; Terra+Aqua; Terra+Npp; UV-Index
Murray-Watson, Rebecca J.; Gryspeerdt, Edward; Goren, TomMurray-Watson, R. J., E. Gryspeerdt, T. Goren, 2023: Investigating the development of clouds within marine cold-air outbreaks. Atmospheric Chemistry and Physics, 23(16), 9365-9383. doi: 10.5194/acp-23-9365-2023. Marine cold-air outbreaks are important parts of the high-latitude climate system and are characterised by strong surface fluxes generated by the air–sea temperature gradient. These fluxes promote cloud formation, which can be identified in satellite imagery by the distinct transformation of stratiform cloud “streets” into a broken field of cumuliform clouds downwind of the outbreak. This evolution in cloud morphology changes the radiative properties of the cloud and therefore is of importance to the surface energy budget. While the drivers of stratocumulus-to-cumulus transitions, such as aerosols or the sea surface temperature gradient, have been extensively studied for subtropical clouds, the factors influencing transitions at higher latitudes are relatively poorly understood. This work uses reanalysis data to create a set of composite trajectories of cold-air outbreaks moving off the Arctic ice edge and co-locates these trajectories with satellite data to generate a unique view of liquid-dominated cloud development within cold-air outbreaks. The results of this analysis show that clouds embedded in cold-air outbreaks have distinctive properties relative to clouds following other trajectories in the region. The initial strength of the outbreak shows a lasting effect on cloud properties, with differences between clouds in strong and weak events visible over 30 h after the air has left the ice edge. However, while the strength (measured by the magnitude of the marine cold-air outbreak index) of the outbreak affects the magnitude of cloud properties, it does not affect the timing of the transition to cumuliform clouds or the top-of-atmosphere albedo. In contrast, the initial aerosol conditions do not strongly affect the magnitude of the cloud properties but are correlated to cloud break-up, leading to an enhanced cooling effect in clouds moving through high-aerosol conditions due to delayed break-up. Both the aerosol environment and the strength and frequency of marine cold-air outbreaks are expected to change in the future Arctic, and these results provide insight into how these changes will affect the radiative properties of the clouds. These results also highlight the need for information about present-day aerosol sources at the ice edge to correctly model cloud development.
Myers, Timothy A.; Zelinka, Mark D.; Klein, Stephen A.Myers, T. A., M. D. Zelinka, S. A. Klein, 2023: Observational Constraints on the Cloud Feedback Pattern Effect. J. Climate, 36(18), 6533-6545. doi: 10.1175/JCLI-D-22-0862.1. Abstract Model evidence for the “pattern effect” assumes that global climate models (GCMs) faithfully simulate how clouds respond to varying sea surface temperature (SST) patterns and associated meteorological perturbations. We exploit time-invariant satellite-based estimates of the sensitivity of marine low clouds to meteorological perturbations to estimate how these clouds responded to time-varying SST patterns and meteorology between 1870 and 2014. GCMs and reanalyses provide estimates of the historical meteorological changes. Observations suggest that increasing estimated inversion strength (EIS) between 1980 and 2014 produced a negative low cloud feedback, opposite to the positive feedback expected from increasing CO2. This indicates that the processes responsible for marine cloud changes from 1980 to the near present are distinct from those associated with an increase in CO2. We also observationally constrain the difference between the historical near-global marine low cloud feedback, λcloudhist, and that arising from increasing CO2, λcloud4xCO2. We find that this cloud feedback pattern effect depends strongly on time period and reanalysis dataset, and that varying changes in EIS and SST with warming explain much of its variability. Between 1980 and 2014, we estimate that λcloud4xCO2−λcloudhist=0.78±0.21 W m−2 K−1 (90% confidence) assuming meteorological changes from the Multiple Reanalysis Ensemble, implying a total pattern effect (that arising from all climate feedbacks) of 1.86 ± 0.45 W m−2 K−1. This observational evidence corroborates previous quantitative estimates of the pattern effect, which heretofore relied largely upon GCM-based cloud changes. However, disparate historical meteorological changes across individual reanalyses contribute to considerable uncertainty in its magnitude.
Nair, H. R. C. R.; Budhavant, Krishnakant; Manoj, M. R.; Andersson, August; Satheesh, S. K.; Ramanathan, V.; Gustafsson, ÖrjanNair, H. R. C. R., K. Budhavant, M. R. Manoj, A. Andersson, S. K. Satheesh, V. Ramanathan, Ö. Gustafsson, 2023: Aerosol demasking enhances climate warming over South Asia. npj Climate and Atmospheric Science, 6(1), 1-8. doi: 10.1038/s41612-023-00367-6. Anthropogenic aerosols mask the climate warming caused by greenhouse gases (GHGs). In the absence of observational constraints, large uncertainties plague the estimates of this masking effect. Here we used the abrupt reduction in anthropogenic emissions observed during the COVID-19 societal slow-down to characterize the aerosol masking effect over South Asia. During this period, the aerosol loading decreased substantially and our observations reveal that the magnitude of this aerosol demasking corresponds to nearly three-fourths of the CO2-induced radiative forcing over South Asia. Concurrent measurements over the northern Indian Ocean unveiled a ~7% increase in the earth’s surface-reaching solar radiation (surface brightening). Aerosol-induced atmospheric solar heating decreased by ~0.4 K d−1. Our results reveal that under clear sky conditions, anthropogenic emissions over South Asia lead to nearly 1.4 W m−2 heating at the top of the atmosphere during the period March–May. A complete phase-out of today’s fossil fuel combustion to zero-emission renewables would result in rapid aerosol demasking, while the GHGs linger on. Climate-change impacts; Atmospheric chemistry
Najarian, Hrag; Sakaeda, NaokoNajarian, H., N. Sakaeda, 2023: The Influence of Cloud Types on Cloud-Radiative Forcing During DYNAMO/AMIE. Journal of Geophysical Research: Atmospheres, 128(8), e2022JD038006. doi: 10.1029/2022JD038006. Cloud-radiative feedback is known to be an important process for the Madden-Julian Oscillation (MJO) and its accurate representation in general circulation models. The MJO is known to have a stronger cloud-radiative feedback compared to higher frequency convectively coupled equatorial waves (CCEW), for reasons that remain unclear. The objective of this study is to use data from the Dynamics of the MJO/Atmospheric Radiation Measurement MJO Investigation Experiment field campaign to investigate how cloud type evolution and their associated cloud-radiative forcing (CRF) differ between the MJO and CCEWs and their application to MJO dynamics under moisture mode theory. This study finds that the amplitude of CRF is the largest within the MJO compared to the higher frequency CCEWs, and CRF maximizes after the maximum precipitation (enhanced phase) of the MJO. We suggest this delay in the timing of maximum CRF occurs because most cloud types (congestus, deep, anvil, and cirrus) simultaneously maximize in frequency after the enhanced phase of the MJO, which is not seen for the higher frequency CCEWs. These specific cloud types help maintain the MJO through their radiatively-driven moistening which acts to prolong the enhanced phase of the MJO. The decomposition of radiatively-driven moistening by cloud types shows that simultaneous moistening by deep, anvil, and congestus clouds are particularly responsible for the maintenance of the MJO under moisture mode theory. This analysis suggests the importance of capturing the correct evolution of different cloud types and their associated radiative effects to better understand the thermodynamics of the MJO. cloud-radiative feedback; clouds; convectively-coupled equatorial waves; DYNAMO/AMIE; Madden-Julian Oscillation; moisture mode
Nguyen, Chuyen; Nachamkin, Jason E.; Sidoti, David; Gull, Jacob; Bienkowski, Adam; Bankert, Rich; Surratt, MelindaNguyen, C., J. E. Nachamkin, D. Sidoti, J. Gull, A. Bienkowski, R. Bankert, M. Surratt, 2023: Machine Learning–Based Cloud Forecast Corrections for Fusions of Numerical Weather Prediction Model and Satellite Data. Artificial Intelligence for the Earth Systems, 2(3). doi: 10.1175/AIES-D-22-0072.1. Abstract Given the diversity of cloud-forcing mechanisms, it is difficult to classify and characterize all cloud types through the depth of a specific troposphere. Importantly, different cloud families often coexist even at the same atmospheric level. The Naval Research Laboratory (NRL) is developing machine learning–based cloud forecast models to fuse numerical weather prediction model and satellite data. These models were built for the dual purpose of understanding numerical weather prediction model error trends as well as improving the accuracy and sensitivity of the forecasts. The framework implements a UNet convolutional neural network (UNet-CNN) with features extracted from clouds observed by the Geostationary Operational Environmental Satellite-16 (GOES-16) as well as clouds predicted by the Coupled Ocean–Atmosphere Mesoscale Prediction System (COAMPS). The fundamental idea behind this novel framework is the application of UNet-CNN for separate variable sets extracted from GOES-16 and COAMPS to characterize and predict broad families of clouds that share similar physical characteristics. A quantitative assessment and evaluation based on an independent dataset for upper-tropospheric (high) clouds suggests that UNet-CNN models capture the complexity and error trends of combined data from GOES-16 and COAMPS, and also improve forecast accuracy and sensitivity for different lead time forecasts (3–12 h). This paper includes an overview of the machine learning frameworks as well as an illustrative example of their application and a comparative assessment of results for upper-tropospheric clouds. Significance Statement Clouds are difficult to forecast because they require, in addition to spatial location, accurate height, depth, and cloud type. Satellite imagery is useful for verifying geographical location but is limited by 2D technology. Multiple cloud types can coexist at various heights within the same pixel. In this situation, cloud/no cloud verification does not convey much information about why the forecast went wrong. Sorting clouds by physical attributes such as cloud-top height, atmospheric stability, and cloud thickness contributes to a better understanding since very different physical mechanisms produce various types of clouds. Using a fusion of numerical model outputs and GOES-16 observations, we derive variables related to atmospheric conditions that form and move the clouds for our machine learning–based cloud forecast. The resulting verification over the U.S. mid-Atlantic region revealed our machine learning–based cloud forecast corrects systematic errors associated with high atmospheric clouds and provides accurate and consistent cloud forecasts from 3 to 12 h lead times.
Noda, Akira T.; Ohno, Tomoki; Kodama, Chihiro; Chen, Ying-Wen; Kuba, Naomi; Seiki, Tatsuya; Yamada, Yohei; Satoh, MasakiNoda, A. T., T. Ohno, C. Kodama, Y. Chen, N. Kuba, T. Seiki, Y. Yamada, M. Satoh, 2023: Recent global nonhydrostatic modeling approach without using a cumulus parameterization to understand the mechanisms underlying cloud changes due to global warming. Progress in Earth and Planetary Science, 10(1), 48. doi: 10.1186/s40645-023-00583-x. Clouds are the primary source of uncertainty in the prediction of climate change. To reduce the uncertainty of cloud simulations and overcome this difficulty in prediction, many climate modeling centers are now developing a new type of climate model, the global nonhydrostatic atmospheric model, which reduces the uncertainty arising from a cumulus parameterization by computing clouds explicitly using a cloud microphysics scheme. Among the global nonhydrostatic atmospheric models used in recent intercomparison studies, NICAM aims to project climate change by improving our understanding of cloud changes due to warming and related physical processes. NICAM is the first global nonhydrostatic model and was developed by our research team. This review summarizes the outcomes of a recent major five-year research program in Japan for studying climate using NICAM, as well as providing an overview of current issues regarding the use of global kilometer-scale simulations in high-resolution climate modeling. Clouds; Global nonhydrostatic model; Global warming; High-resolution climate simulation; Model improvement
Nuncio, M.; Athulya, R.; Nandanan, Naveen; Chatterjee, Sourav; Satheesan, K.; Acharya, Asutosh; Subeesh, M. P.; Vidya, P. J.Nuncio, M., R. Athulya, N. Nandanan, S. Chatterjee, K. Satheesan, A. Acharya, M. P. Subeesh, P. J. Vidya, 2023: Hails in Ny Alesund, Svalbard-atmospheric vertical structure and dependence on circulation. Natural Hazards, 117(2), 1365-1380. doi: 10.1007/s11069-023-05907-0. Hails observed at Ny Alesund, Svalbard in the Arctic during December–February 2018–19 is examined along with the atmospheric circulation patterns. When hail was noticed, surface warming and southwesterly—westerly winds were noticed. Atmospheric circulation pattern was characterised by high pressure anomaly over northwestern Europe. High clouds as well as excess liquid water were present when the high pressure systems were active over northwestern Europe. This is because winds blowing over ocean collect more moisture as well as transport nucleating particles to Svalbard. Also, hourly winds from ERA 5 reanalysis indicated vertical shear required for hail formation. When hails were observed, mixed precipitation types were recorded with the maximum intensities arising from the hails. The West Spitzbergen Current (WSC) induces a strong east west sea surface temperature (SST) gradient in the ocean west of Svalbard. A corresponding gradient in the atmospheric temperature is also maintained by the WSC in the west to east direction in the lower atmosphere. Moisture laden westerlies cross the SST gradient and induce strong frontal activity in the lower atmosphere resulting intense precipitation and hail. The upward vertical velocity noted in the lower troposphere supports the frontal activity. Human activities in the Arctic as elsewhere are bound to increase. Hence, there is a need to study the intense precipitation in the Arctic as well as its reasons as it can impact the Arctic environment and human activity. This calls for more continuous observations to clearly identify mechanisms and frequency of intense precipitation in the Arctic. Precipitation; Atmospheric circulation; Climate change; Hail; Seasurface temperature
Ouhechou, Amine; Philippon, Nathalie; Morel, Béatrice; Trentmann, Jörg; Graillet, Alexandre; Mariscal, Armand; Nouvellon, YannOuhechou, A., N. Philippon, B. Morel, J. Trentmann, A. Graillet, A. Mariscal, Y. Nouvellon, 2023: Inter-comparison and validation against in-situ measurements of satellite estimates of incoming solar radiation for Central Africa: From the annual means to the diurnal cycles. Atmospheric Research, 287, 106711. doi: 10.1016/j.atmosres.2023.106711. This study pictures for the first time incoming solar radiation mean evolution in Central Africa, intercomparing 8 gridded products (namely CERES-EBAF, CERES-SYN1deg, TPDC, CMSAF SARAH-2, CMSAF CLARA-A2, CAMS-JADE satellite products, as well as ERA5 reanalysis and WorldClim 2 interpolated measurements) and station-based estimations (FAOCLIM 2) or measurements. At the mean annual scale, all products picture low levels of global horizontal irradiance (GHI) to the west (SW Cameroon to SW Republic of Congo) and higher levels towards the north and south margins of the region. However, GHI levels in the CMSAF products are much higher than in CERES and TPDC. The mean annual cycles of GHI extracted for 6 sub-regions are bimodal, with two maxima during the two rainy seasons (March–May and September–November) and two minima during the two dry seasons (December–February and June–August). These seasonal cycles are well reproduced by most products except their amplitude which is dampened in TPDC. At the daily and sub-daily time-scales, products were compared with in-situ measurements from ten meteorological stations located in the western part of Central Africa. The products' performance is assessed through scores as bias and RMSE but also by considering the diurnal cycles' shape, amplitude and frequency of occurrence along the annual cycle. The products properly reproduce the shape of the four types of diurnal cycles with nonetheless noticeable differences in the cycle's frequencies of occurrence. Central Africa; Solar radiation; Diurnal cycle; Satellite estimates
Painemal, David; Chellappan, Seethala; Smith Jr., William L.; Spangenberg, Douglas; Park, J. Minnie; Ackerman, Andrew; Chen, Jingyi; Crosbie, Ewan; Ferrare, Richard; Hair, Johnathan; Kirschler, Simon; Li, Xiang-Yu; McComiskey, Allison; Moore, Richard H.; Sanchez, Kevin; Sorooshian, Armin; Tornow, Florian; Voigt, Christiane; Wang, Hailong; Winstead, Edward; Zeng, Xubin; Ziemba, Luke; Zuidema, PaquitaPainemal, D., S. Chellappan, W. L. Smith Jr., D. Spangenberg, J. M. Park, A. Ackerman, J. Chen, E. Crosbie, R. Ferrare, J. Hair, S. Kirschler, X. Li, A. McComiskey, R. H. Moore, K. Sanchez, A. Sorooshian, F. Tornow, C. Voigt, H. Wang, E. Winstead, X. Zeng, L. Ziemba, P. Zuidema, 2023: Wintertime synoptic patterns of midlatitude boundary layer clouds over the western North Atlantic: Climatology and insights from in-situ ACTIVATE observations. Journal of Geophysical Research: Atmospheres, n/a(n/a), e2022JD037725. doi: 10.1029/2022JD037725. The winter synoptic evolution of the western North Atlantic and its influence on the atmospheric boundary layer is described by means of a regime classification based on Self Organizing Maps applied to 12 year of data (2009-2020). The regimes are classified into categories according to daily 600-hPa geopotential height: dominant ridge, trough to ridge eastward transition (trough-ridge), dominant trough, and ridge to trough eastward transition (ridge-trough). A fifth synoptic regime resembles the winter climatological mean. Coherent changes in sea-level pressure and large-scale winds are in concert with the synoptic regimes: 1) the ridge regime is associated with a well-developed anticyclone; 2) the trough-ridge gives rise to a low pressure center over the ocean, ascents, and northerly winds over the coastal zone; 3) trough is associated with the eastward displacement of a cyclone, coastal subsidence, and northerly winds, all representative characteristics of cold-air outbreaks; 4) the ridge-trough regime features the development of an anticyclone and weak coastal winds. Low clouds are characteristic of the trough regime, with both trough and trough-ridge featuring synoptic maxima in cloud droplet number concentration (Nd). The Nd increase is primarily observed near the coast, concomitant with strong surface heat fluxes exceeding by more than 400 W m-2 compared to fluxes further east. Five consecutive days of aircraft observations collected during the ACTIVATE campaign corroborates the climatological characterization, confirming the occurrence of high Nd for days identified as trough. This study emphasizes the role of boundary-layer dynamics and aerosol activation and their roles in modulating cloud microphysics.
Pan, Yuying; Cheng, Lijing; Schuckmann, Karina von; Trenberth, Kevin E.; Li, Guancheng; Abraham, John; Liu, Yuanxin; Gouretski, Viktor; Yu, Yongqiang; Liu, Hailong; Liu, ChunleiPan, Y., L. Cheng, K. v. Schuckmann, K. E. Trenberth, G. Li, J. Abraham, Y. Liu, V. Gouretski, Y. Yu, H. Liu, C. Liu, 2023: Annual Cycle in Upper-Ocean Heat Content and the Global Energy Budget. J. Climate, 36(15), 5003-5026. doi: 10.1175/JCLI-D-22-0776.1. Abstract As a major component of Earth’s energy budget, ocean heat content (OHC) plays a vital role in buffering climate change. The annual cycle is the most prominent change in OHC but has always been removed to study variations and changes in Earth’s energy budget. Here, we investigate the annual cycle of the upper-2000-m OHC at regional to global scales and assess the robustness of the signals using the spread of multiple observational products. The potential drivers are also investigated by comparing the annual OHC signal with the corresponding change in top-of-atmosphere radiation, surface heat flux, ocean heat divergence, and meridional heat transport. Results show that the robust signal of annual OHC change is significant down to a 1000-m depth globally and can reach down to 1500 m in some areas such as the tropical ocean. The global OHC (0–1500 m) changes from positive anomalies within September–February to negative anomalies within March–August, mainly because of the larger ocean area in the Southern Hemisphere and the seasonal migration of solar irradiance. Owing to the huge ocean heat capacity, the annual cycle of OHC dominates that of the global energy budget. The difference among the OHC annual cycles in the three major ocean basins is mainly attributed to ocean heat transport, especially in the tropics. In the upper 1500 m at mid- and high latitudes and in the upper 50 m of the tropics, the net sea surface heat flux dominates the OHC annual cycle, while in the tropics below 50 m, wind-driven Ekman heat transport associated with the geostrophic flow is the main driver.
Pearce, F. A.; Bodas-Salcedo, A.Pearce, F. A., A. Bodas-Salcedo, 2023: Implied Heat Transport from CERES Data: Direct Radiative Effect of Clouds on Regional Patterns and Hemispheric Symmetry. J. Climate, 36(12), 4019-4030. doi: 10.1175/JCLI-D-22-0149.1. Abstract We calculate the implied horizontal heat transport due to the spatial anomalies of radiative fluxes at the top of the atmosphere (TOA). The regional patterns of implied heat transport for different components of the TOA fluxes are calculated by solving the Poisson equation with the flux components as source terms. The shortwave (SW) part of the spectrum governs the spatial patterns of the total implied heat transport. Using the cloud radiative effect (CRE) as source term, we show that the direct effect of clouds is to reduce the poleward heat transport in the majority of the Northern Hemisphere and at high southern latitudes. Clouds flatten the gradients of the clear-sky energy flux potential and hence reduce the implied heat transport with respect to clear skies. Clouds reduce the implied cross-equatorial heat transport with respect to clear sky through changes in the SW part of the spectrum. It changes from 0.83 PW in clear sky to −0.01 PW in all sky, equivalent to the hemispheric albedo symmetry reported in previous studies. We investigate hemispheric symmetry by introducing a metric that measures the symmetry of implied meridional heat transports at all latitudes. The direct effect of clouds is to increase the symmetry in the implied heat transport, and this is achieved through an increase in symmetry in the SW part of the spectrum in the tropics. Whether this is trivial or the result of a fundamental control in the climate system is still an open question.
Pei, Zhangcheng; Fiddes, Sonya L.; French, W. John R.; Alexander, Simon P.; Mallet, Marc D.; Kuma, Peter; McDonald, AdrianPei, Z., S. L. Fiddes, W. J. R. French, S. P. Alexander, M. D. Mallet, P. Kuma, A. McDonald, 2023: Assessing the cloud radiative bias at Macquarie Island in the ACCESS-AM2 model. Atmospheric Chemistry and Physics, 23(23), 14691-14714. doi: 10.5194/acp-23-14691-2023. As a long-standing problem in climate models, large positive shortwave radiation biases exist at the surface over the Southern Ocean, impacting the accurate simulation of sea surface temperature, atmospheric circulation, and precipitation. Underestimations of low-level cloud fraction and liquid water content are suggested to predominantly contribute to these radiation biases. Most model evaluations for radiation focus on summer and rely on satellite products, which have their own limitations. In this work, we use surface-based observations at Macquarie Island to provide the first long-term, seasonal evaluation of both downwelling surface shortwave and longwave radiation in the Australian Community Climate and Earth System Simulator Atmosphere-only Model version 2 (ACCESS-AM2) over the Southern Ocean. The capacity of the Clouds and the Earth’s Radiant Energy System (CERES) product to simulate radiation is also investigated. We utilize the novel lidar simulator, the Automatic Lidar and Ceilometer Framework (ALCF), and all-sky cloud camera observations of cloud fraction to investigate how radiation biases are influenced by cloud properties. Overall, we find an overestimation of +9.5±33.5 W m−2 for downwelling surface shortwave radiation fluxes and an underestimation of -2.3±13.5 W m−2 for downwelling surface longwave radiation in ACCESS-AM2 in all-sky conditions, with more pronounced shortwave biases of +25.0±48.0 W m−2 occurring in summer. CERES presents an overestimation of +8.0±18.0 W m−2 for the shortwave and an underestimation of -12.1±12.2 W m−2 for the longwave in all-sky conditions. For the cloud radiative effect (CRE) biases, there is an overestimation of +4.8±28.0 W m−2 in ACCESS-AM2 and an underestimation of -7.9±20.9 W m−2 in CERES. An overestimation of downwelling surface shortwave radiation is associated with an underestimated cloud fraction and low-level cloud occurrence. We suggest that modeled cloud phase is also having an impact on the radiation biases. Our results show that the ACCESS-AM2 model and CERES product require further development to reduce these radiation biases not just in shortwave and in all-sky conditions, but also in longwave and in clear-sky conditions.
Priestley, Matthew D. K.; Ackerley, Duncan; Catto, Jennifer L.; Hodges, Kevin I.Priestley, M. D. K., D. Ackerley, J. L. Catto, K. I. Hodges, 2023: Drivers of Biases in the CMIP6 Extratropical Storm Tracks. Part II: Southern Hemisphere. J. Climate, 36(5), 1469-1486. doi: 10.1175/JCLI-D-20-0977.1. Abstract The Southern Hemisphere storm tracks are commonly simulated too far equatorward in climate models for the historical period. In the latest generation of climate models from phase 6 of the Coupled Model Intercomparison Project (CMIP6), the equatorward bias that was present in CMIP5 models still persists, although it is reduced considerably. A further reduction of the equatorward bias is found in atmosphere-only simulations. Using diagnostic large-scale fields, we propose that an increase in the midlatitude temperature gradients contributes to the reduced equatorward bias in CMIP6 and AMIP6 models, reducing the biases relative to ERA5. These changes increase baroclinicity in the atmosphere and are associated with a storm track that is situated farther poleward. In CMIP6 models, the poleward shift of the storm tracks is associated with an amelioration of cold midlatitude SST biases in CMIP5 and not through a reduction of the long-standing warm Southern Ocean SST bias. We propose that increases in midlatitude temperature gradients in the atmosphere and ocean are connected to changes in the cloud radiative effect. Persistent track density biases to the south of Australia are shown to be connected to an apparent standing-wave pattern originating in the tropics, which modifies the split jet structure near Australia and subsequently the paths of cyclones.
Qin, Hongchen; Klein, Stephen A.; Ma, Hsi-Yen; Van Weverberg, Kwinten; Feng, Zhe; Chen, Xiaodong; Best, Martin; Hu, Huancui; Leung, L. Ruby; Morcrette, Cyril J.; Rumbold, Heather; Webster, StuartQin, H., S. A. Klein, H. Ma, K. Van Weverberg, Z. Feng, X. Chen, M. Best, H. Hu, L. R. Leung, C. J. Morcrette, H. Rumbold, S. Webster, 2023: Summertime Near-Surface Temperature Biases Over the Central United States in Convection-Permitting Simulations. Journal of Geophysical Research: Atmospheres, 128(22), e2023JD038624. doi: 10.1029/2023JD038624. Convection-Permitting Model (CPM) simulations of the Central United States climate for the summer of 2011 are studied to understand the causes of warm biases in 2-m air temperature (T2m) and related underestimates of precipitation including that from mesoscale convective systems (MCSs). Based on 10 CPM simulations and 9 coarser-resolution model simulations, we quantify contributions from evaporative fraction (EF) and radiation to the T2m bias with both types of models overestimating T2m largely because they underestimate EF. The performance of CPMs in capturing MCS characteristics (frequency, rainfall, propagation) varies. The pre-summer precipitation bias has large correlation with mean summertime T2m bias but the relationship between summertime MCS mean rainfall bias and T2m bias is non-monotonic. Analysis of lifting condensation level deficit and convective available potential energy suggests that models with T2m warm biases and low EF have too dry and stable boundary layers, inhibiting the formation of clouds, precipitation and MCSs. Among the CPMs with differing model formulations (e.g., transpiration, infiltration, cloud macrophysics and microphysics), evidence suggests that altering the land-surface model is more effective than altering the atmospheric model in reducing T2m biases. These results demonstrate that land-atmosphere interactions play a very important role in determining the summertime climate of the Central United States. warm bias; 2-m air temperature; central US; convection-permitting model; mesoscale convective systems
Raghuraman, Shiv Priyam; Paynter, David; Menzel, Raymond; Ramaswamy, V.Raghuraman, S. P., D. Paynter, R. Menzel, V. Ramaswamy, 2023: Forcing, Cloud Feedbacks, Cloud Masking, and Internal Variability in the Cloud Radiative Effect Satellite Record. J. Climate, 36(12), 4151-4167. doi: 10.1175/JCLI-D-22-0555.1. Abstract Satellite observations show a near-zero trend in the top-of-atmosphere global-mean net cloud radiative effect (CRE), suggesting that clouds did not further cool nor heat the planet over the last two decades. The causes of this observed trend are unknown and can range from effective radiative forcing (ERF) to cloud feedbacks, cloud masking, and internal variability. We find that the near-zero NetCRE trend is a result of a significant negative trend in the longwave (LW) CRE and a significant positive trend in the shortwave (SW) CRE, cooling and heating the climate system, respectively. We find that it is exceptionally unlikely (
Raghuraman, Shiv Priyam; Paynter, David; Ramaswamy, V.; Menzel, Raymond; Huang, XiangleiRaghuraman, S. P., D. Paynter, V. Ramaswamy, R. Menzel, X. Huang, 2023: Greenhouse Gas Forcing and Climate Feedback Signatures Identified in Hyperspectral Infrared Satellite Observations. Geophysical Research Letters, 50(24), e2023GL103947. doi: 10.1029/2023GL103947. Global greenhouse gas forcing and feedbacks are the primary causes of climate change but have limited direct observations. Here we show that continuous, stable, global, hyperspectral infrared satellite measurements (2003–2021) display decreases in outgoing longwave radiation (OLR) in the CO2, CH4, and N2O absorption bands and increases in OLR in the window band and H2O absorption bands. By conducting global line-by-line radiative transfer simulations with 2003–2021 meteorological conditions, we show that increases in CO2, CH4, and N2O concentrations caused an instantaneous radiative forcing and stratospheric cooling adjustment that decreased OLR. The climate response, comprising surface and atmospheric feedbacks to radiative forcings and unforced variability, increased OLR. The spectral trends predicted by our climate change experiments using our general circulation model identify three bedrock principles of the physics of climate change in the satellite record: an increasing greenhouse effect, stratospheric cooling, and surface-tropospheric warming. climate change; outgoing longwave radiation; satellite observations; spectral; climate model; radiation model
Ramachandran, S.; Rupakheti, Maheswar; Cherian, Ribu; Lawrence, Mark G.Ramachandran, S., M. Rupakheti, R. Cherian, M. G. Lawrence, 2023: Aerosols heat up the Himalayan climate. Science of The Total Environment, 894, 164733. doi: 10.1016/j.scitotenv.2023.164733. The impact of aerosols, especially the absorbing aerosols, in the Himalayan region is important for climate. We closely examine ground-based high-quality observations of aerosol characteristics including radiative forcing from several locations in the Indo-Gangetic Plain (IGP), the Himalayan foothills and the Tibetan Plateau, relatively poorly studied regions with several sensitive ecosystems of global importance, as well as highly vulnerable large populations. This paper presents a state-of-the-art treatment of the warming that arises from these particles, using a combination of new measurements and modeling techniques. This is a first-time analysis of its kind, including ground-based observations, satellite data, and model simulations, which reveals that the aerosol radiative forcing efficiency (ARFE) in the atmosphere is clearly high over the IGP and the Himalayan foothills (80–135 Wm−2 per unit aerosol optical depth (AOD)), with values being greater at higher elevations. AOD is >0.30 and single scattering albedo (SSA) is ∼0.90 throughout the year over this region. The mean ARFE is 2–4 times higher here than over other polluted sites in South and East Asia, owing to higher AOD and aerosol absorption (i.e., lower SSA). Further, the observed annual mean aerosol-induced atmospheric heating rates (0.5–0.8 Kelvin/day), which are significantly higher than previously reported values for the region, imply that the aerosols alone could account for >50 % of the total warming (aerosols + greenhouse gases) of the lower atmosphere and surface over this region. We demonstrate that the current state-of-the-art models used in climate assessments significantly underestimate aerosol-induced heating, efficiency and warming over the Hindu Kush – Himalaya – Tibetan Plateau (HKHTP) region, indicating a need for a more realistic representation of aerosol properties, especially of black carbon and other aerosols. The significant, regionally coherent aerosol-induced warming that we observe in the high altitudes of the region, is a significant factor contributing to increasing air temperature, observed accelerated retreat of the glaciers, and changes in the hydrological cycle and precipitation patterns over this region. Thus, aerosols are heating up the Himalayan climate, and will remain a key factor driving climate change over the region. Atmospheric aerosols; Himalayas; Model simulations; Observations; Radiative effects; South Asia
Ray, Sulagna; Stefanova, Lydia; Fu, Bing; Guan, Hong; Wang, Jiande; Meixner, Jessica; Mehra, Avichal; Zhu, YuejianRay, S., L. Stefanova, B. Fu, H. Guan, J. Wang, J. Meixner, A. Mehra, Y. Zhu, 2023: Improved forecast of 2015/16 El Niño event in an experimental coupled seasonal ensemble forecasting system. Climate Dynamics. doi: 10.1007/s00382-023-06746-2. To improve NOAA’s seasonal forecasting capabilities, a new coupled system within the Unified Forecast System (UFS) framework is being developed through a community-wide effort led by NOAA’s Environmental Modeling Center targeting the configuration of a future operational Seasonal Forecast System (SFS v1). An experimental version of this ensemble seasonal forecasting system is tested on forecasting the strong El Niño of 2015/16. The then-operational systems and NCEP real-time seasonal forecasts (CFSv2) underestimated its strength towards the end of 2015 and beginning of 2016. In addition to perturbing the atmospheric initial conditions, run-time stochastic physics-based perturbations are applied in both atmosphere and ocean components of this new coupled system to represent the model uncertainties. The UFS ensembles are initialized on June 1st, 2015 and run through a 9-month period. Compared to CFSv2, the forecast of Niño 3.4 SST and intra-seasonal zonal windstress for the 2015/16 El Niño in the UFS system are improved, as is the ensemble spread. A cold SST forecast error develops in the central equatorial Pacific, likely from excess evaporative cooling, shallower thermocline, and an excessively strong vertical current shear driven cooling. Near the eastern equatorial Pacific coast, on the other hand, warm surface and cool subsurface errors persist from initialization until the end of the forecast. The results suggest that further improvement in the seasonal forecast may be achieved by a combination of factors, including, but not limited to, improving the coupled system initialization, along with the atmospheric physics. El Niño; Ensemble prediction; Equatorial Kelvin waves; Equatorial ocean dynamics; Seasonal forecasts; Westerly wind bursts
Reed, K. A.; Stansfield, A. M.; Hsu, W.-C.; Kooperman, G. J.; Akinsanola, A. A.; Hannah, W. M.; Pendergrass, A. G.; Medeiros, B.Reed, K. A., A. M. Stansfield, W. Hsu, G. J. Kooperman, A. A. Akinsanola, W. M. Hannah, A. G. Pendergrass, B. Medeiros, 2023: Evaluating the Simulation of CONUS Precipitation by Storm Type in E3SM. Geophysical Research Letters, 50(12), e2022GL102409. doi: 10.1029/2022GL102409. Conventional low-resolution (LR) climate models, including the Energy Exascale Earth System Model (E3SMv1), have well-known biases in simulating the frequency, intensity, and timing of precipitation. Approaches to next-generation E3SM, whether the high-resolution (HR) or multiscale modeling framework (MMF) configuration, improve the simulation of the intensity and frequency of precipitation, but regional and seasonal deficiencies still exist. Here we apply a methodology to assess the contribution of tropical cyclones (TCs), extratropical cyclones (ETCs), and mesoscale convective systems (MCSs) to simulated precipitation in E3SMv1-HR and E3SMv1-MMF relative to E3SMv1-LR. Across the United States, E3SMv1-MMF provides the best simulation in terms of precipitation accumulation, frequency and intensity from MCSs and TCs compared to E3SMv1-LR and E3SMv1-HR. All E3SMv1 configurations overestimate precipitation amounts from and the frequency of ETCs over CONUS, with conventional E3SMv1-LR providing the best simulation compared to observations despite limitations in precipitation intensity within these events. Earth system model; precipitation; energy exascale earth system model; high resolution; extremes; multiscale modeling framework
Regayre, Leighton A.; Deaconu, Lucia; Grosvenor, Daniel P.; Sexton, David M. H.; Symonds, Christopher; Langton, Tom; Watson-Paris, Duncan; Mulcahy, Jane P.; Pringle, Kirsty J.; Richardson, Mark; Johnson, Jill S.; Rostron, John W.; Gordon, Hamish; Lister, Grenville; Stier, Philip; Carslaw, Ken S.Regayre, L. A., L. Deaconu, D. P. Grosvenor, D. M. H. Sexton, C. Symonds, T. Langton, D. Watson-Paris, J. P. Mulcahy, K. J. Pringle, M. Richardson, J. S. Johnson, J. W. Rostron, H. Gordon, G. Lister, P. Stier, K. S. Carslaw, 2023: Identifying climate model structural inconsistencies allows for tight constraint of aerosol radiative forcing. Atmospheric Chemistry and Physics, 23(15), 8749-8768. doi: 10.5194/acp-23-8749-2023. Aerosol radiative forcing uncertainty affects estimates of climate sensitivity and limits model skill in terms of making climate projections. Efforts to improve the representations of physical processes in climate models, including extensive comparisons with observations, have not significantly constrained the range of possible aerosol forcing values. A far stronger constraint, in particular for the lower (most-negative) bound, can be achieved using global mean energy balance arguments based on observed changes in historical temperature. Here, we show that structural deficiencies in a climate model, revealed as inconsistencies among observationally constrained cloud properties in the model, limit the effectiveness of observational constraint of the uncertain physical processes. We sample the uncertainty in 37 model parameters related to aerosols, clouds, and radiation in a perturbed parameter ensemble of the UK Earth System Model and evaluate 1 million model variants (different parameter settings from Gaussian process emulators) against satellite-derived observations over several cloudy regions. Our analysis of a very large set of model variants exposes model internal inconsistencies that would not be apparent in a small set of model simulations, of an order that may be evaluated during model-tuning efforts. Incorporating observations associated with these inconsistencies weakens any forcing constraint because they require a wider range of parameter values to accommodate conflicting information. We show that, by neglecting variables associated with these inconsistencies, it is possible to reduce the parametric uncertainty in global mean aerosol forcing by more than 50 %, constraining it to a range (around −1.3 to −0.1 W m−2) in close agreement with energy balance constraints. Our estimated aerosol forcing range is the maximum feasible constraint using our structurally imperfect model and the chosen observations. Structural model developments targeted at the identified inconsistencies would enable a larger set of observations to be used for constraint, which would then very likely narrow the uncertainty further and possibly alter the central estimate. Such an approach provides a rigorous pathway to improved model realism and reduced uncertainty that has so far not been achieved through the normal model development approach.
Ren, Tong; Yang, Ping; Loeb, Norman G.; Smith Jr., William L.; Minnis, PatrickRen, T., P. Yang, N. G. Loeb, W. L. Smith Jr., P. Minnis, 2023: On the Consistency of Ice Cloud Optical Models for Spaceborne Remote Sensing Applications and Broadband Radiative Transfer Simulations. Journal of Geophysical Research: Atmospheres, 128(20), e2023JD038747. doi: 10.1029/2023JD038747. Aqua satellite Moderate Resolution Imaging Spectroradiometer (MODIS) 1-km observations are collocated with Clouds and the Earth's Radiant Energy System (CERES) fields of view taken during July 2008 afternoon satellite passes over the equatorial western Pacific Ocean. Radiation simulations are compared with collocated CERES observations to better understand the sensitivity of computed fluxes to two ice cloud broadband radiation parameterization schemes and inferred ice cloud characteristics. In particular, the radiation computational schemes and ice cloud property retrievals are based on two respective ice particle models, the MODIS Collection 6 (MC6) aggregate model and a more microphysically consistent two-habit model (THM). The simulation results show that both MC6 and THM overestimate the shortwave (SW) and longwave (LW) cloud radiative effects at the top of the atmosphere, as compared to the CERES observations; the difference between the MC6 and THM-based ice cloud retrievals is too small to compensate for the differences between the two model-based radiation schemes. Therefore, the present finding suggests that broadband radiative simulations are more sensitive to the radiation parameterization scheme than to the input cloud properties retrieved using the corresponding ice cloud particle optical property model.
Rizza, Umberto; Avolio, Elenio; Morichetti, Mauro; Di Liberto, Luca; Bellini, Annachiara; Barnaba, Francesca; Virgili, Simone; Passerini, Giorgio; Mancinelli, EnricoRizza, U., E. Avolio, M. Morichetti, L. Di Liberto, A. Bellini, F. Barnaba, S. Virgili, G. Passerini, E. Mancinelli, 2023: On the Interplay between Desert Dust and Meteorology Based on WRF-Chem Simulations and Remote Sensing Observations in the Mediterranean Basin. Remote Sensing, 15(2), 435. doi: 10.3390/rs15020435. In this study, we investigate a series of Saharan dust outbreaks toward the Mediterranean basin that occurred in late June 2021. In particular, we analyze the effect of mineral dust aerosols on radiation and cloud properties (direct, semi-direct and indirect effects), and in turn, on meteorological parameters. This is achieved by running the Weather Research and Forecasting model coupled with Chemistry (WRF-Chem) over a domain covering North Africa and the Central Mediterranean Basin. The simulations were configured using a gradual coupling strategy between the GOCART aerosol model and the Goddard radiation and microphysics schemes available in the WRF-Chem package. A preliminary evaluation of the model performances was conducted in order to verify its capability to correctly reproduce the amount of mineral dust loaded into the atmosphere within the spatial domain considered. To this purpose, we used a suite of experimental data from ground- and space-based remote sensing measurements. This comparison highlighted a model over-estimation of aerosol optical properties to the order of 20%. The evaluation of the desert dust impact on the radiation budget, achieved by comparing the uncoupled and the fully coupled (aerosol–radiation–clouds) simulation, shows that mineral dust induces a net (shortwave–longwave) cooling effect to the order of −10 W m−2. If we consider the net dust radiative forcing, the presence of dust particles induces a small cooling effect at the top of the atmosphere (−1.2 W m−2) and a stronger cooling at the surface (−14.2 W m−2). At the same time, analysis of the perturbation on the surface energy budget yields a reduction of −7 W m−2 when considering the FULL-coupled simulation, a positive perturbation of +3 W m−2 when only considering microphysics coupling and −10.4 W m−2 when only considering radiation coupling. This last result indicates a sort of “superposition” of direct, indirect and semi-direct effects of dust on the radiation budget. This study shows that the presence of dust aerosols significantly influences radiative and cloud properties and specifically the surface energy budget. This suggests (i) that dust effects should be considered in climate models in order to increase the accuracy of climate predictions over the Mediterranean region and (ii) the necessity of performing fully coupled simulations including aerosols and their effects on meteorology at a regional scale. dust–radiation coupling; Mediterranean hot spot; WRF-Chem model
Roach, Lettie A.; Eisenman, Ian; Wagner, Till J. W.; Donohoe, AaronRoach, L. A., I. Eisenman, T. J. W. Wagner, A. Donohoe, 2023: Asymmetry in the Seasonal Cycle of Zonal-Mean Surface Air Temperature. Geophysical Research Letters, 50(10), e2023GL103403. doi: 10.1029/2023GL103403. At most latitudes, the seasonal cycle of zonal-mean surface air temperature is notably asymmetric: the length of the warming season is not equal to the length of the cooling season. The asymmetry varies spatially, with the cooling season being ∼40 days shorter than the warming season in the subtropics and the warming season being ∼100 days shorter than the cooling season at the poles. Furthermore, the asymmetry differs between the Northern Hemisphere and the Southern Hemisphere. Here, we show that these observed features are broadly captured in a simple model for the evolution of temperature forced by realistic insolation. The model suggests that Earth's orbital eccentricity largely determines the hemispheric contrast, and obliquity broadly dictates the meridional structure. Clouds, atmospheric heat flux convergence, and time-invariant effective surface heat capacity have minimal impacts on seasonal asymmetry. This simple, first-order picture has been absent from previous discussions of the surface temperature seasonal cycle. climate; energy balance model; idealized model; insolation; seasonal cycle; temperature
Roemer, Florian E.; Buehler, Stefan A.; Brath, Manfred; Kluft, Lukas; John, Viju O.Roemer, F. E., S. A. Buehler, M. Brath, L. Kluft, V. O. John, 2023: Direct observation of Earth’s spectral long-wave feedback parameter. Nature Geoscience, 1-6. doi: 10.1038/s41561-023-01175-6. The spectral long-wave feedback parameter represents how Earth’s outgoing long-wave radiation adjusts to temperature changes and directly impacts Earth’s climate sensitivity. Most research so far has focused on the spectral integral of the feedback parameter. Spectrally resolving the feedback parameter permits inferring information about the vertical distribution of long-wave feedbacks, thus gaining a better understanding of the underlying processes. However, investigations of the spectral long-wave feedback parameter have so far been limited mostly to model studies. Here we show that it is possible to directly observe the global mean all-sky spectral long-wave feedback parameter using satellite observations of seasonal and interannual variability. We find that spectral bands subject to strong water-vapour absorption exhibit a substantial stabilizing net feedback. We demonstrate that part of this stabilizing feedback is caused by the change of relative humidity with warming, the radiative fingerprints of which can be directly observed. Therefore, our findings emphasize the importance of better understanding processes affecting the present distribution and future trends in relative humidity. This observational constraint on the spectral long-wave feedback parameter can be used to evaluate the representation of long-wave feedbacks in global climate models and to better constrain Earth’s climate sensitivity. Climate change; Atmospheric dynamics; Projection and prediction
Rugenstein, Maria; Hakuba, MariaRugenstein, M., M. Hakuba, 2023: Connecting Hemispheric Asymmetries of Planetary Albedo and Surface Temperature. Geophysical Research Letters, 50(6), e2022GL101802. doi: 10.1029/2022GL101802. Satellite measurements show that the Northern and Southern hemispheres reflect equal amounts of shortwave radiation (“albedo symmetry”), but no theory exists on if, how, and why the symmetry is established and maintained. Ambiguously, climate models are strongly biased in albedo symmetry but agree in the sign of the response to CO2. We find that mean-state biases in albedo symmetry and hemispheric surface temperature asymmetry correlate negatively. Similarly, the response of albedo asymmetry to CO2 forcing correlates negatively with the magnitude of the asymmetry in surface warming. This is true across many and within single climate model simulations: a too warm or stronger warming hemisphere is darker or darkens more than its counterpart. In the 21 years of observations we find the same tendency and hypothesize (a) albedo symmetry is a function of the current climate state and (b) we will observe an evolution toward albedo asymmetry in coming decades.
Salmun, Haydee; Josephs, Holly; Molod, AndreaSalmun, H., H. Josephs, A. Molod, 2023: GRWP-PBLH: Global Radar Wind Profiler Planetary Boundary Layer Height Data. Bull. Amer. Meteor. Soc., 104(5), E1044-E1057. doi: 10.1175/BAMS-D-22-0002.1. Abstract The planetary boundary layer (PBL) is central to the exchange of heat and moisture between Earth’s surface and the atmosphere, to the turbulent transport of aerosol and chemical pollutants affecting air quality, and to near- and long-term climate prediction. Consequently, the PBL has become a major focus of atmospheric and climate science, particularly after its designation as a “targeted observable” by the 2018 National Academies of Science, Engineering, and Medicine Earth Science Decadal Survey. Information about the height of the PBL that is global in scope allows for wide geographical analysis of connections to seasonality, to latitude, proximity to oceans, and synoptic variability. Information about the PBL height at hourly resolution allows for the analysis of diurnal cycles and PBL height growth rates, both of which are critical to the study of near-surface transport processes. This manuscript describes the release of a new global dataset of PBL height estimates retrieved from radar wind profilers (RWPs), called Global Radar Wind Profiler Planetary Boundary Layer Height (GRWP-PBLH). Hourly PBL height estimates are retrieved using an existing algorithm applied to archived signal-to-noise ratio data from a series of networks located around the globe, specifically in Australia, Europe, and Japan. Information about the source data, details of data processing, and production of PBL height estimates are discussed here along with a description of supplementary data and the available software. The GRWP-PBLH dataset is now accessible to the community for ongoing and future research.
Saneev, B. G.; Ivanova, I. Yu.; Shakirov, V. A.Saneev, B. G., I. Y. Ivanova, V. A. Shakirov, 2023: Assessment of Indicators of Solar and Wind Energy Potential of the Republic of Sakha (Yakutia). Geography and Natural Resources, 43(1), S74-S79. doi: 10.1134/S187537282205016X. The potential of renewable energy sources varies over time and significantly depends on natural, climatic, and regional characteristics. This article evaluates a wide group of indicators of the potential of wind and solar energy in the Republic of Sakha (Yakutia) at 47 points to determine the most promising areas for wind power plants (WPPs) and solar power plants (SPPs). The characterization of the wind energy potential is carried out in two stages. At the first stage, a preliminary analysis of the territory is conducted according to the measurements of weather stations for 2018–2020. On the territory of the republic, the average wind speed for this period ranges from 2.8 to 6.1 m/s at a height of 10 m. The greatest wind energy potential is typical for the northern regions. At the second stage, a full set of indicators of wind energy potential for the ten most promising areas is evaluated according to ground-based measurements for 2006–2020. The highest indicators of wind energy potential are typical for points located in close proximity to the coast: Anabar, Ust-Olenek, Stolb Island, and Ambarchik Bay. Most of the criteria and signs of high wind energy potential are met in these areas. The assessment of solar energy potential indicators was carried out for 47 sites based on estimates from the CERES SYN1deg satellite observation database for 1984–2020. To characterize the solar energy potential, three indicators were used: the annual flux of total solar radiation to a horizontal surface, the annual flux of total solar radiation on a surface inclined at an angle of latitude, and the utilization factor of the installed capacity of photovoltaic converters. The receipt of total solar radiation on a horizontal surface is from 784 to 1128 kWh/m2/year. The greatest solar energy potential is observed in the southeastern part of the republic. ground-based measurements; potential of renewable energy sources; satellite observation data; solar energy; wind energy
Sarr, Alioune Badara; Sultan, BenjaminSarr, A. B., B. Sultan, 2023: Predicting crop yields in Senegal using machine learning methods. International Journal of Climatology, 43(4), 1817-1838. doi: 10.1002/joc.7947. Agriculture plays an important role in Senegalese economy and annual early warning predictions of crop yields are highly relevant in the context of climate change. In this study, we used three main machine learning methods (support vector machine, random forest, neural network) and one multiple linear regression method, namely Least Absolute Shrinkage and Selection Operator (LASSO), to predict yields of the main food staple crops (peanut, maize, millet and sorghum) in 24 departments of Senegal. Three combination of predictors (climate data, vegetation data or a combination of both) are used to compare the respective contribution of statistical methods and inputs in the predictive skill. Our results showed that the combination of climate and vegetation with the machine learning methods gives the best performance. The best prediction skill is obtained for peanut yield likely due to its high sensitivity to interannual climate variability. Although more research is needed to integrate the results of this study into an operational framework, this paper provides evidence of the promising performance machine learning methods. The development and operationalization of such prediction and their integration into operational early warning systems could increase resilience of Senegal to climate change and contribute to food security. climate change scenario; crop yield prediction; machine learning; Senegal
Schmidt, Gavin A.; Andrews, Timothy; Bauer, Susanne E.; Durack, Paul J.; Loeb, Norman G.; Ramaswamy, V.; Arnold, Nathan P.; Bosilovich, Michael G.; Cole, Jason; Horowitz, Larry W.; Johnson, Gregory C.; Lyman, John M.; Medeiros, Brian; Michibata, Takuro; Olonscheck, Dirk; Paynter, David; Raghuraman, Shiv Priyam; Schulz, Michael; Takasuka, Daisuke; Tallapragada, Vijay; Taylor, Patrick C.; Ziehn, TiloSchmidt, G. A., T. Andrews, S. E. Bauer, P. J. Durack, N. G. Loeb, V. Ramaswamy, N. P. Arnold, M. G. Bosilovich, J. Cole, L. W. Horowitz, G. C. Johnson, J. M. Lyman, B. Medeiros, T. Michibata, D. Olonscheck, D. Paynter, S. P. Raghuraman, M. Schulz, D. Takasuka, V. Tallapragada, P. C. Taylor, T. Ziehn, 2023: CERESMIP: a climate modeling protocol to investigate recent trends in the Earth's Energy Imbalance. Frontiers in Climate, 5. doi: 10.3389/fclim.2023.1202161. The Clouds and the Earth's Radiant Energy System (CERES) project has now produced over two decades of observed data on the Earth's Energy Imbalance (EEI) and has revealed substantive trends in both the reflected shortwave and outgoing longwave top-of-atmosphere radiation components. Available climate model simulations suggest that these trends are incompatible with purely internal variability, but that the full magnitude and breakdown of the trends are outside of the model ranges. Unfortunately, the Coupled Model Intercomparison Project (Phase 6) (CMIP6) protocol only uses observed forcings to 2014 (and Shared Socioeconomic Pathways (SSP) projections thereafter), and furthermore, many of the ‘observed' drivers have been updated substantially since the CMIP6 inputs were defined. Most notably, the sea surface temperature (SST) estimates have been revised and now show up to 50% greater trends since 1979, particularly in the southern hemisphere. Additionally, estimates of short-lived aerosol and gas-phase emissions have been substantially updated. These revisions will likely have material impacts on the model-simulated EEI. We therefore propose a new, relatively low-cost, model intercomparison, CERESMIP, that would target the CERES period (2000-present), with updated forcings to at least the end of 2021. The focus will be on atmosphere-only simulations, using updated SST, forcings and emissions from 1990 to 2021. The key metrics of interest will be the EEI and atmospheric feedbacks, and so the analysis will benefit from output from satellite cloud observation simulators. The Tier 1 request would consist only of an ensemble of AMIP-style simulations, while the Tier 2 request would encompass uncertainties in the applied forcing, atmospheric composition, single and all-but-one forcing responses. We present some preliminary results and invite participation from a wide group of models.
Schuddeboom, A. J.; McDonald, A. J.Schuddeboom, A. J., A. J. McDonald, 2023: Understanding Internal Cluster Variability Through Subcluster Metric Analysis in a Geophysical Context. Earth and Space Science, 10(1), e2022EA002373. doi: 10.1029/2022EA002373. Clustering algorithms are commonly used for inspecting the behavior of clouds in both model and satellite data sets. Often overlooked in cluster analysis is the variability that occurs within any clusters generated. This is particularly important in the geophysics where clusters are often generated with a focus on interpretability over mathematical optimization. Two metrics, the Davies-Bouldin index and the subsom entropy, are used to identify clusters with large internal variability. These metrics are applied to an example set of clusters from prior research that were generated using cloud top pressure-cloud optical thickness joint histograms from the Moderate Resolution Imaging Spectroradiometer data set. Applying these metrics to the clusters identifies one cluster in particular as a major outlier. Examining the calculations behind these metrics in more detail provides further information about the internal variability of the clusters. The clusters are also examined over several geographic regions showing mostly consistent behavior. There are, however, some large anomalies such as the behavior of the clear sky cluster or the behavior of several different clusters over the Arctic Ocean. To aide our interpretation of these results, two clusters are chosen for a detailed analysis of their subclusters. The geographic distributions and radiative properties of these subclusters are examined and clearly identify that subclusters have physically distinct behavior. This result illustrates that these metrics are capable of determining when a cluster contains physically distinct subclusters. This demonstrates the potential utility of these metrics if they were applied to other geophysical data sets. machine learning; cloud modeling; Clouds and the Earth's Radiant Energy System; Moderate Resolution Imaging Spectroradiometer; clustering; entropy
Schulz, Hauke; Stevens, BjornSchulz, H., B. Stevens, 2023: Evaluating Large-Domain, Hecto-Meter, Large-Eddy Simulations of Trade-Wind Clouds Using EUREC4A Data. Journal of Advances in Modeling Earth Systems, 15(10), e2023MS003648. doi: 10.1029/2023MS003648. The meso-scale variability in cloudiness of the marine trade-wind layer is explored with large-eddy simulations of regional extent and validated against observations of the EUREC4A field campaign. 41 days of realistically forced simulations present a representative, statistical view on shallow convection in the winter North Atlantic trades that includes a wide range of meso-scale variability including the four recently identified patterns of spatial organization: Sugar, Gravel, Flowers and Fish. The results show that cloud cover is on average captured well but with discrepancies in its vertical and spatial distribution. Cloudiness at the lifting condensation level depends on the model resolution with the finer one producing on average a more realistic cloud profile. Independent of the resolution, the variability in cloudiness below the trade inversion is not captured, leading to a lack of stratiform cloudiness with implications on the detectability of meso-scale patterns whose cloud patches are characterized by stratiform clouds. The simulations tend to precipitate more frequently than observed, with a narrower distribution of echo intensities. The observed co-variability between cloudiness and environmental conditions is well captured. marine boundary layer clouds; shallow convection; observations; convective organization; large eddy simulation
Sebastian, Dawn E.; Murtugudde, Raghu; Ghosh, SubimalSebastian, D. E., R. Murtugudde, S. Ghosh, 2023: Soil–vegetation moisture capacitor maintains dry season vegetation productivity over India. Scientific Reports, 13(1), 888. doi: 10.1038/s41598-022-27277-6. India receives more than 70% of its annual rainfall in the summer monsoon from June to September. The rainfall is scanty and scattered for the rest of the year. Combining satellite data and model simulations, we show that the soil-vegetation continuum works as a natural capacitor of water, storing the monsoon pulse and releasing the moisture to the atmosphere through evapotranspiration over approximately 135 days when the moisture supply from precipitation is less than the evapotranspiration losses. The total Gross Primary Productivity of vegetation in India during the capacitor period accounts for almost 35% of the total annual GPP value. It primarily depends on the soil moisture at the beginning of the period, a measure of moisture capacitance of soil, with a correlation of 0.6. Given that India is the second largest contributor to recent global greening, its soil-vegetation water capacitance plays a significant role in the global carbon balance. Hydrology; Climate sciences; Ecology
Seifert, Axel; Bachmann, Vanessa; Filipitsch, Florian; Förstner, Jochen; Grams, Christian M.; Hoshyaripour, Gholam Ali; Quinting, Julian; Rohde, Anika; Vogel, Heike; Wagner, Annette; Vogel, BernhardSeifert, A., V. Bachmann, F. Filipitsch, J. Förstner, C. M. Grams, G. A. Hoshyaripour, J. Quinting, A. Rohde, H. Vogel, A. Wagner, B. Vogel, 2023: Aerosol–cloud–radiation interaction during Saharan dust episodes: the dusty cirrus puzzle. Atmospheric Chemistry and Physics, 23(11), 6409-6430. doi: 10.5194/acp-23-6409-2023. Dusty cirrus clouds are extended optically thick cirrocumulus decks that occur during strong mineral dust events. So far they have mostly been documented over Europe associated with dust-infused baroclinic storms. Since today's global numerical weather prediction models neither predict mineral dust distributions nor consider the interaction of dust with cloud microphysics, they cannot simulate this phenomenon. We postulate that the dusty cirrus forms through a mixing instability of moist clean air with drier dusty air. A corresponding sub-grid parameterization is suggested and tested in the ICOsahedral Nonhydrostatic model with Aerosol and Reactive Trace gases (ICON-ART). Only with the help of this parameterization is ICON-ART able to simulate the formation of the dusty cirrus, which leads to substantial improvements in cloud cover and radiative fluxes compared to simulations without this parameterization. A statistical evaluation over six Saharan dust events with and without observed dusty cirrus shows robust improvements in cloud and radiation scores. The ability to simulate dusty cirrus formation removes the linear dependency on mineral dust aerosol optical depth from the bias of the radiative fluxes. For the six Saharan dust episodes investigated in this study, the formation of dusty cirrus clouds is the dominant aerosol–cloud–radiation effect of mineral dust over Europe.
Seo, Minji; Kim, Hyun-Cheol; Seong, Noh-Hun; Sim, Suyoung; Han, Kyung-SooSeo, M., H. Kim, N. Seong, S. Sim, K. Han, 2023: Variability of Surface Radiation Budget over Arctic during Two Recent Decades from Perspective of CERES and ERA5 Data. Remote Sensing, 15(3), 829. doi: 10.3390/rs15030829. This study focused on surface radiation budget, one of the essential factors for understanding climate change. Arctic surface radiation budget was summarized and explained using a satellite product, Clouds and the Earth’s Radiant Energy System (CERES) Energy Balanced and Filled (EBAF), and reanalysis data, ERA5. Net radiation records indicated an increasing trend only in ERA5, with EBAF indicating a decreasing trend in the Arctic Circle (AC; poleward from 65°N) from 2000 to 2018. The differences in the net radiation trend between product types was due to longwave downward radiation. The extreme season was selected according to the seasonality of net radiation, surface air temperature, and sea ice extent. The surface radiation budget was synthesized for extreme season in the AC. Regardless of the data, net radiation tended to increase in the summer on an annual trend. By contrast, in the winter, trend of surface net radiation was observed in which ERA5 increased and EBAF decreased. The difference in surface radiation is represented in longwave of each data. This comprehensive information can be used to analyze and predict the surface energy budget, transport, and interaction between the atmosphere and surface in the Arctic. climate change; Arctic; cryosphere; surface radiation budget
Shan, Shuo; Wang, Yiye; Xie, Xiangying; Fan, Tao; Xiao, Yushun; Zhang, Kanjian; Wei, HaikunShan, S., Y. Wang, X. Xie, T. Fan, Y. Xiao, K. Zhang, H. Wei, 2023: Analysis of regional climate variables by using neural Granger causality. Neural Computing and Applications, 35(22), 16381-16402. doi: 10.1007/s00521-023-08506-z. In recent years, how to discover causality rather than correlation among climate variables and how to use causality to help in time-series tasks have received great concern. However, the high dimensionality and nonlinearity of climate variables are the main issues for causal inference based on historical large-scale climate time series. Therefore, a method based on neural Granger causality inference is proposed to study the interactions of climate variables, with focus on the variables commonly used in the energy field, especially in photovoltaics. Firstly, for each climate variable, the time-varying causality and global causality are, respectively, obtained on each time window and on the whole series by neural Granger causality inference. Secondly, the global causality is used as a feature selection map of the input variables in the prediction task. Finally, compared with some existing feature selection methods, the experiments determine that the proposed method not only reveals the appropriate causality rather than the correlation among climate variables, but also efficiently reduces the input dimensionality and improves the performance and interpretability of the predicting model. Climatic variables interaction; Feature selection; Multi-layer perceptron; Neural Granger causality; Time series prediction
Shankar, Mohan; Loeb, Norman G.; Smith, Nathaniel; Smith, Natividad; Daniels, Janet L.; Thomas, Susan; Walikainen, DaleShankar, M., N. G. Loeb, N. Smith, N. Smith, J. L. Daniels, S. Thomas, D. Walikainen, 2023: Evaluating the Radiometric Performance of the Clouds and the Earth’s Radiant Energy System (CERES) Instruments on Terra and Aqua Over 20 Years. IEEE Transactions on Geoscience and Remote Sensing, 61, 1-11. doi: 10.1109/TGRS.2023.3330398. Six Clouds and the Earth’s Radiant Energy System (CERES) instruments on four satellites are used to produce a global continuous multidecadal record of Earth’s radiation budget (ERB) at the top-of-atmosphere (TOA). Each CERES instrument was calibrated and characterized on the ground before launch, while postlaunch calibration was conducted using onboard calibration sources. The performance of the CERES instruments is verified using vicarious approaches involving both Earth and celestial targets. In this article, we describe the calibration and validation approach and demonstrate the performance of the CERES instruments on the Terra and Aqua spacecraft over the 20-year period since launch. Validation results demonstrate that after applying the appropriate calibration corrections, all four instruments are stable and perform consistently with each other. Comparisons of observations between instruments on the two spacecraft during orbital crossings further confirm the consistent performance across all instruments over the 20-year period. validation; Earth; Clouds and the Earth’s Radiant Energy System (CERES); calibration; Calibration; radiometry; Radiometry; Aqua; Terra; Space vehicles; Mirrors; Optical filters; Telescopes
Sharma, Arushi; Venkataraman, Chandra; Muduchuru, Kaushik; Singh, Vikas; Kesarkar, Amit; Ghosh, Sudipta; Dey, SagnikSharma, A., C. Venkataraman, K. Muduchuru, V. Singh, A. Kesarkar, S. Ghosh, S. Dey, 2023: Aerosol radiative feedback enhances particulate pollution over India: A process understanding. Atmospheric Environment, 298, 119609. doi: 10.1016/j.atmosenv.2023.119609. In this study, we investigate the role of aerosol direct radiative feedback on regional meteorological changes and subsequent distribution of air pollutant with the focus on particulate matter PM2.5 and ozone (O3) over India. WRF-Chem simulations have been applied for Baseline case with both aerosol direct and indirect effects and another simulation including only aerosol indirect effects. The aerosol direct radiative feedback on the meteorology and air quality were investigated by taking the differences between these two simulations. A comprehensive model evaluation showed the model had the capacity to reproduce the observations and well captured the temporal and spatial variation in meteorological and aerosol fields. We found that the reduction in incoming shortwave solar radiation, temperature at 2 m and planetary boundary layer height annually and across all the season due to aerosol radiation interaction (ARI). The concentration of PM2.5 and gaseous precursors like SO2 and NO2 showed enhancements, while O3 concentration mostly showed a reduction. Spatial and annual average PM2.5 concentration was increased by +6%, SO2 concentration was increased by +1.4%, NO2 concentration was increased by +3.4%, and O3 concentration was reduced by −1.4%. Largest regional increases of 40% in particulate pollution induced by ARI occurred over north-western Indian region. The increase in PM2.5 concentration was highly related to stabilisation induced through meteorological variables and increases in primary aerosol concentration. The decrease in O3 concentration was highly related increases in NO2 and SO2 concentration. In the most polluted regions of India, ARI significantly enhance surface-level particulate pollution and related premature mortality, of particular concern considering likely future increasing trends. This study highlights the importance of inclusion and better representations of ARI and for implementing effective mitigation plans. Meteorology; WRF-Chem; Atmospheric chemistry; Air quality simulations; Primary and secondary species
Sharma, Puneet; Ganguly, Dilip; Sharma, Amit Kumar; Kant, Sunny; Mishra, ShiwanshaSharma, P., D. Ganguly, A. K. Sharma, S. Kant, S. Mishra, 2023: Assessing the Aerosols, Clouds and Their Relationship Over the Northern Bay of Bengal Using a Global Climate Model. Earth and Space Science, 10(2), e2022EA002706. doi: 10.1029/2022EA002706. Comprehensive evaluation of aerosol-cloud interactions (ACI) simulated by climate models using observations is crucial for advancing model development. Here, we use Moderate Resolution Imaging Spectroradiometer (MODIS) data to evaluate aerosol and cloud properties obtained from Community Atmosphere Model 5 (CAM5) over northern Bay of Bengal during winter season. We conduct simulations for default model setup as well as for prescribed, and nudged meteorology using Goddard Earth Observing System (GEOS5) reanalysis dataset in order to study the impact of meteorological parameters on simulated ACI. CAM5 captures the spatial variability of cloud optical depth (τc), cloud droplet number concentration (Nc), and liquid water path (LWP), although the values are overestimated in the model. Default model strongly simulates observed negative cloud effective radius (re)-Nc susceptibility but fails to reproduce the observed positive LWP-Nc susceptibility possibly due to evaporative cooling of the large number of smaller droplets. Compared to default and prescribed meteorology simulations, nudging specific humidity (Q) at 6-hr relaxation time scale leads to a positive LWP-Nc susceptibility, and an overall improved simulation of aerosol indirect effects. Increasing the relaxation time scale beyond 6-hr degrade the simulation of indirect effects suggesting high sensitivity of indirect effects to Q and serious deficiencies in Q simulated by the model. Improvement in simulation of aerosol and cloud characteristics are also noted when winds (UV) are nudged but it worsens some of the simulated ACI sensitivities due to increased transport of absorbing aerosols over the study region and a dominant semi-direct effect in the model. aerosol indirect effect; CAM5; nudging; cloud susceptibility
Shaw, Jonah K.; Kay, Jennifer E.Shaw, J. K., J. E. Kay, 2023: Processes Controlling the Seasonally Varying Emergence of Forced Arctic Longwave Radiation Changes. J. Climate, 36(20), 7337-7354. doi: 10.1175/JCLI-D-23-0020.1. Abstract Most observed patterns of recent Arctic surface warming and sea ice loss lie outside of unforced internal climate variability. In contrast, human influence on related changes in outgoing longwave radiation has not been assessed. Outgoing longwave radiation captures the flow of thermal energy from the surface through the atmosphere to space, making it an essential indicator of Arctic change. Furthermore, satellites have measured pan-Arctic radiation for two decades while surface temperature observations remain spatially and temporally sparse. Here, two climate model initial-condition large ensembles and satellite observations are used to investigate when and why twenty-first-century Arctic outgoing longwave radiation changes emerge from unforced internal climate variability. Observationally, outgoing longwave radiation changes from 2001 to 2021 are within the range of unforced internal variability for all months except October. The model-predicted timing of Arctic longwave radiation emergence varies throughout the year. Specifically, fall emergence occurs a decade earlier than spring emergence. These large emergence timing differences result from seasonally dependent sea ice loss and surface warming. The atmosphere and clouds then widen these seasonal differences by delaying emergence more in the spring and winter than in the fall. Finally, comparison of the two ensembles shows that more sea ice and a more transparent atmosphere during the melt season led to an earlier emergence of forced longwave radiation changes. Overall, these findings demonstrate that attributing changes in Arctic outgoing longwave radiation to human influence requires understanding the seasonality of both forced change and internal climate variability.
Shen, Min-Hua; Yu, Jia-YuhShen, M., J. Yu, 2023: Changes in El Niño characteristics and air–sea feedback mechanisms under progressive global warming. Terrestrial, Atmospheric and Oceanic Sciences, 34(1), 19. doi: 10.1007/s44195-023-00051-5. In this study, we investigate the potential changes of El Niño characteristics, including intensity, frequency and CP/EP El Niño ratio, under progressive global warming based on the 140-year CMIP6 model simulation outputs with the 1pctCO2 experiment. Major air-sea feedback mechanisms attributing to the changes are also examined. The CMIP6 ensemble means project a slight enhancement of El Niño intensity by about 2% and a modest increase of El Niño frequency by about 4% from the first to the second 70-year periods. It is found that these small changes result from the opposite response to global warming between CP and EP El Niño, i.e., the intensity of EP El Niño is projected to weaken by nearly 4.6% while the intensity of CP El Niño is projected to increase by about 4.5%. Since CP El Niño occurs more frequently than EP El Niño in CMIP6 simulations, this leads to a slight enhancement of the total El Niño intensity if these two types of El Niño were not separated. A similar situation occurs in projecting the future change of El Niño frequency, i.e., the frequency of EP El Niño is projected to decrease by about 1.4% while the frequency of CP El Niño is projected to increase by about 2%, thereby leading to a modest increase of the total El Niño frequency. By comparing the variance explained by key air-sea feedback mechanism between the two 70-year periods, we also note that the increased CP/EP ratio can be explained by the enhanced role played by the SF (seasonal footprinting) mechanism in a warmer atmosphere. Our study also points out that, as long as a climate model can correctly produce the intensity (variance) of major air-sea feedback mechanisms, the relationship between changes in El Niño characteristics and changes in feedback mechanisms can be physically robust. El Niño; Global warming; Air–sea feedback mechanism
Shen, Pengke; Zhao, Shuqing; Ma, Yongjing; Liu, ShuguangShen, P., S. Zhao, Y. Ma, S. Liu, 2023: Urbanization-induced Earth's surface energy alteration and warming: A global spatiotemporal analysis. Remote Sensing of Environment, 284, 113361. doi: 10.1016/j.rse.2022.113361. As both drivers and first responders, urban areas are rapidly increasing in importance of shaping global climate change. The global imprint of urbanization on surface energy balance (SEB) remains, however, largely unknown. Here, we undertake a global spatiotemporal analysis on urbanization-induced Earth's surface energy alteration using annually dynamic maps of impervious surface and satellite-derived surface energy fluxes and land surface temperature (LST), alongside space-for-time (spatial) and time-for-time (temporal) approaches. Relying on space-for-time substitution, we estimate that global urbanization-driven surface warming of annual mean temperature has reached 0.054 °C (95% CI, −0.009–0.214 °C) between 2003 and 2018 (with temporal stability), especially pronounced in summer daytime (0.122 °C, −0.038–0.495 °C), largely attributed to decline in local latent heat cooling, enlarged long-wave heat dissipation and anthropogenic heat. Temporal quantification of urbanization effects demonstrates consistence with spatial gradient approach, implying that space can substitute time in understanding and predicting future urbanization imprint on SEB and temperature (i.e., cities as harbingers of climate change). We further predict that during the first 35 years of this century annual warming magnitude will be nearly double that of the period 1985–2018, and particularly, urbanization perturbation to SEB will be more intense across countries or regions in the arid and warm temperate climates under global warming. This research provides science-based foundation that can help inform the IPCC special report on cities and climate change, and emphasize urgency to develop tailored mitigation and adaptation strategies against rapidly warming based on SEB attribution and climate background. Surface energy balance; Climate background; Future prediction; Space-for-time substitution; Surface warming; Temporal analysis; Urbanization effects
Sherriff-Tadano, Sam; Abe-Ouchi, Ayako; Yoshimori, Masakazu; Ohgaito, Rumi; Vadsaria, Tristan; Chan, Wing-Le; Hotta, Haruka; Kikuchi, Maki; Kodama, Takanori; Oka, Akira; Suzuki, KentarohSherriff-Tadano, S., A. Abe-Ouchi, M. Yoshimori, R. Ohgaito, T. Vadsaria, W. Chan, H. Hotta, M. Kikuchi, T. Kodama, A. Oka, K. Suzuki, 2023: Southern Ocean Surface Temperatures and Cloud Biases in Climate Models Connected to the Representation of Glacial Deep Ocean Circulation. J. Climate, 36(11), 3849-3866. doi: 10.1175/JCLI-D-22-0221.1. Abstract Simulating and reproducing the past Atlantic meridional overturning circulation (AMOC) with comprehensive climate models are essential to understanding past climate changes as well as to testing the ability of the models in simulating different climates. At the Last Glacial Maximum (LGM), reconstructions show a shoaling of the AMOC compared to modern climate. However, almost all state-of-the-art climate models simulate a deeper LGM AMOC. Here, it is shown that this paleodata–model discrepancy is partly related to the climate model biases in modern sea surface temperatures (SST) over the Southern Ocean (70°–45°S). Analysis of model outputs from three phases of the Paleoclimate Model Intercomparison Project shows that models with warm Southern Ocean SST biases tend to simulate a deepening of the LGM AMOC, while the opposite is observed in models with cold SST biases. As a result, a positive correlation of 0.41 is found between SST biases and LGM AMOC depth anomalies. Using sensitivity experiments with a climate model, we show, as an example, that changes in parameters associated with the fraction of cloud thermodynamic phase in a climate model reduce the biases in the warm SST over the modern Southern Ocean. The less biased versions of the model then reproduce a colder Southern Ocean at the LGM, which increases formation of Antarctic Bottom Water and causes shoaling of the LGM AMOC, without affecting the LGM climate in other regions. The results highlight the importance of sea surface conditions and clouds over the Southern Ocean in simulating past and future global climates. Significance Statement To test the ability of comprehensive climate models, simulations of the Last Glacial Maximum (LGM) have been conducted. However, most models simulated a deeper Atlantic meridional overturning circulation (AMOC) in the LGM, which contradicts paleodata suggesting a shallower AMOC. Here, using multimodel analysis and sensitivity experiments with a climate model, we show that this paleodata–model discrepancy is partly related to model biases in the modern Southern Ocean. Improvements in Southern Ocean surface temperatures and clouds reproduce a colder climate over the Southern Ocean at the LGM, which causes an intense shoaling of the AMOC due to increased formation of Antarctic Bottom Water. These results demonstrate the important effect of model biases over the Southern Ocean on simulating past climates.
Shin, Jihoon; Baik, Jong-JinShin, J., J. Baik, 2023: Global Simulation of the Madden–Julian Oscillation With Stochastic Unified Convection Scheme. Journal of Advances in Modeling Earth Systems, 15(7), e2022MS003578. doi: 10.1029/2022MS003578. A new spectral convection scheme, the stochastic unified convection scheme (stochastic UNICON), is implemented in a general circulation model. The global climate simulation using stochastic UNICON is evaluated and compared with UNICON, focusing on the simulation of the Madden–Julian oscillation (MJO). Stochastic UNICON extends the original UNICON by randomly sampling convective updrafts from the joint probability density function constructed at the near-surface, generating a spectrum of convective updrafts in a physically based manner. The performances of UNICON and stochastic UNICON on simulating observed mean climates are comparable, while stochastic UNICON slightly reduces the mean bias of climate variables. For the simulation of intraseasonal variabilities, stochastic UNICON outperforms UNICON in many aspects. Stochastic UNICON improves the simulation of the intensity and propagation patterns of boreal winter MJO, which are too weakly simulated in UNICON. The coherency between MJO-related convection and large-scale circulation is also enhanced, which many climate models underestimate. The improvement of MJO simulation by stochastic UNICON is related to a better representation of the relationship between moisture and convection in the model. The increased frequency of shallow convection in stochastic UNICON leads to stronger moisture convergence that precedes convection activity peak and results in the more robust development of organized convection and more frequent intense precipitation. A precipitation budget analysis reveals that the moisture tendencies due to horizontal advection and convective process are consistently enhanced during MJO developing periods by stochastic UNICON. global climate model; shallow convection; stochastic parameterization; convection parameterization; Madden–Julian oscillation
Song, Xiaoliang; Zhang, Guang; Wan, Hui; Xie, ShaochengSong, X., G. Zhang, H. Wan, S. Xie, 2023: Incorporating the Effect of Large-Scale Vertical Motion on Convection Through Convective Mass Flux Adjustment in E3SMv2. Journal of Advances in Modeling Earth Systems, 15(10), e2022MS003553. doi: 10.1029/2022MS003553. Recent observational studies suggest that the large-scale dynamical forcing (vertical motion) plays important roles in deep convection development. In this study we propose a convective mass flux adjustment (MAdj) approach to represent the dynamical effects of large-scale vertical motion on convection in the Department of Energy's Energy Exascale Earth System Model version 2 (E3SMv2). With MAdj, convection is enhanced (suppressed) when there is large-scale ascending (descending) motion at the planetary boundary layer top. The coupling of convection with large-scale circulation significantly improves the simulation of climate variability in E3SMv2 across multiple scales from the diurnal cycle, convectively coupled equatorial waves, to the Madden-Julian Oscillation (MJO). The standard E3SMv2 tends to simulate overly weak diurnal amplitude of precipitation and overly weak variance of convectively coupled equatorial Kelvin and westward inertio-gravity (WIG) waves. It also fails to simulate the essential characteristics of the MJO: continuous eastward propagation. With MAdj, the amplitude of diurnal cycle of precipitation is systematically increased and its probability density distribution is much closer to observations. The MAdj can also simulate more realistic eastward propagation of the MJO and much stronger convectively coupled Kelvin and WIG waves. Moreover, the MAdj approach slightly improves the climatology simulations in precipitation, cloud, radiation, circulation, temperature, and moisture fields, with overall root-mean-square error (RMSE) of major climatological fields reduced by about 2%. The MAdj approach suppresses excessive grid-scale precipitation, reducing precipitation wet biases over South China Sea, Philippine Sea, Himalayas, and South Pacific Convergence Zone in western Pacific in summer. climate variability; diurnal cycle; convection parameterization; Madden-Julian oscillation; vertical velocity
Sreenath, A. V.; Abhilash, S.; Ajilesh, P. P.Sreenath, A. V., S. Abhilash, P. P. Ajilesh, 2023: Changes in the dynamical, thermodynamical and hydrometeor characteristics prior to extreme rainfall events along the southwest coast of India in recent decades. Atmospheric Research, 289, 106752. doi: 10.1016/j.atmosres.2023.106752. Extremes in rainfall have links with atmospheric dynamics, thermodynamics, and deep cloud properties. Employing station-based gridded rainfall data, analysis product of sea surface temperature (SST), reanalysis product of dynamic/thermodynamic parameters and remotely sensed cloud properties, we demonstrate the features and evolution of rainfall extremes over the southwest coast of India (8–14°N, 75–77.5°E) during monsoon season. Analysis of the frequency and total amount of extreme rainfall reveals that the northwest coast (14–20°N) typically serves as the central node for the precipitation extremes. However, linear trends in rainfall extremes are remarkably different across the northwest and southwest coasts of India. Specifically, we noted a marked decrease in extreme rain events between 14 and 16°N along the northwest coast, while at the same time, the southwest coast emerges as a hot spot for extreme rain events. Results suggest that the evolution of rainfall extremes on the southwest coast is linked to the warming of the south-central Arabian sea (AS), enhanced SST gradient between north and south AS, and low pressure over the Bay of Bengal (BoB) four days before the event day. Under the influence of these factors, moisture-laden winds shift from the northwest coast to the southwest coast of India. Three days before the extreme precipitation, the BoB low-pressure centre advances westward and eventually merges with the trough of low along the west coast on the event day and creates a considerable increase in the mid-tropospheric vorticity. Meteorological conditions on extreme rainfall days over the southwest coast are portrayed by a significant reduction of sea level pressure, an intense flow of low-level jets from the Arabian sea and a cyclonic vortex at mid-troposphere. These elements favour a substantial rise in moist static energy (MSE) throughout the troposphere, leading to deep convective clouds with copious ice content and extreme rainfall over the southwest coast. Cyclonic vortex; Deep convective clouds; MSE; Rainfall extremes; Southwest coast
Stamatis, Michael; Hatzianastassiou, Nikolaos; Korras-Carraca, Marios-Bruno; Matsoukas, Christos; Wild, Martin; Vardavas, IliasStamatis, M., N. Hatzianastassiou, M. Korras-Carraca, C. Matsoukas, M. Wild, I. Vardavas, 2023: An Assessment of Global Dimming and Brightening during 1984–2018 Using the FORTH Radiative Transfer Model and ISCCP Satellite and MERRA-2 Reanalysis Data. Atmosphere, 14(8), 1258. doi: 10.3390/atmos14081258. In this study, an assessment of the FORTH radiative transfer model (RTM) surface solar radiation (SSR) as well as its interdecadal changes (Δ(SSR)), namely global dimming and brightening (GDB), is performed during the 35-year period of 1984–2018. Furthermore, a thorough evaluation of SSR and (Δ(SSR)) is conducted against high-quality reference surface measurements from 1193 Global Energy Balance Archive (GEBA) and 66 Baseline Surface Radiation Network (BSRN) stations. For the first time, the FORTH-RTM Δ(SSR) was evaluated over an extended period of 35 years and with a spatial resolution of 0.5° × 0.625°. The RTM uses state-of-the-art input products such as MERRA-2 and ISCCP-H and computes 35-year-long monthly SSR and GDB, which are compared to a comprehensive dataset of reference measurements from GEBA and BSRN. Overall, the FORTH-RTM deseasonalized SSR anomalies correlate satisfactorily with either GEBA (R equal to 0.72) or BSRN (R equal to 0.80). The percentage of agreement between the sign of computed GEBA and FORTH-RTM Δ(SSR) is equal to 63.5% and the corresponding percentage for FORTH-RTM and BSRN is 54.5%. The obtained results indicate that a considerable and statistically significant increase in SSR (Brightening) took place over Europe, Mexico, Brazil, Argentina, Central and NW African areas, and some parts of the tropical oceans from the early 1980s to the late 2010s. On the other hand, during the same 35-year period, a strong and statistically significant decrease in SSR (Dimming) occurred over the western Tropical Pacific, India, Australia, Southern East China, Northern South America, and some parts of oceans. A statistically significant dimming at the 95% confidence level, equal to −0.063 Wm−2 year−1 (or −2.22 Wm−2) from 1984 to 2018 is found over the entire globe, which was more prevalent over oceanic than over continental regions (−0.07 Wm−2 year−1 and −0.03 Wm−2 year−1, statistically significant dimming at the 95% confidence level, respectively) in both hemispheres. Yet, this overall 35-year dimming arose from alternating decadal-scale changes, consisting of dimming during 1984–1989, brightening in the 1990s, turning into dimming over 2000–2009, and brightening during 2010–2018. climate; brightening; dimming; stations; surface solar radiation; radiative transfer model
Su, Hua; Wei, Yanan; Lu, Wenfang; Yan, Xiao-Hai; Zhang, HongshengSu, H., Y. Wei, W. Lu, X. Yan, H. Zhang, 2023: Unabated Global Ocean Warming Revealed by Ocean Heat Content from Remote Sensing Reconstruction. Remote Sensing, 15(3), 566. doi: 10.3390/rs15030566. As the most relevant indicator of global warming, the ocean heat content (OHC) change is tightly linked to the Earth’s energy imbalance. Therefore, it is vital to study the OHC and heat absorption and redistribution. Here we analyzed the characteristics of global OHC variations based on a previously reconstructed OHC dataset (named OPEN) with four other gridded OHC datasets from 1993 to 2021. Different from the other four datasets, the OPEN dataset directly obtains OHC through remote sensing, which is reliable and superior in OHC reconstruction, further verified by the Clouds and the Earth’s Radiant Energy System (CERES) radiation flux data. We quantitatively analyzed the changes in the upper 2000 m OHC of the oceans over the past three decades from a multisource and multilayer perspective. Meanwhile, we calculated the global ocean heat uptake to quantify and track the global ocean warming rate and combined it with the Oceanic Niño Index to analyze the global evolution of OHC associated with El Niño–Southern Oscillation variability. The results show that different datasets reveal a continuously increasing and non-decaying global ocean warming from multiple perspectives, with more heat being absorbed by the subsurface and deeper ocean over the past 29 years. The global OHC heating trend from 1993 to 2021 is 7.48 ± 0.17, 7.89 ± 0.1, 10.11 ± 0.16, 7.78 ± 0.17, and 12.8 ± 0.26 × 1022 J/decade according to OPEN, IAP, EN4, Ishii, and ORAS5, respectively, which shows that the trends of the OPEN, IAP, and Ishii datasets are generally consistent, while those of EN4 and ORAS5 datasets are much higher. In addition, the ocean warming characteristics revealed by different datasets are somewhat different. The OPEN OHC dataset from remote sensing reconstruction shows a unique remote sensing mapping advantage, presenting a distinctive warming pattern in the East Indian Ocean. Meanwhile, the OPEN dataset had the largest statistically significant area, with 85.6% of the ocean covered by significant positive trends. The significant and continuous increase in global ocean warming over the past three decades, revealed from remote sensing reconstruction, can provide an important reference for projecting ocean warming in the context of global climate change toward the United Nations Sustainable Development Goals. ENSO; global ocean warming; Ocean Heat Content (OHC); Ocean Heat Uptake (OHU); remote sensing reconstruction
Sun, Chao; Liang, Xin-ZhongSun, C., X. Liang, 2023: Understanding and Reducing Warm and Dry Summer Biases in the Central United States: Analytical Modeling to Identify the Mechanisms for CMIP Ensemble Error Spread. J. Climate, 36(7), 2035-2054. doi: 10.1175/JCLI-D-22-0255.1. Abstract Most climate models in phase 6 of the Coupled Model Intercomparison Project (CMIP6) still suffer pronounced warm and dry summer biases in the central United States (CUS), even in high-resolution simulations. We found that the cloud base definition in the cumulus parameterization was the dominant factor determining the spread of the biases among models and those defining cloud base at the lifting condensation level (LCL) performed the best. To identify the underlying mechanisms, we developed a physically based analytical bias model (ABM) to capture the key feedback processes of land–atmosphere coupling. The ABM has significant explanatory power, capturing 80% variance of temperature and precipitation biases among all models. Our ABM analysis via counterfactual experiments indicated that the biases are attributed mostly by surface downwelling longwave radiation errors and second by surface net shortwave radiation errors, with the former 2–5 times larger. The effective radiative forcing from these two errors as weighted by their relative contributions induces runaway temperature and precipitation feedbacks, which collaborate to cause CUS summer warm and dry biases. The LCL cumulus reduces the biases through two key mechanisms: it produces more clouds and less precipitable water, which reduce radiative energy input for both surface heating and evapotranspiration to cause a cooler and wetter soil; it produces more rainfall and wetter soil conditions, which suppress the positive evapotranspiration–precipitation feedback to damp the warm and dry bias coupling. Most models using non-LCL schemes underestimate both precipitation and cloud amounts, which amplify the positive feedback to cause significant biases.
Sun, Chunfa; Liu, Dongxia; Xiao, Xian; Chen, Yichen; Liu, Zirui; Sun, YangSun, C., D. Liu, X. Xiao, Y. Chen, Z. Liu, Y. Sun, 2023: The electrical activity of a thunderstorm under high dust circumstances over Beijing metropolis region. Atmospheric Research, 285, 106628. doi: 10.1016/j.atmosres.2023.106628. A rare dust-thunderstorm affected the Beijing area on April 15, 2021, generating frequent lightning, dirt precipitation, and gusting. Based on comprehensive data from satellite retrieval, in-situ observation, weather radar, and reanalysis data, this study investigated the electrical activity of this dust-thunderstorm. The results showed that dust aerosols from Mongolia were involved in the growth process of the thunderstorm. During the evolution of the thunderstorm, the ground electrical field always changed positively with the highest value of 9 kV, and PM2.5 and PM10 increased rapidly with the highest values of 1500 μg/m3 and 250 μg/m3. The positive cloud-to-ground (+CG) lightning accounted for a high percentage with an average ratio of >50%. The dust aerosols acting as effective ice nuclei (IN) and cloud condensation nuclei (CCN) invading the thunderstorm were likely to increase the content of ice-phase particles and supercooled water, resulting in a high proportion of +CG lightning. It is deduced that the dust-thunderstorm possibly presented an inverted charge structure. Dust aerosol; +CG lightning; Invert charge structure; Lightning activity
Sweeney, Aodhan; Fu, Qiang; Pahlavan, Hamid A.; Haynes, PeterSweeney, A., Q. Fu, H. A. Pahlavan, P. Haynes, 2023: Seasonality of the QBO Impact on Equatorial Clouds. Journal of Geophysical Research: Atmospheres, n/a(n/a), e2022JD037737. doi: 10.1029/2022JD037737. The Quasi-Biennial Oscillation (QBO) dominates the interannual variability in the tropical lower stratosphere and is characterized by the descent of alternating easterly and westerly zonal winds. The QBO impact on tropical clouds and convection has received great attention in recent years due to its implications for weather and climate. In this study, a 15-year record of high vertical resolution cloud observations from CALIPSO and a 50 hPa zonal wind QBO index from ERA5 are used to document the QBO impact on equatorial (10°S-10°N) clouds. Observations from radio occultations, the CERES instrument, and the ERA5 reanalysis are also used to document the QBO impact on temperature, cloud radiative effect, and zonal wind, respectively. It is shown that the QBO impact on zonal mean equatorial cloud fraction has a strong seasonality. The strongest cloud fraction response to the QBO occurs in boreal spring and early summer, which extends from above the mean tropopause to ∼12.5 km and results in a significant longwave cloud radiative effect anomaly of 1 W/m2. The seasonality of the QBO impact on cloud fraction is synchronized with the QBO impacts on temperature and zonal wind in the tropical upper troposphere. Cirrus Clouds; Quasi-Biennial Oscillation; Seasonality
Szewczyk, Z. Peter; Smith, G. Louis; Daniels, Janet L.; Priestley, Kory J.Szewczyk, Z. P., G. L. Smith, J. L. Daniels, K. J. Priestley, 2023: Comparison of unfiltered CERES shortwave radiances measured in the minor plane over snow/ice of Greenland during summer solstices. Remote Sensing of Clouds and the Atmosphere XXVIII, 12730, 83-93. doi: 10.1117/12.2678565. A purpose of this paper is to present comparison of unfiltered radiances measured by CERES scanners when their scanning is aligned in the plane orthogonal to the solar plane and targeting Greenland around the time of summer solstice. Since the summer solstice in 2002, FM1 on Terra and FM4/FM3 on Aqua have been scanning in the minor plane for the month of June to collect comparison data. Measurements of FM5 on S-NPP and FM6 on NOAA20 have been added to this dataset starting in 2012 and 2018, respectively, with the data collection extended from May to July due to orbit characteristics. This unique dataset presents one-of-a-kind opportunity to compare radiances measured from four different platforms to assess CERES calibrations, particularly the consistency of their shortwave channel, as the solar zenith angles are the smallest for high latitudes producing relatively strong SW signal over ice/snow/clouds of Greenland. Results of comparison reported in this paper will be used in work to release new and updated versions, Edition 5, of ERBE-like (ES8) data products, for Terra and Aqua scanners.
Takahashi, Naoya; Richards, Kelvin J.; Schneider, Niklas; Stuecker, Malte F.; Annamalai, Hariharasubramanian; Nonaka, MasamiTakahashi, N., K. J. Richards, N. Schneider, M. F. Stuecker, H. Annamalai, M. Nonaka, 2023: Observed Relative Contributions of Anomalous Heat Fluxes and Effective Heat Capacity to Sea Surface Temperature Variability. Geophysical Research Letters, 50(17), e2023GL103165. doi: 10.1029/2023GL103165. Sea surface temperatures (SSTs) vary not only due to heat exchange across the air-sea interface but also due to changes in effective heat capacity as primarily determined by mixed layer depth (MLD). Here, we investigate seasonal and regional characteristics of the contribution of MLD anomalies to the month-to-month variability of SST using observational datasets. First, we propose a metric called Flux Divergence Angle, which can quantify the relative contributions of surface heat fluxes and MLD anomalies to SST variability. Using this metric, we find that MLD anomalies tend to amplify SST anomalies in the extra-tropics, especially in the eastern ocean basins, during spring and summer. In contrast, MLD anomalies tend to suppress SST anomalies in the eastern tropical Pacific during December-January-February. This paper provides the first global picture of the observed importance of MLD anomalies to the local SST variability.
Talib, Joshua; Müller, Omar V.; Barton, Emma J.; Taylor, Christopher M.; Vidale, Pier LuigiTalib, J., O. V. Müller, E. J. Barton, C. M. Taylor, P. L. Vidale, 2023: The Representation of Soil Moisture-Atmosphere Feedbacks across the Tibetan Plateau in CMIP6. Advances in Atmospheric Sciences, 40(11), 2063-2081. doi: 10.1007/s00376-023-2296-2. Thermal processes on the Tibetan Plateau (TP) influence atmospheric conditions on regional and global scales. Given this, previous work has shown that soil moisture–driven surface flux variations feed back onto the atmosphere. Whilst soil moisture is a source of atmospheric predictability, no study has evaluated soil moisture–atmosphere coupling on the TP in general circulation models (GCMs). In this study, we use several analysis techniques to assess soil moisture-atmosphere coupling in CMIP6 simulations including: instantaneous coupling indices; analysis of flux and atmospheric behaviour during dry spells; and a quantification of the preference for convection over drier soils. Through these metrics we partition feedbacks into their atmospheric and terrestrial components. Tibetan Plateau; model evaluation; precipitation; surface energy balance; land–atmosphere feedbacks; 模式评估; 表面能量平衡; 陆-气反馈; 降水; 青藏高原
Talib, Joshua; Taylor, Christopher M.; Harris, Bethan L.; Wainwright, Caroline M.Talib, J., C. M. Taylor, B. L. Harris, C. M. Wainwright, 2023: Surface-driven amplification of Madden–Julian oscillation circulation anomalies across East Africa and its influence on the Turkana jet. Quarterly Journal of the Royal Meteorological Society, 149(754), 1890-1912. doi: 10.1002/qj.4487. In semi-arid environments, rainfall-driven soil moisture fluctuations exert a strong influence on surface turbulent fluxes. Intraseasonal rainfall variability can therefore impact low-level atmospheric temperatures and influence regional circulations. Using satellite observations and an atmospheric reanalysis, we investigate whether rainfall variability induced by the Madden–Julian oscillation (MJO) triggers land–atmosphere feedbacks across East Africa. We identify that surface fluxes during the East African wet seasons (March–May and October–December) are sensitive to MJO-induced precipitation variations across low-lying regions of South Sudan and highland regions of Uganda and southwest Kenya. For example, during MJO phases 6 to 8, when rainfall is suppressed, surface temperatures and sensible heat fluxes increase, whilst evapotranspiration decreases. Spatial variations in the surface flux response to rainfall variability feed back onto the atmosphere through amplifying MJO-associated pressure anomalies. During dry MJO events for instance, surface warming across the exit region of the Turkana channel increases the low-tropospheric along-channel pressure gradient and intensifies the Turkana jet. We conclude that average surface-driven temperature fluctuations during a single day are responsible for approximately 12% of MJO-associated variability of the Turkana jet speed. However, we expect that the accumulation of heat over multiple days to the west of the East African Highlands further amplifies anomalies in the pressure gradient and jet intensity. Modelling experiments are required to quantify the accumulated impact of the surface forcing. Surface-driven Turkana jet variations influence the East African moisture budget and affect the intensity and inland propagation of coastal convection. Not only is this the first study to investigate the importance of intraseasonal land–atmosphere feedbacks across East Africa, but it is also the first to show that Turkana jet characteristics are partly driven by surface conditions. This work motivates an investigation into whether subseasonal forecast models fully harness the predictability from surface-induced jet variations. convection; intraseasonal variability; East Africa; land surface; soil moisture–atmosphere feedbacks
Tana, Gegen; Ri, Xu; Shi, Chong; Ma, Run; Letu, Husi; Xu, Jian; Shi, JianchengTana, G., X. Ri, C. Shi, R. Ma, H. Letu, J. Xu, J. Shi, 2023: Retrieval of cloud microphysical properties from Himawari-8/AHI infrared channels and its application in surface shortwave downward radiation estimation in the sun glint region. Remote Sensing of Environment, 290, 113548. doi: 10.1016/j.rse.2023.113548. Satellite remote sensing of cloud property retrieval and shortwave downward radiation (SWDR) estimation is essential for global radiation budget and climate change studies. Sun glint areas remain a challenge for the existing cloud and SWDR algorithms based on the visible channel since surface specular reflection has a significant impact on satellite retrieval. In this study, a set of algorithms for cloud detection and cloud microphysical parameter estimation were developed using infrared multichannel data from the new generation geostationary satellite Himawari-8 based on the random forest method. The results indicated that the cloud retrieval algorithm exhibited better performance in the sun glint areas where the official Himawari-8 products (cloud detection and cloud optical thickness) were overestimated. We developed a new SWDR estimation algorithm combining the radiative transfer model and machine learning techniques by considering the cloud properties from the cloud retrieval algorithm. The results indicated that the SWDR and cloud radiative forcing derived by the new algorithm were more consistent with those of the well-known radiation products Cloud and the Earth's Radiant Energy System than those estimated using the official-based cloud product, with decreases in the root mean square error of approximately 22% and 41%, respectively. The new algorithms effectively addressed sun glint contamination by providing more data coverage and exhibiting stable performance on a spatiotemporal scale. Cloud; AHI/Himawari-8; Infrared bands; Sun glint; Surface solar radiation
Tang, Chenqian; Shi, Chong; Letu, Husi; Ma, Run; Yoshida, Mayumi; Kikuchi, Maki; Xu, Jian; Li, Nan; Zhao, Mengjie; Chen, Liangfu; Shi, GuangyuTang, C., C. Shi, H. Letu, R. Ma, M. Yoshida, M. Kikuchi, J. Xu, N. Li, M. Zhao, L. Chen, G. Shi, 2023: Evaluation and uncertainty analysis of Himawari-8 hourly aerosol product version 3.1 and its influence on surface solar radiation before and during the COVID-19 outbreak. Science of The Total Environment, 892, 164456. doi: 10.1016/j.scitotenv.2023.164456. The hourly Himawari-8 version 3.1 (V31) aerosol product has been released and incorporates an updated Level 2 algorithm that uses forecast data as an a priori estimate. However, there has not been a thorough evaluation of V31 data across a full-disk scan, and V31 has yet to be applied in the analysis of its influence on surface solar radiation (SSR). This study firstly investigates the accuracy of V31 aerosol products, which includes three categories of aerosol optical depth (AOD) (AODMean, AODPure, and AODMerged) as well as the corresponding Ångström exponent (AE), using ground-based measurements from the AERONET and SKYNET. Results indicate that V31 AOD products are more consistent with ground-based measurements compared to previous products (V30). The highest correlation and lowest error were seen in the AODMerged, with a correlation coefficient of 0.8335 and minimal root mean square error of 0.1919. In contrast, the AEMerged shows a larger discrepancy with measurements unlike the AEMean and AEPure. Error analysis reveals that V31 AODMerged has generally stable accuracy across various ground types and geometrical observation angles, however, there are higher uncertainties in areas with high aerosol loading, particularly for fine aerosols. The temporal analysis shows that V31 AODMerged performs better compared to V30, particularly in the afternoon. Finally, the impacts of aerosols on SSR based on the V31 AODMerged are investigated through the development of a sophisticated SSR estimation algorithm in the clear sky. Results demonstrate that the estimated SSR is significant consistency with those of well-known CERES products, with preservation of 20 times higher spatial resolution. The spatial analysis reveals a significant reduction of AOD in the North China Plain before and during the COVID-19 outbreak, resulting in an average 24.57 W m−2 variation of the surface shortwave radiative forcing in clear sky daytime. AERONET and SKYNET; Aerosol optical depth; Aerosol type; COVID-19; Himawari-8; Surface shortwave radiative forcing
Taylor, Patrick C.; Monroe, EmilyTaylor, P. C., E. Monroe, 2023: Isolating the Surface Type Influence on Arctic Low-Clouds. Journal of Geophysical Research: Atmospheres, 128(16), e2022JD038098. doi: 10.1029/2022JD038098. Interactions between sea ice and clouds represent a mechanism through which sea ice influences climate. We composite cloud properties for ice-free, marginal ice zone (MIZ), and ice-covered surfaces during MIZ crossing events to analyze the cloud property differences between surface types. Restricting the analysis to MIZ crossing events enables the isolation of the sea ice effect on clouds from meteorological factors. We find larger cloud fraction (CF) and total water concentration below ∼1.5 km over ice-free relative to ice-covered surfaces during non-summer months. During summer, the results suggest larger CF and total water concentration over ice-free surfaces, however differences do not exceed observational uncertainty. Cloud property differences are linked to atmospheric thermodynamic profile differences, namely ice-free surfaces are warmer, moister, less stable, and have more positive surface turbulent fluxes than ice-covered surfaces. Ice-free minus ice-covered cloud property differences scale with surface temperature differences and are only found in the presence of a surface temperature difference. Our results suggest a 0.02 CF and 0.005 g m−3 total water concentration increase (∼5%) at the level of maximum CF between 2000 and 2021 due to the observed Arctic sea ice decline in fall, corresponding to ∼2 W m−2 increase in the net surface radiative flux. Our results support a positive sea ice-cloud radiative feedback in fall and winter and a negative sea ice-cloud radiative feedback in spring. We propose an updated conceptual model where the average surface type influence on cloud properties is mediated by surface temperature differences between ice-free and ice-covered surfaces.
Thandlam, Venugopal; Rutgersson, Anna; Rahaman, Hasibur; Yabaku, Mounika; Kaagita, Venkatramana; Sakirevupalli, Venkatramana ReddyThandlam, V., A. Rutgersson, H. Rahaman, M. Yabaku, V. Kaagita, V. R. Sakirevupalli, 2023: Quantifying Uncertainties in CERES/MODIS Downwelling Radiation Fluxes in the Global Tropical Oceans. Ocean-Land-Atmosphere Research, 2, 0003. doi: 10.34133/olar.0003. The Clouds and the Earth's Radiant Energy System program, which uses the Moderate Resolution Imaging Spectroradiometer (CM), has been updated with the launch of new satellites and the availability of newly upgraded radiation data. The spatial and temporal variability of daily averaged synoptic 1-degree CM version 3 (CMv3) (old) and version 4 (CMv4) (new) downwelling shortwave (QS) and longwave radiation (QL) data in the global tropical oceans spanning 30°S–30°N from 2000 to 2017 is investigated. Daily in situ data from the Global Tropical Moored Buoy Array were used to validate the CM data from 2000 to 2015. When compared to CMv3, both QS and QL in CMv4 show significant improvements in bias, root-mean-square error, and standard deviations. Furthermore, a long-term trend analysis shows that QS has been increasing by 1 W m−2 per year in the Southern Hemisphere. In contrast, the Northern Hemisphere has a −0.7 W m−2 annual decreasing trend. QS and QL exhibit similar spatial trend patterns. However, in the Indian Ocean, Indo-Pacific warm pool region, and Southern Hemisphere, QL spatial patterns in CMv3 and CMv4 differ with an opposite trend (0.5 W m−2). These annual trends in QS and QL could cause the sea surface temperature to change by −0.2 to 0.3 °C per year in the tropical oceans. These results stress the importance of accurate radiative flux data, and CMv4 can be an alternative to reanalysis or other model-simulated data.
Tian, Yinglin; Zhong, Deyu; Ghausi, Sarosh Alam; Wang, Guangqian; Kleidon, AxelTian, Y., D. Zhong, S. A. Ghausi, G. Wang, A. Kleidon, 2023: Understanding variations in downwelling longwave radiation using Brutsaert's equation. EGUsphere, 1-17. doi: 10.5194/egusphere-2023-451. Abstract. A dominant term in the surface energy balance and central to global warming is downwelling longwave radiation (Rld). It is influenced by radiative properties of the atmospheric column, in particular by greenhouse gases, water vapour, clouds and differences in atmospheric heat storage. We use the semi-empirical equation derived by Brutsaert (1975) to identify the leading terms responsible for the spatio-temporal climatological variations in Rld. This equation requires only near-surface observations of air temperature and humidity. We first evaluated this equation and its extension by Crawford and Duchon (1999) with observations from FLUXNET, the NASA-CERES dataset , and the ERA5 reanalysis. We found a strong agreement with r2 ranging from 0.87 to 0.99 across the datasets for clear-sky and all-sky conditions. We then used the equations to show that diurnal and seasonal variations in Rld are predominantly controlled by changes in atmospheric heat storage. Variations in the emissivity of the atmosphere form a secondary contribution to the variation in Rld, and are mainly controlled by anomalies in cloud cover. We also found that as aridity increases, the contributions from changes in emissivity and atmospheric heat storage tend to offset each other (−40 W m−2 and 20−30 W m−2, respectively), explaining the relatively small decrease in Rld with aridity (−(10−20) W/m−2). These equations thus provide a solid physical basis for understanding the spatio-temporal variability of surface downwelling longwave radiation. This should help to better understand and interpret climatological changes, such as those associated with extreme events and global warming.
Tomassini, Lorenzo; Willett, Martin; Sellar, Alistair; Lock, Adrian; Walters, David; Whitall, Michael; Sanchez, Claudio; Heming, Julian; Earnshaw, Paul; Rodriguez, José M.; Ackerley, Duncan; Xavier, Prince; Franklin, Charmaine; Senior, Catherine A.Tomassini, L., M. Willett, A. Sellar, A. Lock, D. Walters, M. Whitall, C. Sanchez, J. Heming, P. Earnshaw, J. Rodriguez, . M., D. Ackerley, P. Xavier, C. Franklin, C. A. Senior, 2023: Confronting the Convective Gray Zone in the Global Configuration of the Met Office Unified Model. Journal of Advances in Modeling Earth Systems, 15(5), e2022MS003418. doi: 10.1029/2022MS003418. In atmospheric models with kilometer-scale grids the resolution approaches the scale of convection. As a consequence the most energetic eddies in the atmosphere are partially resolved and partially unresolved. The modeling challenge to represent convection partially explicitly and partially as a subgrid process is called the convective gray zone problem. The gray zone issue has previously been discussed in the context of regional models, but the evolution in regional models is constrained by the lateral boundary conditions. Here we explore the convective gray zone starting from a defined global configuration of the Met Office Unified Model using initialized forecasts and comparing different model formulations to observations. The focus is on convection and turbulence, but some aspects of the model dynamics are also considered. The global model is run at nominal 5 km resolution and thus contributions from both resolved and subgrid turbulent and convective fluxes are non-negligible. The main conclusion is that in the present assessment, the configurations which include scale-aware turbulence and a carefully reduced and simplified mass-flux convection scheme outperform both the configuration with fully parameterized convection as well as a configuration in which the subgrid convection parameterization is switched off completely. The results are more conclusive with regard to convective organization and tropical variability than extratropical predictability. The present study thus endorses the strategy to further develop scale-aware physics schemes and to pursue an operational implementation of the global 5 km-resolution model to be used alongside other ensemble forecasts to allow researchers and forecasters to further assess these simulations. atmospheric variability and predictability; convection-circulation interaction; convective gray zone; kilometer-scale global atmospheric modeling
Valkenborg, Bram; De Lannoy, Gabriëlle J. M.; Gruber, Alexander; Miralles, Diego G.; Köhler, Philipp; Frankenberg, Christian; Desai, Ankur R.; Humphreys, Elyn; Klatt, Janina; Lohila, Annalea; Nilsson, Mats B.; Tuittila, Eeva-Stiina; Bechtold, MichelValkenborg, B., G. J. M. De Lannoy, A. Gruber, D. G. Miralles, P. Köhler, C. Frankenberg, A. R. Desai, E. Humphreys, J. Klatt, A. Lohila, M. B. Nilsson, E. Tuittila, M. Bechtold, 2023: Drought and Waterlogging Stress Regimes in Northern Peatlands Detected Through Satellite Retrieved Solar-Induced Chlorophyll Fluorescence. Geophysical Research Letters, 50(19), e2023GL105205. doi: 10.1029/2023GL105205. The water table depth (WTD) in peatlands determines the soil carbon decomposition rate and influences vegetation growth, hence the above-ground carbon assimilation. Here, we used satellite-observed Solar-Induced chlorophyll Fluorescence (SIF) as a proxy of Gross Primary Production (GPP) to investigate water-related vegetation stress over northern peatlands. A linear model with interaction effects was used to relate short- and long-term anomalies in SIF with WTD anomalies and the absolute WTD. Most locations showed the occurrence of drought and waterlogging stress though regions with exclusively waterlogging or drought stress were also detected. As a spatial median, minimal water-related vegetation stress was found for a WTD of −0.22 m (short-term) and −0.20 m (long-term) (±0.01 m, 95% confidence interval of statistical uncertainty). The stress response observed with SIF is supported by an analysis of in situ GPP data. Our findings provide insight into how changes in WTD of northern peatlands could affect GPP under climate change. carbon cycle; drought; hydrology; gross primary production; peatlands; solar induced chlorophyll fluorescence
Wall, Casey J.; Storelvmo, Trude; Possner, AnnaWall, C. J., T. Storelvmo, A. Possner, 2023: Global observations of aerosol indirect effects from marine liquid clouds. Atmospheric Chemistry and Physics, 23(20), 13125-13141. doi: 10.5194/acp-23-13125-2023. Interactions between aerosols and liquid clouds are one of the largest sources of uncertainty in the historical radiative forcing of climate. One widely shared goal to reduce this uncertainty is to decompose radiative anomalies arising from aerosol–cloud interactions into components associated with changes in cloud-droplet number concentration (Twomey effect), liquid-water-path adjustments, and cloud-fraction adjustments. However, there has not been a quantitative foundation for simultaneously estimating these components with global satellite observations. Here we present a method for assessing shortwave radiative flux anomalies from the Twomey effect and cloud adjustments over ocean between 55∘ S and 55∘ N. We find that larger aerosol concentrations are associated with widespread cloud brightening from the Twomey effect, a positive radiative adjustment from decreasing liquid water path in subtropical stratocumulus regions, and a negative radiative adjustment from increasing cloud fraction in the subtropics and midlatitudes. The Twomey effect and total cloud adjustment have contributed −0.77 ± 0.25 and −1.02 ± 0.43 W m−2, respectively, to the effective radiative forcing since 1850 over the domain (95 % confidence). Our findings reduce uncertainty in these components of aerosol forcing and suggest that cloud adjustments make a larger contribution to the forcing than is commonly believed.
Wang, Meihua; Su, Jing; Xu, Ying; Han, Xinyi; Peng, Nan; Ge, JinmingWang, M., J. Su, Y. Xu, X. Han, N. Peng, J. Ge, 2023: Radiative contributions of different cloud types to regional energy budget over the SACOL site. Climate Dynamics. doi: 10.1007/s00382-022-06651-0. Different cloud types have distinct radiative effects on the energy budget of the earth–atmosphere system. To better understand the cloud radiative impacts, it is necessary to distinguish the effects of different cloud types, which can be achieved through the cloud radar data that can provide cloud profiles for both day-to-day and diurnal variations. In this study, we use 6-year high-temporal resolution data from the Ka-Band Zenith Radar (KAZR) at the Semi-Arid Climate and Environment Observatory of Lanzhou University (SACOL) site to analyze the physical properties and radiative effects of main cloud types. The three types of clouds that occur most frequently at the SACOL site are single-layer ice clouds, single-layer water clouds, and double-layer clouds with the annual occurrence frequencies being 29.1%, 3.4%, and 8.3%, respectively. By using the Fu–Liou radiative transfer model simulation, it is found that the distinct diurnal variations of both the occurrence frequency and their macro- and micro-physical properties significantly affect the cloud-radiation. On annual mean, the single-layer ice clouds have a positive radiative forcing of 7.4 W/m2 to heat the system, which is a result of reflecting 12.9 W/m2 shortwave (SW) radiation and retaining 20.3 W/m2 longwave (LW) radiation; while the single-layer water clouds and double-layer clouds have much stronger SW cooling effect than LW warming effect, causing a net negative forcing of 8.5 W/m2. Although all these clouds have an overall small cooling effect of 1.1 W/m2 on the annual radiative energy budget, the significant differences of the diurnal and seasonal distributions for different type clouds can lead to distinct radiative forcing. Especially the LW warming effect induced by the exclusive ice clouds in the cold season may have an important contribution to the rapid winter warming over the semi-arid regions.
Wang, Shaoyin; Liu, Jiping; Cheng, Xiao; Greatbatch, Richard J.; Wei, Zixin; Chen, Zhuoqi; Li, HuaWang, S., J. Liu, X. Cheng, R. J. Greatbatch, Z. Wei, Z. Chen, H. Li, 2023: Separation of Atmospheric Circulation Patterns Governing Regional Variability of Arctic Sea Ice in Summer. Advances in Atmospheric Sciences, 40(12), 2344-2361. doi: 10.1007/s00376-022-2176-1. In recent decades, Arctic summer sea ice extent (SIE) has shown a rapid decline overlaid with large interannual variations, both of which are influenced by geopotential height anomalies over Greenland (GL-high) and the central Arctic (CA-high). In this study, SIE along coastal Siberia (Sib-SIE) and Alaska (Ala-SIE) is found to account for about 65% and 21% of the Arctic SIE interannual variability, respectively. Variability in Ala-SIE is related to the GL-high, whereas variability in Sib-SIE is related to the CA-high. A decreased Ala-SIE is associated with decreased cloud cover and increased easterly winds along the Alaskan coast, promoting ice—albedo feedback. A decreased Sib-SIE is associated with a significant increase in water vapor and downward longwave radiation (DLR) along the Siberian coast. The years 2012 and 2020 with minimum recorded ASIE are used as examples. Compared to climatology, summer 2012 is characterized by a significantly enhanced GL-high with major sea ice loss along the Alaskan coast, while summer 2020 is characterized by an enhanced CA-high with sea ice loss focused along the Siberian coast. In 2012, the lack of cloud cover along the Alaskan coast contributed to an increase in incoming solar radiation, amplifying ice-albedo feedback there; while in 2020, the opposite occurs with an increase in cloud cover along the Alaskan coast, resulting in a slight increase in sea ice there. Along the Siberian coast, increased DLR in 2020 plays a dominant role in sea ice loss, and increased cloud cover and water vapor both contribute to the increased DLR. Arctic sea ice; water vapor; shortwave and longwave radiation; cloud cover; Arctic circulation patterns; 云量; 北极海冰; 北极环流型; 水汽; 短波和长波辐射
Wang, Youcun; Li, Min; Jiang, Kecai; Li, Wenwen; Zhao, Qile; Fang, Rongxin; Wei, Na; Mu, RenhaiWang, Y., M. Li, K. Jiang, W. Li, Q. Zhao, R. Fang, N. Wei, R. Mu, 2023: Improving Precise Orbit Determination of LEO Satellites Using Enhanced Solar Radiation Pressure Modeling. Space Weather, 21(1), e2022SW003292. doi: 10.1029/2022SW003292. Precise orbit knowledge is a fundamental requirement for low Earth orbit (LEO) satellites. High-precision non-gravitational force modeling directly improves the overall quality of LEO precise orbit determination (POD). To address the potential systematic errors in solar radiation pressure (SRP), we introduce observed radiation data and modeled physical effects to describe the real in-flight environment of satellites. Time-dependent solar irradiance data and a highly physical shadow model are considered for SRP modeling. We develop an advanced thermal reradiation model for satellite solar panels. A set of improved non-gravitational force models is performed for LEO POD, and we discuss the benefits of the enhanced dynamic models on orbit quality and dependence on empirical parameters. The Gravity Recovery and Climate Experiment Follow-On (GRACE-FO), Jason-3, and Haiyang-2B missions are selected for the POD process. Estimated empirical acceleration and scale parameters and independent satellite laser ranging (SLR) are used to validate the final orbit solutions. The magnitude of empirical acceleration estimated in POD is reduced by 19% with the enhanced dynamic modeling, and the estimated scale factor for the SRP converges to stable and reasonable level. Furthermore, the steady-state temperature model used in thermal reradiation can effectively reduce mismodeled effects in the SRP, and the systematic linear dependency revealed by the SLR residuals is significantly reduced for the GRACE-C and Jason-3 satellites, with improvements of approximately 61% and 49%, respectively. Overall, advances are made in the explicit modeling of non-gravitational forces to pursue superior satellite orbits, suggesting a more dynamic orbit solution.
Weaver, Clark Jay; Herman, Jay; Marshak, Alexander; Lorentz, Steven R.; Yu, Yinan; Smith, Allan W.; Szabo, AdamWeaver, C. J., J. Herman, A. Marshak, S. R. Lorentz, Y. Yu, A. W. Smith, A. Szabo, 2023: Shortwave reflected energy from NISTAR and the Earth Polychromatic Imaging Camera onboard the DSCOVR spacecraft. EGUsphere, 1-18. doi: 10.5194/egusphere-2023-638. Abstract. We describe a new method for estimating the total reflected shortwave energy from the Earth Polychromatic Imaging Camera (EPIC) and compare it with direct measurements from the NIST Advanced Radiometer (NISTAR) instrument (Electrical substitution radiometer) – both are onboard the Lagrange-1 orbiting Deep Space Climate Observatory (DSCOVR). The 6 narrow-band wavelength channels (340 to 780 nm) available from EPIC provide a framework for estimating the integrated spectral energy for each EPIC pixel. The Airborne Visible/Infrared Imaging Spectrometer (AVIRIS) and the SCIAMACHY instrument provide spectral information away from the EPIC wavelengths, particularly for wavelengths longer than 780 nm. The total area-weighted reflected shortwave energy from an entire EPIC image is compared with co-temporal Band B Shortwave reflected energy observed by NISTAR. Our analysis from March to December 2017 shows the two are highly correlated with differences ranging from -10 to 10 Watts m-2. The offset bias over the entire period is less than 0.2 Watts m-2. We also compare our EPIC energy maps with the Clouds and the Earth’s Radiant Energy System (CERES) Single Scanner Footprint (SSF) Shortwave (SW) reflected energy observed within 3 hours of an EPIC image. Our EPIC-AVIRIS SW estimate is 5–20 % higher near the EPIC image center and 5–20 % lower near the image edges compared with the CERES SSF.
Wei, Jian; Ren, Tong; Yang, Ping; DiMarco, Steven F.; Huang, XiangleiWei, J., T. Ren, P. Yang, S. F. DiMarco, X. Huang, 2023: Sensitivity of Arctic Surface Temperature to Including a Comprehensive Ocean Interior Reflectance to the Ocean Surface Albedo Within the Fully Coupled CESM2. Journal of Advances in Modeling Earth Systems, 15(12), e2023MS003702. doi: 10.1029/2023MS003702. Almost all current climate models simplify the ocean surface albedo (OSA) by assuming the reflected solar energy without the ocean interior contribution. In this study, an improved ocean surface albedo scheme is incorporated into the Community Earth System Model version 2 (CESM2) to assess the sensitivity of Arctic surface temperature to including ocean interior reflectance to the OSA. Fully coupled CESM2 simulations with and without ocean interior reflectance are subsequently performed, we focus on the analysis of Arctic surface temperature responses. Incorporating ocean interior reflectance increases absorbed solar radiation and warms the ocean, enhancing seasonal heat storage and release across the Arctic Ocean, and increasing sea ice reduction and positive climate feedbacks that elevates Arctic surface temperature. Seasonal variations in air-surface temperature differences induce changes in turbulent heat flux patterns, concurrently modifying dynamic advection and moisture processes that affect boundary layer humidity and low clouds, especially in winter. Based on partitioning physical processes in the thermodynamic energy equation, surface air warming is induced primarily through positive heating anomalies of vertical advection, latent heat release, and longwave radiative forcing. Through an examination of the surface energy budget, skin temperature warming is driven predominantly by increased downward longwave radiation, positive surface albedo feedback in summer, and increased conductive heat transport from the ocean particularly in winter. Significant effects of ocean interior reflectance on the Arctic Ocean, including sea surface warming and sea ice reduction, justify the importance of ocean interior reflectance in climate models for better understanding of ongoing Arctic climate changes. ocean surface albedo; Arctic surface temperature; fully coupled climate model simulation; ocean interior reflectance
Wei, Jiangfeng; Lu, Boyan; Song, Yuanyuan; Chen, Haishan; Weng, ZhimeiWei, J., B. Lu, Y. Song, H. Chen, Z. Weng, 2023: Anthropogenic Aerosols Weaken Land–Atmosphere Coupling Over North China. Geophysical Research Letters, 50(20), e2023GL105685. doi: 10.1029/2023GL105685. North China, characterized by its strong land–atmosphere coupling, also has a high concentration of atmospheric aerosols from anthropogenic emissions. However, the impact of aerosols on land–atmosphere coupling in this region remains partially unclear. Here, we use Weather Research and Forecasting model coupled with Chemistry (WRF-Chem) experiments to show that the aerosol radiative effect weakens land–atmosphere coupling in North China. This weakening occurs across all five indexes used to measure different aspects of land–atmosphere coupling. Notably, the weakening is more pronounced for indexes that describe surface coupling compared to the index that characterizes the coupling between the planetary boundary layer (PBL) and clouds. The mechanisms underlying the aerosol influence can be primarily attributed to the reduction of land surface fluxes and their sensitivities to soil moisture, while the weakened entrainment of moisture at the upper boundary of the PBL may also contribute to the effects.
Wen, Guoyong; Marshak, AlexanderWen, G., A. Marshak, 2023: Effect of scattering angle on DSCOVR/EPIC observations. Frontiers in Remote Sensing, 4. doi: 10.3389/frsen.2023.1188056. The Earth Polychromatic Imaging Camera (EPIC) on the Deep Space Climate Observatory (DSCOVR) routinely captures reflected radiation from the whole sunlit side of the Earth in the near backward direction to monitor the changing planet. The instrument had routinely operated until 27 June 2019, when the spacecraft was placed in an extended safe hold due to degradation of an inertial navigation unit. DSCOVR returned to full operations on 2 March 2020. Since then, the range of scattering angles between the incident sunlight and sensor direction has been larger than before and the largest scattering angle reaches ∼178°, only 2° from perfect backscattering, proving a unique opportunity to study the top-of-atmosphere (TOA) reflectance under such extreme conditions. In the paper, we compare EPIC global spectral reflectances in 2021–2016. We found that there are four occasions when the scattering angle reaches about 178° and associated with them enhanced global daily average spectral reflectances in 2021. The scattering angle related reflectance enhancements are not found in 2016 data when the maximum scattering angle is about 174.5°. CERES data do not show such occasions in global daily reflected shortwave flux. As a result, those enhanced reflectance occasions are primarily due to the change in scattering angle. The enhancement due to changes in scattering angle depends strongly on wavelength, primarily because of wavelength dependence of cloud scattering phase function. Radiative transfer calculations show that the change in scattering angles has the largest impact on reflectance in the red and NIR channels at 680 nm and 780 nm and the smallest influence on reflectance in the UV channel at 388 nm, consistent with EPIC observations. The change of global average cloud amount also plays an important role in the reflectance enhancement. The influence of the cloud effect depends on whether the change is in phase or not with the change of scattering angle.
Windler, Grace; Tierney, Jessica E.; deMenocal, Peter B.Windler, G., J. E. Tierney, P. B. deMenocal, 2023: Hydroclimate Variability in the Equatorial Western Indian Ocean for the Last 250,000 Years. Paleoceanography and Paleoclimatology, 38(2), e2022PA004530. doi: 10.1029/2022PA004530. Indian Ocean sea surface temperatures impact precipitation across the basin through coupled ocean-atmosphere responses to changes in climate. To understand the hydroclimate response over the western Indian Ocean and equatorial east Africa to different forcing mechanisms, we present four new proxy reconstructions from core VM19-193 (2.98°N, 51.47°E) that span the last 250 ky. Sub-surface water temperatures (Sub-T; TEX86) show strong precessional (23 ky) variability that is primarily influenced by maximum incoming solar radiation (insolation) during the Northern Hemisphere spring season, likely indicating that local insolation dominates the upper water column at this tropical location over time. Leaf waxes, on the other hand, reflect two different precipitation signals: δ13Cwax (in phase with boreal fall insolation) is likely reflecting vegetation changes in response to local rainfall over east Africa, whereas δDprecip (primarily driven by boreal summer insolation) represents changes in regional circulation associated with the summer monsoon. Glacial-interglacial changes in ocean temperatures support glacial shelf exposure over the Maritime Continent in the eastern Indian Ocean and the subsequent weakening of the Indian Walker Circulation as a mechanism driving 100 ky climate variability across the tropical Indo-Pacific. Additionally, the 100 ky spectral power in δDprecip supports a basin-wide weakening of summer monsoon circulation in response to glacial climates. Overall, the proxy records from VM19-193 indicate that both precession and glacial-interglacial cycles exert control over hydroclimate at this tropical location. Indian Ocean; alkenone; leaf wax; Pleistocene paleoclimate; TEX86
Wong, Vox Kalai; Zhang, Chujun; Zhang, Zhuoqiong; Hao, Mingwei; Zhou, Yuanyuan; So, Shu KongWong, V. K., C. Zhang, Z. Zhang, M. Hao, Y. Zhou, S. K. So, 2023: 0.01 to 0.5 Sun is a Realistic and Alternative Irradiance Window to Analyze Urban Outdoor Photovoltaic Cells. Materials Today Energy, 101347. doi: 10.1016/j.mtener.2023.101347. Solar cells have penetrated many cities as Building Integrated Photovoltaic (BIPV) or the energy source for standalone Internet of Things (IoT) devices. Traditionally, photovoltaic (PV) cells are evaluated using 1 sun irradiance. However, in a city, factors such as air pollution, cloudiness and cell installation orientation may attenuate the receivable solar energy. Also, the power conversion efficiency (PCE) of a PV cell is highly irradiance-dependent. Evaluating urban outdoor PV cells using 1 sun irradiance could lead to inaccurate prediction of PCE and overestimated output power in actual usage. Herein, we analyzed daytime irradiances of 11 cities located across the globe. Our results show that realistic irradiances (RI) in most cities are between 0.01 and 0.5 sun, reflecting the irradiance under a cloudy to mostly sunny sky. Under such an RI window, the PCEs of 9 different PV technologies were compared. 7 PV technologies have compromised performance. 2 PV technologies, organic and perovskite PVs, show enhanced PCE under the RI window and are favorable for urban outdoor applications. The potential of powering IoT devices by these PV technologies under sub-optimal irradiance conditions in cities is also highlighted.
Wu, Jie; Pallé, Enric; Guo, Huadong; Ding, YixingWu, J., E. Pallé, H. Guo, Y. Ding, 2023: Long-term trends in albedo as seen from a lunar observatory. Advances in Space Research. doi: 10.1016/j.asr.2023.06.028. The Earth’s albedo is the fraction of short-wave solar radiation that is reflected back to space, and is key to understand the observed trends in climate change. Although there have been many observational approaches to estimate the Earth’s albedo, different methods have their own drawbacks, for example, artificial satellites have a finite life time, and are operating in a hard environment that could quickly degrade the detectors. The Moon, the only natural satellite of Earth, offers an additional platform for monitoring the Earth’s albedo. In this paper, we calculate the global TOA (top-of-atmosphere) albedo that would be observed by a theoretical observatory on the Moon, and compare it with long-term trends derived from CERES (Clouds and the Earth’s Radiant Energy System, 2000-2020) and earthshine data (1999-2017). We find that the global hourly mean albedo observed in the direction of the Moon is more variable because of the orbital movement of the Moon. However, the regional and long-term global mean albedo anomalies that would be observed by CERES and has a good general agreement by a lunar observer over 20 years the data spans. Similarly, earthshine data show a steady decline during two decades of about 0.7 W/m2 which is in line with the decline of 0.5 W/m2 that would be observed from the Moon. Besides, to compare the regional changes of albedo with CERES, the spatially-resolved decadal anomalies in the albedo are also calculated for analysis. We find that a lunar-based observatory would be capable of detecting similar changes seen from CERES. Thus, it is a a practical option to monitor the long-term trends in albedo from the point of view of capturing the variability in the TOA fluxes of the Earth’s atmosphere. CERES; earthshine; Albedo; lunar observatory
Wu, S.-N.; Soden, B. J.; Alaka Jr., G. J.Wu, S., B. J. Soden, G. J. Alaka Jr., 2023: The Influence of Radiation on the Prediction of Tropical Cyclone Intensification in a Forecast Model. Geophysical Research Letters, 50(2), e2022GL099442. doi: 10.1029/2022GL099442. This study examines the influence of radiative heating on the prediction of tropical cyclone (TC) intensification in the Hurricane Weather Research and Forecasting (HWRF) model. Previous idealized modeling and observational studies demonstrated that radiative heating can substantially modulate the evolution of TC intensity. However, the relevance of this process under realistic conditions remains unclear. Here, we use observed longwave radiative heating to explore the performance of TC forecasts in HWRF simulations. The performance of TC intensity forecasts is then investigated in the context of radiative heating forecasts. In observations and HWRF forecasts, high clouds near the TC center increase the convergence of radiative fluxes. A sharp spatial gradient (≥60 W/m2) in the flux convergence from the TC center outward toward the environment is associated with subsequent TC intensification. More accurate simulation of the spatial structure of longwave radiative heating is associated with more accurate TC intensity forecasts. radiation; radiative feedback; tropical cyclone; hurricane forecasting; hurricane model
Xia, Yan; Hu, Yongyun; Huang, Yi; Bian, Jianchun; Zhao, Chuanfeng; Lin, Jintai; Xie, Fei; Zhou, ChunjiangXia, Y., Y. Hu, Y. Huang, J. Bian, C. Zhao, J. Lin, F. Xie, C. Zhou, 2023: Stratospheric Ozone Loss Enhances Summer Precipitation Over the Southern Slope of the Tibetan Plateau. Geophysical Research Letters, 50(15), e2023GL103742. doi: 10.1029/2023GL103742. Heavy summer precipitation over the southern slope of the Tibetan Plateau has dramatic influences on water resources and hydrological disasters in South Asia. It experienced increasing trends over 1979–1996 and decreasing trends over 1996–2022, which are not yet well understood. Here we show observational and numerical evidence that stratospheric ozone has significant impacts on long-term trends of summer precipitation in this strong convection area. It is found that stratospheric ozone depletion, by modulating the lower stratospheric temperature and upper-tropospheric static stability, enhances deep convection and precipitation over the southern slope of the Tibetan Plateau. The results suggest that the ozone recovery in the future may reduce the summer precipitation over the southern slope of the Tibetan Plateau in the first half of the 21st century, which would be imperative for future water resource management in South Asia. South Asia; Tibetan Plateau; deep convection; stratospheric ozone; precipitation; long-term changes
Xiang, Baoqiang; Xie, Shang-Ping; Kang, Sarah M.; Kramer, Ryan J.Xiang, B., S. Xie, S. M. Kang, R. J. Kramer, 2023: An emerging Asian aerosol dipole pattern reshapes the Asian summer monsoon and exacerbates northern hemisphere warming. npj Climate and Atmospheric Science, 6(1), 1-10. doi: 10.1038/s41612-023-00400-8. Since the early 2010s, anthropogenic aerosols have started decreasing in East Asia (EA) while have continued to increase in South Asia (SA). Yet the climate impacts of this Asian aerosol dipole (AAD) pattern remain largely unknown. Using a state-of-the-art climate model, we demonstrate that the climate response is distinctly different between the SA aerosol increases and EA aerosol decreases. The SA aerosol increases lead to ~2.7 times stronger land summer precipitation change within the forced regions than the EA aerosol decreases. Contrastingly, the SA aerosol increases, within the tropical monsoon regime, produce weak and tropically confined responses, while the EA aerosol decreases yield a pronounced northern hemisphere warming aided by extratropical mean westerly and positive air-sea feedbacks over the western North Pacific. By scaling the observed instantaneous shortwave radiative forcing, we reveal that the recent AAD induces a pronounced northern hemisphere extratropical (beyond 30°N) warming (0.024 ± 0.010 °C decade−1), particularly over Europe (0.049 ± 0.009 °C decade−1). These findings highlight the importance of the pattern effect of forcings in driving global climate and have important implications for decadal prediction. Atmospheric dynamics; Climate and Earth system modelling
Xu, Jianglei; Liang, Shunlin; He, Tao; Ma, Han; Zhang, Yufang; Zhang, Guodong; Liang, HuiXu, J., S. Liang, T. He, H. Ma, Y. Zhang, G. Zhang, H. Liang, 2023: Variability and trends in land surface longwave radiation fluxes from six satellite and reanalysis products. International Journal of Digital Earth, 16(1), 2912-2940. doi: 10.1080/17538947.2023.2239795. Earth surface longwave radiation (SLR), including downward (DLR), upward (ULR), and net longwave radiation (NLR), significantly impacts the surface radiation budget and global climate evolution. However, the spatiotemporal variation in SLR remains poorly understood. In this study, three satellite products (GLASS-MODIS V40, GLASS-AVHRR, and CERES-SYN) and three reanalysis datasets (ERA5, MERRA-2, and GLDAS) were validated using ground measurements from 288 sites at seven observation networks. The mean biases and root mean square errors of the monthly DLR (ULR, NLR) estimates from the six products were −6.36 (−3.56, −2.86) Wm-2 and 16.63 (14.33, 13.38) Wm-2, respectively. Large differences in the spatial distribution of the SLR were mainly observed at high-latitude, high-altitude and desert/barren-covered regions. Large interannual variability was detected at high latitudes. GLASS-AVHRR and ERA5 better captured the long-term variability in DLR and ULR, whereas GLASS-AVHRR and MERRA-2 better detected trends in NLR. An increasing trend in DLR and ULR was observed between 1982 and 2015, followed by a decreasing trend from 2016 to 2021; the NLR flux did not exhibit a significant trend. Overall, the GLASS-AVHRR and ERA5 SLR estimates were more accurate and stable than those of the other products in accuracy, spatiotemporal distribution, and trend analysis. satellite remote sensing; annual mean value; long-term variability; spatiotemporal distributions; Surface longwave radiation
Xu, Jianglei; Liang, Shunlin; Ma, Han; He, Tao; Zhang, Yufang; Zhang, GuodongXu, J., S. Liang, H. Ma, T. He, Y. Zhang, G. Zhang, 2023: A daily 5-km all-sky sea-surface longwave radiation product based on statistically modified deep neural network and spatiotemporal analysis for 1981–2018. Remote Sensing of Environment, 290, 113550. doi: 10.1016/j.rse.2023.113550. Longwave radiation components, including downward, upward, and net longwave radiation (DLR, ULR, and NLR, respectively), are essential parameters in heat flux exchange across the ocean–atmosphere interface. However, few long-term, high-resolution, and accurate sea–surface longwave radiation (SSLR) products are available. We generated the first high-resolution (5-km) all-sky daily SSLR product from Advanced Very High-Resolution Radiometer (AVHRR) top-of-atmosphere observations, combined with the European Center for Medium-Range Weather Forecasts Reanalysis V5 near-surface meteorological variables and National Oceanic and Atmospheric Administration sea–surface temperatures from 1981 to 2018. We coupled the densely connected convolutional neural network and bidirectional long short-term memory neural network as a retrieval algorithm. The training dataset was generated using integrated SSLR samples from 2002 to 2012 at 437 globally distributed locations. The archived product, SSLR_AVHRR, showed a high accuracy against 81,546 buoy-based observations from eight observation networks, with an R2 of 0.96 (1.00, 0.77), root mean square error of 10.27 (4.51, 9.27) Wm−2, and mean bias error of −1.30 (0.30, −0.72) Wm−2 for DLR (ULR, NLR) retrievals. Based on SSLR_AVHRR, the global DLR (ULR) flux exhibited a significantly (p-value Climate change; AVHRR; Deep learning; Longwave radiation; Spatiotemporal variations; Trend analysis
Xu, Kuan-Man; Zhou, Yaping; Sun, Moguo; Kato, Seiji; Hu, YongxiangXu, K., Y. Zhou, M. Sun, S. Kato, Y. Hu, 2023: Observed Cloud Type-Sorted Cloud Property and Radiative Flux Changes with the Degree of Convective Aggregation from CERES Data. Journal of Geophysical Research: Atmospheres, n/a(n/a), e2023JD039152. doi: 10.1029/2023JD039152. Cloud-radiation interactions are a critical mechanism for convective self-aggregation, especially the longwave radiative cooling of low clouds and environments. In this study, two data products from CERES observations combined with MERRA-2 reanalysis are used to understand the changes of cloud properties and radiative fluxes by cloud type with the degree of convective aggregation at the 1000-km scale, which is represented by the number of cloud objects (N), simple convective aggregation index (SCAI), modified SCAI (MCAI) or convective organization potential (COP). The changes with SCAI are similar to those with N as an index, agreeing with previous studies using grid-averaged properties. For changes from weak to strong degrees of aggregation using N and SCAI, area fractions of middle- and high-level cloud types decrease by up to 4% but those of low-level cloud types increase by up to 2%, and more infrared radiation is emitted to space (2 8 W m-2) from optically thin cloud types but more solar radiation is reflected (2 4 W m-2) from optically-thick cloud types. However, using COP (MCAI to lesser extent), area fractions of optically-thick cloud types increase, which emit less infrared radiation and reflect more solar radiation, whereas the area fractions of low-level clouds decrease. These results can be explained by greater expansion of cloud object sizes for COP than MCAI/SCAI as the degree of convective aggregation increases, which also explains the difference between SCAI and MCAI pertaining to the opposite changes of optically-thick high-level clouds. These results can have implications for understanding convective self-aggregation. CERES; Radiative fluxes; Cloud properties; Convective aggregation; Flux by cloud type; Observational Analysis
Xun, Lina; Liu, Xue; Lu, Hui; Zhang, Jingjing; Yan, QingXun, L., X. Liu, H. Lu, J. Zhang, Q. Yan, 2023: Screening Approach of the Langley Calibration Station for Sun Photometers in China. Atmosphere, 14(11), 1641. doi: 10.3390/atmos14111641. A sun photometer is a type of photometer that points at the sun, and it has been playing an increasingly important role in characterizing aerosols across the world. As long as the solar photometer is accurately calibrated, the optical thickness of the aerosol can be obtained from the measured value of this device. When the calibration of a single instrument is not accurate, the inversion quantity varies greatly. The calibration constant of the sun photometer changes during its use process; thus, calibrations are frequently needed in order to ensure the accuracy of the measured value. The calibration constant of the solar photometer is usually determined using the Langley method. Internationally, AERONET has two Langley calibration stations: the Mauna Loa observatory in the United States and the Izaña observatory in Spain. So far, the International Comparison and Calibration System has been established in Beijing, similar to AERONET at GSFC, but the Langley calibration system has not yet been established. Therefore, it is necessary to select a suitable calibration station in China. This paper studies the requirements of the calibration station using the Langley method. We used long-term records of satellite-derived measurements and survey data belonging to the aerosol optical thickness data of SNPP/VIIRS, CERES, MERRA-2, etc., in order to gain a better understanding of whether these stations are suitable for calibration. From the existing astronomical observation stations, meteorological stations, and the Sun–Sky Radiometer Observation Network (SONET) observation stations in China, the qualified stations were selected. According to the statistical data from the Ali observatory, the monthly average of clear sky is 20.21 days, and it is always greater than 15 days. The monthly average of aerosol is not more than 0.15 and is less than 0.3. We believe that the atmosphere above the Ali observatory is stable, and the results show that the Ali observatory has excellent weather conditions. This study can provide a selection of calibration sites for solar photometer calibrations in China that may need to be further characterized and evaluated, and at the same time provide a method to exclude unsuitable calibration sites. calibration; atmospheric stability; boundary layer depth; langley plot method; sun photometer
Yang, Shuyue; Zhang, Xiaotong; Guan, Shikang; Zhao, Wenbo; Duan, Yanjun; Yao, Yunjun; Jia, Kun; Jiang, BoYang, S., X. Zhang, S. Guan, W. Zhao, Y. Duan, Y. Yao, K. Jia, B. Jiang, 2023: A review and comparison of surface incident shortwave radiation from multiple data sources: satellite retrievals, reanalysis data and GCM simulations. International Journal of Digital Earth, 16(1), 1332-1357. doi: 10.1080/17538947.2023.2198262. Surface incident shortwave radiation (Rs) can promote the circulation of substance and energy, and the accuracy of its estimation is of great significance for climate studies. The Rs can be acquired from satellite retrievals, reanalysis predictions and general circulation model (GCM) simulations. Although Rs estimates have been evaluated and compared in previous studies, most of them focus on evaluating the Rs estimates over specific regions using ground measurements from limited stations. Therefore, it is essential to comprehensively validate Rs estimates from multiple data sources. In this study, ground measurements of 690 stations from BSRN, GEBA, CMA, GC-NET and buoys were employed to validate the Rs estimates from seven representative products (GLASS, GEWEX-SRB, CERES-EBAF, ERA5, MERRA2, CFSR and CMIP6). The validation results indicated that the selected products overestimated Rs globally, with biases ranged from 0.48 to 21.27 W/m2. The satellite retrievals showed relatively better accuracy among seven datasets compared to ground measurements at the selected stations. Moreover, the selected seven products were all in poor accuracy at high-latitude regions with RMSEs greater than 50 W/m2. The long-term variation trends were also analyzed in this study. Downward shortwave radiation; general circulation model; reanalysis; satellite
Ye, Jiacheng; Wang, Zhuo; Yang, Fanglin; Harris, Lucas; Jensen, Tara; Miller, Douglas E.; Kalb, Christina; Adriaansen, Daniel; Li, WeiweiYe, J., Z. Wang, F. Yang, L. Harris, T. Jensen, D. E. Miller, C. Kalb, D. Adriaansen, W. Li, 2023: Evaluation and Process-Oriented Diagnosis of the GEFSv12 Reforecasts. J. Climate, 36(12), 4255-4274. doi: 10.1175/JCLI-D-22-0772.1. Abstract Three levels of process-oriented model diagnostics are applied to evaluate the Global Ensemble Forecast System version 12 (GEFSv12) reforecasts. The level-1 diagnostics are focused on model systematic errors, which reveals that precipitation onset over tropical oceans occurs too early in terms of column water vapor accumulation. Since precipitation acts to deplete water vapor, this results in prevailing negative biases of precipitable water in the tropics. It is also associated with overtransport of moisture into the mid- and upper troposphere, leading to a dry bias in the lower troposphere and a wet bias in the mid–upper troposphere. The level-2 diagnostics evaluate some major predictability sources on the extended-range time scale: the Madden–Julian oscillation (MJO) and North American weather regimes. It is found that the GEFSv12 can skillfully forecast the MJO up to 16 days ahead in terms of the Real-time Multivariate MJO indices (bivariate correlation ≥ 0.6) and can reasonably represent the MJO propagation across the Maritime Continent. The weakened and less coherent MJO signals with increasing forecast lead times may be attributed to humidity biases over the Indo-Pacific warm pool region. It is also found that the weather regimes can be skillfully predicted up to 12 days ahead with persistence comparable to the observation. In the level-3 diagnostics, we examined some high-impact weather systems. The GEFSv12 shows reduced mean biases in tropical cyclone genesis distribution and improved performance in capturing tropical cyclone interannual variability, and midlatitude blocking climatology in the GEFSv12 also shows a better agreement with the observations than in the GEFSv10. Significance Statement The latest U.S. operational weather prediction model—Global Ensemble Forecast System version 12—is evaluated using a suite of physics-based diagnostic metrics from a climatic perspective. The foci of our study consist of three levels: 1) systematic biases in physical processes, 2) tropical and extratropical extended-range predictability sources, and 3) high-impact weather systems like hurricanes and blockings. Such process-oriented diagnostics help us link the model performance to the deficiencies of physics parameterization and thus provide useful information on future model improvement.
Yost, Christopher R.; Minnis, Patrick; Sun-Mack, Sunny; Smith, William L.; Trepte, Qing Z.Yost, C. R., P. Minnis, S. Sun-Mack, W. L. Smith, Q. Z. Trepte, 2023: VIIRS Edition 1 Cloud Properties for CERES, Part 2: Evaluation with CALIPSO. Remote Sensing, 15(5), 1349. doi: 10.3390/rs15051349. The decades-long Clouds and Earth’s Radiant Energy System (CERES) Project includes both cloud and radiation measurements from instruments on the Aqua, Terra, and Suomi National Polar-orbiting Partnership (SNPP) satellites. To build a reliable long-term climate data record, it is important to determine the accuracies of the parameters retrieved from the sensors on each satellite. Cloud amount, phase, and top height derived from radiances taken by the Visible Infrared Imaging Radiometer Suite (VIIRS) on the SNPP are evaluated relative to the same quantities determined from measurements by the Cloud-Aerosol Lidar with Orthogonal Polarization (CALIOP) on the Cloud Aerosol Lidar and Infrared Pathfinder Satellite Observation (CALIPSO) spacecraft. The accuracies of the VIIRS cloud fractions are found to be as good as or better than those for the CERES amounts determined from Aqua MODerate-resolution Imaging Spectroradiometer (MODIS) data and for cloud fractions estimated by two other operational algorithms. Sensitivities of cloud fraction bias to CALIOP resolution, matching time window, and viewing zenith angle are examined. VIIRS cloud phase biases are slightly greater than their CERES MODIS counterparts. A majority of cloud phase errors are due to multilayer clouds during the daytime and supercooled liquid water clouds at night. CERES VIIRS cloud-top height biases are similar to those from CERES MODIS, except for ice clouds, which are smaller than those from CERES MODIS. CERES VIIRS cloud phase and top height uncertainties overall are very similar to or better than several operational algorithms, but fail to match the accuracies of experimental machine learning techniques. The greatest errors occur for multilayered clouds and clouds with phase misclassification. Cloud top heights can be improved by relaxing tropopause constraints, improving lapse-rate to model temperature profiles, and accounting for multilayer clouds. Other suggestions for improving the retrievals are also discussed. validation; cloud; CALIPSO; cloud height; cloud optical depth; cloud phase; cloud remote sensing; Clouds and the Earth’s Radiant Energy System (CERES); Suomi National Polar-orbiting Partnership (SNPP); Visible Infrared Imaging Radiometer Suite (VIIRS)
Yousufzai, Usama Ayub; Iqbal, Dr Javed; Afridi, FaisalYousufzai, U. A., D. J. Iqbal, F. Afridi, 2023: Analysis and Evaluation of Infrared Radiations from Top of the Atmosphere. doi: 10.2139/ssrn.4597712. The purpose of this study is to forecast infrared radiations coming from top of the atmosphere and approaches for the upper atmospheric region over 6 cities of Pakistan collected over 10 years from the Synoptic TOA and surface fluxes and clouds (SYN) Ed4A, which is the data product of Clouds and the Earth’s Radiant Energy System (CERES) used for collection of daily ten-year local weather data. This study is an attempt to investigate quantification of infrared radiations using exploratory data analysis. To predict average daily infrared variation, Artificial neural network has been used for Karachi, Thatta, Mirpurkhas, Gilgit, Kalam and Astore, cities in Pakistan. The network was trained, validated and tested for seven years with infrared flux recorded from 2011-2018. The average daily infrared flux was predicted and with the help of training and validation parameters of the hidden layer. A study of this nature will allow us to explore the shifts in the Earth's climate over time, which are influenced by several factors. For the validation of the statistical errors, Mean Squared Error (MSE), Mean Absolute Percentage Error (MAPE), correlation coefficient (R), Root Mean Square Error (RMSE), and Mean Bias Error (MBE) are determined. The statistical errors show that neural network model provide good prediction of infrared radiations for Thatta city and average predictions are made for Mirpurkhas city and Astore, Gilgit and Kalam respectively. Best fitting for correlation can be seen for Astore while Thatta, Karachi, Kalam, Gilgit and Mispurkhas come afterward. ANN Modeling; Infrared Radiations; IR Evaluation; Top of the Atmosphere; Upper Atmosphere
Yu, Laibo; Liu, Guoxiang; Zhang, RuiYu, L., G. Liu, R. Zhang, 2023: Differences Evaluation among Three Global Remote Sensing SDL Products. Remote Sensing, 15(17), 4244. doi: 10.3390/rs15174244. At present, a variety of global remote sensing surface downwelling longwave radiation (SDL) products are used for atmospheric science research; however, there are few studies on the quantitative evaluation of differences among different SDL products. In order to evaluate the differences among different SDL products quantitatively, we have selected three commonly used SDL products—Clouds and the Earth’s Radiant Energy System-Synoptic Radiative Fluxes and Clouds (CERES-SYN), the European Centre for Medium Range Weather Forecasts-Surface Radiation Budget (ECMWF-SRB) and the Global Energy and Water Exchanges Project-Surface Radiation Budget (GEWEX-SRB)—to comprehensively study in this paper. The results show that there are significant differences among the three SDL products in some areas, such as in the Arctic, the Antarctic, the Sahara, the Tibet Plateau, and Greenland. The maximum absolute root mean square error (RMSEab) in these areas is greater than 20 Wm−2, the maximum relative root mean square error (RMSEre) is greater than 20%, the maximum and minimum absolute mean bias error (MBEab) are about 20 Wm−2 and −20 Wm−2, respectively, and the maximum and minimum relative mean bias error (MBEre) are about 10% and −10%, respectively. Among the three SDL products, the difference between the ECMWF-SRB and GEWEX-SRB is the most significant. In addition, this paper also analyzed the differences among different SDL products based on three aspects. Firstly, the differences among the three SDL products show that there is significant seasonality, and the differences among different months may vary greatly. However, the differences are not sensitive to years. Secondly, there are some differences in cloud-forcing radiative fluxes (CFRFs) of different SDL products, which is also an important factor affecting the difference between different SDL products. Finally, in the process of converting high temporal resolution SDL products into monthly SDL products, data processing also affects the difference between different SDL products. CERES-SYN; GEWEX-SRB; ECMWF-SRB; surface downwelling longwave radiation
Zeng, Qi; Cheng, Jie; Guo, MengfeiZeng, Q., J. Cheng, M. Guo, 2023: A Comprehensive Evaluation of Three Global Surface Longwave Radiation Products. Remote Sensing, 15(12), 2955. doi: 10.3390/rs15122955. Surface longwave radiation is sensitive to climate change on Earth. This study first comprehensively evaluates the accuracies of surface longwave upward radiation (SLUR) and surface longwave downward radiation (SLDR) among the mainstream surface longwave (LW) radiation products (GLASS, CERES SYN and ERA5); then, the global annual mean values of surface LW radiation as well as its temporal variations from 2003 to 2020 are quantified. The ERA5 SLUR and SLDR show the best accuracies by direct validation, with biases/Stds/RMSEs of −1.05/18.34/18.37 W/m2 and −9.41/24.15/25.92 W/m2, respectively. The GLASS SLUR has the best accuracy under clear-sky conditions with a bias/Std/RMSE of −6.73/14.21/15.72 W/m2. The accuracy of the GLASS SLDR is comparable to CERES SYN. The merit of the GLASS LW radiation is that it can provide rich spatial details due to its high spatial resolution. The global annual mean SLUR is 399.77/398.92/398.19 W/m2, and that of the SLDR is 342.64/347.98/340.47 W/m2 for GLASS, CERES SYN and ERA5, respectively. The interannual variation trends for the three products produce substantially growing long-term trends for the global mean SLUR and SDLR over the globe and land, while there are almost no trends over the ocean. The long-term trends of the seasonal mean SLUR and SDLR in the Northern and Southern Hemispheres are asymmetrical. Our comprehensive evaluation and trend analysis of the mainstream surface LW radiation products can aid in understanding the global energy balance and climate change. ERA5; surface radiation budget; GLASS; surface longwave downward radiation (SLDR); CERES SYN; surface longwave upward radiation (SLUR)
Zhan, Chuan; Liang, ShunlinZhan, C., S. Liang, 2023: Generation of global 1-km daily top-of-atmosphere outgoing longwave radiation product from 2000 to 2021 using machine learning. International Journal of Digital Earth, 16(1), 2002-2012. doi: 10.1080/17538947.2023.2220611. Top-of-atmosphere (TOA) outgoing longwave radiation (OLR), a key component of the Earth’s energy budget, serves as a diagnostic of the Earth’s climate system response to incoming solar radiation. However, existing products are typically estimated using broadband sensors with coarse spatial resolutions. This paper presents a machine learning method to estimate TOA OLR by directly linking Moderate Resolution Imaging Spectroradiometer (MODIS) TOA radiances with TOA OLR determined by Clouds and the Earth’s Radiant Energy System (CERES) and other information, such as the viewing geometry, land surface temperature and cloud top temperature determined by Modern-Era Retrospective analysis for Research and Applications, Version 2 (MERRA-2). Models are built separately under clear- and cloudy-sky conditions using a gradient boosting regression tree. Independent test results show that the root mean square errors (RMSEs) of the clear-sky and cloudy-sky models for estimating instantaneous values are 4.1 and 7.8 W/m2, respectively. Real-time conversion ratios derived from CERES daily and hourly OLR data are used to convert the instantaneous MODIS OLR to daily results. Inter-comparisons of the daily results show that the RMSE of the estimated MODIS OLR is 8.9 W/m2 in East Asia. The developed high resolution dataset will be beneficial in analyzing the regional energy budget. CERES; machine learning; MODIS; Earth’s energy budget; TOA outgoing longwave radiation
Zhan, Chuan; Yang, Jing; Li, Yan; Chen, Yong; Miao, Zuohua; Zeng, Xiangyang; Li, JunZhan, C., J. Yang, Y. Li, Y. Chen, Z. Miao, X. Zeng, J. Li, 2023: Evaluation of Five Global Top-of-Atmosphere Outgoing Longwave Radiation Products. Remote Sensing, 15(15), 3722. doi: 10.3390/rs15153722. Five global monthly top-of-atmosphere (TOA) outgoing longwave radiation (OLR) products are evaluated in this study, including the products derived from the High-Resolution Infrared Radiation Sounder (HIRS), Clouds and the Earth’s Radiant Energy System (CERES), Advanced Very High Resolution Radiometer (AVHRR), the CM SAF cLoud, Albedo and surface RAdiation dataset from AVHRR data (CLARA), and the Global Energy and Water Cycle EXchanges (GEWEX) project. Results show that overall there is good consistency among these five products. Larger differences are found between GEWEX and CERES (HIRS) after (before) 2000 (RMSE ~ 5 W/m2), particularly in the tropical regions. In terms of global mean values, GEWEX shows large differences with the other products from the year 1992 to 2002, and CLARA shows large differences from the year 1979 to 1981, which are more obvious in the global ocean values. Large discrepancies among these products exist at low latitudinal bands, particularly before the year 2000. Australia and Asia (mid–low latitude part) are two typical regions in which larger differences are found. CERES; AVHRR; outgoing longwave radiation; evaluation; HIRS; CLARA; GEWEX
Zhang, Haotian; Zhao, Chuanfeng; Xia, Yan; Yang, YikunZhang, H., C. Zhao, Y. Xia, Y. Yang, 2023: North Atlantic Oscillation–Associated Variation in Cloud Phase and Cloud Radiative Forcing over the Greenland Ice Sheet. J. Climate, 36(10), 3203-3215. doi: 10.1175/JCLI-D-22-0718.1. Abstract The Greenland ice sheet (GrIS) has been losing mass at an accelerating rate in recent decades due to warming, and understanding the underlying mechanisms, such as the impacts of clouds, is essential. Using spaceborne data, this study investigates the spatial distribution of ice clouds and liquid-bearing clouds (LBCs) over the GrIS and their surface radiative forcing effects during summer daytime from 2006 to 2017, along with their characteristics during the North Atlantic Oscillation (NAO) events. Due to the perennial high-albedo surface, both ice and LBCs have a less important shortwave radiative cooling effect than in other environments. Based on the spatial variation pattern of clouds with the NAO index, the GrIS can be divided into three regions: the western, central, and eastern GrIS. During the positive NAO, the westerly wind strengthens in the western region, which causes the fraction of both ice clouds and LBCs to increase, and the cloud radiative effect at the surface increases by 2.07 W m−2; the temperature decreases in the central region, the fraction of ice clouds increases, the fraction of LBCs decreases, and the net radiative forcing is −2.05 W m−2; and sinking airflow is generated in the eastern region, both ice cloud and LBCs decrease, and the net cloud radiative effect at the surface is −1.34 W m−2. The spatial and temporal variations in clouds in different phases over the GrIS are closely related to the NAO, and the response of clouds to changes in the atmospheric circulation field during the NAO varies in different regions of the GrIS. Significance Statement This study investigates the associations between the North Atlantic Oscillation and the spatiotemporal variations in clouds, including both cloud fraction and cloud phases, and further examines the impacts of these changes on the surface radiation balance. The findings can help us improve our understanding of cloud variability and the corresponding influence on surface radiation over the GrIS, which are essential for better prediction of ice coverage over this region and for more efficient protection of ecosystems located there.
Zhang, Hua; Wang, Haibo; Liu, Yangang; Jing, Xianwen; Liu, YiZhang, H., H. Wang, Y. Liu, X. Jing, Y. Liu, 2023: Influences of Cloud Vertical Overlapping on the Calculated Cloud Albedo and Their Validation with Satellite Observations. J. Atmos. Sci., 81(1), 65-76. doi: 10.1175/JAS-D-22-0219.1. Abstract Cloud albedo is expected to influence cloud radiative forcing in addition to cloud fraction, and inadequate description of the cloud overlapping effects on the cloud fraction may influence the simulated cloud fraction, and thus the relative cloud radiative forcing (RCRF) and cloud albedo. In this study, we first present a new formula by extending that presented previously to consider multilayer clouds directly in the relationship between cloud albedo, cloud fraction, and RCRF, and then quantitatively evaluate the effects of different cloud vertical overlapping structures, represented by the decorrelation length scales (Lcf), on the simulated cloud albedos. We use the BCC_AGCM2.0_CUACE/Aero model with simultaneous validation by observations from the Clouds and the Earth’s Radiation Energy System (CERES) satellite. When Lcf < 4 km (i.e., the cloud overlap is closer to the random overlap), the simulated cloud albedos are generally in good agreement with the satellite-based albedos for December–February and June–August; when Lcf ≥ 4 km (i.e., the cloud vertical overlap is closer to the maximum overlap), the difference between simulated and observed cloud albedos became larger, due mainly to significant differences in cloud fractions and RCRF. Further quantitative analysis shows that the relative Euclidean distance, which represents the degree of overall model–observation disagreement, increases with the Lcf for all three variables (cloud albedo, cloud fraction, and RCRF), indicating the importance of cloud vertical overlapping in determining the accuracy of the calculated cloud albedo for multilayer clouds. Significance Statement The purpose of this study is presenting a new formula to consider multilayer clouds directly in the relationship between cloud albedo, cloud fraction, and relative cloud radiative forcing (RCRF). This is important because the effects of different cloud vertical overlapping structures, represented by the decorrelation length scales (Lcf), can affect the simulated cloud albedos. Our results provide a guide on the importance of cloud vertical overlapping in determining the accuracy of the calculated cloud albedo for multilayer clouds.
Zhang, Jiahui; You, Wei; Yu, Biao; Fan, DongmingZhang, J., W. You, B. Yu, D. Fan, 2023: GRACE-FO accelerometer performance analysis and calibration. GPS Solutions, 27(4), 158. doi: 10.1007/s10291-023-01487-5. As a crucial payload on dedicated gravity satellites, the accelerometer (ACC) measures the non-gravitational force acting on the satellite. The unknown scale and bias contaminate the raw ACC data, preventing the direct use in precise orbit determination (POD) and gravity recovery, and thus ACC data need to be calibrated. We analyze the performance of GRACE-FO ACC and calibrate the ACC data from 2018 to 2021 based on a step-by-step calibration method. First, we give an overview of temperature records and ACC operational modes, which reflect the operational status of the ACC. The calibration method consists of four steps: pre-calibration, two POD processes with different parameterizations, and bias fitting. Low-degree/order (10 × 10) spherical harmonic coefficients (SHCs) are estimated with scale, bias, and other dynamic parameters in POD. As an assessment, we compare the calibrated ACC data and the modeled non-gravitational force products. The average differences between them are less than 5 nm/s2 in the SRF-X direction and 6 nm/s2 in other directions. The obtained orbits based on ACC data and GPS observations are compared with precise science orbits. Furthermore, six tests show that introducing low-order/degree SHCs could effectively improve the consistency of the calibrated ACC data with non-gravitational force models and enhance orbit determination. Otherwise, empirical accelerations should be estimated with loose constraints to ensure POD results. Accelerometer calibration; GRACE-FO; Non-gravitational force; Precise orbit determination; Spaceborne GNSS
Zhang, Jianhao; Feingold, GrahamZhang, J., G. Feingold, 2023: Distinct regional meteorological influences on low-cloud albedo susceptibility over global marine stratocumulus regions. Atmospheric Chemistry and Physics, 23(2), 1073-1090. doi: 10.5194/acp-23-1073-2023. Marine stratocumuli cool the Earth effectively due to their high reflectance of incoming solar radiation and persistent occurrence. The susceptibility of cloud albedo to droplet number concentration perturbations depends strongly on large-scale meteorological conditions. Studies focused on the meteorological dependence of cloud adjustments often overlook the covariability among meteorological factors and their geographical and temporal variability. We use 8 years of satellite observations sorted by day and geographical location to show the global distribution of marine low-cloud albedo susceptibility. We find an overall cloud brightening potential for most marine warm clouds, which is more pronounced over subtropical coastal regions. A weak cloud darkening potential in the annual mean is evident over the remote SE Pacific and SE Atlantic. We show that large-scale meteorological fields from the ERA5 reanalysis data, including lower-tropospheric stability, free-tropospheric relative humidity, sea surface temperature, and boundary layer depth, have distinct covariabilities over each of the eastern subtropical ocean basins where marine stratocumuli prevail. This leads to a markedly different annual cycle in albedo susceptibility over each basin. Moreover, we find that basin-specific regional relationships between key meteorological factors and albedo susceptibilities are absent in a global analysis. Our results stress the importance of considering the geographical distinctiveness of temporal meteorological covariability when scaling up the local-to-global response of cloud albedo to aerosol perturbations.
Zhang, Pengfei; Chen, Gang; Ting, Mingfang; Ruby Leung, L.; Guan, Bin; Li, LaifangZhang, P., G. Chen, M. Ting, L. Ruby Leung, B. Guan, L. Li, 2023: More frequent atmospheric rivers slow the seasonal recovery of Arctic sea ice. Nature Climate Change, 13(3), 266-273. doi: 10.1038/s41558-023-01599-3. In recent decades, Arctic sea-ice coverage underwent a drastic decline in winter, when sea ice is expected to recover following the melting season. It is unclear to what extent atmospheric processes such as atmospheric rivers (ARs), intense corridors of moisture transport, contribute to this reduced recovery of sea ice. Here, using observations and climate model simulations, we find a robust frequency increase in ARs in early winter over the Barents–Kara Seas and the central Arctic for 1979–2021. The moisture carried by more frequent ARs has intensified surface downward longwave radiation and rainfall, caused stronger melting of thin, fragile ice cover and slowed the seasonal recovery of sea ice, accounting for 34% of the sea-ice cover decline in the Barents–Kara Seas and central Arctic. A series of model ensemble experiments suggests that, in addition to a uniform AR increase in response to anthropogenic warming, tropical Pacific variability also contributes to the observed Arctic AR changes. Climate change; Cryospheric science
Zhang, Yuan; Dewitte, Steven; Bi, ShengshanZhang, Y., S. Dewitte, S. Bi, 2023: A Model for Estimating the Earth’s Outgoing Radiative Flux from A Moon-Based Radiometer. Remote Sensing, 15(15), 3773. doi: 10.3390/rs15153773. A Moon-based radiometer can provide continuous measurements for the Earth’s full-disk broadband irradiance, which is useful for studying the Earth’s Radiation Budget (ERB) at the height of the Top of the Atmosphere (TOA). The ERB describes how the Earth obtains solar energy and emits energy to space through the outgoing broadband Short-Wave (SW) and emitted thermal Long-Wave (LW) radiation. In this work, a model for estimating the Earth’s outgoing radiative flux from the measurements of a Moon-based radiometer is established. Using the model, the full-disk LW and SW outgoing radiative flux are gained by converting the unfiltered entrance pupil irradiances (EPIs) with the help of the anisotropic characteristics of the radiances. Based on the radiative transfer equation, the unfiltered EPI time series is used to validate the established model. By comparing the simulations for a Moon-based radiometer with the satellite-based data from the National Institute of Standards and Technology Advanced Radiometer (NISTAR) and the Clouds and the Earth’s Radiant Energy System (CERES) datasets, the simulations show that the daytime SW fluxes from the Moon-based measurements are expected to vary between 194 and 205 Wm−2; these simulations agree well with the CERES data. The simulations are about 5 to 20 Wm−2 smaller than the NISTAR data. For the simulated Moon-based LW fluxes, the range is 251~287 Wm−2. The Moon-based and NISTAR fluxes are consistently 5~15 Wm−2 greater than CERES LW fluxes, and both of them also show larger diurnal variations compared with the CERES fluxes. The correlation coefficients of SW fluxes for Moon-based data and NISTAR data are 0.97, 0.63, and 0.53 for the months of July, August, and September, respectively. Compared with the SW flux, the correlation of LW fluxes is more stable for the same period and the correlation coefficients are 0.87, 0.69, and 0.61 for July to September 2017. CERES; radiation budget; radiometer; Earth observation; Moon-based; NISTAR
Zhang, Yuan; Dewitte, Steven; Bi, ShengshanZhang, Y., S. Dewitte, S. Bi, 2023: The Uncertainty Analysis of the Entrance Pupil Irradiance for a Moon-Based Earth Radiation Observation Instrument. Remote Sensing, 15(17), 4132. doi: 10.3390/rs15174132. Moon-Based Earth Radiation Observation (MERO) is expected to improve and enrich the current Earth radiation budget (ERB). For the design of MERO’s instrument and the interpretation of Moon-based data, evaluating the uncertainty of the instrument’s Entrance Pupil Irradiance (EPI) is an important part. In this work, by analyzing the effect of the Angular Distribution Models (ADMs), Earth’s Top of Atmosphere (TOA) flux, and the Earth–Moon distance on the EPI, the uncertainty of EPI is finally studied with the help of the theory of errors. Results show that the ADMs have a stronger influence on the Short-Wave (SW) EPI than those from the Long-Wave (LW). For the change of TOA flux, the SW EPI could keep the attribute of varying hourly time scales, but the LW EPI will lose its hourly-scale variability. The variation in EPI caused by the hourly change of the Moon–Earth distance does not exceed 0.13 mW∙m−2 (1σ). The maximum hourly combined uncertainty reveals that the SW and LW combined uncertainties are about 5.18 and 1.08 mW∙m−2 (1σ), respectively. The linear trend extraction of the EPI demonstrates that the Moon-based data can effectively capture the overall linear change trend of Earth’s SW and LW outgoing radiation, and the uncertainty does not change the linear trend of data. The variation of SW and LW EPIs in the long term are 0.16 mW∙m−2 (SW) and 0.23 mW∙m−2 (LW) per decade, respectively. Based on the constraint of the uncertainty, a simplified dynamic response model is built for the cavity radiometer, a kind of MERO instrument, and the results illuminate that the Cassegrain optical system and electrical substitution principle can realize the detection of Earth’s outing radiation with the sensitivity design goal 1 mW∙m−2. radiation budget; uncertainty analysis; irradiance; moon-based earth observation
Zhang, Yuanchong; Rossow, William B.Zhang, Y., W. B. Rossow, 2023: Global Radiative Flux Profile Data Set: Revised and Extended. Journal of Geophysical Research: Atmospheres, 128(5), e2022JD037340. doi: 10.1029/2022JD037340. The third generation of the radiative flux profile data product, called ISCCP-FH, is described. The revisions over the previous generation (called ISCCP-FD) include improvements in the radiative model representation of gaseous and aerosol effects, as well as a refined statistical model of cloud vertical layer variations with cloud types, and increased spatial resolution. The new product benefits from the changes in the new H-version of the ISCCP cloud products (called ISCCP-H): higher spatial resolution, revised radiance calibration and treatment of ice clouds, treatment of aerosol effects, and revision of all the ancillary atmosphere and surface property products. The ISCCP-FH product is evaluated against more direct measurements from the Clouds and the Earth’s Radiant Energy System and the Baseline Surface Radiation Network products, showing some small, overall reductions in average flux uncertainties; but the main results are similar to ISCCP-FD: the ISCCP-FH uncertainties remain ≲10 Wm−2 at the top-of-atmosphere (TOA) and ≲15 Wm−2 at surface for monthly, regional averages. The long-term variations of TOA, surface and in-atmosphere net fluxes are documented and the possible transient cloud feedback implications of a long-term change of clouds are investigated. The cloud and flux variations from 1998 to 2012 suggest a positive cloud-radiative feedback on the oceanic circulation and a negative feedback on the atmospheric circulation. This example demonstrates that the ISCCP-FH product can provide useful diagnostic information about weather-to-interannual scale variations of radiation induced by changes in cloudiness as well as atmospheric and surface properties. cloud feedback; ISCCP-FH; cloud trends; ISCCP-H; radiative flux profile; radiative flux trends
Zhao, Pengfei; Bai, Yang; Zhang, Zhaoyang; Wang, Lijun; Guo, Jianzhong; Wang, JiayaoZhao, P., Y. Bai, Z. Zhang, L. Wang, J. Guo, J. Wang, 2023: Differences in diffuse photosynthetically active radiation effects on cropland light use efficiency calculated via contemporary remote sensing and crop production models. Ecological Informatics, 73, 101948. doi: 10.1016/j.ecoinf.2022.101948. Diffuse photosynthetically active radiation (PARdiff) is instrumental to the light use efficiency (LUE) of vegetation. Accurately assessing the impact of PARdiff on crop LUE can better our understanding of the carbon cycle in cropland ecosystems. LUE estimates from six remote sensing models (including four big-leaf models and two two-leaf models) and two crop production models were compared with measured FLUXNET LUE data from cropland sites under different PARdiff fraction (FDIFFPAR) intervals. Compared with the FLUXNET observations, the Eddy Covariance-Light Use Efficiency (EC-LUEa) model exhibited the best LUE estimation (R2 = 0.250, RMSE = 0.868 gC·MJ−1, and Bias = −0.005 gC·MJ−1) owing to the use of more accurate calculation scheme of environmental stress factors. LUEs calculated from FLUXNET observational data were positively correlated with FDIFFPAR, but only LUEs simulated by the Moderate Resolution Imaging Spectroradiometer Photosynthesis (MOD17) and Two-Leaf Light Use Efficiency (TL-LUE) models increased with increasing FDIFFPAR. This is attributed to the fact that the MOD17 model divides the crop growth types into cereal and broadleaf, while the TL-LUE model considers the change of light interception with increased FDIFFPAR. Furthermore, the maximum LUE (LUEmax) increased with FDIFFPAR at FLUXNET observational sites, but the eight models could not capture the effects of PARdiff on the crop LUEmax. Among the eight models, the LUEmax–FDIFFPAR relationship simulated by the two-leaf models fluctuated because the crops were divided into sunlit and shaded leaves, while the big-leaf and crop production models used a constant LUEmax and showed a constant LUEmax–FDIFFPAR relationship. Additionally, big-leaf models performed better than two-leaf models for gross primary production (GPP) simulation in the cropland ecosystem, which is related to the planting density and vegetation structure. These results demonstrate the importance of considering the impact of FDIFFPAR on LUEmax in LUE modeling. Cropland ecosystem; Diffuse radiation fraction; Gross primary production; Light use efficiency; Maximum light use efficiency
Zhao, Xu; Yue, Xu; Tian, Chenguang; Zhou, Hao; Wang, Bin; Chen, Yuwen; Zhao, Yuan; Fu, Weijie; Hu, YihanZhao, X., X. Yue, C. Tian, H. Zhou, B. Wang, Y. Chen, Y. Zhao, W. Fu, Y. Hu, 2023: Multimodel ensemble projection of photovoltaic power potential in China by the 2060s. Atmospheric and Oceanic Science Letters, 100403. doi: 10.1016/j.aosl.2023.100403. China's demand for solar energy has been growing rapidly to meet energy transformation targets. However, the potential of solar energy is affected by weather conditions and is expected to change under climate warming. Here, the authors project the photovoltaic (PV) power potential over China under low and high emission scenarios by the 2060s, taking advantage of meteorological variables from 24 CMIP6 models and 4 PV models with varied formats. The ensemble mean of these models yields an average PV power of 277.2 KWh m−2 yr−1 during 2004–2014, with a decreasing tendency from the west to east. By 2054–2064, the national average PV power potential is projected to increase by 2.29% under a low emission scenario but decrease by 0.43% under a high emission scenario. The emission control in the former scenario significantly enhances surface solar radiation and promotes PV power in the east. On the contrary, strong warming causes inhibitions to PV power generation under the high emission scenario. Extreme warming events on average decrease the PV power potential by 0.28% under the low emission scenario and 0.44% under the high emission scenario, doubling and tripling the present-day loss, respectively. The projections reveal large benefits of controlling emissions for the future solar energy in China due to both the clean atmosphere and the moderate warming. 摘要 为了实现能源转型的目标, 中国对太阳能的需求一直在极速增长. 然而, 太阳能发电潜力受到天气条件的影响并预期在气候变暖背景下发生改变. 本文中, 作者利用第六次国际耦合模式比较计划 (CMIP6) 24个气候模式的气象变量以及4个不同形式的光伏模型, 预估了在2060年代低排放或高排放情况下中国的光伏发电潜力. 多模式集合平均光伏功率在2004–2014年为277.2 KWh m−2 yr−1, 并呈现出从西到东的下降趋势. 到2054–2064年, 在低排放情景下, 全国平均光伏发电潜力将增加2.29%, 而在高排放情景下则减少0.43%. 低排放情景的排放控制大大增强了地表太阳辐射, 促进了东部的光伏发电. 相反, 在高排放情景下, 强烈的变暖对光伏发电产生了抑制作用. 极端暖事件使光伏发电潜力在低排放情景下降低0.28%, 而高排放情景下降低0.44%, 分别相当于当代损失量的两倍和三倍. 预估表明排放控制带来的清洁空气和适度变暖对中国未来的太阳能利用是有益的. CMIP6; Climate change; Ensemble projection; Photovoltaic power; Warming extremes; 光伏发电; 极端暖事件; 气候变化; 第六次国际耦合模式比较计划; 集合预估
Zhi Xiang, Jonas Koh; Bairoliya, Sakcham; Cho, Zin Thida; Cao, BinZhi Xiang, J. K., S. Bairoliya, Z. T. Cho, B. Cao, 2023: Plastic-microbe interaction in the marine environment: Research methods and opportunities. Environment International, 171, 107716. doi: 10.1016/j.envint.2022.107716. Approximately 9 million metric tons of plastics enters the ocean annually, and once in the marine environment, plastic surfaces can be quickly colonised by marine microorganisms, forming a biofilm. Studies on plastic debris-biofilm associations, known as plastisphere, have increased exponentially within the last few years. In this review, we first briefly summarise methods and techniques used in exploring plastic-microbe interactions. Then we highlight research gaps and provide future research opportunities for marine plastisphere studies, especially, on plastic characterisation and standardised biodegradation tests, the fate of “environmentally friendly” plastics, and plastisphere of coastal habitats. Located in the tropics, Southeast Asian (SEA) countries are significant contributors to marine plastic debris. However, plastisphere studies in this region are lacking and therefore, we discuss how the unique environmental conditions in the SEA seas may affect plastic-microbe interaction and why there is an imperative need to conduct plastisphere studies in SEA marine environments. Finally, we also highlight the lack of understanding of the pathogenicity and ecotoxicological effects of plastisphere on marine ecosystems. Biofilm; Marine debris; Plastic-microbe interaction; Plastisphere
Zhi-Lun, Z. H. A. N. G.; Feng-Ming, H. U. I.; Vihma, Timo; Granskog, Mats A.; Cheng, Bin; Zhuo-Qi, C. H. E. N.; Cheng, XiaoZhi-Lun, Z. H. A. N. G., H. U. I. Feng-Ming, T. Vihma, M. A. Granskog, B. Cheng, C. H. E. N. Zhuo-Qi, X. Cheng, 2023: On the turbulent heat fluxes: A comparison among satellite-based estimates, atmospheric reanalyses, and in-situ observations during the winter climate over Arctic sea ice. Advances in Climate Change Research. doi: 10.1016/j.accre.2023.04.004. The surface energy budget is crucial for Arctic sea ice mass balance calculation and climate systems, among which turbulent heat fluxes significantly affect the air–sea exchanges of heat and moisture in the atmospheric boundary layer. Satellite observations (e.g. CERES and APP-X) and atmospheric reanalyses (e.g., ERA5) are often used to represent components of the energy budget at regional and pan-Arctic scales. However, the uncertainties of the satellite-based turbulent heat fluxes are largely unknown, and cross-comparisons with reanalysis data and in-situ observations are limited. In this study, satellite-based turbulent heat fluxes were assessed against in-situ observations from the N-ICE2015 drifting ice station (north of Svalbard, January–June 2015) and ERA5 reanalysis. The turbulent heat fluxes were calculated by two approaches using the satellite-based ice surface temperature and radiative fluxes, surface atmospheric parameters from ERA5, and snow/sea ice thickness from the pan-Arctic Ice Ocean Modeling and Assimilation System (PIOMAS). We found that the bulk-aerodynamic formula based results could better capture the variations of turbulent heat fluxes, while the maximum entropy production based estimates are comparable with ERA5 in terms of root-mean-square error (RMSE). CERES-based estimates outperform the APP-X-based ones but ERA5 performs the best in all seasons (RMSE of 18 and 7 W m−2 for sensible and latent heat flux, respectively). The air–ice temperature/humidity differences and the surface radiation budget were found the primary driving factors in the bulk-formula method and maximum entropy production (MEP) method, respectively. Furthermore, errors in the surface and near-surface temperature and humidity explain almost 50% of the uncertainties in the estimates based on the bulk-formula, whereas errors in the net radiative fluxes explain more than 50% of the uncertainties in the MEP-based results. Arctic sea ice; Bulk-aerodynamic formula; Maximum entropy production; Reanalysis; Satellite observation; Surface energy budget; Turbulent heat flux
Zhong, Ziqian; He, Bin; Chen, Hans W.; Chen, Deliang; Zhou, Tianjun; Dong, Wenjie; Xiao, Cunde; Xie, Shang-ping; Song, Xiangzhou; Guo, Lanlan; Ding, Ruiqiang; Zhang, Lixia; Huang, Ling; Yuan, Wenping; Hao, Xingming; Ji, Duoying; Zhao, XiangZhong, Z., B. He, H. W. Chen, D. Chen, T. Zhou, W. Dong, C. Xiao, S. Xie, X. Song, L. Guo, R. Ding, L. Zhang, L. Huang, W. Yuan, X. Hao, D. Ji, X. Zhao, 2023: Reversed asymmetric warming of sub-diurnal temperature over land during recent decades. Nature Communications, 14(1), 7189. doi: 10.1038/s41467-023-43007-6. In the latter half of the twentieth century, a significant climate phenomenon “diurnal asymmetric warming” emerged, wherein global land surface temperatures increased more rapidly during the night than during the day. However, recent episodes of global brightening and regional droughts and heatwaves have brought notable alterations to this asymmetric warming trend. Here, we re-evaluate sub-diurnal temperature patterns, revealing a substantial increase in the warming rates of daily maximum temperatures (Tmax), while daily minimum temperatures have remained relatively stable. This shift has resulted in a reversal of the diurnal warming trend, expanding the diurnal temperature range over recent decades. The intensified Tmax warming is attributed to a widespread reduction in cloud cover, which has led to increased solar irradiance at the surface. Our findings underscore the urgent need for enhanced scrutiny of recent temperature trends and their implications for the wider earth system. Environmental impact; Climate-change mitigation
Zhou, Lu; Heuzé, Céline; Mohrmann, MartinZhou, L., C. Heuzé, M. Mohrmann, 2023: Sea Ice Production in the 2016 and 2017 Maud Rise Polynyas. Journal of Geophysical Research: Oceans, 128(2), e2022JC019148. doi: 10.1029/2022JC019148. Sea ice production within polynyas, an outcome of the atmosphere-ice-ocean interaction, is a major source of dense water and hence key to the global overturning circulation, but is poorly quantified over open-ocean polynyas. Using the two recent extensive open-ocean polynyas within the wider Maud Rise region of the Weddell Sea in 2016 and 2017, we here explore the sea ice energy budget and estimate their sea ice production based on satellite retrievals, in-situ hydrographic observations and the Japanese 55-year Reanalysis. We find that the oceanic heat flux amounts to 36.1 and 30.7 W m−2 within the 2016 and 2017 polynyas, respectively. Especially the 2017 open-ocean polynya produced nearly 200 km3 of new sea ice, which is comparable to the production in the largest Antarctic coastal polynyas. Finally, we determine that ice production is highly correlated with and sensitive to skin temperature and wind speed, which affect the turbulent fluxes. It is also strongly sensitive to uncertainties in the sea ice concentration and 1,000 hPa temperature, which all urgently need to be better monitored at high latitudes. Lastly, more process-oriented campaigns are required to further elucidate the role of open-ocean polynya on the local and global ocean circulations. energy budget; Maud Rise polynya; ocean heat flux; sea ice production
Zhou, Wenyu; Leung, L. Ruby; Siler, Nicholas; Lu, JianZhou, W., L. R. Leung, N. Siler, J. Lu, 2023: Future precipitation increase constrained by climatological pattern of cloud effect. Nature Communications, 14(1), 6363. doi: 10.1038/s41467-023-42181-x. The fractional increase in global mean precipitation ($$\triangle \bar{P}/\bar{P}$$) is a first-order measure of the hydrological cycle intensification under anthropogenic warming. However, $$\triangle \bar{P}/\bar{P}$$varies by a factor of more than three among model projections, hindering credible assessments of the associated climate impacts. The uncertainty in $$\triangle \bar{P}/\bar{P}$$stems from uncertainty in both hydrological sensitivity (global mean precipitation increase per unit warming) and climate sensitivity (global mean temperature increase per forcing). Here, by investigating hydrological and climate sensitivities in a unified surface-energy-balance perspective, we find that both sensitivities are significantly correlated with surface shortwave cloud feedback, which is further linked to the climatological pattern of cloud shortwave effect. The observed pattern of cloud effect thus constrains both sensitivities and consequently constrains $$\triangle \bar{P}/\bar{P}$$. The 5%-95% uncertainty range of $$\triangle \bar{P}/\bar{P}$$from 1979-2005 to 2080-2100 under the high-emission (moderate-emission) scenario is constrained from 6.34$$\pm$$3.53% (4.19$$\pm$$2.28%) in the raw ensemble-model projection to 7.03$$\pm$$2.59% (4.63$$\pm$$1.71%). The constraint thus suggests a higher most-likely $$\triangle \bar{P}/\bar{P}$$and reduces the uncertainty by ~25%, providing valuable information for impact assessments. Atmospheric dynamics; Projection and prediction; Hydrology
Zhou, Xiaoli; Feingold, GrahamZhou, X., G. Feingold, 2023: Impacts of Mesoscale Cloud Organization on Aerosol-Induced Cloud Water Adjustment and Cloud Brightness. Geophysical Research Letters, 50(13), e2023GL103417. doi: 10.1029/2023GL103417. The role of mesoscale cellular convection (MCC) in regulating aerosol-induced cloud brightness remains unaddressed. Using 7 years of satellite-based observations of cloud water adjustment to aerosol-induced perturbations for closed MCCs across different sizes (8, 16, 32, and 64 km) over the North Atlantic Ocean, we show that MCC cell-size plays a nontrivial role in regulating aerosol-induced cloud brightness via cloud water adjustment. In cells that are primarily non-precipitating, the adjustment in small-scale MCCs can be 10 times more negative than in large-scale MCCs, consistent with stronger evaporation via cloud top entrainment. Consequently, the response of cloud brightness is significantly stronger for large-scale MCCs. We also find notable intra-cell co-variability between cloud liquid water path (LWP) and drop concentration (Nd) within MCCs that varies with cell size. Erroneously considering such co-variability as a LWP response to Nd can lead to a significant positive bias, especially for small scale MCCs.
Zo, Il-Sung; Jee, Joon-Bum; Lee, Kyu-Tae; Lee, Kwon-Ho; Lee, Mi-Young; Kwon, Yong-SoonZo, I., J. Jee, K. Lee, K. Lee, M. Lee, Y. Kwon, 2023: Radiative Energy Budget for East Asia Based on GK-2A/AMI Observation Data. Remote Sensing, 15(6), 1558. doi: 10.3390/rs15061558. The incident and emitted radiative energy data for the top of the atmosphere (TOA) are essential in climate research. Since East Asia (11–61°N, 80–175°E) is complexly composed of land and ocean, real-time satellite data are used importantly for analyzing the detailed energy budget or climate characteristics of this region. Therefore, in this study, the radiative energy budget for East Asia, during the year 2021, was analyzed using GEO-KOMPSAT-2A/Advanced Metrological Imager (GK-2A/AMI) and the European Centre for Medium-range Weather Forecasts reanalysis (ERA5) data. The results showed that the net fluxes for the TOA and surface were −4.09 W·m−2 and −8.24 W·m−2, respectively. Thus, the net flux difference of 4.15 W·m−2 between TOA and surface implied atmospheric warming. These results, produced by GK-2A/AMI, were well-matched with the ERA5 data. However, they varied with surface characteristics; the atmosphere over ocean areas warmed because of the large amounts of longwave radiation emitted from surfaces, while the atmosphere over the plain area was relatively balanced and the atmosphere over the mountain area was cooled because large amount of longwave radiation was emitted to space. Although the GK2A/AMI radiative products used for this study have not yet been sufficiently compared with surface observation data, and the period of data used was only one year, they were highly correlated with the CERES (Clouds and the Earth’s Radiant Energy System of USA), HIMAWARI/AHI (Geostationary Satellite of Japan), and ERA5 data. Therefore, if more GK-2A/AMI data are accumulated and analyzed, it could be used for the analysis of radiant energy budget and climate research for East Asia, and it will be an opportunity to greatly increase the utilization of total meteorological products of 52 types, including radiative products. ERA5; East Asia; European center for medium-range weather forecasts reanalysis data; Geo-KOMPSAT-2A; geostationary-Korean multi-purpose satellite-2A; GK-2A/AMI; radiative energy budget
Andersen, Hendrik; Cermak, Jan; Zipfel, Lukas; Myers, Timothy A.Andersen, H., J. Cermak, L. Zipfel, T. A. Myers, 2022: Attribution of Observed Recent Decrease in Low Clouds Over the Northeastern Pacific to Cloud-Controlling Factors. Geophysical Research Letters, 49(3), e2021GL096498. doi: 10.1029/2021GL096498. Marine low clouds cool the Earth's climate, with their coverage (LCC) being controlled by their environment. Here, an observed significant decrease of LCC in the northeastern Pacific over the past two decades is linked quantitatively to changes in cloud-controlling factors. In a comparison of different statistical and machine learning methods, a decrease in the inversion strength and near-surface winds, and an increase in sea surface temperatures (SSTs) are unanimously shown to be the main causes of the LCC decrease. While the decreased inversion strength leads to more entrainment of dry free-tropospheric air, the increasing SSTs are shown to lead to an increased vertical moisture gradient that enhances evaporation when entrainment takes place. While the LCC trend is likely driven by natural variability, the trend-attribution framework developed here can be used with any method in future analyses. We find the choice of predictors is more important than the method. satellite data; machine learning; low clouds; trend analysis; cloud-controlling factors
Andrews, Timothy; Bodas-Salcedo, Alejandro; Gregory, Jonathan M.; Dong, Yue; Armour, Kyle C.; Paynter, David; Lin, Pu; Modak, Angshuman; Mauritsen, Thorsten; Cole, Jason N. S.; Medeiros, Brian; Benedict, James J.; Douville, Hervé; Roehrig, Romain; Koshiro, Tsuyoshi; Kawai, Hideaki; Ogura, Tomoo; Dufresne, Jean-Louis; Allan, Richard P.; Liu, ChunleiAndrews, T., A. Bodas-Salcedo, J. M. Gregory, Y. Dong, K. C. Armour, D. Paynter, P. Lin, A. Modak, T. Mauritsen, J. N. S. Cole, B. Medeiros, J. J. Benedict, H. Douville, R. Roehrig, T. Koshiro, H. Kawai, T. Ogura, J. Dufresne, R. P. Allan, C. Liu, 2022: On the Effect of Historical SST Patterns on Radiative Feedback. Journal of Geophysical Research: Atmospheres, 127(18), e2022JD036675. doi: 10.1029/2022JD036675. We investigate the dependence of radiative feedback on the pattern of sea-surface temperature (SST) change in 14 Atmospheric General Circulation Models (AGCMs) forced with observed variations in SST and sea-ice over the historical record from 1871 to near-present. We find that over 1871–1980, the Earth warmed with feedbacks largely consistent and strongly correlated with long-term climate sensitivity feedbacks (diagnosed from corresponding atmosphere-ocean GCM abrupt-4xCO2 simulations). Post 1980, however, the Earth warmed with unusual trends in tropical Pacific SSTs (enhanced warming in the west, cooling in the east) and cooling in the Southern Ocean that drove climate feedback to be uncorrelated with—and indicating much lower climate sensitivity than—that expected for long-term CO2 increase. We show that these conclusions are not strongly dependent on the Atmospheric Model Intercomparison Project (AMIP) II SST data set used to force the AGCMs, though the magnitude of feedback post 1980 is generally smaller in nine AGCMs forced with alternative HadISST1 SST boundary conditions. We quantify a “pattern effect” (defined as the difference between historical and long-term CO2 feedback) equal to 0.48 ± 0.47 [5%–95%] W m−2 K−1 for the time-period 1871–2010 when the AGCMs are forced with HadISST1 SSTs, or 0.70 ± 0.47 [5%–95%] W m−2 K−1 when forced with AMIP II SSTs. Assessed changes in the Earth's historical energy budget agree with the AGCM feedback estimates. Furthermore satellite observations of changes in top-of-atmosphere radiative fluxes since 1985 suggest that the pattern effect was particularly strong over recent decades but may be waning post 2014. climate sensitivity; climate models; observations; climate feedback; pattern effect; historical record
Aparna, A. R.; Girishkumar, M. S.Aparna, A. R., M. S. Girishkumar, 2022: Mixed layer heat budget in the eastern equatorial Indian Ocean during the two consecutive positive Indian Ocean dipole events in 2018 and 2019. Climate Dynamics. doi: 10.1007/s00382-021-06099-8. The Indian Ocean hosted a strong positive Indian Ocean Dipole (pIOD) event in 2019–2020, and a weak event in 2018–2019, such as the magnitude of the cold sea surface temperature anomaly (SSTA) during June-December in the former case is a factor of two higher (~ − 1.5 °C) than the latter (~ − 0.75 °C) at the western periphery of the eastern IOD zone at 5° S, 95° E. The plausible mechanisms responsible for this difference in the SSTA between these two events are examined using the mixed layer heat budget estimate using the moored buoy measurements. It is found that the enhanced cooling during June-December in 2019–2020 is determined primarily by the anomalous cooling due to the vertical processes associated with the combined effect of the anomalous thin barrier layer (BL), shallow thermocline, weak near-surface stratification, and strong wind speed induced vertical mixing, and secondarily by the enhancement in the latent heat flux (LHF) loss from the ocean. Conversely, the magnitude of cooling due to the vertical processes is much smaller in 2018–2019 due to the near-climatological states such as a thick BL, deep thermocline, and weak wind speed. During these events, the warming tendency by the horizontal advection dampens the cooling tendency associated with the vertical processes and LHF. These characteristics are distinct from the past study that suggested that the horizontal advection was responsible for the cool SSTA at the exact location during an extreme pIOD event in 2006–2007.
Atlas, R.l.; Bretherton, C.s.; Khairoutdinov, M.f.; Blossey, P.n.Atlas, R., C. Bretherton, M. Khairoutdinov, P. Blossey, 2022: Hallett-Mossop rime splintering dims cumulus clouds over the Southern Ocean: New insight from nudged global storm-resolving simulations. AGU Advances, n/a(n/a), e2021AV000454. doi: 10.1029/2021AV000454. In clouds containing both liquid and ice with temperatures between − 3°C and − 8°C, liquid droplets collide with large ice crystals, freeze, and shatter, producing a plethora of small ice splinters. This process, known as Hallett-Mossop rime splintering, and other forms of secondary ice production, can cause clouds to reflect less sunlight and to have shorter lifetimes. We show its impact on Southern Ocean shallow cumuli using a novel suite of five global storm-resolving simulations, which partition the Earth’s atmosphere into 2-4 km wide columns. We evaluate simulated clouds and radiation over the Southern Ocean with aircraft observations from the Southern Ocean Clouds, Radiation, Aerosol Transport Experimental Study (SOCRATES), and satellite observations from Clouds and the Earth’s Radiant Energy System (CERES) and Himawari. Simulations with large concentrations of ice crystals in boundary layer clouds, which agree better with SOCRATES observations, have reduced mixed-phase cumulus cloud cover and weaker shortwave cloud radiative effects that are less biased compared with CERES. Using a pair of simulations differing only in their treatment of Hallett-Mossop rime splintering, we show that including this process increases ice crystal concentrations in cumulus clouds and weakens shortwave cloud radiative effects over the Southern Ocean by 10 W m−2. We also demonstrate the key role that global storm-resolving models can play in detangling the effects of clouds on Earth’s climate across scales, making it possible to trace the impact of changes in individual cumulus cloud anvils (10 km2) on the radiative budget of the massive Southern Ocean basin (108 km2). Boundary layer; Southern Ocean; Global cloud-resolving simulations; Hallett-Mossop rime splintering; Open cell cumuli; Secondary ice production
Atmoko, Dwi; Lin, Tang-HuangAtmoko, D., T. Lin, 2022: Sea Salt Aerosol Identification Based on Multispectral Optical Properties and Its Impact on Radiative Forcing over the Ocean. Remote Sensing, 14(13), 3188. doi: 10.3390/rs14133188. The ground-based measurement of sea salt (SS) aerosol over the ocean requires the massive utilization of satellite-derived aerosol products. In this study, n-order spectral derivatives of aerosol optical depth (AOD) based on wavelength were examined to characterize SS and other aerosol types in terms of their spectral dependence related to their optical properties such as particle size distributions and complex refractive indices. Based on theoretical simulations from the second simulation of a satellite signal in the solar spectrum (6S) model, AOD spectral derivatives of SS were characterized along with other major types including mineral dust (DS), biomass burning (BB), and anthropogenic pollutants (APs). The approach (normalized derivative aerosol index, NDAI) of partitioning aerosol types with intrinsic values of particle size distribution and complex refractive index from normalized first- and second-order derivatives was applied to the datasets from a moderate resolution imaging spectroradiometer (MODIS) as well as by the ground-based aerosol robotic network (AERONET). The results after implementation from multiple sources of data indicated that the proposed approach could be highly effective for identifying and segregating abundant SS from DS, BB, and AP, across an ocean. Consequently, each aerosol’s shortwave radiative forcing and its efficiency could be further estimated in order to predict its impact on the climate. particle size; sea salt aerosol; aerosol optical depth (AOD); complex refractive index; normalized derivative aerosol index (NDAI); spectral derivatives
Bai, Jianhui; Zong, Xuemei; Lanconelli, Christian; Lupi, Angelo; Driemel, Amelie; Vitale, Vito; Li, Kaili; Song, TaoBai, J., X. Zong, C. Lanconelli, A. Lupi, A. Driemel, V. Vitale, K. Li, T. Song, 2022: Long-Term Variations of Global Solar Radiation and Its Potential Effects at Dome C (Antarctica). International Journal of Environmental Research and Public Health, 19(5), 3084. doi: 10.3390/ijerph19053084. An empirical model to predict hourly global solar irradiance under all-sky conditions as a function of absorbing and scattering factors has been applied at the Dome C station in the Antarctic, using measured solar radiation and meteorological variables. The calculated hourly global solar irradiance agrees well with measurements at the ground in 2008–2011 (the model development period) and at the top of the atmosphere (TOA). This model is applied to compute global solar irradiance at the ground and its extinction in the atmosphere caused by absorbing and scattering substances during the 2006–2016 period. A sensitivity study shows that the responses of global solar irradiance to changes in water vapor and scattering factors (expressed by water vapor pressure and S/G, respectively; S and G are diffuse and global solar irradiance, respectively) are nonlinear and negative, and that global solar irradiance is more sensitive to changes in scattering than to changes in water vapor. Applying this empirical model, the albedos at the TOA and the surface in 2006–2016 are estimated and found to agree with the satellite-based retrievals. During 2006–2016, the annual mean observed and estimated global solar exposures decreased by 0.05% and 0.09%, respectively, and the diffuse exposure increased by 0.68% per year, associated with the yearly increase of the S/G ratio by 0.57% and the water vapor pressure by 1.46%. The annual mean air temperature increased by about 1.80 °C over the ten years, and agrees with the warming trends for all of Antarctica. The annual averages were 316.49 Wm−2 for the calculated global solar radiation, 0.332 for S/G, −46.23 °C for the air temperature and 0.10 hPa for the water vapor pressure. The annual mean losses of solar exposure due to absorbing and scattering substances and the total loss were 4.02, 0.19 and 4.21 MJ m−2, respectively. The annual mean absorbing loss was much larger than the scattering loss; their contributions to the total loss were 95.49% and 4.51%, respectively, indicating that absorbing substances are dominant and play essential roles. The annual absorbing, scattering and total losses increased by 0.01%, 0.39% and 0.28% per year, respectively. The estimated and satellite-retrieved annual albedos increased at the surface. The mechanisms of air-temperature change at two pole sites, as well as a mid-latitude site, are discussed. albedo; energy balance; air temperature; climate and climate change; absorbing and scattering substances
Bai, Jianhui; Zong, Xuemei; Ma, Yaoming; Wang, Binbin; Zhao, Chuanfeng; Yang, Yikung; Guang, Jie; Cong, Zhiyuan; Li, Kaili; Song, TaoBai, J., X. Zong, Y. Ma, B. Wang, C. Zhao, Y. Yang, J. Guang, Z. Cong, K. Li, T. Song, 2022: Long-Term Variations in Global Solar Radiation and Its Interaction with Atmospheric Substances at Qomolangma. International Journal of Environmental Research and Public Health, 19(15), 8906. doi: 10.3390/ijerph19158906. An empirical model to estimate global solar radiation was developed at Qomolangma Station using observed solar radiation and meteorological parameters. The predicted hourly global solar radiation agrees well with observations at the ground in 2008–2011. This model was used to calculate global solar radiation at the ground and its loss in the atmosphere due to absorbing and scattering substances in 2007–2020. A sensitivity analysis shows that the responses of global solar radiation to changes in water vapor and scattering factors (expressed as water-vapor pressure and the attenuation factor, AF, respectively) are nonlinear, and global solar radiation is more sensitive to changes in scattering than to changes in absorption. Further applying this empirical model, the albedos at the top of the atmosphere (TOA) and the surface in 2007–2020 were computed and are in line with satellite-based retrievals. During 2007–2020, the mean estimated annual global solar radiation increased by 0.22% per year, which was associated with a decrease in AF of 1.46% and an increase in water-vapor pressure of 0.37% per year. The annual mean air temperature increased by about 0.16 °C over the 14 years. Annual mean losses of solar radiation caused by absorbing and scattering substances and total loss were 2.55, 0.64, and 3.19 MJ m−2, respectively. The annual average absorbing loss was much larger than the scattering loss; their contributions to the total loss were 77.23% and 22.77%, indicating that absorbing substances play significant roles. The annual absorbing loss increased by 0.42% per year, and scattering and total losses decreased by 2.00% and 0.14% per year, respectively. The estimated and satellite-derived annual albedos increased at the TOA and decreased at the surface. This study shows that solar radiation and its interactions with atmospheric absorbing and scattering substances have played key but different roles in regional climate and climate change at the three poles. energy; air temperature; absorbing and scattering; climate and climate change; wind speed
Barrientos-Velasco, Carola; Deneke, Hartwig; Hünerbein, Anja; Griesche, Hannes J.; Seifert, Patric; Macke, AndreasBarrientos-Velasco, C., H. Deneke, A. Hünerbein, H. J. Griesche, P. Seifert, A. Macke, 2022: Radiative closure and cloud effects on the radiation budget based on satellite and ship-borne observations during the Arctic summer research cruise PS106. Atmospheric Chemistry and Physics Discussions, 1-71. doi: 10.5194/acp-2021-1004. Abstract. For understanding Arctic climate change, it is critical to quantify and address uncertainties in climate data records on clouds and radiative fluxes derived from long-term passive satellite observations. A unique set of observations collected during the research vessel Polarstern PS106 expedition (28 May to 16 July 2017) by the OCEANET facility is exploited here for this purpose and compared with the CERES SYN1deg Ed. 4.1 satellite remote sensing products. Mean cloud fraction (CF) of 86.7 % for CERES and 76.1 % for OCEANET were found for the entire cruise. The difference of CF between both data sets is due to different spatial resolution and momentary data gaps due to technical limitations of the set of ship-borne instruments. A comparison of radiative fluxes during clear-sky conditions enables radiative closure for CERES products by means of independent radiative transfer simulations. Several challenges were encountered to accurately represent clouds in radiative transfer under cloudy conditions, especially for ice-containing clouds and low-level stratus (LLS) clouds. During LLS conditions, the OCEANET retrievals were in particular compromised by the altitude detection limit of 155 m of the cloud radar. Radiative fluxes from CERES show a good agreement with ship observations, having a bias (standard deviation) of −6.0 (14.6) W m−2 and 23.1 (59.3) W m−2 for the downward longwave (LW) and shortwave (SW) fluxes, respectively. Based on CERES products, mean values of the radiation budget and the cloud radiative effect (CRE) were determined for the PS106 cruise track and the central Arctic region (70°–90° N). For the period of study, the results indicate a strong influence of the SW flux in the radiation budget, which is reduced by clouds leading to a net surface CRE of −8.8 W m−2 and −9.3 W m−2 along the PS106 cruise and for the entire Arctic, respectively. The similarity of local and regional CRE supports that the PS106 cloud observations can be considered to be representative of Arctic cloudiness during early summer.
Baxter, Ian; Ding, QinghuaBaxter, I., Q. Ding, 2022: An Optimal Atmospheric Circulation Mode in the Arctic Favoring Strong Summertime Sea Ice Melting and Ice–Albedo Feedback. J. Climate, 35(20), 3027-3045. doi: 10.1175/JCLI-D-21-0679.1. Abstract The rapid decline of summer Arctic sea ice over the past few decades has been driven by a combination of increasing greenhouse gases and internal variability of the climate system. However, uncertainties remain regarding spatial and temporal characteristics of the optimal internal atmospheric mode that most favors summer sea ice melting on low-frequency time scales. To pinpoint this mode, we conduct a suite of simulations in which atmospheric circulation is constrained by nudging tropospheric Arctic (60°–90°N) winds within the Community Earth System Model, version 1 (CESM1), to those from reanalysis. Each reanalysis year is repeated for over 10 model years using fixed greenhouse gas concentrations and the same initial conditions. Composites show the strongest September sea ice losses are closely preceded by a common June–August (JJA) barotropic anticyclonic circulation in the Arctic favoring shortwave absorption at the surface. Successive years of strong wind-driven melting also enhance declines in Arctic sea ice through enhancement of the ice–albedo feedback, reaching a quasi-equilibrium response after repeated wind forcing for over 5–6 years, as the effectiveness of the wind-driven ice–albedo feedback becomes saturated. Strong melting favored by a similar wind pattern as observations is detected in a long preindustrial simulation and 400-yr paleoclimate reanalysis, suggesting that a summer barotropic anticyclonic wind pattern represents the optimal internal atmospheric mode maximizing sea ice melting in both the model and natural world over a range of time scales. Considering strong contributions of this mode to changes in Arctic climate, a better understanding of its origin and maintenance is vital to improving future projections of Arctic sea ice.
Bhattarai, Santosh; Ziebart, Marek; Springer, Tim; Gonzalez, Francisco; Tobias, GuillermoBhattarai, S., M. Ziebart, T. Springer, F. Gonzalez, G. Tobias, 2022: High-precision physics-based radiation force models for the Galileo spacecraft. Advances in Space Research, 69(12), 4141-4154. doi: 10.1016/j.asr.2022.04.003. We present two new high-precision physics-based radiation force models for the In-Orbit Validation (IOV) and Full Operational Capability (FOC) spacecraft (s/c) of the Galileo Global Navigation Satellite System (GNSS). In both cases, the s/c bus surfaces are covered in material types, i.e., Laser Retro-reflector Array (LRA), Optical Surface Reflector (OSR) and Single-Layer Insulation (SLI) coverings, that were either not encountered or not specifically dealt with in earlier work. To address this, a number of modelling enhancements were proposed and tested, including: a specific model to account for the direct and reflected solar radiation force for LRA surfaces; a design update of the bus model computation process to allow for more than one insulation material; a specific thermal force model for OSR surfaces; a thermal force model for the Navigation Antenna (NAVANT) surface that includes a temperature model derived from on-orbit temperature measurements; and force models to account for thermal emissions from radiator panels on the +X and ±Y surfaces for both IOV and FOC, and on the -Z surface for FOC only. In the UCL2+ model each of these effects are accounted for. The theoretical impact of each modelling concept introduced is assessed, individually, by considering the magnitude of its effect in acceleration-space. The impact on orbit accuracy is confirmed through a rigorous set of Precise Orbit Determination (POD) validation tests, in which observations from all active Galileo s/c over two full years, 2017 and 2018, including during eclipsing periods, are included in the analysis. The UCL2+ approach results in day boundary discontinuities of 22 mm, 17 mm and 27 mm in the radial, across-track and along-track components, respectively. Analysis of the one-way Satellite Laser Ranging (SLR) residuals suggests that radial accuracy at better than 1 cm (3.7 mm mean residuals) and precision at better than 2 cm (17 mm root mean square (rms) error) is achievable with the UCL2+ model. Precise orbit determination; Full operational capability; Galileo; Global Navigation Satellite Systems (GNSS); In-orbit validation; Radiation force modelling
Blanchard-Wrigglesworth, Edward; Webster, Melinda; Boisvert, Linette; Parker, Chelsea; Horvat, ChristopherBlanchard-Wrigglesworth, E., M. Webster, L. Boisvert, C. Parker, C. Horvat, 2022: Record Arctic Cyclone of January 2022: Characteristics, Impacts, and Predictability. Journal of Geophysical Research: Atmospheres, 127(21), e2022JD037161. doi: 10.1029/2022JD037161. Arctic cyclones are a fundamental component of Arctic climate, influencing atmospheric heat and moisture transport into the region and surface energy, moisture, and momentum fluxes. Arctic cyclones can also drive changes in sea ice and energize ocean waves. Here we investigate a record low sea level pressure (SLP) Arctic cyclone which formed in East Greenland and tracked NE over the Barents and Kara seas between 21 and 27 January 2022. At its peak intensity on 24 January, the cyclone reached an estimated depth of 932.2 mb at 79.5°N 20°E. North of 70°N, this is the lowest SLP in the ERA-5 reanalysis over 1979 to present. The cyclone resulted in a record (over the period 1979–2022) weekly loss of regional sea ice area and surface wind speeds, and generated ocean waves exceeding 8 m that impinged on sea ice in the Barents sea, observed via satellite altimetry as large waves-in-sea ice up to 2 m in amplitude more than 100 km into the ice pack. Surface heat fluxes were strongly impacted by the cyclone, with record atmosphere-to-surface turbulent fluxes. However, the direct atmospheric thermodynamic impact on sea ice loss was modest, and the record sea ice changes were likely mainly driven by dynamical and/or ocean processes. While the storm was well predicted up to 8 days in advance, subsequent changes in sea ice cover were not, likely due to biases in the forecasts' sea ice initial conditions and missing physics in the forecast model such as wave-sea ice interaction.
Boudala, Faisal S.; Milbrandt, Jason A.; Isaac, George A.Boudala, F. S., J. A. Milbrandt, G. A. Isaac, 2022: Evaluation of CanESM Cloudiness, Cloud Type and Cloud Radiative Forcing Climatologies Using the CALIPSO-GOCCP and CERES Datasets. Remote Sensing, 14(15), 3668. doi: 10.3390/rs14153668. In this study, the annual and seasonal climatology of cloud fraction (CF) and cloud type simulated by the Canadian Environmental System Models (CanESMs) version 5 (CanESM5) and version 2 (CanESM2) at their fully coupled and AMIP configurations were validated against the CALIPSO-GOCCP-based CF. The CFs produced using the CALIPSO-COSP simulator based on the CanESMs data at their atmospheric (AMIP) configuration are also evaluated. The simulated shortwave, longwave, and net cloud radiative forcing using the AMIP version of the CanESM5 were also validated against satellite observations based on the recent CERES radiation satellite products. On average, all models have a negative bias in the total CF with global mean biases (MBs) of 2%, 2.4%, 3.9%, 6.4%, 5.6%, and 7.1% for the coupled-CanESM5, AMIP-CanESM5, COSP-AMIP-CanESM5, coupled-CanESM2, AMIP-CanESM2, and COSP-AMIP-CanESM2, respectively, indicating that the CanESM5 has a smaller MB. There were no significant differences between AMIP and coupled versions of the model, but the COSP-based model-simulated data showed larger biases. Although the models captured well the climatological features of CF, they also exhibited a significant bias in CF reaching up to 40% over some geographical locations. This is particularly prevalent over the low level (LL) marine stratocumulus/cumulus, convectively active tropical latitudes that are normally dominated by high level (HL) clouds and at the polar regions where all models showed negative, positive, and positive bias corresponding to these locations, respectively. The AMIP-CanESM5 model performed reasonably well simulating the global mean cloud radiative forcing (CRF) with slight negative biases in the NetCRF at the TOA and surface that would be expected if the model has a positive bias in CF. This inconsistent result may be attributed to the parameterization of the optical properties in the model. The geographical distributions of the model bias in the NetCRF, however, can be significant reaching up to ±40 Wm−2 depending on the location and atmospheric level. The Pearson correlation showed that there is a strong correlation between the global distribution of model bias in NetCRF and CF and it is significantly influenced by the LL and HL clouds. satellite data; cloud radiative forcing; cloud fraction; GCM model evaluation
Cao, Qimeng; Liu, Yan; Sun, Xue; Yang, LiuCao, Q., Y. Liu, X. Sun, L. Yang, 2022: Country-level evaluation of solar radiation data sets using ground measurements in China. Energy, 241, 122938. doi: 10.1016/j.energy.2021.122938. Solar radiation is a crucial parameter that affects the thermal environment in buildings. The spatial and temporal distributions of solar radiation data are important for energy-efficient building design. Models that correlate solar radiation with other parameters can address the lack of solar radiation data. Satellite-derived products and reanalysis data sets have been produced using solar radiation models. The accuracy of these products directly affects building thermal environment design. To choose the most appropriate data set, it is necessary to evaluate the deviation in different data sets based on ground measurements. We used data acquired between 2001 and 2016 from 98 solar radiation measurement stations in China to verify two satellite-derived products (SARAH-E and CERES-SYN1deg) and two reanalysis data sets (ERA5 and MERRA-2). The CERES-SYN1deg and SARAH-E products performed better than the ERA5 and MERRA-2 data sets at estimating the daily global solar radiation. The daily global radiation products were more accurate than direct, diffuse, and hourly global solar radiation products. The models merged ground measurements show good performance. Further improvement in solar radiation estimation especially direct and diffuse in areas where there are no ground measurements and taking into account the effect of inadequate weather conditions on the hourly solar radiation is required. These findings may provide the basis for solar radiation models and products, especially applications in the building industry. Global solar radiation; Direct solar radiation; Reanalysis data set; Satellite-derived product
Cao, Yunfeng; Li, Manyao; Zhang, YuzhenCao, Y., M. Li, Y. Zhang, 2022: Estimating the Clear-Sky Longwave Downward Radiation in the Arctic from FengYun-3D MERSI-2 Data. Remote Sensing, 14(3), 606. doi: 10.3390/rs14030606. Surface longwave downward radiation (LWDR) plays a key role in determining the Arctic surface energy budget, especially in insolation-absent boreal winter. A reliable LWDR product is essential for understanding the intrinsic physical mechanisms of the rapid changes in the Arctic climate. The Medium-Resolution Spectral Imager (MERSI-2), a major payload of the Chinese second-generation polar-orbiting meteorological satellite, FengYun-3D (FY-3D), was designed similar to the NASA Moderate-Resolution Imaging Spectroradiometer (MODIS) in terms of the spectral bands. Although significant progress has been made in estimating clear-sky LWDR from MODIS observations using a variety of methods, few studies have focused on the retrieval of clear-sky LWDR from FY-3D MERSI-2 observations. In this study, we propose an advanced method to directly estimate the clear-sky LWDR in the Arctic from the FY-3D MERSI-2 thermal infrared (TIR) top-of-atmosphere (TOA) radiances and auxiliary information using the extremely randomized trees (ERT) machine learning algorithm. The retrieval accuracy of RMSE and bias, validated with the Baseline Surface Radiation Network (BSRN) in situ measurements, are 14.14 W/m2 and 4.36 W/m2, respectively, which is comparable and even better than previous studies. The scale effect in retrieval accuracy evaluation was further analyzed and showed that the validating window size could significantly influence the retrieval accuracy of the MERSI-2 clear-sky LWDR dataset. After aggregating to a spatial resolution of 9 km, the RMSE and bias of MERSI-2 retrievals can be reduced to 9.43 W/m2 and −0.14 W/m2, respectively. The retrieval accuracy of MERSI-2 clear-sky LWDR at the CERES SSF FOV spatial scale (approximately 20 km) can be further reduced to 8.64 W/m2, which is much higher than the reported accuracy of the CERES SSF products. This study demonstrates the feasibility of producing LWDR datasets from Chinese FY-3D MERSI-2 observations using machine learning methods. machine learning; satellite observation; Arctic region; surface downward longwave radiation; FengYun-3D; MERSI-2
Cesana, Grégory V.; Khadir, Théodore; Chepfer, Hélène; Chiriaco, MarjolaineCesana, G. V., T. Khadir, H. Chepfer, M. Chiriaco, 2022: Southern Ocean Solar Reflection Biases in CMIP6 Models Linked to Cloud Phase and Vertical Structure Representations. Geophysical Research Letters, 49(22), e2022GL099777. doi: 10.1029/2022GL099777. Over the Southern Ocean (SO, 40°S–70°S), climate models have consistently underestimated solar reflection. Here we evaluate the relationship between cloud profiles, cloud phase and radiation over the SO in Coupled Model Intercomparison Project Phase 6 (CMIP6) models against Clouds and the Earth's Radiant Energy System and Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observations. We find that the lack of solar reflection is slightly improved in CMIP6 models compared to CMIP5's, attributable to a better representation of cloud fraction and phase. We show that clouds have a different vertical structure and radiative effect south and north of where the 0°C isotherm meets the surface (∼55°S). Although the models capture the greater vertical extent of clouds south of 55°S, they fail to reproduce the observed increase in solar reflection, which we pinpoint to cloud phase biases. Increasing CMIP6 supercooled liquid cloud opacity should help reduce their persistent shortwave biases. cloud phase; climate models; radiation; evaluation; CALIPSO-GOCCP; southern ocean
Chakraborty, T.; Lee, X.; Lawrence, D. M.Chakraborty, T., X. Lee, D. M. Lawrence, 2022: Diffuse Radiation Forcing Constraints on Gross Primary Productivity and Global Terrestrial Evapotranspiration. Earth's Future, 10(8), e2022EF002805. doi: 10.1029/2022EF002805. The diffuse radiation fertilization effect—the increase in plant productivity in the presence of higher diffuse radiation (K↓,d)—is an important yet understudied aspect of atmosphere-biosphere interactions and can modify the terrestrial carbon, energy, and water budgets. The K↓,d fertilization effect links the carbon cycle with clouds and aerosols, all of which are large sources of uncertainties for our current understanding of the Earth system and for future climate projections. Here we establish to what extent observational and modeling uncertainty in sunlight's diffuse fraction (kd) affects simulated gross primary productivity (GPP) and terrestrial evapotranspiration (λE). We find only 48 eddy covariance sites with simultaneous sufficient measurements of K↓,d with none in the tropical climate zone, making it difficult to constrain this mechanism globally using observations. Using a land modeling framework based on the latest version of the Community Land Model, we find that global GPP ranges from 114 Pg C year−1 when using kd forcing from the Modern-Era Retrospective analysis for Research and Applications, version 2 reanalysis to a ∼7% higher value of 122 Pg C year−1 when using the Clouds and the Earth's Radiant Energy System satellite product, with especially strong differences apparent over the tropical region (mean increase ∼9%). The differences in λE, although smaller (−0.4%) due to competing changes in shaded and sunlit leaf transpiration, can be greater than regional impacts of individual forcing agents like aerosols. Our results demonstrate the importance of comprehensively and systematically validating the simulated kd by atmosphere modules as well as the response to differences in kd within land modules across Earth System Models. evapotranspiration; atmosphere-biosphere interactions; diffuse radiation fertilization effect; gross primary productivity; land-surface models
Chan, Man-Yau; Chen, Xingchao; Leung, L. RubyChan, M., X. Chen, L. R. Leung, 2022: A High-Resolution Tropical Mesoscale Convective System Reanalysis (TMeCSR). Journal of Advances in Modeling Earth Systems, 14(9), e2021MS002948. doi: 10.1029/2021MS002948. Modern global reanalysis products have greatly accelerated meteorological research in synoptic-to-planetary-scale phenomena. However, their use in studying tropical mesoscale convective systems (MCSs) and their regional-to-global impact has mostly been limited to supplying initial and boundary conditions for MCS-resolving simulations and providing information about the large-scale environments of MCSs. These limitations are due to difficulties in resolving tropical MCS dynamics in the relatively low-resolution global models and that tropical MCSs often occur over poorly observed regions. In this work, a Tropical MCS-resolving Reanalysis product (TMeCSR) was created over a region with frequent tropical MCSs. This region spans the tropical Indian Ocean, tropical continental Asia, Maritime Continent, and Western Pacific. TMeCSR is produced by assimilating all-sky infrared radiances from geostationary satellites and other conventional observations into an MCS-resolving regional model using the Ensemble Kalman Filter. The resulting observation-constrained high-resolution (9-km grid spacing) data set is available hourly during the boreal summer (June-August) of 2017, during which widespread severe flooding occurred. Comparisons of TMeCSR and European Center for Medium Range Weather Forecast Reanalysis version 5 (ERA5) against independent satellite retrievals indicate that TMeCSR's cloud and multiscale rain fields are better than those of ERA5. Furthermore, TMeCSR better captured the diurnal variability of rainfall and the statistical characteristics of MCSs. Forecasts initialized from TMeCSR also have more accurate rain and clouds than those initialized from ERA5. The TMeCSR and ERA5 forecasts have similar performances with respect to sounding and surface observations. These results indicate that TMeCSR is a promising MCS-resolving data set for tropical MCS studies. reanalysis; data assimilation; mesoscale convective system
Chao, Li-Wei; Muller, Jacob C.; Dessler, Andrew E.Chao, L., J. C. Muller, A. E. Dessler, 2022: Impacts of the Unforced Pattern Effect on the Cloud Feedback in CERES Observations and Climate Models. Geophysical Research Letters, 49(2), e2021GL096299. doi: 10.1029/2021GL096299. The equilibrium climate sensitivity estimated from different sources is inconsistent due to its dependence on the surface warming pattern. Cloud feedbacks have been identified as the major contributor to this so-called pattern effect. We find a large unforced pattern effect in CERES data, with cloud feedback estimated from two consecutive 125-month periods (March 2000–July 2010 and August 2010–December 2020) changing from −0.45 ± 0.85 to +1.2 ± 0.78 W/m2/K. When comparing to models, 27% of consecutive 10-year segments in CMIP6 control runs have differences similar to the observations. We also compare the spatial patterns in the CERES data to those in climate models and find they are similar, with the East Pacific playing a key role. This suggests that the impact of the unforced pattern effect can be significant and that models are capable of reproducing its global-average magnitude. cloud feedback; climate models; pattern effect
Chen, Annan; Zhao, Chuanfeng; Fan, TianyiChen, A., C. Zhao, T. Fan, 2022: Spatio-temporal distribution of aerosol direct radiative forcing over mid-latitude regions in north hemisphere estimated from sat
