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2024

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. atmospheric general circulation model; convection scheme; tropical cyclone; tropical variability
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.
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
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.
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
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.
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
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.
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.
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, 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. aerosol vertical distribution; Clouds and the Earth’s Radiant Energy System (CERES); 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). Atmospheric science; Climate change
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
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
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. aerosol optical depth; CERES-SYN; cloud optical thickness; downward shortwave radiation; ERA5; Tibetan Plateau
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.
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. bias-corrected downscaling; double-ITCZ; dynamical downscaling; pseudo-global warming approach; regional climate model
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°). all-weather; downward surface longwave fluxes; ECMWF-ERA5; machine learning; Meteosat Second Generation; multivariate adaptive regression splines
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. atmospheric water cycle; constrained variational analysis; 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
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
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
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; large ensembles; model evaluation; ocean-atmosphere interaction; pattern effect; radiation
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. atmospheric science; climate modeling; cloud physics; multi-scale modeling; superparameterization
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
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.
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
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. East China Sea; latent heat flux; platform observation; sea land breeze; sensible heat flux; 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
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.
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. Atmosphere; Cloud cover; Cloud height; Cloud radiative properties; Cloud types; Microphysical properties; Satellite remote sensing
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; feedback; moisture convergence; precipitation; Southern Ocean
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, 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, 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. J. Climate, -1(aop). doi: 10.1175/JCLI-D-23-0170.1. Abstract 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 non-linear 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 Extended Pathfinder Atmospheres (Patmos-x) observational dataset.
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
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. Cloud microphysics; Model improvement; Precipitation; The Sichuan-Xizang Railway
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. disk-integrated measurement; Earth’s ellipsoid model; Earth’s radiant anisotropy; Moon-based platform; outgoing longwave radiation (OLR)
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.
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, 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. cloud simulation; equilibrium climate sensitivity; explainable machine learning approach; horizontal temperature advection; stratocumulus evolution
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, 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, 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
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. BCC-CSM2; Deep convection scheme; Improvement; MJO; MJO simulation
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

2023

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. CERES4; Daily downward shortwave radiation; DSRMT; estimation; modeling; remote sensing; 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

2022

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 satellite observations. Atmospheric Research, 266, 105938. doi: 10.1016/j.atmosres.2021.105938. An empirical method is used to estimate the aerosol direct radiative forcing (ADRF) over 20oN − 40oN regions from March 2000 to March 2019. The ADRF is calculated as the difference between the cloud-free sky and clean-sky (non-aerosol) radiative fluxes, which are fitted to an exponential function of the aerosol optical depth (AOD). The regional averaged ADRFs are negative (cooling effect) at the surface (SUR) and the top of atmosphere (TOA) and positive (warming effect) in the atmosphere (ATM). The spatial and temporal distributions of ADRF are closely linked to the spatio-temporal distributions of AOD. Higher AOD and stronger ADRF are found in spring (March to May) and summer (June to August). ADRFs are larger in regions with frequent sandstorm outbreaks and rapid economic growth since 2000 than other regions. The uncertainty of ADRF due to data source is 1.12 W/m2 at the surface and 0.91 W/m2 at the TOA according to the stochastic error propagation function. The ADRFs in our study regions show statistically significant but different changes of −0.074 W/m2 /year and 0.1 W/m2 /year at the surface during 2000 to 2009 and 2010 to 2019, respectively. Recent trend analysis also shows that the reduced aerosol contributes to the increasing short-wave flux about 0.32 W/m2 under the background of the global warming during the period from 2000 to 2019 in our study area, which indicates that it may alter the pattern of atmospheric circulation or enhance the global warming effect. Aerosol optical depth; Aerosol direct radiative forcing; Anthropogenic activity; Mid-latitude region; Sandstorm
Chen, Guangcan; Zhang, Xiangdong; Fu, YunfeiChen, G., X. Zhang, Y. Fu, 2022: Diurnal Variation in Clouds and Radiative Budgets Over the Tibetan Plateau During Summer Using CERES Data. Journal of Geophysical Research: Atmospheres, 127(16), e2021JD036329. doi: 10.1029/2021JD036329. Diurnal variations in clouds and radiation budgets over four subareas of the Tibetan Plateau (TP) during summer (June–August) are analyzed using the Clouds and the Earth's Radiant Energy System (CERES) synoptic 1° (SYN1deg) data from 2000 to 2020. The results show that the total cloud amount decreases from southeast to northwest and is larger during daytime (71.1%) than nighttime (67.2%) over the entire TP. High-clouds develop in the afternoon, persist during nighttime, and dissipate after sunrise. Low clouds develop after sunrise and dissipate in the afternoon over the entire TP, but show opposite temporal variation over the Kunlun Mountains. The net radiation budget at the top-of-atmosphere reaches its maximum at noon. The surface net radiation budget is positive in the daytime and negative at nighttime. These features are mainly adjusted by the cloud distribution. The diurnal variations in heating rate over the four subareas are similar in the upper atmosphere but different in the lower layer. The low-atmosphere heating rate shows a maximum value over the center-south (CS) subarea, while it is lowest over the west (W) subarea. Internal cloud forcing has distinct regional differences over the four subareas: it shows a heating effect in the low atmosphere and a cooling effect in the middle atmosphere over the CS subarea, whereas over the W subarea it shows a radiative cooling effect in the low atmosphere and no significant radiative effect in the middle layer. The findings of this study help toward improving our understanding of the TP's energy cycle. diurnal variation; heating rate; cloud cover; internal cloud forcing; Tibet Plateau
Chen, Jiang; He, Tao; Liang, ShunlinChen, J., T. He, S. Liang, 2022: Estimation of Daily All-wave Surface Net Radiation with Multispectral and Multitemporal Observations from GOES-16 ABI. IEEE Transactions on Geoscience and Remote Sensing, 1-1. doi: 10.1109/TGRS.2022.3140335. As a vital parameter describing the Earth surface energy budget, surface all-wave net radiation (Rn) drives many physical and biological processes. Remote estimation of Rn using satellite data is an effective approach to monitor the spatial and temporal dynamics of Rn. Accurate daily Rn estimation typically depends on the spatio-temporal resolutions of satellite data. There are currently few high-spatial-resolution daily Rn products from polar-orbiting satellite data, and they exhibit limited accuracy due to sparse diurnal observations. In addition, traditional estimation approaches typically require cloud mask and clear-sky albedo as inputs and ignore the length ratio of daytime (LRD), which may lead to large errors. To overcome these challenges and obtain Rn data with improved spatial resolution and accuracy, an operational approach was proposed in this study to derive daily 1-km Rn, which takes the advantages from a radiative transfer model, a machine learning algorithm, and multispectral and dense diurnal temporal information of geostationary satellite observations. An improved all-sky hybrid model (AHM) coupling radiative transfer simulations with a random forest (RF) model was first developed to estimate the shortwave net radiation (Rns). Then, another RF model was developed to estimate the daily Rn from Rns, incorporating the LRD, which is called extended hybrid model (EHM). Data from the Advanced Baseline Imager (ABI) onboard the new-generation Geostationary Operational Environmental Satellite (GOES)-16 with a 5-min temporal resolution and a 1-km spatial resolution were used to test the proposed method. Compared to traditional look-up table (LUT) algorithms, the results show that AHM not only makes the process of Rns estimation simple and efficient, but also has high accuracy in estimating instantaneous all-sky Rns. Benefiting from high spatio-temporal resolutions, our daily Rns estimates using GOSE-16 data exhibited superior performance compared to using the 1-km Moderate Resolution Imaging Spectroradiometer (MODIS) and 1° Clouds and the Earth’s Radiant Energy System (CERES) product. Using accurate daily Rns estimates and LRD as inputs, the EHM model shows reasonably good results for estimating Rn (R2, RMSE, and bias of 0.91, 20.95 W/m2, and -0.05 W/m2, respectively). Maps of 1-km Rns and Rn exhibit similar spatial patterns to those from the 1° CERES product, but with substantially more spatial details. Overall, the proposed Rn retrieval scheme can accurately estimate all-sky 1-km Rns and Rn at mid- to low-latitudes and can be easily adapted and applied to other GOES-16-like satellites, such as Himawari-8, METEOSAT Third Generation (MTG) and Fenyun-4. This study demonstrates the advantages of estimating Rn using geostationary satellites with improved accuracy and resolutions. Atmospheric modeling; Clouds; Estimation; Spatial resolution; MODIS; Remote sensing; geostationary satellite; all-sky hybrid model; daily net radiation; extended hybrid model; Geostationary satellites; length ratio of daytime
Chen, Jingyi; Wang, Hailong; Li, Xiangyu; Painemal, David; Sorooshian, Armin; Thornhill, Kenneth Lee; Robinson, Claire; Shingler, TaylorChen, J., H. Wang, X. Li, D. Painemal, A. Sorooshian, K. L. Thornhill, C. Robinson, T. Shingler, 2022: Impact of Meteorological Factors on the Mesoscale Morphology of Cloud Streets during a Cold-Air Outbreak over the Western North Atlantic. J. Atmos. Sci., 79(11), 2863-2879. doi: 10.1175/JAS-D-22-0034.1. Abstract Postfrontal clouds (PFC) are ubiquitous in the marine boundary layer, and their morphology is essential to estimating the radiation budget in weather and climate models. Here we examine the roles of sea surface temperature (SST) and meteorological factors in controlling the mesoscale morphology and evolution of shallow clouds associated with a cold-air outbreak that occurred on 1 March 2020 during phase I of the Aerosol Cloud Meteorology Interactions over the Western Atlantic Experiment (ACTIVATE). Our results show that the simulated PFC structure and ambient conditions by the Weather Research and Forecasting (WRF) Model are generally consistent with observations from GOES-16 and dropsonde measurements. We also examine the thermodynamical and dynamical influences in the cloud mesoscale morphology using WRF sensitivity experiments driven by two meteorological forcing datasets with different domain-mean SST and spatial gradients, which lead to dissimilar values of hydrometeor water path and cloud core fraction. The SST from ERA5 leads to weaker stability and higher inversion height than the SST from FNL does. In addition, the use of large-scale meteorological forcings from ERA5 yields a distinctive time evolution of wind direction shear in the inner domain, which favors the formation and persistence of longer cloud rolls. Both factors contribute to a change in the time evolution of domain-mean water path and cloud core fraction of cloud streets. Our study takes advantage of the simulation driven by the differences between two large-scale forcing datasets to illustrate the importance of SST and wind direction shear in the cloud street morphology in a realistic scenario.
Chen, Xingan; Huang, Yuefei; Nie, Chong; Zhang, Shuo; Wang, Guangqian; Chen, Shiliu; Chen, ZhichaoChen, X., Y. Huang, C. Nie, S. Zhang, G. Wang, S. Chen, Z. Chen, 2022: A long-term reconstructed TROPOMI solar-induced fluorescence dataset using machine learning algorithms. Scientific Data, 9(1), 427. doi: 10.1038/s41597-022-01520-1. Photosynthesis is a key process linking carbon and water cycles, and satellite-retrieved solar-induced chlorophyll fluorescence (SIF) can be a valuable proxy for photosynthesis. The TROPOspheric Monitoring Instrument (TROPOMI) on the Copernicus Sentinel-5P mission enables significant improvements in providing high spatial and temporal resolution SIF observations, but the short temporal coverage of the data records has limited its applications in long-term studies. This study uses machine learning to reconstruct TROPOMI SIF (RTSIF) over the 2001–2020 period in clear-sky conditions with high spatio-temporal resolutions (0.05° 8-day). Our machine learning model achieves high accuracies on the training and testing datasets (R2 = 0.907, regression slope = 1.001). The RTSIF dataset is validated against TROPOMI SIF and tower-based SIF, and compared with other satellite-derived SIF (GOME-2 SIF and OCO-2 SIF). Comparing RTSIF with Gross Primary Production (GPP) illustrates the potential of RTSIF for estimating gross carbon fluxes. We anticipate that this new dataset will be valuable in assessing long-term terrestrial photosynthesis and constraining the global carbon budget and associated water fluxes. Phenology; Ecosystem ecology
Chen, Zhe; Wang, Minghuai; Zhang, Haipeng; Lin, Shuheng; Guo, Zhun; Jiang, Yiquan; Zhou, ChenChen, Z., M. Wang, H. Zhang, S. Lin, Z. Guo, Y. Jiang, C. Zhou, 2022: Long-term change in low-cloud cover in Southeast China during cold seasons. Atmospheric and Oceanic Science Letters, 15(6), 100222. doi: 10.1016/j.aosl.2022.100222. Southeast China has comparable stratus cloud to that over the oceans, especially in the cold seasons (winter and spring), and this cloud has a substantial impact on energy and hydrological cycles. However, uncertainties remain across datasets and simulation results about the long-term trend in low-cloud cover in Southeast China, making it difficult to understand climate change and related physical processes. In this study, multiple datasets and numerical simulations were applied to show that low-cloud cover in Southeast China has gone through two stages since 1980—specifically, a decline and then a rise, with the turning point around 2008. The regional moisture transport plays a crucial role in low-cloud cover changes in the cold seasons and is mainly affected by the Hadley Cell in winter and the Walker Circulation in spring, respectively. The moisture transport was not well simulated in CMIP6 climate models, leading to poor simulation of the low-cloud cover trend in these models. This study provides insights into further understanding the regional climate changes in Southeast China. 摘要 中国东南地区在冬春冷季节盛行低云, 对局地能量平衡和水文循环有重要的作用. 本研究使用多套数据和数值模拟结果, 分析这一地区冷季节内低云云量在1980年至2017年的长期变化. 结果表明, 低云云量经历了先下降后上升的趋势变化, 转折点出现在2008年左右. 局地水汽通量输送在影响低云云量的变化中起着至关重要的作用, 其在冬季和春季分别受到哈德莱环流和沃克环流的影响. CMIP6中的气候模式对水汽通量输送的模拟能力欠佳, 影响了对低云云量的模拟结果. Hadley cell; Large-scale circulation; Low-cloud cover; Pacific walker circulation; 低云云量; 关键词:; 哈德莱环流; 大尺度环流场; 沃克环流
Cheng, Anning; Yan, FanglinCheng, A., F. Yan, 2022: Direct Radiative Effects of Aerosols on Numerical Weather Forecast -- A Comparison of Two Aerosol Datasets in the NCEP GFS. doi: 10.25923/RB1N-ZA92. This study compares aerosol direct radiative effects on numerical weather forecasts made by the NCEP Global Forecast Systems (GFS) with two different aerosol datasets, the OPAC and MERRA2 aerosol climatologies. The OPAC overestimates the aerosol loading from sea salt in storm track regions over the Northern and Southern Hemisphere ocean and underestimates the aerosol loading over most continents. The experiments made with MERRA2 aerosols showed improvements in GFS forecasts of aerosol optical depth (AOD) over the globe when verified against satellite retrievals. The experiment made with the OPAC aerosols largely underestimated the AOD over northwest Africa, central to east Africa, southeast Asia, and the Indo-Gangetic Plain, and overestimated the AOD in the storm track regions in both hemispheres. Surface downward short-wave (SW) and long- wave (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 AOD biases, especially in northwest Africa and the storm track regions. These biases are reduced in the forecasts made with MERRA2 aerosols. The improvements are most noticeable in the surface downward SW fluxes. GFS medium-range weather forecasts made with the MERRA2 aerosols demonstrated improved forecast accuracy of circulation and precipitation over the India and East Asian summer monsoon region. Forecasts of Africa easterly jets are also improved. Impacts on large-scale skill scores such as 500hPa geopotential height anomaly correlation are generally positive in the Northern Hemisphere and the Pacific and North American regions in the winter and summer seasons.
Chtirkova, Boriana; Folini, Doris; Correa, Lucas Ferreira; Wild, MartinChtirkova, B., D. Folini, L. F. Correa, M. Wild, 2022: Internal Variability of All-Sky and Clear-Sky Surface Solar Radiation on Decadal Timescales. Journal of Geophysical Research: Atmospheres, 127(12), e2021JD036332. doi: 10.1029/2021JD036332. Internal variability comprises all processes that occur within the climate system without any natural or anthropogenic forcing. Climate-driving variables like the surface solar radiation (SSR) are shown to exhibit unforced trends (i.e., trends due to internal variability) of magnitudes comparable to the magnitude of the forced signal even on decadal timescales. We use annual mean data from 50 models participating in the preindustrial control experiment (piControl) of the Coupled Model Intercomparison Project-Phase 6 (CMIP6) to give quantitative grid-box specific estimates of the magnitudes of unforced trends. To characterize a trend distribution, symmetrical around 0, we use the 75th percentile of all possible values, which corresponds to a positive trend with 25% chance of occurrence. For 30-year periods and depending on geographical location, this trend has a magnitude between 0.15 and 2.1 W m−2/decade for all-sky and between 0.04 and 0.38 W m−2/decade for clear-sky SSR. The corresponding area-weighted medians are 0.69 W m−2/decade for all-sky trends and 0.17 W m−2/decade for clear-sky trends. The influence of internal variability is on average six times smaller in clear-sky, compared to all-sky SSR. The relative uncertainties in the physical representation, derived from the CMIP6 inter-model spread, are ±32% for all-sky and ±43% for clear-sky SSR trends. Reasons for differences between models like horizontal resolution, aerosol handling, and the representation of atmospheric and oceanic phenomena are investigated. The results can be used in the analysis of observational time series by attributing a probability for a trend to be caused by internal variability, given its magnitude, length, and location. CMIP6; surface solar radiation; dimming and brightening; internal variability; unforced trends
Chu, Wenchao; Lin, Yanluan; Zhao, MingChu, W., Y. Lin, M. Zhao, 2022: Implementation and Evaluation of a Double-Plume Convective Parameterization in NCAR CAM5. J. Climate, 35(2), 617-637. doi: 10.1175/JCLI-D-21-0267.1. Abstract Performance of global climate models (GCMs) is strongly affected by the cumulus parameterization (CP) used. Similar to the approach in GFDL AM4, a double-plume CP, which unifies the deep and shallow convection in one framework, is implemented and tested in the NCAR Community Atmospheric Model version 5 (CAM5). Based on the University of Washington (UW) shallow convection scheme, an additional plume was added to represent the deep convection. The shallow and deep plumes share the same cloud model, but use different triggers, fractional mixing rates, and closures. The scheme was tested in single-column, short-term hindcast, and AMIP simulations. Compared with the default combination of the Zhang–McFarlane scheme and UW scheme in CAM5, the new scheme tends to produce a top-heavy mass flux profile during the active monsoon period in the single-column simulations. The scheme increases the intensity of tropical precipitation, closer to TRMM observations. The new scheme increased subtropical marine boundary layer clouds and high clouds over the deep tropics, both in better agreement with observations. Sensitivity tests indicate that regime-dependent fractional entrainment rates of the deep plume are desired to improve tropical precipitation distribution and upper troposphere temperature. This study suggests that a double-plume approach is a promising way to combine shallow and deep convections in a unified framework.
Cui, Jiangpeng; Lian, Xu; Huntingford, Chris; Gimeno, Luis; Wang, Tao; Ding, Jinzhi; He, Mingzhu; Xu, Hao; Chen, Anping; Gentine, Pierre; Piao, ShilongCui, J., X. Lian, C. Huntingford, L. Gimeno, T. Wang, J. Ding, M. He, H. Xu, A. Chen, P. Gentine, S. Piao, 2022: Global water availability boosted by vegetation-driven changes in atmospheric moisture transport. Nature Geoscience, 15(12), 982-988. doi: 10.1038/s41561-022-01061-7. Surface-water availability, defined as precipitation minus evapotranspiration, can be affected by changes in vegetation. These impacts can be local, due to the modification of evapotranspiration and precipitation, or non-local, due to changes in atmospheric moisture transport. However, the teleconnections of vegetation changes on water availability in downwind regions remain poorly constrained by observations. By linking measurements of local precipitation to a new hydrologically weighted leaf area index that accounts for both local and upwind vegetation contributions, we demonstrate that vegetation changes have increased global water availability at a rate of 0.26 mm yr−2 for the 2001–2018 period. Critically, this increase has attenuated about 15% of the recently observed decline in global water availability. The water availability increase is due to a greater rise in precipitation relative to evapotranspiration for over 53% of the global land surface. We also quantify the potential hydrological impacts of regional vegetation increases at any given location across global land areas. We find that enhanced vegetation is beneficial to both local and downwind water availability for ~45% of the land surface, whereas it is adverse elsewhere, primarily in water-limited or high-elevation regions. Our results highlight the potential strong effects of deliberate vegetation changes, such as afforestation programmes, on water resources beyond local and regional scales. Climate change; Atmospheric dynamics; Hydrology; Climate sciences; Environmental impact
Cutler, Lauren; Brunke, Michael A.; Zeng, XubinCutler, L., M. A. Brunke, X. Zeng, 2022: Re-Evaluation of Low Cloud Amount Relationships With Lower-Tropospheric Stability and Estimated Inversion Strength. Geophysical Research Letters, 49(12), e2022GL098137. doi: 10.1029/2022GL098137. Lower-tropospheric stability (LTS) and estimated inversion strength (EIS) have a widely accepted relationship with low cloud amount and are key observational foundations for understanding and modeling low-level stratiform clouds. Using the updated surface-based and satellite cloud data, we find that low cloud amount is not as strongly correlated with LTS, and not as sensitive to LTS, as established in the past. EIS does not provide a stronger correlation with low cloud amount than LTS over all eight regions (including the midlatitudes). Further analyzing the relationships between LTS and EIS with different types of low clouds, we find that there is a strong correlation of LTS and EIS with stratocumulus only. This explains the weaker correlation of low cloud fraction (including cumulus, stratocumulus, and stratus) to both LTS and EIS. These results also suggest the need to re-evaluate these relationships in Earth system models.
Dadashazar, Hossein; Corral, Andrea F.; Crosbie, Ewan; Dmitrovic, Sanja; Kirschler, Simon; McCauley, Kayla; Moore, Richard; Robinson, Claire; Schlosser, Joseph S.; Shook, Michael; Thornhill, K. Lee; Voigt, Christiane; Winstead, Edward; Ziemba, Luke; Sorooshian, ArminDadashazar, H., A. F. Corral, E. Crosbie, S. Dmitrovic, S. Kirschler, K. McCauley, R. Moore, C. Robinson, J. S. Schlosser, M. Shook, K. L. Thornhill, C. Voigt, E. Winstead, L. Ziemba, A. Sorooshian, 2022: Organic enrichment in droplet residual particles relative to out of cloud over the northwestern Atlantic: analysis of airborne ACTIVATE data. Atmospheric Chemistry and Physics, 22(20), 13897-13913. doi: 10.5194/acp-22-13897-2022. Cloud processing is known to generate aerosol species such as sulfate and secondary organic aerosol, yet there is a scarcity of airborne data to examine this issue. The NASA Aerosol Cloud meTeorology Interactions oVer the western ATlantic Experiment (ACTIVATE) was designed to build an unprecedented dataset relevant to aerosol–cloud interactions with two coordinated aircraft over the northwestern Atlantic, with aerosol mass spectrometer data used from four deployments between 2020–2021 to contrast aerosol composition below, in (using a counterflow virtual impactor) and above boundary layer clouds. Consistent features in all time periods of the deployments (January–March, May–June, August–September) include the mass fraction of organics and relative amount of oxygenated organics (m/z 44) relative to total organics (f44) increasing in droplet residuals relative to below and above cloud. Detailed analysis comparing data below and in cloud suggests a possible role for in-cloud aqueous processing in explaining such results; an intriguing aspect though requiring more attention is that only approximately a quarter of the cloud cases (29 of 110) showed higher organic mass fractions either below or above cloud. Of those 29 cases, the majority (25) showed higher organic mass fraction below cloud base where the cloud processing signature is presumably more evident as compared to above cloud. These results are consistent with the few past studies analyzing droplet residuals pointing to higher organic enrichment than in adjacent cloud-free areas. The data findings are important as other datasets (e.g., reanalysis) suggest that sulfate is both more abundant than organics (in contrast to this work) and more closely related to drop number concentrations in the winter when aerosol–cloud interactions are strongest. Here we show that organics are more abundant than sulfate in the droplet residuals and that aerosol interaction with clouds potentially decreases particle hygroscopicity due to the increase in organic:sulfate ratio for droplet residuals relative to surrounding cloud-free air. These results are important in light of the growing importance of organics over the northwestern Atlantic in recent decades relative to sulfate owing to the success of regulatory activity over the eastern United States to cut sulfur dioxide emissions.
Dasari, Hari Prasad; Viswanadhapalli, Yesubabu; Langodan, Sabique; Abualnaja, Yasser; Desamsetti, Srinivas; Vankayalapati, Koteswararao; Thang, Luong; Hoteit, IbrahimDasari, H. P., Y. Viswanadhapalli, S. Langodan, Y. Abualnaja, S. Desamsetti, K. Vankayalapati, L. Thang, I. Hoteit, 2022: High-resolution climate characteristics of the Arabian Gulf based on a validated regional reanalysis. Meteorological Applications, 29(5), e2102. doi: 10.1002/met.2102. The regional climate of the Arabian Gulf (AG) and its variability are examined based on a 40-year (1980–2019), 5-km regional reanalysis of the Arabian Peninsula (AP reanalysis). The AP reanalysis fields were first validated against the available observations over the AG, suggesting that this high-resolution reanalysis well reproduces the spatio-temporal features of the AG atmospheric circulations. The validated AP reanalysis fields were then analysed to examine the climatic characteristics over the AG including the monthly mean, maximum and minimum temperatures, and the seasonal variations in winds, relative humidity and rainfall over the AG. The AG climate is mostly dry between May and October, and experiences moderate rainfall between December and January. The higher (lower) pressure difference between the northwest and southeast AG during summer (winter) generates the northwesterly Shamal winds over the north (central) AG. The mean Shamal winds are relatively stronger (weaker) and prolonged (shorter) during summer (winter); however, the short lived Shamal jet events in winter can be occasionally stronger than summer. In terms of interannual variability, the Shamal winds are stronger and more persistent in summer during El Niño years and in winter during La Niña years. These differences are mainly associated with changes in temperature gradients between the eastern AG and northwestern AP. temperature; Arabian Gulf; climate variability; regional reanalysis; Shamal winds
Datseris, George; Blanco, Joaquin; Hadas, Or; Bony, Sadrine; Caballero, Rodrigo; Kaspi, Yohai; Stevens, BjornDatseris, G., J. Blanco, O. Hadas, S. Bony, R. Caballero, Y. Kaspi, B. Stevens, 2022: Minimal Recipes for Global Cloudiness. Geophysical Research Letters, 49(20), e2022GL099678. doi: 10.1029/2022GL099678. Clouds are primary modulators of Earth's energy balance. It is thus important to understand the links connecting variabilities in cloudiness to variabilities in other state variables of the climate system, and also describe how these links would change in a changing climate. A conceptual model of global cloudiness can help elucidate these points. In this work we derive simple representations of cloudiness, that can be useful in creating a theory of global cloudiness. These representations illustrate how both spatial and temporal variability of cloudiness can be expressed in terms of basic state variables. Specifically, cloud albedo is captured by a nonlinear combination of pressure velocity and a measure of the low-level stability, and cloud longwave effect is captured by surface temperature, pressure velocity, and standard deviation of pressure velocity. We conclude with a short discussion on the usefulness of this work in the context of global warming response studies. energy balance; cloud controlling factors; global cloudiness
Dauhut, Thibaut; Hohenegger, CathyDauhut, T., C. Hohenegger, 2022: The Contribution of Convection to the Stratospheric Water Vapor: The First Budget Using a Global Storm-Resolving Model. Journal of Geophysical Research: Atmospheres, 127(5), e2021JD036295. doi: 10.1029/2021JD036295. The deepest convection on Earth injects water in the tropical stratosphere, but its contribution to the global stratospheric water budget remains uncertain. The Global Storm-Resolving Model ICOsahedral Non-hydrostatic is used to simulate the moistening of the lower stratosphere for 40 days during boreal summer. The decomposition of the water vapor budget in the tropical lower stratosphere (TLS, 10°S–30°N, and 17–20 km altitude) indicates that the average moistening (+21 Tg) over the simulated 40-day period is the result of the combined effect of the vertical water vapor transport from the troposphere (+27 Tg), microphysical phase changes and subgrid-scale transport (+2 Tg), partly compensated by horizontal water vapor export (−8 Tg). The very deep convective systems, explicitly represented thanks to the employed 2.5 km grid spacing of the model, are identified using the very low Outgoing Longwave Radiation of their cold cloud tops. The water vapor budget reveals that the vertical transport, the sublimation and the subgrid-scale transport at their top contribute together to 11% of the water vapor mass input into the TLS. convection; water vapor; budget; global storm-resolving model; ICON; stratosphere
Devi, Archana; Satheesh, Sreedharan K.Devi, A., S. K. Satheesh, 2022: Global maps of aerosol single scattering albedo using combined CERES-MODIS retrieval. Atmospheric Chemistry and Physics, 22(8), 5365-5376. doi: 10.5194/acp-22-5365-2022. Abstract. Single scattering albedo (SSA) is a leading contributor to the uncertainty in aerosol radiative impact assessments. Therefore accurate information on aerosol absorption is required on a global scale. In this study, we have applied a multi-satellite algorithm to retrieve SSA (550 nm) using the concept of critical optical depth. Global maps of SSA were generated following this approach using spatially and temporally collocated data from Clouds and the Earth's Radiant Energy System (CERES) and Moderate Resolution Imaging Spectroradiometer (MODIS) sensors on board Terra and Aqua satellites. Limited comparisons against airborne observations over India and surrounding oceans were generally in agreement within ±0.03. Global mean SSA estimated over land and ocean is 0.93 and 0.97, respectively. Seasonal and spatial distribution of SSA over various regions are also presented. Sensitivity analysis to various parameters indicate a mean uncertainty around ±0.044 and shows maximum sensitivity to changes in surface albedo. The global maps of SSA, thus derived with improved accuracy, provide important input to climate models for assessing the climatic impact of aerosols on regional and global scales.
Diamond, Michael S.; Gristey, Jake J.; Kay, Jennifer E.; Feingold, GrahamDiamond, M. S., J. J. Gristey, J. E. Kay, G. Feingold, 2022: Anthropogenic aerosol and cryosphere changes drive Earth’s strong but transient clear-sky hemispheric albedo asymmetry. Communications Earth & Environment, 3(1), 1-10. doi: 10.1038/s43247-022-00546-y. A striking feature of the Earth system is that the Northern and Southern Hemispheres reflect identical amounts of sunlight. This hemispheric albedo symmetry comprises two asymmetries: The Northern Hemisphere is more reflective in clear skies, whereas the Southern Hemisphere is cloudier. Here we show that the hemispheric reflection contrast from differences in continental coverage is offset by greater reflection from the Antarctic than the Arctic, allowing the net clear-sky asymmetry to be dominated by aerosol. Climate model simulations suggest that historical anthropogenic aerosol emissions drove a large increase in the clear-sky asymmetry that would reverse in future low-emission scenarios. High-emission scenarios also show decreasing asymmetry, instead driven by declines in Northern Hemisphere ice and snow cover. Strong clear-sky hemispheric albedo asymmetry is therefore a transient feature of Earth’s climate. If all-sky symmetry is maintained, compensating cloud changes would have uncertain but important implications for Earth’s energy balance and hydrological cycle. Cryospheric science; Climate and Earth system modelling; Atmospheric chemistry
Ding, Qinghua; Schweiger, Axel; Baxter, IanDing, Q., A. Schweiger, I. Baxter, 2022: Nudging Observed Winds in the Arctic to Quantify Associated Sea Ice Loss from 1979 to 2020. J. Climate, 35(20), 3197-3213. doi: 10.1175/JCLI-D-21-0893.1. Abstract Over the past decades, Arctic climate has exhibited significant changes characterized by strong pan-Arctic warming and a large-scale wind shift trending toward an anticyclonic anomaly centered over Greenland and the Arctic Ocean. Recent work has suggested that this wind change is able to warm the Arctic atmosphere and melt sea ice through dynamically driven warming, moistening, and ice drift effects. However, previous examination of this linkage lacks a capability to fully consider the complex nature of the sea ice response to the wind change. In this study, we perform a more rigorous test of this idea by using a coupled high-resolution modeling framework with observed winds nudged over the Arctic that allows for a comparison of these wind-induced effects with observations and simulated effects forced by anthropogenic forcing. Our nudging simulation can well capture observed variability of atmospheric temperature, sea ice, and the radiation balance during the Arctic summer and appears to simulate around 30% of Arctic warming and sea ice melting over the whole period (1979–2020) and more than 50% over the period 2000–12, which is the fastest Arctic warming decade in the satellite era. In particular, in the summer of 2020, a similar wind pattern reemerged to induce the second-lowest sea ice extent since 1979, suggesting that large-scale wind changes in the Arctic are essential in shaping Arctic climate on interannual and interdecadal time scales and may be critical to determine Arctic climate variability in the coming decades. Significance Statement This work conducts a set of new CESM1 nudging simulations to quantify the impact of the observed evolution of large-scale high-latitude atmospheric winds on Arctic climate variability over the past four decades. Variations in climate parameters, including sea ice, radiation, and atmospheric temperatures are well replicated in the model when observed winds are imposed in the Arctic. By investigating simulated sea ice melting processes in the simulation, we illustrate and estimate how large-scale winds in the Arctic help melt sea ice in summer. The nudging method has the potential to make Arctic climate attribution more tangible and to unravel the important physical processes underlying recent abrupt climate change in the Arctic.
Dodson, J. Brant; Robles, Marilé Colón; Rogerson, Tina M.; Taylor, Jessica E.Dodson, J. B., M. Robles, . Colón, T. M. Rogerson, J. E. Taylor, 2022: Do citizen science Intense Observation Periods increase data usability? A deep dive of the NASA GLOBE Clouds data set with satellite comparisons. Earth and Space Science, n/a(n/a), e2021EA002058. doi: 10.1029/2021EA002058. The Global Learning and Observations to Benefit the Environment (GLOBE) citizen science program has recently conducted a series of month-long intensive observation periods (IOPs), asking the public to submit daily reports on cloud and sky conditions from all regions of Earth. This provides a wealth of crowdsourced observations from the ground, which complements other conventional scientific cloud data. In addition, the GLOBE reports are matched in space and time with geostationary and low Earth orbit satellites, which allows for a straightforward comparison of cloud properties, and minimizes the biases associated with mismatched sampling between participants and satellites. The matched GLOBE dataset is used to calculate the mean observed cloud cover by atmospheric level both worldwide and by region. The overall magnitudes of cloud cover between the GLOBE participants and the matched satellites agree within 10%, which is notable given the distinctly different natures of the data sources. The mean vertical cloud profiles show GLOBE reporting more low-level clouds and fewer high-level clouds than satellites. The low cloud disagreement is likely related to satellites missing low clouds when high clouds block their view. Conversely, the high cloud disagreement is related primarily to cloud opacity, as satellites may miss some optically thin clouds. Monte Carlo testing shows the results to be robust, and the tripled amount of IOP data reduces uncertainty by half. These findings also highlight ways in which citizen science IOP data may be used to support scientific research while accounting for their unique properties. Monte Carlo; citizen science; cloud cover; global data set; satellite validation; vertical cloud structure
Doelling, David R.; Haney, Conor; Bhatt, Rajendra; Scarino, Benjamin; Gopalan, ArunDoelling, D. R., C. Haney, R. Bhatt, B. Scarino, A. Gopalan, 2022: Daily monitoring algorithms to detect geostationary imager visible radiance anomalies. Journal of Applied Remote Sensing, 16(1), 014502. doi: 10.1117/1.JRS.16.014502. The NASA Clouds and the Earth’s Radiant Energy System (CERES) project provides observed flux and cloud products for the climate science community. Geostationary satellite (GEO) imager measured clouds and broadband derived fluxes are incorporated in the CERES SYN1deg product to provide regional diurnal information in between Sun-synchronous Terra and Aqua CERES measurements. The recently launched GEO imagers with onboard calibration systems have active calibration teams that incrementally update the calibration in order to mitigate calibration drifts. However, short-term L1B radiance anomalies and calibration adjustment discontinuities may still exist in the record. To avoid any GEO cloud and flux artifacts in the CERES SYN1deg product, these calibration events must be addressed while scaling the GEO imagers to the Aqua-moderate resolution imaging spectroradiometer (MODIS) calibration reference. All-sky tropical ocean ray-matching (ATO-RM) and deep convective cloud invariant target (DCC-IT)-based monitoring algorithms are presented to detect calibration-driven daily anomalies in the GOES-16 Advanced Baseline Imager L1B visible (0.65 μm) radiance measurements. Sufficient daily ATO-RM sampling was obtained both by ray-matching GOES-16 with multiple MODIS and visible-infrared imaging radiometer suite imagers as well as by increasing the grid resolution. Optimized angular matching and outlier filtering were most effective in reducing the ATO-RM daily gain algorithm noise. The DCC-IT daily calibration algorithm utilized a larger domain and included more GOES-16 scan times. The DCC-IT daily gain uncertainty was reduced by normalizing the DCC regional reflectance on a regional, seasonal, and diurnal basis. The combination of ATO-RM and DCC-IT daily monitoring algorithms is shown to detect, with a high degree of confidence, daily GOES-16 L1B calibration-driven radiance anomalies >2.4 % , while keeping false positives at a minimum. Remarkably, the ATO-RM and DCC-IT daily gains are mostly within 0.5%. The ATO-RM and DCC-IT daily monitoring algorithms can be easily adapted to other GEO imagers and visible channels.
Duan, Wentao; Jin, ShuanggenDuan, W., S. Jin, 2022: An improved methodology for quantifying pixel-scale entrance pupil irradiance of a Moon-based Earth radiation observatory. ISPRS Journal of Photogrammetry and Remote Sensing, 183, 389-402. doi: 10.1016/j.isprsjprs.2021.11.019. The establishment of a Moon-based Earth Radiation Observatory (MERO) is expected to improve current Earth radiation budget observations. In terms of the MERO instrument design, the pixel-scale entrance pupil irradiance (EPI), which acts as the true input radiation to the MERO detector unit, is essential to judge the detector optimization and systematic parameter adjustment. The primary motivation of this study is to improve the pixel-scale EPI quantification quality by proposing a modified methodology. Evaluations indicated that the new pixel ground field of view (GFOV) positioning method would bring accuracy improvements of 7.79% and 3.84% for pixel-scale shortwave (SW) EPI and longwave (LW) EPI quantifications respectively; while the accuracy enhancements result from the newly proposed Earth top of atmosphere (TOA) radiant anisotropy method in this study are about 20.67% and 12.15% for the pixel-scale SW EPI and LW EPI estimations respectively. Following this modified methodology, an 18.6-year pixel-scale EPI variability prediction was accomplished to facilitate the MERO instrument design coping with change in future decades. This prediction fully considers the influences from the MERO-Earth geometry evolution, Earth TOA radiant anisotropic factor temporal change, the Earth TOA flux temporal variation and MERO location change. Results showed that the SW EPI would vary from approximately 3.32 × 10−6 to 2.16 × 10−4 W/m2 over the future 18.6-year period (March 2019 to November 2037); while the LW EPI would change between 4.43 × 10–6 and 4.91 × 10−4 W/m2. Earth radiation budget; Moon-based Earth Radiation Observatory; Pixel-scale entrance pupil irradiance
Erfani, Ehsan; Blossey, Peter; Wood, Robert; Mohrmann, Johannes; Doherty, Sarah J.; Wyant, Matthew; O, Kuan-TingErfani, E., P. Blossey, R. Wood, J. Mohrmann, S. J. Doherty, M. Wyant, K. O, 2022: Simulating Aerosol Lifecycle Impacts on the Subtropical Stratocumulus-to-Cumulus Transition Using Large-Eddy Simulations. Journal of Geophysical Research: Atmospheres, 127(21), e2022JD037258. doi: 10.1029/2022JD037258. Observed stratocumulus to cumulus transitions (SCTs) and their sensitivity to aerosols are studied using a large-eddy simulation (LES) model that simulates the aerosol lifecycle, including aerosol sources and sinks. To initialize, force, and evaluate the LES, we used a combination of reanalysis, satellite, and aircraft data from the 2015 Cloud System Evolution in the Trades field campaign over the Northeast Pacific. The simulations follow two Lagrangian trajectories from initially overcast stratocumulus (Sc) to the tropical shallow cumulus region near Hawaii. The first trajectory is characterized by an initially clean, well-mixed Sc-topped marine boundary layer (MBL), then continuous MBL deepening and precipitation onset followed by a clear SCT and a consistent reduction of aerosols that ultimately leads to an ultra-clean layer in the upper MBL. The second trajectory is characterized by an initially polluted and decoupled MBL, weak precipitation, and a late SCT. Overall, the LES simulates the observed general MBL features. Sensitivity studies with different aerosol initial and boundary conditions reveal aerosol-induced changes in the transition, and albedo changes are decomposed into the Twomey effect and adjustments of cloud liquid water path and cloud fraction. Impacts on precipitation play a key role in the sensitivity to aerosols: for the first case, runs with enhanced aerosols exhibit distinct changes in microphysics and macrophysics such as enhanced cloud droplet number concentration, reduced precipitation, and delayed SCT. Cloud adjustments are dominant in this case. For the second case, enhancing aerosols does not affect cloud macrophysical properties significantly, and the Twomey effect dominates. aerosols; clouds; marine boundary layer; large eddy simulations; stratocumulus to cumulus transition
Espinoza, Jhan-Carlo; Marengo, José Antonio; Schongart, Jochen; Jimenez, Juan CarlosEspinoza, J., J. Marengo, . Antonio, J. Schongart, J. C. Jimenez, 2022: The new historical flood of 2021 in the Amazon River compared to major floods of the 21st century: Atmospheric features in the context of the intensification of floods. Weather and Climate Extremes, 35, 100406. doi: 10.1016/j.wace.2021.100406. In June 2021 a new extreme flood was reported in the Amazon Basin, the largest hydrological system on Earth. During this event water level was above 29 m (the emergency threshold) for 91 days at Manaus station (Brazil), surpassing even the previous historical flood of 2012. Since the late 1990s, 9 extreme floods occurred, while only 8 events were reported from 1903 to 1998. Here we report that the 2021 flood is associated with an intensification of the atmospheric upward motion in the northern Amazonia (5°S-5°N), which is related to an intensification of the Walker circulations. This atmospheric feature is associated with an enhanced of deep convective clouds and intense rainfall over the northern Amazonia that produce positive anomalies of terrestrial water storage over northern Amazonia in the 2021 austral summer. The intensification of Walker circulation is associated with La Niña conditions that characterize the major floods observed in Amazonia during the 21st century (2009, 2012 and 2021). However, during the 2021 an intensification of the continental Hadley circulation is also observed. This feature produces simultaneous dry conditions over southern and southeastern Amazonia, where negative rainfall anomalies, low frequency of deep convective clouds and negative anomalies of terrestrial water storage are observed.
Fasullo, J. T.; Lamarque, Jean-Francois; Hannay, Cecile; Rosenbloom, Nan; Tilmes, Simone; DeRepentigny, Patricia; Jahn, Alexandra; Deser, ClaraFasullo, J. T., J. Lamarque, C. Hannay, N. Rosenbloom, S. Tilmes, P. DeRepentigny, A. Jahn, C. Deser, 2022: Spurious Late Historical-Era Warming in CESM2 Driven by Prescribed Biomass Burning Emissions. Geophysical Research Letters, 49(2), e2021GL097420. doi: 10.1029/2021GL097420. A spurious increase in the interannual variability of prescribed biomass burning (BB) emissions in the CMIP6 forcing database during the satellite era of wildfire monitoring (1997–2014) is found to lead to warming in the Northern Hemisphere extratropics in simulations with the Community Earth System Model version 2 (CESM2). Using targeted sensitivity experiments with the CESM2 in which prescribed BB emissions are homogenized and variability is removed, we show that the warming is specifically attributable to BB variability from 40° to 70°N and arises from a net thinning of the cloud field and an associated increase in absorbed solar radiation. Our results also demonstrate the potential pitfalls of introducing discontinuities in climate forcing data sets when trying to incorporate novel observations. global climate models; land/atmosphere interactions; aerosol/cloud interactions; global change
Feng, Chunjie; Zhang, Xiaotong; Xu, Jiawen; Yang, Shuyue; Guan, Shikang; Jia, Kun; Yao, YunjunFeng, C., X. Zhang, J. Xu, S. Yang, S. Guan, K. Jia, Y. Yao, 2022: Comprehensive assessment of global atmospheric downward longwave radiation in the state-of-the-art reanalysis using satellite and flux tower observations. Climate Dynamics. doi: 10.1007/s00382-022-06366-2. The atmospheric downward longwave radiation at the Earth’s surface (Ld) is an important parameter for investigating greenhouse effects and global climate changes. Reanalysis data have been widely applied to obtain surface radiation components. Since new generation reanalysis data have been released, a comprehensive evaluation of the Ld predictions from the latest reanalysis data using ground measurements is still necessary. In this study, the Ld estimates of four representative reanalysis data (CFSR, JRA-55, ERA5, and MERRA2) were evaluated using ground observations at 383 stations from the AmeriFlux, AsiaFlux, BSRN, Buoy, FLUXNET, and SURFEAD networks. The evaluation results manifested that the overall root mean square errors (mean bias errors) of daily mean Ld values over the global surface were 21.1 (− 1.8) W m−2, 22.4 (− 3.9) W m−2, 19.3 (− 3.6) W m−2, 25.2 (− 12.6) W m−2, and 20.5 (3.1) W m−2 for CFSR, JRA-55, ERA5, MERAA2, and CERES-SYN, respectively. Compared with the CERES-SYN satellite retrievals, the ERA5 (CFSR) daily mean Ld estimates had relatively smaller overall root mean square errors (mean bias errors) over the global land surface. Over the global ocean surface, the JRA-55 daily mean Ld estimates had comparable mean bias errors (MBEs) with CERES-SYN. After removing the MBEs, the best annual mean Ld estimate was 344.0 (± 3) W m−2 over the global surface of 2001 to 2020. The spatial distributions and long-term trends of Ld for the selected four reanalysis data and CERES-SYN were also investigated in this study. The comprehensive assessment of the Ld products from reanalysis data and satellite retrievals in this study would be helpful for climate change studies. Reanalysis; CERES-SYN; Surface downward longwave radiation; Ground observation
Feng, Huihui; Xiong, Jian; Ye, Shuchao; Zou, Bin; Wang, WeiFeng, H., J. Xiong, S. Ye, B. Zou, W. Wang, 2022: Vegetation change enhanced the positive global surface radiation budget. Advances in Space Research, 70(2), 324-335. doi: 10.1016/j.asr.2022.04.038. Surface radiation budget was an important variable for global climate and eco-environment change. Vegetation exerted significant influences on the budget by altering the surface thermal properties and land-atmospheric interactions, while the sign and magnitude remained unclear. With the aid of satellite observations, this study estimated the vegetation influences through a semi-physical approach. Methodologically, a physical model of the total surface radiation budget (Rnet) was firstly built. Then, the empirical regressions between vegetation with radiation albedo and thermal emissivity were adopted. Finally, the vegetation influences were estimated by measuring the response of budgets (Rsnet, Rlnet and subsequently Rnet) to vegetation perturbance. Our results demonstrated that the global Rnet presented a positive budget (73.20 W/m2) over the past two decades (2001–2020), which was dominated by the positive Rsnet (135.52 W/m2). In contrast, the Rlnet showed a negative value (−60.92 W/m2), which helped to mitigate the warming trend. Vegetation tended to enhance the positive surface radiation budgets. Overall, the vegetation influences on Rsnet, Rlnet and Rnet were 56.20 W/m2, −6.65 W/m2, and 50.29 W/m2, accounting for 41.47 %, 10.92 % and 68.70 % of the total budgets. Temporally, the vegetation influences showed increasing trends of 0.019 W/m2/yr (Rsnet), 0.007 W/m2/yr (Rlnet) and 0.031 W/m2/yr (Rnet). Physically, temporal variations of the vegetation influences were strongly affected by the interactions of atmospheric factors, particularly of the cloud, aerosol, and greenhouse gases (GHGs). Results of this study help to capture characteristics of surface radiation budgets and corresponding mechanism, which could support the climatic adaption and eco-environment management. Climate change; Satellite; Radiation budget; Globe; Vegetation change
Ferris, Laur; Gong, Donglai; Clayson, Carol Anne; Merrifield, Sophia; Shroyer, Emily L.; Smith, Madison; Laurent, Louis StFerris, L., D. Gong, C. A. Clayson, S. Merrifield, E. L. Shroyer, M. Smith, L. S. Laurent, 2022: Shear Turbulence in the High-Wind Southern Ocean Using Direct Measurements. J. Phys. Oceanogr., 52(10), 2325-2341. doi: 10.1175/JPO-D-21-0015.1. Abstract The ocean surface boundary layer is a gateway of energy transfer into the ocean. Wind-driven shear and meteorologically forced convection inject turbulent kinetic energy into the surface boundary layer, mixing the upper ocean and transforming its density structure. In the absence of direct observations or the capability to resolve subgrid-scale 3D turbulence in operational ocean models, the oceanography community relies on surface boundary layer similarity scalings (BLS) of shear and convective turbulence to represent this mixing. Despite their importance, near-surface mixing processes (and ubiquitous BLS representations of these processes) have been undersampled in high-energy forcing regimes such as the Southern Ocean. With the maturing of autonomous sampling platforms, there is now an opportunity to collect high-resolution spatial and temporal measurements in the full range of forcing conditions. Here, we characterize near-surface turbulence under strong wind forcing using the first long-duration glider microstructure survey of the Southern Ocean. We leverage these data to show that the measured turbulence is significantly higher than standard shear-convective BLS in the shallower parts of the surface boundary layer and lower than standard shear-convective BLS in the deeper parts of the surface boundary layer; the latter of which is not easily explained by present wave-effect literature. Consistent with the CBLAST (Coupled Boundary Layers and Air Sea Transfer) low winds experiment, this bias has the largest magnitude and spread in the shallowest 10% of the actively mixing layer under low-wind and breaking wave conditions, when relatively low levels of turbulent kinetic energy (TKE) in surface regime are easily biased by wave events. Significance Statement Wind blows across the ocean, turbulently mixing the water close to the surface and altering its properties. Without the ability to measure turbulence in remote locations, oceanographers use approximations called boundary layer scalings (BLS) to estimate the amount of turbulence caused by the wind. We compared turbulence measured by an underwater robot to turbulence estimated from wind speed to determine how well BLS performs in stormy places. We found that in both calm and stormy conditions, estimates are 10 times too large closest to the surface and 10 times too small deeper within the turbulently mixed surface ocean.
Fiddes, Sonya L.; Protat, Alain; Mallet, Marc D.; Alexander, Simon P.; Woodhouse, Matthew T.Fiddes, S. L., A. Protat, M. D. Mallet, S. P. Alexander, M. T. Woodhouse, 2022: Southern Ocean cloud and shortwave radiation biases in a nudged climate model simulation: does the model ever get it right?. Atmospheric Chemistry and Physics, 22(22), 14603-14630. doi: 10.5194/acp-22-14603-2022. The Southern Ocean radiative bias continues to impact climate and weather models, including the Australian Community Climate and Earth System Simulator (ACCESS). The radiative bias, characterised by too much shortwave radiation reaching the surface, is attributed to the incorrect simulation of cloud properties, including frequency and phase. To identify cloud regimes important to the Southern Ocean, we use k-means cloud histogram clustering, applied to a satellite product and then fitted to nudged simulations of the latest-generation ACCESS atmosphere model. We identify instances when the model correctly or incorrectly simulates the same cloud type as the satellite product for any point in time or space. We then evaluate the cloud and radiation biases in these instances. We find that when the ACCESS model correctly simulates the cloud type, cloud property and radiation biases of equivalent, or in some cases greater, magnitude remain compared to when cloud types are incorrectly simulated. Furthermore, we find that even when radiative biases appear small on average, cloud property biases, such as liquid or ice water paths or cloud fractions, remain large. Our results suggest that simply getting the right cloud type (or the cloud macrophysics) is not enough to reduce the Southern Ocean radiative bias. Furthermore, in instances where the radiative bias is small, it may be so for the wrong reasons. Considerable effort is still required to improve cloud microphysics, with a particular focus on cloud phase.
Francis, Diana; Fonseca, Ricardo; Nelli, Narendra; Bozkurt, Deniz; Picard, Ghislain; Guan, BinFrancis, D., R. Fonseca, N. Nelli, D. Bozkurt, G. Picard, B. Guan, 2022: Atmospheric rivers drive exceptional Saharan dust transport towards Europe. Atmospheric Research, 266, 105959. doi: 10.1016/j.atmosres.2021.105959. This study highlights the occurrence of atmospheric rivers (ARs) over northwest Africa towards Europe, which were accompanied by intense episodes of Saharan dust transport all the way to Scandinavia, in the winter season. Using a combination of observational and reanalysis data, we investigate two extreme dusty AR events in February 2021 and assess their impact on snow melt in the Alps. The warm, moist, and dusty air mass (spatially-averaged 2-meter temperature and water vapour mixing ratio anomalies of up to 8 K and 3 g kg−1, and aerosol optical depths and dust loadings of up to 0.85 and 11 g m−2, respectively) led to a 50% and 40% decrease in snow depth and surface albedo, respectively, in less than one month during the winter season. ARs over northwest Africa show increasing trends over the past 4 decades, with 78% of AR events associated with severe dust episodes over Europe. Dust aerosols; Atmospheric rivers; European Alps; Sahara Desert; Snow melting; Water vapour
Francis, Diana; Fonseca, Ricardo; Nelli, Narendra; Teixido, Oriol; Mohamed, Ruqaya; Perry, RichardFrancis, D., R. Fonseca, N. Nelli, O. Teixido, R. Mohamed, R. Perry, 2022: Increased Shamal winds and dust activity over the Arabian Peninsula during the COVID-19 lockdown period in 2020. Aeolian Research, 55, 100786. doi: 10.1016/j.aeolia.2022.100786. While anthropogenic pollutants have decreased during the lockdown imposed as an effort to contain the spread of the Coronavirus disease 2019 (COVID-19), changes in particulate matter (PM) do not necessarily exhibit the same tendency. This is the case for the eastern Arabian Peninsula, where in March–June 2020, and with respect to the same period in 2016–2019, a 30 % increase in PM concentration is observed. A stronger than normal nocturnal low-level jet and subtropical jet over parts of Saudi Arabia, in response to anomalous convection over the tropical Indian Ocean, promoted enhanced and more frequent episodes of Shamal winds over the Arabian Peninsula. Increased surface winds associated with the downward mixing of momentum to the surface fostered, in turn, dust lifting and increased PM concentrations. The stronger low-level winds also favoured long-range transport of aerosols, changing the PM values downstream. The competing effects of reduced anthropogenic and increased dust concentrations leave a small positive signal (20 W m−2 with respect to the baseline period, owing to a clearer environment and weaker winds. It is concluded that a reduction in anthropogenic emissions due to the lockdown does not necessarily go hand in hand with lower particulate matter concentrations. Therefore, emissions reduction strategies need to account for feedback effects in order to reach the planned long-term outcomes. Arabian Peninsula; Low-level jet; Particulate Matter; Rossby Wavetrain; Shamal Winds; Surface Radiation Budget
Francis, Diana; Nelli, Narendra; Fonseca, Ricardo; Weston, Michael; Flamant, Cyrille; Cherif, CharfeddineFrancis, D., N. Nelli, R. Fonseca, M. Weston, C. Flamant, C. Cherif, 2022: The dust load and radiative impact associated with the June 2020 historical Saharan dust storm. Atmospheric Environment, 268, 118808. doi: 10.1016/j.atmosenv.2021.118808. In June 2020, a major dust outbreak occurred in the Sahara that impacted the tropical Atlantic Ocean. In this study, the dust load and radiative forcing of the dust plumes on both the atmosphere and ocean surface is investigated by means of observations and modelling. We estimated dust loadings in excess of 8 Tg over the eastern tropical Atlantic, comparable to those observed over the desert during major Saharan dust storms. The dust induced an up to 1.1 K net warming of the ocean surface and a 1.8K warming of the air temperature (i.e., two to three times the respective climatological standard deviations), with a +14 W m−2 (∼28% of the mean value) increase in the surface net radiation flux at night. As the dust plumes extended all the way to the Caribbean, it is possible that this historical dust event helped fuel the record-breaking 2020 Atlantic hurricane season. Dust aerosols; Radiative forcing; WRF-Chem; Sahara; Tropical Atlantic
Gao, Zhibo; Zhao, Chuanfeng; Yan, Xiaodong; Guo, Yan; Liu, Sichang; Luo, Neng; Song, Shuaifeng; Zhao, ZihuiGao, Z., C. Zhao, X. Yan, Y. Guo, S. Liu, N. Luo, S. Song, Z. Zhao, 2022: Effects of cumulus and radiation parameterization on summer surface air temperature over eastern China. Climate Dynamics. doi: 10.1007/s00382-022-06601-w. Cloud-radiation process has a strong impact on surface air temperature (SAT). Using the Weather Research and Forecasting (WRF) model, this study investigates the effects of cumulus and radiation parameterization on SAT simulation over Eastern China (EC) during the summer season from 2001 to 2020. Four experiments are performed at a 30 km resolution using the combination of two cumulus schemes (KF and KF-CUP) and two radiation schemes (CAM and RRTMG). The results indicate that the KF and RRTMG scheme can produce warmer SAT than KF-CUP and CAM, respectively. By decomposing the differences in SAT simulation, it is found that KF and RRTMG have greater surface downward shortwave radiation (DSR), and the DSR shows a significant positive correlation with SAT in most parts of EC. Further analysis reveals that low-level cloud (LC) can strongly reflect the DSR, and the LC fraction (LCF) of KF and RRTMG is less than that of KF-CUP and CAM, respectively. The reason for this phenomenon is that the sub-grid cumulus heating rate is higher in KF and RRTMG, resulting in their higher air temperature (T) and greater differences between T and dew point (Td), which is not conducive to the formation of large-scale stratiform cloud and the increase of LCF. As a result, KF and RRTMG have more DSR and higher SAT than KF-CUP and CAM, respectively. The same mechanism can also explain the differences in the sub-seasonal cycle simulations between the four experiments. By comparing the SAT error in each subregion, this study can also provide a reference for future dynamic downscaling over the EC region.
García Pedreros, Julián Guillermo; Ospina-Noreña, Jesús EfrénGarcía Pedreros, J. G., J. E. Ospina-Noreña, 2022: Spatial distribution model of terrestrial radiation imbalance measured by means of orbiting radiometers. Remote Sensing Applications: Society and Environment, 28, 100857. doi: 10.1016/j.rsase.2022.100857. A spatial distribution model was applied to net radiation levels in central Colombia obtained from remote sensing data; this model was based on the use of spatial interpolation geostatistical techniques and consists of three essential phases: an evaluation of the quality of the spectral scenes, the application of spatial interpolation techniques and the statistical evaluation of the model. These procedures allowed a more accurate analysis of the variables that influence the spatial patterns of terrestrial radiation imbalance (T.R.I) in specific areas of the country. The input data used in this model are called FlashFlux Time Integrated and Spatially Averaged (TISA) and come from observations of the Terra and Aqua satellites of the CERES (Clouds and the Earths Radiant Energy System) and MODIS (Moderate-Resolution Imaging Spectroradiometer) projects. In summary, the way in which this research was carried out was initially with an evaluation of the image quality, to analyse the potential and statistical characteristics of the FlashFlux TISA data; subsequently, a kriging interpolation method was applied adapting the radiometric data for a correct analysis and the patterns of terrestrial radiation imbalance in the centre of the country were analysed, trying to explore variables that influence these spatial dynamics. Finally, an evaluation of the spatial distribution model of terrestrial radiation imbalance was established, where the virtues, relevance and limitations of the techniques used in it were validated. This research was able to implement statistical methods of spatial interpolation, specifically the Ordinary Kriging technique, allowing the modelling of the recent situation of terrestrial radiation imbalance in central Colombia, identifying some processes and factors that are closely related to this atmospheric phenomenon responsible for the effects of regional warming. Remote sensing; Kriging interpolation; Spatial modelling; Terrestrial radiation
Ghate, Virendra P.; Carlton, Annmarie G.; Surleta, Thomas; Burns, Alyssa MarieGhate, V. P., A. G. Carlton, T. Surleta, A. M. Burns, 2022: Changes in Aerosols, Meteorology, and Radiation in the Southeastern U.S. Warming Hole Region during 2000 to 2019. J. Climate, 35(23), 4125-4137. doi: 10.1175/JCLI-D-22-0073.1. Abstract Surface air temperatures in the southeastern United States that did not change from the climatological mean from 1900 to 2000 have increased since the year 2000. Analyzed herein are factors modulating the surface air temperatures in the region for a 20-yr period (2000–19) using space- and surface-based observations, and output from a reanalysis model. The 20-yr period is segregated into two decades, 2000–09 and 2010–19, corresponding to different tropospheric chemical regimes. Changes in seasonal and decadal averages are examined. The later decade experienced higher average surface air temperatures with significant warming during summer and fall seasons. Decadal and seasonal averages of cloud properties, column water vapor, rain rates, and top-of-atmosphere outgoing longwave radiation did not exhibit statistically significant differences between the two decades. The region experienced strong warm and moist advection during the winter months and very weak advection during the summer months. The later decade exhibited higher low-level moisture advection during the winter months than the earlier decade with insignificant changes in the temperature advection between the two decades. The later decade had significantly lower aerosol dry and liquid water mass during all seasons, along with lower aerosol optical depth, higher single scattering albedo, and lower top-of-the-atmosphere outgoing shortwave radiation during cloud-free conditions in the summer season. Collectively, these results suggest that changes in the aerosol direct radiative forcing are responsible for warming during summer months that experience weak advection and highlight seasonal differences in the temperature controlling mechanisms in the region.
Ghayas, Humaira; Radhakrishnan, S. R.; Sehgal, Vinay Kumar; Singh, SachchidanandGhayas, H., S. R. Radhakrishnan, V. K. Sehgal, S. Singh, 2022: Measurement and comparison of photosynthetically active radiation by different methods at Delhi. Theoretical and Applied Climatology, 150(3), 1559-1571. doi: 10.1007/s00704-022-04252-9. Photosynthetically active radiation (PAR) received at the earth surface is the primary driver of plant growth and biomass production. The absence of a dedicated sensor network for regular measurements of PAR over the Indian region poses a challenge to the crop modelers and the decision makers. In the absence of any long-term study of PAR from this region, the present study from Delhi provides 4 years (2013–2016) of dedicated PAR measurements and also compares it with three other different methods of PAR estimation. PAR has been measured at the surface using Kipp and Zonen PQS1 PAR sensor and the data has been compared with the remotely sensed CERES-derived all-sky PAR values. It was also compared with the PAR estimated by fractional method using shortwave (SW) flux measured by pyranometer and the ratio of PAR/SW fraction using long-term satellite data for Delhi. It was further compared with the TUV radiative transfer model–derived PAR on clear-sky days. The daily mean PAR observed at Delhi is in the range 7.9 to 185.3 Wm−2 (average 94.5 ± 1.1 Wm−2) which nearly matched with the CERES-derived PAR in the range 10.8 to 144.3 Wm−2 (average 89.4 ± 0.8 Wm−2) and PAR derived by fractional method range 8.9 to 187 Wm−2 (with average 88.1 ± 0.8 Wm−2). The TUV model–estimated PAR on clear-sky days was found in the range 39.1–154.9 Wm−2 (average 96.8 ± 1.4 Wm−2) which showed a strong correlation of 0.82 with the observed PAR values on concurrent days. PAR estimated by all the three methods showed a good correlation with the observations (> 0.80). It may be concluded that in the absence of a regular PAR measurements, any of the three above methods of PAR estimation can give fairy accurate value at a point but CERES gives added advantage of providing PAR over large spatial area in the region. CERES; PAR; Radiation; TUV model
Giraldo, Jorge A.; del Valle, Jorge I.; González-Caro, Sebastián; Sierra, Carlos A.Giraldo, J. A., J. I. del Valle, S. González-Caro, C. A. Sierra, 2022: Intra-annual isotope variations in tree rings reveal growth rhythms within the least rainy season of an ever-wet tropical forest. Trees, 36(3), 1039-1052. doi: 10.1007/s00468-022-02271-7. Isotope variation (δ18O) in wood suggests new insights on growth rhythms in trees growing in tropical forest with extremely high precipitation, without seasonal droughts or flooding. Biogeographical Chocó region; C isotopes; Dendrochronology; O isotopes; Tropical trees
Golaz, Jean-Christophe; Van Roekel, Luke P.; Zheng, Xue; Roberts, Andrew F.; Wolfe, Jonathan D.; Lin, Wuyin; Bradley, Andrew M.; Tang, Qi; Maltrud, Mathew E.; Forsyth, Ryan M.; Zhang, Chengzhu; Zhou, Tian; Zhang, Kai; Zender, Charles S.; Wu, Mingxuan; Wang, Hailong; Turner, Adrian K.; Singh, Balwinder; Richter, Jadwiga H.; Qin, Yi; Petersen, Mark R.; Mametjanov, Azamat; Ma, Po-Lun; Larson, Vincent E.; Krishna, Jayesh; Keen, Noel D.; Jeffery, Nicole; Hunke, Elizabeth C.; Hannah, Walter M.; Guba, Oksana; Griffin, Brian M.; Feng, Yan; Engwirda, Darren; Di Vittorio, Alan V.; Dang, Cheng; Conlon, LeAnn M.; Chen, Chih-Chieh-Jack; Brunke, Michael A.; Bisht, Gautam; Benedict, James J.; Asay-Davis, Xylar S.; Zhang, Yuying; Zhang, Meng; Zeng, Xubin; Xie, Shaocheng; Wolfram, Phillip J.; Vo, Tom; Veneziani, Milena; Tesfa, Teklu K.; Sreepathi, Sarat; Salinger, Andrew G.; Reeves Eyre, J. E. Jack; Prather, Michael J.; Mahajan, Salil; Li, Qing; Jones, Philip W.; Jacob, Robert L.; Huebler, Gunther W.; Huang, Xianglei; Hillman, Benjamin R.; Harrop, Bryce E.; Foucar, James G.; Fang, Yilin; Comeau, Darin S.; Caldwell, Peter M.; Bartoletti, Tony; Balaguru, Karthik; Taylor, Mark A.; McCoy, Renata B.; Leung, L. Ruby; Bader, David C.Golaz, J., L. P. Van Roekel, X. Zheng, A. F. Roberts, J. D. Wolfe, W. Lin, A. M. Bradley, Q. Tang, M. E. Maltrud, R. M. Forsyth, C. Zhang, T. Zhou, K. Zhang, C. S. Zender, M. Wu, H. Wang, A. K. Turner, B. Singh, J. H. Richter, Y. Qin, M. R. Petersen, A. Mametjanov, P. Ma, V. E. Larson, J. Krishna, N. D. Keen, N. Jeffery, E. C. Hunke, W. M. Hannah, O. Guba, B. M. Griffin, Y. Feng, D. Engwirda, A. V. Di Vittorio, C. Dang, L. M. Conlon, C. Chen, M. A. Brunke, G. Bisht, J. J. Benedict, X. S. Asay-Davis, Y. Zhang, M. Zhang, X. Zeng, S. Xie, P. J. Wolfram, T. Vo, M. Veneziani, T. K. Tesfa, S. Sreepathi, A. G. Salinger, J. E. J. Reeves Eyre, M. J. Prather, S. Mahajan, Q. Li, P. W. Jones, R. L. Jacob, G. W. Huebler, X. Huang, B. R. Hillman, B. E. Harrop, J. G. Foucar, Y. Fang, D. S. Comeau, P. M. Caldwell, T. Bartoletti, K. Balaguru, M. A. Taylor, R. B. McCoy, L. R. Leung, D. C. Bader, 2022: The DOE E3SM Model Version 2: Overview of the Physical Model and Initial Model Evaluation. Journal of Advances in Modeling Earth Systems, 14(12), e2022MS003156. doi: 10.1029/2022MS003156. This work documents version two of the Department of Energy's Energy Exascale Earth System Model (E3SM). E3SMv2 is a significant evolution from its predecessor E3SMv1, resulting in a model that is nearly twice as fast and with a simulated climate that is improved in many metrics. We describe the physical climate model in its lower horizontal resolution configuration consisting of 110 km atmosphere, 165 km land, 0.5° river routing model, and an ocean and sea ice with mesh spacing varying between 60 km in the mid-latitudes and 30 km at the equator and poles. The model performance is evaluated with Coupled Model Intercomparison Project Phase 6 Diagnosis, Evaluation, and Characterization of Klima simulations augmented with historical simulations as well as simulations to evaluate impacts of different forcing agents. The simulated climate has many realistic features of the climate system, with notable improvements in clouds and precipitation compared to E3SMv1. E3SMv1 suffered from an excessively high equilibrium climate sensitivity (ECS) of 5.3 K. In E3SMv2, ECS is reduced to 4.0 K which is now within the plausible range based on a recent World Climate Research Program assessment. However, a number of important biases remain including a weak Atlantic Meridional Overturning Circulation, deficiencies in the characteristics and spectral distribution of tropical atmospheric variability, and a significant underestimation of the observed warming in the second half of the historical period. An analysis of single-forcing simulations indicates that correcting the historical temperature bias would require a substantial reduction in the magnitude of the aerosol-related forcing. climate modeling; DOE E3SM
González-Bárcena, David; Bermejo-Ballesteros, Juan; Pérez-Grande, Isabel; Sanz-Andrés, ÁngelGonzález-Bárcena, D., J. Bermejo-Ballesteros, I. Pérez-Grande, Á. Sanz-Andrés, 2022: Selection of time-dependent worst-case thermal environmental conditions for Low Earth Orbit spacecrafts. Advances in Space Research, 70(7), 1847-1868. doi: 10.1016/j.asr.2022.06.060. When facing the thermal analysis of a Low Earth Orbit satellite, selecting the worst-case orbit where the minimum and maximum temperatures are reached is essential for ensuring the success of the mission. Typical orbits have a non-constant Solar Beta Angle throughout the year providing a wide range of orbits with different heat loads and eclipses. It is possible to focus the analysis on a single orbit configuration by a rough analysis using a simple model. In order to achieve this, every potential orbit with their corresponding thermal environmental parameters must be analysed based on real data. The direct solar radiation, the albedo and the Earth Outgoing Longwave Radiation (OLR) characterize the thermal environment to be taken into account. However, their values have a wide variability which depend on many parameters. Based on the characteristics of the orbit and the system thermo-optical properties and characteristic time, it is possible to obtain particularized profiles of albedo and OLR that would lead the system to its maximum and minimum temperatures. The conventional criteria, which is studied here in depth, provides two constant values of albedo and OLR as the hot and cold worst-cases. This is suitable for massive system or cases in which the characteristics times of the system are high. For lighter elements or low characteristic times, temperatures throughout the orbit deviate considerably from the real behaviour. In contrast, the methodology here proposed provides a time-dependant profile that allows for the determination of a system temperature response closer to the real one, together with the potential minimum and maximum temperatures of the orbit, in order to optimize the design and avoid the oversizing. OLR; Albedo; Thermal environment; LEO; Thermal analysis; Worst-case
Guo, Huan; Ming, Yi; Fan, Songmiao; Wittenberg, Andrew T.; Zhang, Rong; Zhao, Ming; Zhou, LinjiongGuo, H., Y. Ming, S. Fan, A. T. Wittenberg, R. Zhang, M. Zhao, L. Zhou, 2022: Performance of Two-Moment Stratiform Microphysics With Prognostic Precipitation in GFDL's CM4.0. Journal of Advances in Modeling Earth Systems, 14(12), e2022MS003111. doi: 10.1029/2022MS003111. We describe the model performance of a new global coupled climate model configuration, CM4-MG2. Beginning with the Geophysical Fluid Dynamics Laboratory's fourth-generation physical climate model (CM4.0), we incorporate a two-moment Morrison-Gettelman bulk stratiform microphysics scheme with prognostic precipitation (MG2), and a mineral dust and temperature-dependent cloud ice nucleation scheme. We then conduct and analyze a set of fully coupled atmosphere-ocean-land-sea ice simulations, following Coupled Model Intercomparison Project Phase 6 protocols. CM4-MG2 generally captures CM4.0's baseline simulation characteristics, but with several improvements, including better marine stratocumulus clouds off the west coasts of Africa and North and South America, a reduced bias toward “double” Intertropical Convergence Zones south of the equator, and a stronger Madden-Julian Oscillation (MJO). Some degraded features are also identified, including excessive Arctic sea ice extent and a stronger-than-observed El Nio-Southern Oscillation. Compared to CM4.0, the climate sensitivity is reduced by about 10% in CM4-MG2. GCM; coupled; GFDL; CM4.0; MG2
Haghighatnasab, Mahnoosh; Kretzschmar, Jan; Block, Karoline; Quaas, JohannesHaghighatnasab, M., J. Kretzschmar, K. Block, J. Quaas, 2022: Impact of Holuhraun volcano aerosols on clouds in cloud-system-resolving simulations. Atmospheric Chemistry and Physics, 22(13), 8457-8472. doi: 10.5194/acp-22-8457-2022. Abstract. Increased anthropogenic aerosols result in an enhancement in cloud droplet number concentration (Nd), which consequently modifies the cloud and precipitation process. It is unclear how exactly the cloud liquid water path (LWP) and cloud fraction respond to aerosol perturbations. A volcanic eruption may help to better understand and quantify the cloud response to external perturbations, with a focus on the short-term cloud adjustments. The goal of the present study is to understand and quantify the response of clouds to a selected volcanic eruption and to thereby advance the fundamental understanding of the cloud response to external forcing. In this study we used the ICON (ICOsahedral Non-hydrostatic) model in its numerical weather prediction setup at a cloud-system-resolving resolution of 2.5 km horizontally, to simulate the region around the Holuhraun volcano for 1 week (1–7 September 2014). A pair of simulations, with and without the volcanic aerosol plume, allowed us to assess the simulated effective radiative forcing and its mechanisms, as well as its impact on adjustments of LWP and cloud fraction to the perturbations of Nd. In comparison to MODIS (Moderate Resolution Imaging Spectroradiometer) satellite retrievals, a clear enhancement of Nd due to the volcanic aerosol is detected and attributed. In contrast, no changes in either LWP or cloud fraction could be attributed. The on average almost unchanged LWP is a result of some LWP enhancement for thick clouds and a decrease for thin clouds.
Ham, Seung-Hee; Kato, Seiji; Rose, Fred G.; Sun-Mack, Sunny; Chen, Yan; Miller, Walter F.; Scott, Ryan C.Ham, S., S. Kato, F. G. Rose, S. Sun-Mack, Y. Chen, W. F. Miller, R. C. Scott, 2022: Combining Cloud Properties from CALIPSO, CloudSat, and MODIS for Top-of-Atmosphere (TOA) Shortwave Broadband Irradiance Computations: Impact of Cloud Vertical Profiles. J. Appl. Meteor. Climatol., 61(10), 1449-1471. doi: 10.1175/JAMC-D-21-0260.1. Abstract Cloud vertical profile measurements from the CALIPSO and CloudSat active sensors are used to improve top-of-atmosphere (TOA) shortwave (SW) broadband (BB) irradiance computations. The active sensor measurements, which occasionally miss parts of the cloud columns because of the full attenuation of sensor signals, surface clutter, or insensitivity to a certain range of cloud particle sizes, are adjusted using column-integrated cloud optical depth derived from the passive MODIS sensor. Specifically, we consider two steps in generating cloud profiles from multiple sensors for irradiance computations. First, cloud extinction coefficient and cloud effective radius (CER) profiles are merged using available active and passive measurements. Second, the merged cloud extinction profiles are constrained by the MODIS visible scaled cloud optical depth, defined as a visible cloud optical depth multiplied by (1 − asymmetry parameter), to compensate for missing cloud parts by active sensors. It is shown that the multisensor-combined cloud profiles significantly reduce positive TOA SW BB biases, relative to those with MODIS-derived cloud properties only. The improvement is more pronounced for optically thick clouds, where MODIS ice CER is largely underestimated. Within the SW BB (0.18–4 μm), the 1.04–1.90-μm spectral region is mainly affected by the CER, where both the cloud absorption and solar incoming irradiance are considerable. Significance Statement The purpose of this study is to improve shortwave irradiance computations at the top of the atmosphere by using combined cloud properties from active and passive sensor measurements. Relative to the simulation results with passive sensor cloud measurements only, the combined cloud profiles provide more accurate shortwave simulation results. This is achieved by more realistic profiles of cloud extinction coefficient and cloud particle effective radius. The benefit is pronounced for optically thick clouds composed of large ice particles.
Hartmann, Dennis L.; Dygert, Brittany D.Hartmann, D. L., B. D. Dygert, 2022: Global Radiative Convective Equilibrium With a Slab Ocean: SST Contrast, Sensitivity and Circulation. Journal of Geophysical Research: Atmospheres, 127(12), e2021JD036400. doi: 10.1029/2021JD036400. Warming experiments with a uniformly insolated, non-rotating climate model with a slab ocean are conducted by increasing the solar irradiance. As the global mean surface temperature is varied across the range from 289 to 319K, the sea surface temperature (SST) contrast at first declines, then increases then declines again. Increasing SST contrast with global warming is associated with reduced climate sensitivity, while decreasing SST contrast is associated with enhanced climate sensitivity. The changing SST contrast and climate sensitivity are both related fundamentally to the effect of water vapor on clear-sky radiative cooling. The clouds in the convective region are always more reflective than those in the subsiding region and so always act to reduce the SST contrast. At lower temperatures between 289 and 297 K the shortwave suppression of SST contrast increases faster than the longwave enhancement of SST contrast. At warmer temperatures between 297 and 309 K the longwave enhancement of SST contrast with warming is stronger than the shortwave suppression of SST contrast, so that the SST contrast increases. Above 309 K the greenhouse effect in the subsiding region begins to grow, the SST contrast declines and the climate sensitivity increases. The transitions at 297 and 309 K can be related to the increasing vapor pressure path with warming. The mass circulation rate between warm and cool regions consists of shallow and deep cells. Both cells increase in strength with SST contrast. The lower cell remains connected to the surface, while the upper cell rises to maintain a roughly constant temperature. climate change; climate model; climate feedbacks
Heidinger, Andrew K.; Foster, Michael J.; Knapp, Kenneth R.; Schmit, Timothy J.Heidinger, A. K., M. J. Foster, K. R. Knapp, T. J. Schmit, 2022: Using GOES-R ABI Full-Disk Reflectance as a Calibration Source for the GOES Imager Visible Channels. Remote Sensing, 14(15), 3630. doi: 10.3390/rs14153630. The availability of onboard calibration for solar reflectance channels on recently launched advanced geostationary imagers provides an opportunity to revisit the calibration of the visible channels on past geostationary imagers, which lacked onboard calibration systems. This study used the data from the Advanced Baseline Imager (ABI) on GOES-16 and GOES-17 to calibrate the visible channels on the GOES-IP (GOES-8, -9, -10, -11, -12, -13, and -15) sensors (1994–2021). The visible channels are dominant sources of information for many of the essential climate variables from these sensors. The technique developed uses the stability of the integrated full-disk reflectance to define a calibration target that is applied to past sensors to generate new calibration equations. These equations are found to be stable and agree well with other established techniques. Given the lack of assumptions and ease of application, this technique offers a new calibration method that can be used to complement existing techniques used by the operational space agencies with the GSICS Project. In addition, its simplicity allows for its application to data that existed prior to many of the reference data employed in current calibration methods. climate; calibration; GOES
Herrington, Adam R.; Lauritzen, Peter H.; Lofverstrom, Marcus; Lipscomb, William H.; Gettelman, Andrew; Taylor, Mark A.Herrington, A. R., P. H. Lauritzen, M. Lofverstrom, W. H. Lipscomb, A. Gettelman, M. A. Taylor, 2022: Impact of grids and dynamical cores in CESM2.2 on the surface mass balance of the Greenland Ice Sheet. Journal of Advances in Modeling Earth Systems, n/a(n/a), e2022MS003192. doi: 10.1029/2022MS003192. Six different configurations, a mixture of grids and atmospheric dynamical cores available in the Community Earth System Model, version 2.2 (CESM2.2), are evaluated for their skill in representing the climate of the Arctic and the surface mass balance of the Greenland Ice Sheet (GrIS). The finite-volume dynamical core uses structured, latitude-longitude grids, whereas the spectral-element dynamical core is built on unstructured meshes, permitting grid flexibility such as quasi-uniform grid spacing globally. The 1° − 2° latitude-longitude and quasi-uniform unstructured grids systematically overestimate both accumulation and ablation over the GrIS. Of these 1° − 2° grids, the latitude-longitude grids outperform the quasi-uniform unstructured grids because they have more degrees of freedom to represent the GrIS. Two Arctic-refined meshes, with 1/4° and 1/8° refinement over Greenland, were developed for the spectral-element dynamical core and are documented here as newly supported configurations in CESM2.2. The Arctic meshes substantially improve the simulated clouds and precipitation rates in the Arctic. Over Greenland, these meshes skillfully represent accumulation and ablation processes, leading to a more realistic GrIS surface mass balance. As CESM is in the process of transitioning away from conventional latitude-longitude grids, these new Arctic-refined meshes improve the representation of polar processes in CESM by recovering resolution lost in the transition to quasi-uniform grids, albeit at increased computational cost.
Hu, Zhiyuan; Jin, Qinjian; Ma, Yuanyuan; Ji, Zhenming; Zhu, Xian; Dong, WenjieHu, Z., Q. Jin, Y. Ma, Z. Ji, X. Zhu, W. Dong, 2022: How Does COVID-19 Lockdown Impact Air Quality in India?. Remote Sensing, 14(8), 1869. doi: 10.3390/rs14081869. Air pollution is a severe environmental problem in the Indian subcontinent. Largely caused by the rapid growth of the population, industrialization, and urbanization, air pollution can adversely affect human health and environment. To mitigate such adverse impacts, the Indian government launched the National Clean Air Programme (NCAP) in January 2019. Meanwhile, the unexpected city-lockdown due to the COVID-19 pandemic in March 2020 in India greatly reduced human activities and thus anthropogenic emissions of gaseous and aerosol pollutants. The NCAP and the lockdown could provide an ideal field experiment for quantifying the extent to which various levels of human activity reduction impact air quality in the Indian subcontinent. Here, we study the improvement in air quality due to COVID-19 and the NCAP in the India subcontinent by employing multiple satellite products and surface observations. Satellite data shows significant reductions in nitrogen dioxide (NO2) by 17% and aerosol optical depth (AOD) by 20% during the 2020 lockdown with reference to the mean levels between 2005–2019. No persistent reduction in NO2 nor AOD is detectable during the NCAP period (2019). Surface observations show consistent reductions in PM2.5 and NO2 during the 2020 lockdown in seven cities across the Indian subcontinent, except Mumbai in Central India. The increase in relative humidity and the decrease in the planetary boundary layer also play an important role in influencing air quality during the 2020 lockdown. With the decrease in aerosols during the lockdown, net radiation fluxes show positive anomalies at the surface and negative anomalies at the top of the atmosphere over most parts of the Indian subcontinent. The results of this study could provide valuable information for policymakers in South Asia to adjust the scientific measures proposed in the NCAP for efficient air pollution mitigation. COVID-19; air quality; AOD; India subcontinent; NO2; PM2.5
Huang, Xianglei; Chen, Xiuhong; Fan, Chongxing; Kato, Seiji; Loeb, Norman; Bosilovich, Michael; Ham, Seung-Hee; Rose, Fred G.; Strow, Lawrence L.Huang, X., X. Chen, C. Fan, S. Kato, N. Loeb, M. Bosilovich, S. Ham, F. G. Rose, L. L. Strow, 2022: A Synopsis of AIRS Global-Mean Clear-Sky Radiance Trends From 2003 to 2020. Journal of Geophysical Research: Atmospheres, 127(24), e2022JD037598. doi: 10.1029/2022JD037598. Atmospheric Infrared Sounder (AIRS) aboard the National Aeronautics and Space Administration (NASA) Aqua satellite has been operating since September 2002. Its information content, superb instrument performance, and dense sampling pattern make the AIRS radiances an invaluable data set for climate studies. The trends of global-mean, nadir-view, clear-sky AIRS radiances from 2003 to 2020 are studied here, together with the counterparts of synthetic radiances based on two reanalyzes, European Centre for Medium-Range Weather Forecasts Reanalysis V5 (ECMWF ERA5) and NASA Goddard Earth Observing System V5.4.1 (GEOS-5.4.1; a reanalysis product without assimilation of hyperspectral radiances such as AIRS). The AIRS observation shows statistically significant negative trends in most of its CO2 channels, positive but non-significant trends in the channels over the window regions, and statistically significant positive trends in some of its H2O channels. The best agreements between observed and simulated radiance trends are seen over the CO2 tropospheric channels, while the observed and simulated trends over the CO2 stratospheric channels are opposite. ERA5 results largely agree with the AIRS observation over the H2O channels. The comparison in the H2O channels helps reveal a data continuity issue in the GEOS-5.4.1. Contributions from individual variables to the radiance trends are also assessed by performing separate simulations. This study provides the first synopsis of the global-mean trend of AIRS radiances over all its thermal-IR channels. reanalysis; infrared radiation; linear trend; spectral radiance
Huang, Yiyi; Taylor, Patrick C.; Rose, Fred G.; Rutan, David A.; Shupe, Matthew D.; Webster, Melinda A.; Smith, Madison M.Huang, Y., P. C. Taylor, F. G. Rose, D. A. Rutan, M. D. Shupe, M. A. Webster, M. M. Smith, 2022: Toward a more realistic representation of surface albedo in NASA CERES-derived surface radiative fluxes: A comparison with the MOSAiC field campaign: Comparison of CERES and MOSAiC surface radiation fluxes. Elementa: Science of the Anthropocene, 10(1), 00013. doi: 10.1525/elementa.2022.00013. Accurate multidecadal radiative flux records are vital to understand Arctic amplification and constrain climate model uncertainties. Uncertainty in the NASA Clouds and the Earth’s Radiant Energy System (CERES)-derived irradiances is larger over sea ice than any other surface type and comes from several sources. The year-long Multidisciplinary drifting Observatory for the Study of Arctic Climate (MOSAiC) expedition in the central Arctic provides a rare opportunity to explore uncertainty in CERES-derived radiative fluxes. First, a systematic and statistically robust assessment of surface shortwave and longwave fluxes was conducted using in situ measurements from MOSAiC flux stations. The CERES Synoptic 1degree (SYN1deg) product overestimates the downwelling shortwave flux by +11.40 Wm–2 and underestimates the upwelling shortwave flux by –15.70 Wm–2 and downwelling longwave fluxes by –12.58 Wm–2 at the surface during summer. In addition, large differences are found in the upwelling longwave flux when the surface approaches the melting point (approximately 0°C). The biases in downwelling shortwave and longwave fluxes suggest that the atmosphere represented in CERES is too optically thin. The large negative bias in upwelling shortwave flux can be attributed in large part to lower surface albedo (–0.15) in satellite footprint relative to surface sensors. Additionally, the results show that the spectral surface albedo used in SYN1deg overestimates albedo in visible and mid-infrared bands. A series of radiative transfer model perturbation experiments are performed to quantify the factors contributing to the differences. The CERES-MOSAiC broadband albedo differences (approximately 20 Wm–2) explain a larger portion of the upwelling shortwave flux difference than the spectral albedo shape differences (approximately 3 Wm–2). In addition, the differences between perturbation experiments using hourly and monthly MOSAiC surface albedo suggest that approximately 25% of the sea ice surface albedo variability is explained by factors not correlated with daily sea ice concentration variability. Biases in net shortwave and longwave flux can be reduced to less than half by adjusting both albedo and cloud inputs toward observed values. The results indicate that improvements in the surface albedo and cloud data would substantially reduce the uncertainty in the Arctic surface radiation budget derived from CERES data products.
Ito, Masato; Masunaga, HirohikoIto, M., H. Masunaga, 2022: Process-level Assessment of the Iris Effect over Tropical Oceans. Geophysical Research Letters, n/a(n/a), e2022GL097997. doi: 10.1029/2022GL097997. The iris hypothesis suggests a cloud feedback mechanism that a reduction in the tropical anvil cloud fraction (CF) in a warmer climate may act to mitigate the warming by enhanced outgoing longwave radiation. Two different physical processes, one involving precipitation efficiency and the other focusing on upper-tropospheric stability, have been argued in the literature to be responsible for the iris effect. In this study, A-Train observations and reanalysis data are analyzed to assess these two processes. Major findings are as follows: (1) the anvil CF changes evidently with upper-tropospheric stability as expected from the stability iris theory, (2) precipitation efficiency is unlikely to have control on the anvil CF but is related to mid- and low-level CFs, and (3) the day and nighttime cloud radiative effects are expected to largely cancel out when integrated over a diurnal cycle, suggesting a neutral cloud feedback.
J.-L. F, Li; Xu, Kuan-Man; Lee, Wei-Liang; Jiang, J. H.; Fetzer, Eric; Stephens, Graeme; Wang, Yi-Hui; Yu, Jia-YuhJ.-L. F, L., K. Xu, W. Lee, J. H. Jiang, E. Fetzer, G. Stephens, Y. Wang, J. Yu, 2022: Exploring Radiation Biases over the Tropical and Subtropical Oceans Based on Treatments of Frozen Hydrometeor Radiative Properties in CMIP6 Models. Journal of Geophysical Research: Atmospheres, n/a(n/a), e2021JD035976. doi: 10.1029/2021JD035976. To explore the impacts of hydrometeor radiative effects over subtropical and tropical Pacific and Atlantic Oceans, we quantify the mean radiation biases in historical climate simulations based on how frozen hydrometeors radiative properties are calculated in CMIP6 models. CMIP6 models are divided with cloud ice only (NOS), with combined (SON1), and with separate treatments (SON2) of cloud ice and falling ice (snow) radiative properties. Over the deep convective regions, NOS models overestimate outgoing longwave radiation (RLUT) and surface shortwave irradiance (RSDS), while underestimate top-of-atmosphere reflected shortwave radiation (RSUT). SON2 models reduce these biases by 4—14 W m-2. However, this improvement is not seen in SON1 against NOS. Spatially-averaged absolute biases in radiative fluxes for SON1 models are larger than those of NOS, suggesting that the SON1 approach of falling ice radiative effects may not produce the expected hydrometeor-radiation interactions. Over the south Pacific trade-wind regions, both SON2 and SON1 show similar improvements in RLUT, RSUT and RSDS with positive absolute bias differences up to 20 W m-2 against NOS, leading to improvement of CMIP6 over CMIP5 ensembles. The seasonal cycles are consistent with the annual means over these two regions except with larger differences between subsets of models during January–May than during June–December. In general, improvement from CMIP5 to CMIP6 due to more participating SON2 models is limited because of offset by SON1. These results suggest that a separate treatment of frozen-hydrometeor radiative properties may be critical for reducing the spread of CMIP models. CMIP6; GCM; cloud radiations; frozen hydrometeors; tropical oceans
Jahani, Babak; Andersen, Hendrik; Calbó, Josep; González, Josep-Abel; Cermak, JanJahani, B., H. Andersen, J. Calbó, J. González, J. Cermak, 2022: Longwave radiative effect of the cloud–aerosol transition zone based on CERES observations. Atmospheric Chemistry and Physics, 22(2), 1483-1494. doi: 10.5194/acp-22-1483-2022. Abstract. This study presents an approach for the quantification of cloud–aerosol transition-zone broadband longwave radiative effects at the top of the atmosphere (TOA) during daytime over the ocean, based on satellite observations and radiative transfer simulation. Specifically, we used several products from MODIS (MODerate Resolution Imaging Spectroradiometer) and CERES (Clouds and the Earth's Radiant Energy System) sensors for the identification and selection of CERES footprints with a horizontally homogeneous transition-zone and clear-sky conditions. For the selected transition-zone footprints, radiative effect was calculated as the difference between the instantaneous CERES TOA upwelling broadband longwave radiance observations and corresponding clear-sky radiance simulations. The clear-sky radiances were simulated using the Santa Barbara DISORT (DIScrete Ordinates Radiative Transfer program for a multi-Layered plane-parallel medium) Atmospheric Radiative Transfer model fed by the hourly ERA5 reanalysis (fifth generation ECMWF ReAnalysis) atmospheric and surface data. The CERES radiance observations corresponding to the clear-sky footprints detected were also used for validating the simulated clear-sky radiances. We tested this approach using the radiative measurements made by the MODIS and CERES instruments on board the Aqua platform over the southeastern Atlantic Ocean during August 2010. For the studied period and domain, transition-zone radiative effect (given in flux units) is on average equal to 8.0 ± 3.7 W m−2 (heating effect; median: 5.4 W m−2), although cases with radiative effects as large as 50 W m−2 were found.
Jenkins, Stuart; Povey, Adam; Gettelman, Andrew; Grainger, Roy; Stier, Philip; Allen, MylesJenkins, S., A. Povey, A. Gettelman, R. Grainger, P. Stier, M. Allen, 2022: Is Anthropogenic Global Warming Accelerating?. J. Climate, 35(24), 4273-4290. doi: 10.1175/JCLI-D-22-0081.1. Abstract Estimates of the anthropogenic effective radiative forcing (ERF) trend have increased by 50% since 2000 (from +0.4 W m−2 decade−1 in 2000–09 to +0.6 W m−2 decade−1 in 2010–19), the majority of which is driven by changes in the aerosol ERF trend, as a result of aerosol emissions reductions. Here we study the extent to which observations of the climate system agree with these ERF assumptions. We use a large ERF ensemble from the IPCC’s Sixth Assessment Report (AR6) to attribute the anthropogenic contributions to global mean surface temperature (GMST), top-of-atmosphere radiative flux, and we use aerosol optical depth observations. The GMST trend has increased from +0.18°C decade−1 in 2000–09 to +0.35°C decade−1 in 2010–19, coinciding with the anthropogenic warming trend rising from +0.19°C decade−1 in 2000–09 to +0.24°C decade−1 in 2010–19. This, as well as observed trends in top-of-atmosphere radiative fluxes and aerosol optical depths, supports the claim of an aerosol-induced temporary acceleration in the rate of warming. However, all three observation datasets additionally suggest that smaller aerosol ERF trend changes are compatible with observations since 2000, since radiative flux and GMST trends are significantly influenced by internal variability over this period. A zero-trend-change aerosol ERF scenario results in a much smaller anthropogenic warming acceleration since 2000 but is poorly represented in AR6’s ERF ensemble. Short-term ERF trends are difficult to verify using observations, so caution is required in predictions or policy judgments that depend on them, such as estimates of current anthropogenic warming trend, and the time remaining to, or the outstanding carbon budget consistent with, 1.5°C warming. Further systematic research focused on quantifying trends and early identification of acceleration or deceleration is required.
Jia, Aolin; Liang, Shunlin; Wang, DongdongJia, A., S. Liang, D. Wang, 2022: Generating a 2-km, all-sky, hourly land surface temperature product from Advanced Baseline Imager data. Remote Sensing of Environment, 278, 113105. doi: 10.1016/j.rse.2022.113105. By characterizing high-frequency surface thermal dynamics at a medium spatial scale, hourly land surface temperatures (LST), retrieved from geostationary satellite thermal infrared (TIR) observations, shows great potential to be used across a range of scientific applications; however, cloud cover typically leads to data gaps and degraded retrieval accuracy in TIR LST products, such as the official Advanced Baseline Imager (ABI) LST product. Studies have focused on the LST gap reconstruction; however, most interpolation-based methods only work for a short-term cloud duration and are unable to adequately compensate for cloud effects, and traditional surface energy balance (SEB)-based methods are able to handle cloud coverage while they are not feasible for use at night. Moreover, few studies have concentrated on recovering the abnormal retrievals of partial cloud pixels. In this study, an all-sky diurnal, hourly LST estimation method based on SEB theory was proposed; the proposed method involved three major steps: 1) an original spatiotemporal dynamic model of LST was constructed from ECMWF Reanalysis v.5 (ERA5); 2) clear-sky ABI LST was then assimilated to the dynamic model to generate a continuous LST series; 3) the diurnal cloud effects were superimposed on cloudy time estimated by an innovative optimization method from satellite radiation products. A 2-km, all-sky, hourly LST product was produced over the contiguous US and Mexico from July 2017 to June 2021. Validation was conducted using ground measurements at 18 sites from Surface Radiation (SURFRAD) and core AmeriFlux networks, and produced an overall root-mean-square error (RMSE) of 2.44 K, a bias of −0.19 K, and an R2 of 0.97 based on 408,300 samples. For clear-sky samples, the RMSE values were 2.37 and 2.24 K for day and nighttime, respectively, which was a notable improvement over the corresponding values of the official ABI LST product (2.73 and 2.86 K, respectively). The RMSE values on cloudy-sky were 2.78 and 2.23 K for day and nighttime, respectively. The daily mean LST by aggregating all-sky, hourly LST had an RMSE of 1.13 K and R2 of 0.99. Overall, this product showed reliability under consistent cloud durations, although it was slightly affected by surface elevation. The diurnal temperature cycle climatology of major land cover types was also characterized. The product is freely available at: http://glass.umd.edu/allsky_LST/ABI/. Data assimilation; Surface energy balance; Land surface temperature; ABI; All-sky; Diurnal temperature cycle
Jia, Aolin; Wang, Dongdong; Liang, Shunlin; Peng, Jingjing; Yu, YunyueJia, A., D. Wang, S. Liang, J. Peng, Y. Yu, 2022: Global daily actual and snow-free blue-sky land surface albedo climatology from 20-year MODIS products. Journal of Geophysical Research: Atmospheres, n/a(n/a), e2021JD035987. doi: 10.1029/2021JD035987. Land surface albedo plays a critical role in climate, hydrological and biogeochemical modeling, and weather forecasting. It is often assigned in models and satellite retrievals by albedo climatology look-up tables using land cover type and other variables; however, there are considerable differences in albedo simulations among models, which partially result from uncertainty in obsolete albedo climatology. Therefore, this study introduces a new global 500 m daily blue-sky land surface albedo climatology dataset under both actual and snow-free surface conditions utilizing 20-year Moderate Resolution Imaging Spectroradiometer (MODIS) products from Google Earth Engine. In situ measurements from 38 long-term-maintained sites were utilized to validate the accuracies of different albedo climatology datasets. The root-mean-square error, bias, and correlation coefficient of the new climatology are 0.031, -0.003, and 0.96, respectively, which are more accurate than the GLASS, GlobAlbedo, and 16 model datasets. Data intercomparison suggests that ERA5 exhibits better performance than MERRA2 and 14 CMIP6 models. However, it contains positive biases in the snow-free season, while MERRA2 underestimates the snow albedo. Global albedo variation associated with basic surface plant functional types was also characterized, and snow impact was considered separately. Temporal variability analysis indicates that traditional climatology datasets with coarser temporal resolutions (≥8 days) cannot capture albedo variation over areas with distinct snow seasons, especially in central Eurasia and boreal regions. These results confirm the high reliability and robustness of the new albedo climatology in model assessment, data assimilation, and satellite product retrievals. MODIS; climatology; satellite retrieval; land surface albedo; model assessment
Jiang, Shuyi; Zhao, Chuanfeng; Xia, YanJiang, S., C. Zhao, Y. Xia, 2022: Distinct response of near surface air temperature to clouds in North China. Atmospheric Science Letters, n/a(n/a), e1128. doi: 10.1002/asl.1128. Using the daily 2 m maximum temperature (Tmax), 2 m minimum temperature (Tmin) and cloud cover data measured at ground sites of the China Meteorological Administration in North China from 2000 to 2017, this study investigates the influence of clouds on the daily temperature range (DTR) defined as the difference between Tmax and Tmin. As expected, the cloud cover shows the similar averaged spatial distribution and monthly variation with Tmin. Surprisingly, it also shows the similar average spatial distribution and monthly variation with Tmax, suggesting the more important roles of regions (latitude) and seasons associated with the variations of land surface temperature, which is further related to solar radiation absorbed and surface heat capacity. By comparing monthly variations of temperature between cloudy and clear skies, we find that clouds can weaken Tmax and increase Tmin, and thus decrease DTR. As a result, the spatial distribution of DTR is opposite to the cloud cover. The clouds have relatively stronger impact on Tmin and DTR over mountain region, which is most likely caused by the stronger longwave cloud radiative forcing associated with higher cloud tops over the mountain region. cloud cover; cloud top; daily temperature range; spatial distribution; temporal variation
Jiao, Zhong-Hu; Mu, XihanJiao, Z., X. Mu, 2022: Single-footprint retrieval of clear-sky surface longwave radiation from hyperspectral AIRS data. International Journal of Applied Earth Observation and Geoinformation, 110, 102802. doi: 10.1016/j.jag.2022.102802. Surface longwave radiation (SLR) derived from remotely sensed data facilitates understanding of the SLR in global climate change. Hyperspectral infrared sounders aboard space platforms provide information on the surface and vertical structure of Earth’s atmosphere. However, currently, SLR products estimated from these observations are unavailable, which hampers their application potential for Earth’s radiation budget in the context of global warming. To address this issue, we developed simple and effective SLR model under clear-sky conditions using at-sensor spectral radiances from Atmospheric Infrared Sounder (AIRS). The model was found to be insensitive to AIRS instrument noise, and showed good performances based on a simulation dataset. The AIRS footprint geometrical model was proposed to match the AIRS and Moderate Resolution Imaging Spectroradiometer (MODIS) data to estimate the cloud fraction. Validation against ground-based measurements found that the surface upward longwave radiation model has a bias of 3.18 W/m2, root-mean-square error (RMSE) of 30.51 W/m2, and R2 of 0.84; the surface downward longwave radiation model has a bias of 0.77 W/m2, RMSE of 29.09 W/m2, and R2 of 0.78. The large validation biases at two ground sites reflect the limited spatial representativeness for AIRS footprints. Terrain-induced altitude differences and spatial inhomogeneity can redistribute the spatial distributions of SLR. Moreover, the model performances were weakly dependent on seasonal variation. The results indicate that the proposed model provides a foundation for the further development of operational SLR products. Surface radiation budget; Surface longwave radiation; Atmospheric Infrared Sounder (AIRS); Hybrid method; Hyperspectral infrared remote sensing; Spatial representativeness
Jin, Daeho; Oreopoulos, Lazaros; Lee, Dongmin; Tan, Jackson; Kim, Kyu-myongJin, D., L. Oreopoulos, D. Lee, J. Tan, K. Kim, 2022: A New Organization Metric for Synoptic Scale Tropical Convective Aggregation. Journal of Geophysical Research: Atmospheres, 127(13), e2022JD036665. doi: 10.1029/2022JD036665. Organization metrics were originally developed to measure how densely convective clouds are arranged at mesoscales. In this work, we apply organization metrics to describe tropical synoptic scale convective activity. Such activity is identified by cloud-precipitation (hybrid) regimes defined at 1-degree and 1-hourly resolution. Existing metrics were found to perform inadequately for such convective regime aggregates because the large domain size and co-existence of sparse aggregate occurrences with noisy isolated convection often violate assumptions inherent in these metrics. In order to capture these characteristics, in this study the existing “convective organization potential” (COP) metric was modified so as to focus on local organization and provide increased weight to aggregate size. The resulting “area-based COP” (ABCOP) follows the principle that the more numerous the objects, the higher the chance of organization. It is thus optimized to capture large-scale convective events occurring during phenomena such as ENSO and MJO, while also performs as well as existing metrics for small domain sizes. tropical convection; cloud-precipitation regime; organization metric
Johnson, Richard H.; Ciesielski, Paul E.; Schubert, Wayne H.Johnson, R. H., P. E. Ciesielski, W. H. Schubert, 2022: Hydrometeor Storage and Advection Effects in DYNAMO Budget Analyses. J. Atmos. Sci., 80(1), 181-188. doi: 10.1175/JAS-D-21-0266.1. Abstract The Dynamics of the Madden–Julian Oscillation (MJO) (DYNAMO) field campaign over the central Indian Ocean captured three strong MJO events during October–December 2011. Using the conventional budget approach of Yanai et al. surface rainfall P0 is computed as a residual from the vertically integrated form of the moisture budget equation. This budget-derived P0 is spatially averaged over the Gan Island NCAR S-PolKa radar domain and compared with rainfall estimates from the radar itself. To isolate the MJO signal, these rainfall time series are low-pass (LP) filtered and a three-MJO composite is created based on the time of maximum LP-filtered S-PolKa rainfall for each event. A comparison of the two composite rainfall estimates shows that the budget rainfall overestimates the radar rainfall by ∼15% in the MJO buildup stage and underestimates radar rainfall by ∼8% in the MJO decay stage. These rainfall differences suggest that hydrometeor (clouds and rain) storage and advection effects, which are neglected in the budget approach, are likely significant. Satellite and ground-based observations are used to investigate these hydrometeor storage and advection effects. While the findings are qualitatively consistent with expectations from theory, they fall short of explaining their full magnitude, suggesting even more refined experimental designs and measurements will be needed to adequately address this issue.
Jönsson, Aiden; Bender, Frida A.-M.Jönsson, A., F. A. Bender, 2022: Corrigendum. J. Climate, 35(15), 5233-5234. doi: 10.1175/JCLI-D-22-0128.1. "Corrigendum" published on 01 Aug 2022 by American Meteorological Society.
Jönsson, Aiden; Bender, Frida A.-M.Jönsson, A., F. A. Bender, 2022: Persistence and Variability of Earth’s Interhemispheric Albedo Symmetry in 19 Years of CERES EBAF Observations. J. Climate, 35(1), 249-268. doi: 10.1175/JCLI-D-20-0970.1. Abstract Despite the unequal partitioning of land and aerosol sources between the hemispheres, Earth’s albedo is observed to be persistently symmetric about the equator. This symmetry is determined by the compensation of clouds to the clear-sky albedo. Here, the variability of this interhemispheric albedo symmetry is explored by decomposing observed radiative fluxes in the CERES EBAF satellite data record into components reflected by the atmosphere, clouds, and the surface. We find that the degree of interhemispheric albedo symmetry has not changed significantly throughout the observational record. The variability of the interhemispheric difference in reflected solar radiation (asymmetry) is strongly determined by tropical and subtropical cloud cover, particularly those related to nonneutral phases of El Niño–Southern Oscillation (ENSO). As ENSO is the most significant source of interannual variability in reflected radiation on a global scale, this underscores the interhemispheric albedo symmetry as a robust feature of Earth’s current annual mean climate. Comparing this feature in observations with simulations from coupled models reveals that the degree of modeled albedo symmetry is mostly dependent on biases in reflected radiation in the midlatitudes, and that models that overestimate its variability the most have larger biases in reflected radiation in the tropics. The degree of model albedo symmetry is improved when driven with historical sea surface temperatures, indicating that the degree of symmetry in Earth’s albedo is dependent on the representation of cloud responses to coupled ocean–atmosphere processes.
Jungclaus, J.h.; Lorenz, S.j.; Schmidt, H.; Brovkin, V.; Brüggemann, N.; Chegini, F.; Crüger, T.; De-Vrese, P.; Gayler, V.; Giorgetta, M.a; Gutjahr, O.; Haak, H.; Hagemann, S.; Hanke, M.; Ilyina, T.; Korn, P.; Kröger, J.; Linardakis, L.; Mehlmann, C.; Mikolajewicz, U.; Müller, W.a.; Nabel, J.e.m.s; Notz, D.; Pohlmann, H.; Putrasahan, D.a.; Raddatz, T.; Ramme, L.; Redler, R.; Reick, C.h.; Riddick, T.; Sam, T.; Schneck, R.; Schnur, R.; Schupfner, M.; Storch, J.-S. von; Wachsmann, F.; Wieners, K.-H.; Ziemen, F.; Stevens, B.; Marotzke, J.; Claussen, M.Jungclaus, J., S. Lorenz, H. Schmidt, V. Brovkin, N. Brüggemann, F. Chegini, T. Crüger, P. De-Vrese, V. Gayler, M. Giorgetta, O. Gutjahr, H. Haak, S. Hagemann, M. Hanke, T. Ilyina, P. Korn, J. Kröger, L. Linardakis, C. Mehlmann, U. Mikolajewicz, W. Müller, J. Nabel, D. Notz, H. Pohlmann, D. Putrasahan, T. Raddatz, L. Ramme, R. Redler, C. Reick, T. Riddick, T. Sam, R. Schneck, R. Schnur, M. Schupfner, J. v. Storch, F. Wachsmann, K. Wieners, F. Ziemen, B. Stevens, J. Marotzke, M. Claussen, 2022: The ICON Earth System Model Version 1.0. Journal of Advances in Modeling Earth Systems, n/a(n/a), e2021MS002813. doi: 10.1029/2021MS002813. This work documents the ICON-Earth System Model (ICON-ESM V1.0), the first coupled model based on the ICON (ICOsahedral Non-hydrostatic) framework with its unstructured, icosahedral grid concept. The ICON-A atmosphere uses a nonhydrostatic dynamical core and the ocean model ICON-O builds on the same ICON infrastructure, but applies the Boussinesq and hydrostatic approximation and includes a sea-ice model. The ICON-Land module provides a new framework for the modelling of land processes and the terrestrial carbon cycle. The oceanic carbon cycle and biogeochemistry are represented by the Hamburg Ocean Carbon Cycle module. We describe the tuning and spin-up of a base-line version at a resolution typical for models participating in the Coupled Model Intercomparison Project (CMIP). The performance of ICON-ESM is assessed by means of a set of standard CMIP6 simulations. Achievements are well-balanced top-of-atmosphere radiation, stable key climate quantities in the control simulation, and a good representation of the historical surface temperature evolution. The model has overall biases, which are comparable to those of other CMIP models, but ICON-ESM performs less well than its predecessor, the Max Planck Institute Earth System Model. Problematic biases are diagnosed in ICON-ESM in the vertical cloud distribution and the mean zonal wind field. In the ocean, sub-surface temperature and salinity biases are of concern as is a too strong seasonal cycle of the sea-ice cover in both hemispheres. ICON-ESM V1.0 serves as a basis for further developments that will take advantage of ICON-specific properties such as spatially varying resolution, and configurations at very high resolution. Earth; Model; System
Kelleher, Mitchell K.; Grise, Kevin M.Kelleher, M. K., K. M. Grise, 2022: Varied midlatitude shortwave cloud radiative responses to Southern Hemisphere circulation shifts. Atmospheric Science Letters, 23(1), e1068. doi: 10.1002/asl.1068. Changes in midlatitude clouds as a result of shifts in general circulation patterns are widely thought to be a potential source of radiative feedbacks onto the climate system. Previous work has suggested that two general circulation shifts anticipated to occur in a warming climate, poleward shifts in the midlatitude jet streams and a poleward expansion of the Hadley circulation, are associated with differing effects on midlatitude clouds. This study examines two dynamical cloud-controlling factors, mid-tropospheric vertical velocity, and the estimated inversion strength (EIS) of the marine boundary layer temperature inversion, to explain why poleward shifts in the Southern Hemisphere midlatitude jet and Hadley cell edge have varying shortwave cloud-radiative responses at midlatitudes. Changes in vertical velocity and EIS occur further equatorward for poleward shifts in the Hadley cell edge than they do for poleward shifts of the midlatitude jet. Because the sensitivity of shortwave cloud radiative effects (SWCRE) to variations in vertical velocity and EIS is a function of latitude, the SWCRE anomalies associated with jet and Hadley cell shifts differ. The dynamical changes associated with a poleward jet shift occur further poleward in a regime where the sensitivities of SWCRE to changes in vertical velocity and EIS balance, leading to a near-net zero change in SWCRE in midlatitudes with a poleward jet shift. Conversely, the dynamical changes associated with Hadley cell expansion occur further equatorward at a latitude where the sensitivity of SWCRE is more strongly associated with changes in mid-tropospheric vertical velocity, leading to a net shortwave cloud radiative warming effect in midlatitudes. Hadley cell expansion; midlatitude jet shifts; shortwave cloud radiative effects
Kenny, Darragh; Fiedler, StephanieKenny, D., S. Fiedler, 2022: Which gridded irradiance data is best for modelling photovoltaic power production in Germany?. Solar Energy, 232, 444-458. doi: 10.1016/j.solener.2021.12.044. Model estimates of expected photovoltaic (PV) power production rely on accurate irradiance data. Reanalysis and satellite products freely provide irradiance data with a high temporal and spatial resolution including locations for which no ground-based measurements are available. We assess differences in such gridded irradiance data and quantify the subsequent bias propagation from individual radiation components to capacity factors in a contemporary PV model. PV power production is simulated based on four reanalysis (ERA5, COSMO-REA6, COSMO-REA6pp, COSMO-REA2) and three satellite products (CAMS, SARAH-2, CERES Syn1Deg). The results are compared against simulations using measurements from 30 weather stations of the German Weather Service. We compute metrics characterizing biases in seasonal and annual means, day-to-day variability and extremes in PV power. Our results highlight a bias of −1.4% (COSMO-REA6) to +8.2% (ERA5) in annual and spatial means of PV power production for Germany. No single data set is best in all metrics, although SARAH-2 and the postprocessed COSMO-REA6 data (COSMO-REA6pp) outperform the other products for many metrics. SARAH-2 yields good results in summer, but overestimates PV output in winter by 16% averaged across all stations. COSMO-REA6pp represents day-to-day variability in the PV power production of a simulated PV fleet best and has a particularly small bias of 0.5% in annual means. This is at least in parts due to compensating biases in local and seasonal means. Our results imply that gridded irradiance data should be used with caution for site assessments and ideally be complemented by local measurements. Satellite; Data evaluation; Irradiance data; PV power model; Re-analysis; Station observations
Khairoutdinov, Marat F.; Blossey, Peter N.; Bretherton, Christopher S.Khairoutdinov, M. F., P. N. Blossey, C. S. Bretherton, 2022: Global System for Atmospheric Modeling: Model Description and Preliminary Results. Journal of Advances in Modeling Earth Systems, 14(6), e2021MS002968. doi: 10.1029/2021MS002968. The extension of a cloud-resolving model, the System for Atmospheric Modeling (SAM), to global domains is described. The resulting global model, gSAM, is formulated on a latitude-longitude grid. It uses an anelastic dynamical core with a single reference profile (as in SAM), but its governing equations differ somewhat from other anelastic models. For quasihydrostatic flows, they are isomorphic to the primitive equations (PE) in pressure coordinates but with the globally uniform reference pressure playing the role of actual pressure. As a result, gSAM can exactly maintain steady zonally symmetric baroclinic flows that have been specified in pressure coordinates, produces accurate simulations when initialized or nudged with global reanalyses, and has a natural energy conservation equation despite the drawbacks of using the anelastic system to model global scales. gSAM employs a novel treatment of topography using a type of immersed boundary method, the Quasi-Solid Body Method, where the instantaneous flow velocity is forced to stagnate in grid cells inside a prescribed terrain. The results of several standard tests designed to evaluate the accuracy of global models with and without topography as well as results from real Earth simulations are presented. model description; global cloud-resolving model; anelastic dynamical core; global storm-resolving model; system for atmospheric modeling
Knippertz, Peter; Gehne, Maria; Kiladis, George N.; Kikuchi, Kazuyoshi; Rasheeda Satheesh, Athul; Roundy, Paul E.; Yang, Gui-Ying; Žagar, Nedjeljka; Dias, Juliana; Fink, Andreas H.; Methven, John; Schlueter, Andreas; Sielmann, Frank; Wheeler, Matthew C.Knippertz, P., M. Gehne, G. N. Kiladis, K. Kikuchi, A. Rasheeda Satheesh, P. E. Roundy, G. Yang, N. Žagar, J. Dias, A. H. Fink, J. Methven, A. Schlueter, F. Sielmann, M. C. Wheeler, 2022: The intricacies of identifying equatorial waves. Quarterly Journal of the Royal Meteorological Society, 148(747), 2814-2852. doi: 10.1002/qj.4338. Equatorial waves (EWs) are synoptic- to planetary-scale propagating disturbances at low latitudes with periods from a few days to several weeks. Here, this term includes Kelvin waves, equatorial Rossby waves, mixed Rossby–gravity waves, and inertio-gravity waves, which are well described by linear wave theory, but it also other tropical disturbances such as easterly waves and the intraseasonal Madden–Julian Oscillation with more complex dynamics. EWs can couple with deep convection, leading to a substantial modulation of clouds and rainfall. EWs are amongst the dynamic features of the troposphere with the longest intrinsic predictability, and models are beginning to forecast them with an exploitable level of skill. Most of the methods developed to identify and objectively isolate EWs in observations and model fields rely on (or at least refer to) the adiabatic, frictionless linearized primitive equations on the sphere or the shallow-water system on the equatorial β$$ \beta $$-plane. Common ingredients to these methods are zonal wave-number–frequency filtering (Fourier or wavelet) and/or projections onto predefined empirical or theoretical dynamical patterns. This paper gives an overview of six different methods to isolate EWs and their structures, discusses the underlying assumptions, evaluates the applicability to different problems, and provides a systematic comparison based on a case study (February 20–May 20, 2009) and a climatological analysis (2001–2018). In addition, the influence of different input fields (e.g., winds, geopotential, outgoing long-wave radiation, rainfall) is investigated. Based on the results, we generally recommend employing a combination of wave-number–frequency filtering and spatial-projection methods (and of different input fields) to check for robustness of the identified signal. In cases of disagreement, one needs to carefully investigate which assumptions made for the individual methods are most probably not fulfilled. This will help in choosing an approach optimally suited to a given problem at hand and avoid misinterpretation of the results. convection; equatorial Rossby waves; Kelvin waves; mixed Rossby–gravity waves; spatial projection; time–space filtering; tropical rainfall
Kooperman, G. J.; Akinsanola, A. A.; Hannah, W. M.; Pendergrass, A. G.; Reed, K. A.Kooperman, G. J., A. A. Akinsanola, W. M. Hannah, A. G. Pendergrass, K. A. Reed, 2022: Assessing Two Approaches for Enhancing the Range of Simulated Scales in the E3SMv1 and the Impact on the Character of Hourly US Precipitation. Geophysical Research Letters, 49(4), e2021GL096717. doi: 10.1029/2021GL096717. Improving the representation of precipitation in Earth system models is essential for understanding and projecting water cycle changes across scales. Progress has been hampered by persistent deficiencies in representing precipitation frequency, intensity, and timing in current models. Here, we analyze simulated US precipitation in the low-resolution (LR) configuration of the Energy Exascale Earth System Model (E3SMv1) and assess the effect of two approaches to enhance the range of explicitly resolved scales: high-resolution (HR) and multiscale modeling framework (MMF), which incur similar computational expense. Both E3SMv1-MMF and E3SMv1-HR capture more intense and less frequent precipitation on hourly and daily timescales relative to E3SMv1-LR. E3SMv1-HR improves the intensity over the Eastern and Northwestern US during winter, while E3SMv1-MMF improves the intensity over the Eastern US and summer diurnal timing over the Central US. These results indicate that both methods may be needed to improve simulations of different storm types, seasons, and regions. earth system model; United States; precipitation; energy exascale earth system model; high resolution; multiscale modelling framework
Koppa, Akash; Rains, Dominik; Hulsman, Petra; Poyatos, Rafael; Miralles, Diego G.Koppa, A., D. Rains, P. Hulsman, R. Poyatos, D. G. Miralles, 2022: A deep learning-based hybrid model of global terrestrial evaporation. Nature Communications, 13(1), 1912. doi: 10.1038/s41467-022-29543-7. Terrestrial evaporation (E) is a key climatic variable that is controlled by a plethora of environmental factors. The constraints that modulate the evaporation from plant leaves (or transpiration, Et) are particularly complex, yet are often assumed to interact linearly in global models due to our limited knowledge based on local studies. Here, we train deep learning algorithms using eddy covariance and sap flow data together with satellite observations, aiming to model transpiration stress (St), i.e., the reduction of Et from its theoretical maximum. Then, we embed the new St formulation within a process-based model of E to yield a global hybrid E model. In this hybrid model, the St formulation is bidirectionally coupled to the host model at daily timescales. Comparisons against in situ data and satellite-based proxies demonstrate an enhanced ability to estimate St and E globally. The proposed framework may be extended to improve the estimation of E in Earth System Models and enhance our understanding of this crucial climatic variable. Hydrology; Ecological modelling
Kuwano, A.; Evan, A.Kuwano, A., A. Evan, 2022: A Method to Account for the Impact of Water Vapor on Observation-Based Estimates of the Clear-Sky Shortwave Direct Radiative Effect of Mineral Dust. Journal of Geophysical Research: Atmospheres, 127(17), e2022JD036620. doi: 10.1029/2022JD036620. The shortwave direct radiative effect of dust, the difference between net shortwave radiative flux in a cloud free and cloud and aerosol free atmosphere, is typically estimated using forward calculations made with a radiative transfer model. However, estimates of the direct radiative effect made via this initial method can be highly uncertain due to difficultly in accurately describing the relevant optical and physical properties of dust used in these calculations. An alternative approach to estimate this effect is to determine the forcing efficiency, or the direct radiative effect normalized by aerosol optical depth. While this approach avoids the uncertainties associated with the initial method for calculating the direct effect, random errors and biases associated with this approach have not been thoroughly examined in literature. Here we explore biases in this observation-based approach that are related to atmospheric water vapor. We use observations to show that over the Sahara Desert dust optical depth and column-integrated atmospheric water vapor are positively correlated. We use three idealized radiative models of varying complexity to demonstrate that a positive correlation between dust and water vapor produces a positive bias in the dust forcing efficiency estimated via the observation-based method. We describe a simple modification to the observation-based method that correctly accounts for the correlation between dust and water vapor when estimating the forcing efficiency and use this method to estimate the instantaneous forcing efficiency of dust over the Sahara Desert using satellite data, obtaining −12.3 ± 6.68 to 20.9 ± 11.9 W m−2 per unit optical depth. satellite data; radiative transfer; dust; shortwave; observations; forcing efficiency
Lauer, Axel; Bock, Lisa; Hassler, Birgit; Schröder, Marc; Stengel, MartinLauer, A., L. Bock, B. Hassler, M. Schröder, M. Stengel, 2022: Cloud Climatologies from Global Climate Models—A Comparison of CMIP5 and CMIP6 Models with Satellite Data. J. Climate, 36(2), 281-311. doi: 10.1175/JCLI-D-22-0181.1. Abstract Simulating clouds with global climate models is challenging as the relevant physics involves many nonlinear processes covering a wide range of spatial and temporal scales. As key components of the hydrological cycle and the climate system, an evaluation of clouds from models used for climate projections is an important prerequisite for assessing the confidence in the results from these models. Here, we compare output from models contributing to phase 6 of the Coupled Model Intercomparison Project (CMIP6) with satellite data and with results from their predecessors (CMIP5). We use multiproduct reference datasets to estimate the observational uncertainties associated with different sensors and with internal variability on a per-pixel basis. Selected cloud properties are also analyzed by region and by dynamical regime and thermodynamic conditions. Our results show that for parameters such as total cloud cover, cloud water path, and cloud radiative effect, the CMIP6 multimodel mean performs slightly better than the CMIP5 ensemble mean in terms of mean bias, pattern correlation, and relative root-mean square deviation. The intermodel spread in CMIP6, however, is not reduced compared to CMIP5. Compared with CALIPSO-ICECLOUD data, the CMIP5/6 models overestimate cloud ice, particularly in the lower and middle troposphere, partly due to too high ice fractions for given temperatures. This bias is reduced in the CMIP6 multimodel mean. While many known biases such as an underestimation in cloud cover in stratocumulus regions remain in CMIP6, we find that the CMIP5 problem of too few but too reflective clouds over the Southern Ocean is significantly improved.
Lee, Jae N.; Wu, Dong L.Lee, J. N., D. L. Wu, 2022: Non-Gaussian Distributions of TOA SW Flux as Observed by MISR and CERES. Journal of Geophysical Research: Atmospheres, 127(14), e2022JD036636. doi: 10.1029/2022JD036636. The Top of Atmosphere (TOA) shortwave (SW) flux, converted from Terra Multi-angle Imaging SpectroRadiometer (MISR) narrow band albedos, is compared with that measured from Clouds and the Earth's Radiant Energy System (CERES). We describe the probability density function (PDF) of the monthly TOA SW flux and how the statistical third moment, skewness, can impact the quantification of the flux. The PDF of the SW flux is not normally distributed but positively skewed. In both sets of observations, the near-global (80 S–80 N) median value of the SW flux is ∼3 W/m2 less than the mean value, due to the positive skewness of the distribution. The near-global mean TOA SW flux converted from MISR is about 7 W/m2 (∼7%) less than CERES measured flux during the last two decades. Surprisingly, a hemispheric asymmetry exists with TOA SW observations from the Terra platform. SH reflects 3.92 and 1.15 W/m2 more mean SW flux than NH, from MISR and CERES Single Scanner Footprint products, respectively. We can infer that the offsetting by morning clouds in the SH is greater than the effect of hemispheric imbalance of SW flux caused by different land masses in two hemispheres. While the characteristics of the two SW fluxes broadly agree with each other, differences in the regional PDF from two different SW fluxes are substantial over high cloud regions and high altitude regions. Our analysis shows that some parts of the different skewness from the two measurements may be attributed to the different calibration of the radiance anisotropy over high cloud scenes. CERES; MISR; hemispheric asymmetry; non-Gaussian; TOA SW flux
Lee, Jiheun; Kang, Sarah M.; Kim, Hanjun; Xiang, BaoqiangLee, J., S. M. Kang, H. Kim, B. Xiang, 2022: Disentangling the effect of regional SST bias on the double-ITCZ problem. Climate Dynamics. doi: 10.1007/s00382-021-06107-x. This study investigates the causes of the double intertropical convergence zone (ITCZ) bias, characterized by too northward northern Pacific ITCZ, too dry equatorial Pacific, and too zonally elongated southern Pacific rainband. While the biases within one fully coupled model GFDL CM2.1 are examined, the large-scale bias patterns are broadly common to CMIP5/6 models. We disentangle the individual contribution of regional sea surface temperature (SST) biases to the double-ITCZ bias pattern using a series of slab ocean model experiments. A previously suggested Southern Ocean warm bias effect in displacing the zonal-mean ITCZ southward is manifested in the northern Pacific ITCZ while having little contribution to the zonally elongated wet bias south of the equatorial Pacific. The excessive southern Pacific precipitation is instead induced by the warm bias along the west coast of South America. The Southern Ocean bias effect on the zonal-mean ITCZ position is diminished by the neighboring midlatitude bias of opposite sign in GFDL CM2.1. As a result, the northern extratropical cold bias turns out to be most responsible for a southward-displaced zonal-mean ITCZ. However, this southward ITCZ displacement results from the northern Pacific branch, so ironically fixing the extratropical biases only deteriorates the northern Pacific precipitation bias. Thus, we emphasize that the zonal-mean diagnostics poorly represent the spatial pattern of the tropical Pacific response. Examination of longitude-latitude structure indicates that the overall tropical precipitation bias is mostly locally driven from the tropical SST bias. While our model experiments are idealized with no ocean dynamics, the results shed light on where preferential foci should be applied in model development to improve particular features of tropical precipitation bias.
Leng, Song; Huete, Alfredo; Cleverly, Jamie; Gao, Sicong; Yu, Qiang; Meng, Xianyong; Qi, Junyu; Zhang, Rongrong; Wang, QianfengLeng, S., A. Huete, J. Cleverly, S. Gao, Q. Yu, X. Meng, J. Qi, R. Zhang, Q. Wang, 2022: Assessing the Impact of Extreme Droughts on Dryland Vegetation by Multi-Satellite Solar-Induced Chlorophyll Fluorescence. Remote Sensing, 14(7), 1581. doi: 10.3390/rs14071581. Satellite-estimated solar-induced chlorophyll fluorescence (SIF) is proven to be an effective indicator for dynamic drought monitoring, while the capability of SIF to assess the variability of dryland vegetation under water and heat stress remains challenging. This study presents an analysis of the responses of dryland vegetation to the worst extreme drought over the past two decades in Australia, using multi-source spaceborne SIF derived from the Global Ozone Monitoring Experiment-2 (GOME-2) and TROPOspheric Monitoring Instrument (TROPOMI). Vegetation functioning was substantially constrained by this extreme event, especially in the interior of Australia, in which there was hardly seasonal growth detected by neither satellite-based observations nor tower-based flux measurements. At a 16-day interval, both SIF and enhanced vegetation index (EVI) can timely capture the reduction at the onset of drought over dryland ecosystems. The results demonstrate that satellite-observed SIF has the potential for characterizing and monitoring the spatiotemporal dynamics of drought over water-limited ecosystems, despite coarse spatial resolution coupled with high-retrieval noise as compared with EVI. Furthermore, our study highlights that SIF retrieved from TROPOMI featuring substantially enhanced spatiotemporal resolution has the promising capability for accurately tracking the drought-induced variation of heterogeneous dryland vegetation. SIF; EVI; dryland; extreme drought; TROPOMI
Leng, Song; Huete, Alfredo; Cleverly, Jamie; Yu, Qiang; Zhang, Rongrong; Wang, QianfengLeng, S., A. Huete, J. Cleverly, Q. Yu, R. Zhang, Q. Wang, 2022: Spatiotemporal Variations of Dryland Vegetation Phenology Revealed by Satellite-Observed Fluorescence and Greenness across the North Australian Tropical Transect. Remote Sensing, 14(13), 2985. doi: 10.3390/rs14132985. Accurate characterization of spatial patterns and temporal variations in dryland vegetation is of great importance for improving our understanding of terrestrial ecosystem functioning under changing climates. Here, we explored the spatiotemporal variability of dryland vegetation phenology using satellite-observed Solar-Induced chlorophyll Fluorescence (SIF) and the Enhanced Vegetation Index (EVI) along the North Australian Tropical Transect (NATT). Substantial impacts of extreme drought and intense wetness on the phenology and productivity of dryland vegetation are observed by both SIF and EVI, especially in the arid/semiarid interior of Australia without detectable seasonality in the dry year of 2018–2019. The greenness-based vegetation index (EVI) can more accurately capture the seasonal and interannual variation in vegetation production than SIF (EVI r2: 0.47~0.86, SIF r2: 0.47~0.78). However, during the brown-down periods, the rate of decline in EVI is evidently slower than that in SIF and in situ measurement of gross primary productivity (GPP), due partially to the advanced seasonality of absorbed photosynthetically active radiation. Over 70% of the variability of EVI (except for Hummock grasslands) and 40% of the variability of SIF (except for shrublands) can be explained by the water-related drivers (rainfall and soil moisture). By contrast, air temperature contributed to 25~40% of the variability of the effective fluorescence yield (SIFyield) across all biomes. In spite of high retrieval noises and variable accuracy in phenological metrics (MAE: 8~60 days), spaceborne SIF observations, offsetting the drawbacks of greenness-based phenology products with a potentially lagged end of the season, have the promising capability of mapping and characterizing the spatiotemporal dynamics of dryland vegetation phenology. SIF; EVI; NATT; phenology
Letu, Husi; Nakajima, Takashi Y.; Wang, Tianxing; Shang, Huazhe; Ma, Run; Yang, Kun; Baran, Anthony J.; Riedi, Jerome; Ishimoto, Hiroshi; Yoshida, Mayumi; Shi, Chong; Khatri, Pradeep; Du, Yihan; Chen, Liangfu; Shi, JianchengLetu, H., T. Y. Nakajima, T. Wang, H. Shang, R. Ma, K. Yang, A. J. Baran, J. Riedi, H. Ishimoto, M. Yoshida, C. Shi, P. Khatri, Y. Du, L. Chen, J. Shi, 2022: A New Benchmark for Surface Radiation Products over the East Asia–Pacific Region Retrieved from the Himawari-8/AHI Next-Generation Geostationary Satellite. Bull. Amer. Meteor. Soc., 103(3), E873-E888. doi: 10.1175/BAMS-D-20-0148.1. Abstract Surface downward radiation (SDR), including shortwave downward radiation (SWDR) and longwave downward radiation (LWDR), is of great importance to energy and climate studies. Considering the lack of reliable SDR data with a high spatiotemporal resolution in the East Asia–Pacific (EAP) region, we derived SWDR and LWDR at 10-min and 0.05° resolutions for this region from 2016 to 2020 based on the next-generation geostationary satellite Himawari-8 (H-8). The SDR product is unique in terms of its all-sky features, high accuracy, and high-resolution levels. The cloud effect is fully considered in the SDR product, and the influence of high aerosol loadings and topography on the SWDR are considered. Compared to benchmark products of the radiation, such as Clouds and the Earth’s Radiant Energy System (CERES) and the European Centre for Medium-Range Weather Forecasts (ECMWF) next-generation reanalysis (ERA5), and the Global Land Surface Satellite (GLASS), not only is the resolution of the new SDR product notably much higher, but the product accuracy is also higher than that of those products. In particular, hourly and daily root-mean-square errors of the new SWDR are 104.9 and 31.5 W m−2, respectively, which are much smaller than those of CERES (at 121.6 and 38.6 W m−2, respectively), ERA5 (at 176.6 and 39.5 W m−2, respectively), and GLASS (daily of 36.5 W m−2). Meanwhile, RMSEs of hourly and daily values of the new LWDR are 19.6 and 14.4 W m−2, respectively, which are comparable to that of CERES and ERA5, and even better over high-altitude regions.
Li, JianDong; Wang, Wei-Chyung; Chen, GuoXing; You, QingLongLi, J., W. Wang, G. Chen, Q. You, 2022: Characteristics of top-of-atmosphere radiation budget over the Tibetan Plateau and its bias sources in climate models. Atmospheric Research, 276, 106256. doi: 10.1016/j.atmosres.2022.106256. Observations indicate that the Tibetan Plateau (TP) has an annual-mean ~9.3 W m−2 positive radiation budget (RT) at the top of the atmosphere, the largest at the same continental latitudes. This unique radiative heating is critical to the TP's thermal forcing and hydrological cycle. Here we use satellite and reanalyzed data to investigate the characteristics of RT over the TP in the observation and 28 CMIP6 models. The positive observational RT is mainly caused by low surface temperature associated with high elevation. Most models underestimate annual mean RT over the whole TP, with a multimodel average of 2.0 W m−2. This RT bias results mainly from weaker absorbed shortwave radiation (ASR) that exhibits substantial seasonal and regional differences. Serious RT, ASR, and surface albedo biases appear over the western TP. For instance, their wintertime multimodel-mean biases of −44.9 W m−2, −53.3 W m−2, and 0.23 are larger than the eastern TP's counterparts (−38.6 W m−2, −40.6 W m−2, and 0.15). Simulated RT also shows a large intermodel spread. In the models with worse RT's performance, weaker ASR is primarily attributed to higher surface albedo that coincides well with lower surface temperature. In contrast, the models that reproduce well the RT have less surface albedo bias but somewhat overestimate surface temperature. Weaker simulated cloud radiative cooling reduces reflected shortwave radiation that alleviates the RT bias, especially over the springtime eastern TP. This study highlights the importance of land surface states and clouds in modeling the TP's climate. Significance statement Observations indicate that the Tibetan Plateau (TP) has an annual-mean ~ 9.3 W m−2 positive radiation budget (RT) at the top of the atmosphere, the largest among land regions in the same latitudes. This study aims to investigate the characteristics of RT over the TP in the observation and CMIP6 models. Most models underestimate annual mean RT over the whole TP, with a multimodel average of 2.0 W m−2. This bias results mainly from weaker absorbed shortwave radiation, exhibiting substantial seasonal and regional differences. CMIP6 simulations show a large multimodel spread, especially over the wintertime and springtime western TP. This study highlights the importance of land surface states (e.g., surface temperature and albedo) and clouds in modeling the TP's climate. Tibetan Plateau; Cloud; Radiation budget; CMIP6 models
Li, Liang; Liu, Minxia; Qi, Yuhan; Zhang, Guojuan; Yu, RuixinLi, L., M. Liu, Y. Qi, G. Zhang, R. Yu, 2022: Spatiotemporal variations and relationships of absorbing aerosol-radiation-gross primary productivity over China. Environmental Monitoring and Assessment, 195(1), 169. doi: 10.1007/s10661-022-10775-5. High-load carbonaceous and dust aerosols can significantly reduce direct radiation (DIRR), which would affect photosynthesis in terrestrial ecosystems, thereby further affecting the productivity of vegetation. Based on this, a variety of remote sensing data were used to study the spatiotemporal distributions and changing tendencies of the absorbing aerosols, CO, DIRR, and gross primary productivity (GPP) in China during 2005–2019; then, the relationships were analyzed between different types of absorbing aerosols and DIRR as well as GPP. The results showed that the annual mean absorbing aerosols index (AAI) in China during 2005–2019 was 0.39, with a slow growth rate of 0.02 year−1, and the emission of CO showed a decreasing trend with each passing year, especially in North China Plain and Sichuan Basin. Carbonaceous and dust aerosols were predominantly bounded by Hu line. The east of Hu line was the dominant area of carbonaceous aerosols, and the west of Hu line was the topographical region of dust aerosols. Near the Hu line was the dominant area of carbonaceous-dust aerosols. However, the Karamay–Urumqi–Hami area and Northeast China Plain were exceptional. During the vegetation growing season, different types of absorbing aerosols significantly negatively affected GPP. From a perspective of regional scale variation pattern, the negative effect of absorbing aerosols on vegetation productivity was the most significant in Northeast China; from the perspective of the effects of different vegetation types, the negative effect of absorbing aerosols on grasslands was greater than that of woodlands; from the perspective of the composition characteristics of aerosols, the negative effect of dust aerosols on GPP was greater than that of carbonaceous aerosols. Spatiotemporal variations; Aerosol classification; Correlation; Direct radiation; GPP
Li, Lingfeng; Qiu, Bo; Guo, Weidong; Zhang, Yiping; Song, Qinghai; Chen, JiuyiLi, L., B. Qiu, W. Guo, Y. Zhang, Q. Song, J. Chen, 2022: Phenological and physiological responses of the terrestrial ecosystem to the 2019 drought event in Southwest China: Insights from satellite measurements and the SSiB2 model. International Journal of Applied Earth Observation and Geoinformation, 111, 102832. doi: 10.1016/j.jag.2022.102832. Understanding plant phenological and physiological changes in response to drought will provide key insight into the response of terrestrial ecosystems to climate change, but is still limited due to the increased drought severity and frequency in recent decades. Here, we combine solar-induced chlorophyll fluorescence (SIF) along with SSiB2 (Simplified Simple Biosphere Model) simulations to investigate the plant phenological and physiological responses to the 2019 drought in southwestern China. Our results show that this 2019 drought had substantial impacts on vegetation phenology and photosynthesis due to the soil moisture deficit in spring, while the rewatering process in July alleviated the water deficit and reduced drought damage to plants. Moreover, SIF observations provide a physiology-related vegetation response, as the recovery of plant photosynthesis indicated by fluorescence yield (SIFyield) is much stronger than the recovery of greenness described by vegetation indices during the rewatering in July. The SSiB2 simulations captured the physiological response of plants to moisture deficit during drought period, while the lack of realistic energy dissipation mechanisms under stressed conditions may lead to discrepancies in the timing of peak response to drought. Our findings highlight the prospective application of remote sensing SIF measurements in monitoring the timely response of plant physiology to changes in water conditions and to provide important information for model evaluation and improvement. Drought; Solar-induced chlorophyll fluorescence; Water stress; Plant physiological response
Li, Meng; Chu, Ronghao; Sha, Xiuzhu; Xie, Pengfei; Ni, Feng; Wang, Chao; Jiang, Yuelin; Shen, Shuanghe; Islam, Abu Reza Md TowfiqulLi, M., R. Chu, X. Sha, P. Xie, F. Ni, C. Wang, Y. Jiang, S. Shen, A. R. M. T. Islam, 2022: Monitoring 2019 Drought and Assessing Its Effects on Vegetation Using Solar-Induced Chlorophyll Fluorescence and Vegetation Indexes in the Middle and Lower Reaches of Yangtze River, China. Remote Sensing, 14(11), 2569. doi: 10.3390/rs14112569. Monitoring drought precisely and evaluating drought effects quantitatively can establish a scientific foundation for understanding drought. Although solar-induced chlorophyll fluorescence (SIF) can detect the drought stress in advance, the performance of SIF in monitoring drought and assessing drought-induced gross primary productivity (GPP) losses from lush to senescence remains to be further studied. Taking the 2019 drought in the middle and lower reaches of the Yangtze River (MLRYR) as an example, this study aims to monitor and assess this drought by employing a new global, OCO-2-based SIF (GOSIF) and vegetation indexes (VIs). Results showed that the GPP, GOSIF, and VIs all exhibited significant increasing trends during 2000–2020. GOSIF was most consistent with GPP in spatial distribution and was most correlated with GPP in both annual (linear correlation, R2 = 0.87) and monthly (polynomial correlation, R2 = 0.976) time scales by comparing with VIs. During July–December 2019, the precipitation (PPT), soil moisture, and standardized precipitation evapotranspiration index (SPEI) were generally below the averages during 2011–2020 and reached their lowest point in November, while those of air temperature (Tem), land surface temperature (LST), and photosynthetically active radiation (PAR) were the contrary. For drought monitoring, the spatial distributions of standardized anomalies of GOSIF and VIs were consistent during August–October 2019. In November and December, however, considering vegetation has entered the senescence stage, SIF had an obvious early response in vegetation physiological state monitoring compared with VIs, while VIs can better indicate meteorological drought conditions than SIF. For drought assessment, the spatial distribution characteristics of GOSIF and its standardized anomaly were both most consistent with that of GPP, especially the standardized anomaly in November and December. All the above phenomena verified the good spatial consistency between SIF and GPP and the superior ability of SIF in capturing and quantifying drought-induced GPP losses. Results of this study will improve the understanding of the prevention and reduction in agrometeorological disasters and can provide an accurate and timely method for drought monitoring. drought; solar-induced chlorophyll fluorescence; gross primary productivity; the middle and lower reaches of Yangtze River; vegetation indexes
Li, Ming; Letu, Husi; Peng, Yiran; Ishimoto, Hiroshi; Lin, Yanluan; Nakajima, Takashi Y.; Baran, Anthony J.; Guo, Zengyuan; Lei, Yonghui; Shi, JianchengLi, M., H. Letu, Y. Peng, H. Ishimoto, Y. Lin, T. Y. Nakajima, A. J. Baran, Z. Guo, Y. Lei, J. Shi, 2022: Investigation of ice cloud modeling capabilities for the irregularly shaped Voronoi ice scattering models in climate simulations. Atmospheric Chemistry and Physics, 22(7), 4809-4825. doi: 10.5194/acp-22-4809-2022. Abstract. Both weather–climate models and ice cloud remote sensing applications need to obtain effective ice crystal scattering (ICS) properties and the parameterization scheme. An irregularly shaped Voronoi ICS model has been suggested to be effective in remote sensing applications for several satellite programs, e.g., Himawari-8, GCOM-C (Global Change Observation Mission–Climate) and EarthCARE (Earth Cloud Aerosol and Radiation Explorer). As continuation work of Letu et al. (2016), an ice cloud optical property parameterization scheme (Voronoi scheme) of the Voronoi ICS model is employed in the Community Integrated Earth System Model (CIESM) to simulate the optical and radiative properties of ice clouds. We utilized the single-scattering properties (extinction efficiency, single-scattering albedo and asymmetry factor) of the Voronoi model from the ultraviolet to the infrared, combined with 14 408 particle size distributions obtained from aircraft measurements to complete the Voronoi scheme. The Voronoi scheme and existing schemes (Fu, Mitchell, Yi and Baum-yang05) are applied to the CIESM to simulate 10-year global cloud radiative effects during 2001–2010. Simulated globally averaged cloud radiative forcings at the top of the atmosphere (TOA) for Voronoi and the other four existing schemes are compared to the Clouds and the Earth's Radiant Energy System Energy Balanced and Filled (EBAF) product. The results show that the differences in shortwave and longwave globally averaged cloud radiative forcing at the TOA between the Voronoi scheme simulations and EBAF products are 1.1 % and 1.4 %, which are lower than those of the other four schemes. Particularly for regions (from 30∘ S to 30∘ N) where ice clouds occur frequently, the Voronoi scheme provides the closest match with EBAF products compared with the other four existing schemes. The results in this study fully demonstrated the effectiveness of the Voronoi ICS model in the simulation of the radiative properties of ice clouds in the climate model.
Li, Ruohan; Wang, Dongdong; Liang, Shunlin; Jia, Aolin; Wang, ZhihaoLi, R., D. Wang, S. Liang, A. Jia, Z. Wang, 2022: Estimating global downward shortwave radiation from VIIRS data using a transfer-learning neural network. Remote Sensing of Environment, 274, 112999. doi: 10.1016/j.rse.2022.112999. In recent years, machine learning (ML) has been successfully used in estimating downward shortwave radiation (DSR). To achieve global estimations, traditional ML models need sufficient ground measurements covering various atmospheric and surface conditions globally, which is difficult to accomplish. Training on the simulated data of a radiative transfer model (RTM) is a possible solution, but widely used RTMs ignore some complex cloud conditions which brings bias to simulations. In this study, a neural network applied with the transfer-learning (TL) concept is introduced to utilize both radiative transfer simulations and ground measurement data, achieving global DSR estimation with only top-of-atmosphere and surface albedo at local solar noon as inputs. The proposed method estimates both instantaneous and daily DSR from Visible Infrared Imaging Radiometer Suite (VIIRS) data at 750-m resolution, and both the estimates are validated by 40 independent stations globally. The root mean-square error and relative root mean square error of instantaneous DSR validation over 25 Baseline Surface Radiation Network, seven Surface Radiation Network, and eight Greenland Climate Network stations in 2013 were 91.2 (16.1%), 106.3 (18.3%), 75.0 (24.2%) W/m2, respectively, and the daily validation achieved 30.8 (15.5%), 33.5 (17.6%), and 31.3 (14.4) W/m2, respectively. The proposed method presents significant high accuracy over polar regions and similar performances over other areas compared with traditional ML models, physics models (e.g., look-up tables and direct estimations), and existing DSR products. The algorithm is also applied to VIIRS swath data to test its global efficacy. Instantaneous mapping captures the spatial pattern of the cloud-mask product, and daily mapping shows spatial patterns similar to the Clouds and the Earth's Radiant Energy System Synoptic TOA and surface fluxes and clouds product, but with more detail. Further analysis indicates that model performance is less sensitive to the quantity of training data after TL has been incorporated. This study demonstrates the advantages of TL on boosting both the generality and accuracy of DSR estimation, which can potentially be applied to other variable retrievals. Downward shortwave radiation; Solar energy; VIIRS; Radiative transfer; Machine learning; Transfer learning
Li, Shaopeng; Jiang, Bo; Peng, Jianghai; Liang, Hui; Han, Jiakun; Yao, Yunjun; Zhang, Xiaotong; Cheng, Jie; Zhao, Xiang; Liu, Qiang; Jia, KunLi, S., B. Jiang, J. Peng, H. Liang, J. Han, Y. Yao, X. Zhang, J. Cheng, X. Zhao, Q. Liu, K. Jia, 2022: Estimation of the All-Wave All-Sky Land Surface Daily Net Radiation at Mid-Low Latitudes from MODIS Data Based on ERA5 Constraints. Remote Sensing, 14(1), 33. doi: 10.3390/rs14010033. The surface all-wave net radiation (Rn) plays an important role in the energy and water cycles, and most studies of Rn estimations have been conducted using satellite data. As one of the most commonly used satellite data sets, Moderate Resolution Imaging Spectroradiometer (MODIS) data have not been widely used for radiation calculations at mid-low latitudes because of its very low revisit frequency. To improve the daily Rn estimation at mid-low latitudes with MODIS data, four models, including three models built with random forest (RF) and different temporal expansion models and one model built with the look-up-table (LUT) method, are used based on comprehensive in situ radiation measurements collected from 340 globally distributed sites, MODIS top-of-atmosphere (TOA) data, and the fifth generation of European Centre for Medium-Range Weather Forecasts Reanalysis 5 (ERA5) data from 2000 to 2017. After validation against the in situ measurements, it was found that the RF model based on the constraint of the daily Rn from ERA5 (an RF-based model with ERA5) performed the best among the four proposed models, with an overall validated root-mean-square error (RMSE) of 21.83 Wm−2, R2 of 0.89, and a bias of 0.2 Wm−2. It also had the best accuracy compared to four existing products (Global LAnd Surface Satellite Data (GLASS), Clouds and the Earth’s Radiant Energy System Edition 4A (CERES4A), ERA5, and FLUXCOM_RS) across various land cover types and different elevation zones. Further analyses illustrated the effectiveness of the model by introducing the daily Rn from ERA5 into a “black box” RF-based model for Rn estimation at the daily scale, which is used as a physical constraint when the available satellite observations are too limited to provide sufficient information (i.e., when the overpass time is less than twice per day) or the sky is overcast. Overall, the newly-proposed RF-based model with ERA5 in this study shows satisfactory performance and has strong potential to be used for long-term accurate daily Rn global mapping at finer spatial resolutions (e.g., 1 km) at mid-low latitudes. modeling; MODIS; net radiation; energy balance; ERA5; constraint; mid-low latitude; random forest; temporal expansion
Li, Shuping; Sørland, Silje Lund; Wild, Martin; Schär, ChristophLi, S., S. L. Sørland, M. Wild, C. Schär, 2022: Aerosol sensitivity simulations over East Asia in a convection-permitting climate model. Climate Dynamics. doi: 10.1007/s00382-022-06620-7. The parameterization of deep convection is one of the primary sources of uncertainties in regional climate simulations. Due to computational constraints, long-term kilometer-scale simulations with explicit deep convection have been limited, especially over East Asia. We here conduct a pair of 10-years (2001–2010) reference simulations, one convection-parameterizing simulation at 12 km (0.11$$^{\circ }$$) resolution covering the CORDEX East Asia domain, and one 4.4-km (0.04$$^{\circ }$$) convection-permitting simulation over a subdomain. The two simulations are driven by the ERA5 reanalysis and the coarser-resolution simulation, respectively. The 4.4-km convection-permitting simulation noticeably improves the representation of the top-of-atmosphere outgoing longwave and shortwave radiation as well as precipitation intensity. In addition, sensitivity simulations are performed with perturbed sulfate and black carbon aerosols, considering the direct and semi-direct aerosol radiative effects. For the simulations with sulfate aerosol perturbations, the cloud radiative effect partly offsets the aerosol radiative effects. Decreasing sulfate aerosols leads to low-level warming, destabilizing the atmospheric stratification and thereby increasing mean precipitation and the frequency of wet days. Increasing sulfate aerosols leads to an approximately opposite response. For the simulations with black carbon aerosol perturbations, there is some near-surface warming for both increases and decreases in aerosol concentration. Also, there are significant changes in cloud cover, but changes in precipitation are comparatively weak. While for sulfate aerosol perturbations the response is approximately linear (in the sense that positive and negative perturbations yield approximately opposite effects), the response to black carbon aerosol perturbations is more complex and shows some nonlinearity, regardless of the treatment of deep convection in the simulations. We present a simple interpretation for this surprising result. Black carbon; COSMO; East Asia; Regional climate model; Sulfate
Li, Te; Wang, Minghuai; Guo, Zhun; Yang, Ben; Xu, Yifei; Han, Xiaomen; Sun, JianningLi, T., M. Wang, Z. Guo, B. Yang, Y. Xu, X. Han, J. Sun, 2022: An Updated CLUBB PDF Closure Scheme to Improve Low Cloud Simulation in CAM6. Journal of Advances in Modeling Earth Systems, 14(12), e2022MS003127. doi: 10.1029/2022MS003127. Cloud Layers Unified By Binormals (CLUBB) adopts the joint probability density function (PDF) to close higher-order turbulence and diagnose the cloud fraction. CLUBB assumes the equal PDF width of vertical velocity () as the default closure scheme, called Analytic Double Gaussian 1 (ADG1). In this study, a new unequal width PDF closure scheme is adopted in CLUBB, in which the PDF width of is assumed to be associated with skewness and kurtosis of vertical velocity. Offline calculation shows that the updated closure scheme improves the tail in the joint PDF and produces the saturation area from the joint PDF of the total water and liquid water potential temperature closer to that derived from large-eddy simulations than ADG1. The new PDF scheme implemented in Community Atmosphere Model Version 6 is shown to increase low cloud fraction by 20%–30% in most stratocumulus-to-cumulus transition regions. The updated closure scheme is found to improve the low cloud simulation by simulating more symmetric turbulence in stratocumulus and stronger turbulent transport in shallow cumulus. Furthermore, the updated closure scheme enhances the cloud fraction near the cloud base by interacting with the microphysical scheme. Our work indicates the importance of continuous improvement in the PDF closures for higher-order turbulence schemes. low clouds; cloud parameterization; climate model; higher-order turbulence closure; sub-grid processes
Li, Xiaohan; Zhang, Yi; Peng, Xindong; Chu, Wenchao; Lin, Yanluan; Li, JianLi, X., Y. Zhang, X. Peng, W. Chu, Y. Lin, J. Li, 2022: Improved Climate Simulation by Using a Double-Plume Convection Scheme in a Global Model. Journal of Geophysical Research: Atmospheres, 127(11), e2021JD036069. doi: 10.1029/2021JD036069. Convective parameterization can drastically regulate the mean climate and tropical transient activity of a General circulation model (GCM). In this study, the physics suite of the NCAR Community Atmosphere Model, version 5 (CAM5) was first ported to the Global-to-Regional Integrated Forecast System model. Then, the original convective parameterization of CAM5—with a separate representation of deep convection Zhang–Mcfarlane (ZM) and shallow convection University of Washington (UW)—was replaced by a double-plume (DP) scheme. This DP scheme adopts a quasi-unified representation of shallow and deep convection within a single framework. Results demonstrate that the new scheme brings about several improvements in the modeled climate. The differences in the trigger and closure assumptions, lateral mixing rate, and cloud model for the deep convection result in systematic regional differences in the simulated precipitation pattern, cloud vertical structure, and the associated radiative forcing. Compared with ZM-UW, DP reduces the biases in precipitation over the Indian Ocean, ameliorates the “high-frequency and low-intensity” problem of tropical precipitation, and leads to an improved representation of tropical variability, including the Madden–Julian Oscillation. Double-plume reduces low clouds and increases high clouds in the tropics, due to its internal parallel-split convective processes and smaller cumulus cloud fraction. Discussions related to parametric tuning of convective parameterization are also presented.
Liang, Hui; Jiang, Bo; Liang, Shunlin; Peng, Jianghai; Li, Shaopeng; Han, Jiakun; Yin, Xiuwan; Cheng, Jie; Jia, Kun; Liu, Qiang; Yao, Yunjun; Zhao, Xiang; Zhang, XiaotongLiang, H., B. Jiang, S. Liang, J. Peng, S. Li, J. Han, X. Yin, J. Cheng, K. Jia, Q. Liu, Y. Yao, X. Zhao, X. Zhang, 2022: A global long-term ocean surface daily/0.05° net radiation product from 1983–2020. Scientific Data, 9(1), 337. doi: 10.1038/s41597-022-01419-x. The all-wave net radiation (Rn) on the ocean surface characterizes the available radiative energy balance and is important to understand the Earth’s climate system. Considering the shortcomings of available ocean surface Rn datasets (e.g., coarse spatial resolutions, discrepancy in accuracy, inconsistency, and short duration), a new long-term global daily Rn product at a spatial resolution of 0.05° from 1983 to 2020, as part of the Global High Resolution Ocean Surface Energy (GHOSE) products suite, was generated in this study by fusing several existing datasets including satellite and reanalysis products based on the comprehensive in situ measurements from 68 globally distributed moored buoy sites. Evaluation against in-situ measurements shows the root mean square difference, mean bias error and correlation coefficient squared of 23.56 Wm−2, 0.88 Wm−2 and 0.878. The global average ocean surface Rn over 1983–2020 is estimated to be 119.71 ± 2.78 Wm−2 with a significant increasing rate of 0.16 Wm−2 per year. GHOSE Rn product can be valuable for oceanic and climatic studies. Physical oceanography
Lim, Won-Il; Park, Hyo-Seok; Petty, Alek A.; Seo, Kyong-HwanLim, W., H. Park, A. A. Petty, K. Seo, 2022: The Role of Summer Snowstorms on Seasonal Arctic Sea Ice Loss. Journal of Geophysical Research: Oceans, 127(12), e2021JC018066. doi: 10.1029/2021JC018066. In the Arctic, short-lived summer snowstorms can provide snow cover that can increase surface reflectivity and heat capacity. Despite their potential importance, little research has been done to understand the impact of summer snowstorms on basin-scale Arctic sea ice cover. Our observational analysis shows that a summer snowstorm event is accompanied by cyclonic ice drift, increases in surface albedo and surface air cooling that can persist for up to ∼2 weeks, dampening sea ice loss. Specifically, multiple snowstorm events in a summer, on average, results in net increase in sea ice extent of ∼0.2 × 106 km2 by early September. Experiments with a sophisticated ice-ocean model framework indicate that the initial expansion of sea ice extent is driven by cyclonic wind-driven ice drifts driving sea ice southwards and increasing albedo around the summer ice edge, however the thermal effects from the associated snowfall and atmospheric conditions result in a stronger overall impact on basin-averaged sea ice extent at seasonal scales. Additional model experiments were carried out to isolate the physical processes contributing to the thermal response of Arctic sea ice to summer snowstorms. Our results show the impact of surface air cooling on sea ice extent is about 3.5 times larger than the snowfall/albedo response. However, our simulated albedo response is weaker than the observed response, likely due to the negligible difference in surface albedo between old snow and freshly fallen snow—a limiting factor in our analysis and a topic worthy of future focus. Arctic sea ice; albedo; snowfall
Lin, Qiao-Jun; Yu, Jia-YuhLin, Q., J. Yu, 2022: The potential impact of model horizontal resolution on the simulation of atmospheric cloud radiative effect in CMIP6 models. Terrestrial, Atmospheric and Oceanic Sciences, 33(1), 21. doi: 10.1007/s44195-022-00021-3. The simulations of atmospheric cloud-radiative effect (ACRE) from 54 Coupled Model Intercomparison Project phase 6 (CMIP6) models during the historical period of 2000/03–2014/12 are compared and evaluated against the satellite-based Clouds and the Earth’s Radiant Energy System (CERES) products. For ease of comparison, all CMIP6 models are divided into high-, medium-, and low-resolution groups to examine the potential impact of model horizontal resolution change on the simulations of ACRE distribution over the tropical oceans. The results show that ACRE is positive inside the ITCZs but negative in the subtropics and cold tongue areas, owing to the very different radiative forcing between deep and shallow clouds. Simulations of ACRE are sensitive to the model horizontal resolution used and the finer resolution models generally produce a better performance of ACRE simulations against the CERES observations. The reduced ACRE biases in finer resolution models are mainly contributed by the improved longwave ACRE (i.e., LWACRE) simulations, especially over the Pacific and Atlantic cold tongue areas where shallow stratocumulus clouds prevail. CMIP6; Atmospheric cloud-radiative effect; Model horizontal resolution
Lindzen, Richard S.; Choi, Yong-SangLindzen, R. S., Y. Choi, 2022: The Iris Effect: A Review. Asia-Pacific Journal of Atmospheric Sciences, 58(1), 159-168. doi: 10.1007/s13143-021-00238-1. This study reviews the research of the past 20-years on the role of anvil cirrus in the Earth’s climate – research initiated by Lindzen et al. (Bull. Am. Meteor. Soc. 82:417-432, 2001). The original study suggested that the anvil cirrus would shrink with warming, which was estimated to induce longwave cooling for the Earth. This is referred to as the iris effect since the areal change hypothetically resembles the light control by the human eye’s iris. If the effect is strong enough, it exerts a significant negative climate feedback which stabilizes tropical temperatures and limits climate sensitivity. Initial responses to Lindzen et al. (Bull. Am. Meteor. Soc. 82:417-432, 2001) denied the existence and effectiveness of the iris effect. Assessment of the debatable issues in these responses will be presented later in this review paper. At this point, the strong areal reduction of cirrus with warming appears very clearly in both climate models and satellite observations. Current studies found that the iris effect may not only come from the decreased cirrus outflow due to increased precipitation efficiency, but also from concentration of cumulus cores over warmer areas (the so-called aggregation effect). Yet, different opinions remain as to the radiative effect of cirrus clouds participating in the iris effect. For the iris effect to be most important, it must involve cirrus clouds that are not as opaque for visible radiation as they are for infrared radiation. However, current climate models often simulate cirrus clouds that are opaque in both visible and infrared radiation. This issue requires thorough examination as it seems to be opposed to conventional wisdom based on explicit observations. This paper was written in the hope of stimulating more effort to carefully evaluate these important issues.
Lipzig, Nicole P. M. van; Walle, Jonas Van de; Belušić, Danijel; Berthou, Ségolène; Coppola, Erika; Demuzere, Matthias; Fink, Andreas H.; Finney, Declan L.; Glazer, Russell; Ludwig, Patrick; Marsham, John H.; Nikulin, Grigory; Pinto, Joaquim G.; Rowell, David P.; Wu, Minchao; Thiery, WimLipzig, N. P. M. v., J. V. d. Walle, D. Belušić, S. Berthou, E. Coppola, M. Demuzere, A. H. Fink, D. L. Finney, R. Glazer, P. Ludwig, J. H. Marsham, G. Nikulin, J. G. Pinto, D. P. Rowell, M. Wu, W. Thiery, 2022: Representation of precipitation and top-of-atmosphere radiation in a multi-model convection-permitting ensemble for the Lake Victoria Basin (East-Africa). Climate Dynamics. doi: 10.1007/s00382-022-06541-5. The CORDEX Flagship Pilot Study ELVIC (climate Extremes in the Lake VICtoria basin) was recently established to investigate how extreme weather events will evolve in this region of the world and to provide improved information for the climate impact community. Here we assess the added value of the convection-permitting scale simulations on the representation of moist convective systems over and around Lake Victoria. With this aim, 10 year present-day model simulations were carried out with five regional climate models at both PARameterized (PAR) scales (12–25 km) and Convection-Permitting (CP) scales (2.5–4.5 km), with COSMO-CLM, RegCM, AROME, WRF and UKMO. Most substantial systematic improvements were found in metrics related to deep convection. For example, the timing of the daily maximum in precipitation is systematically delayed in CP compared to PAR models, thereby improving the agreement with observations. The large overestimation in the total number of rainy events is alleviated in the CP models. Systematic improvements were found in the diurnal cycle in Top-Of-Atmosphere (TOA) radiation and in some metrics for precipitation intensity. No unanimous improvement nor deterioration was found in the representation of the spatial distribution of total rainfall and the seasonal cycle when going to the CP scale. Furthermore, some substantial biases in TOA upward radiative fluxes remain. Generally our analysis indicates that the representation of the convective systems is strongly improved in CP compared to PAR models, giving confidence that the models are valuable tools for studying how extreme precipitation events may evolve in the future in the Lake Victoria basin and its surroundings. Convection permitting simulations; CORDEX Flagship Pilot Study; Equatorial Africa; Extreme weather events; Kilometer-scale resolution; Lake Victoria basin; Regional climate models; Tropical deep convection
Liu, Chunlei; Chen, Ni; Long, Jingchao; Cao, Ning; Liao, Xiaoqing; Yang, Yazhu; Ou, Niansen; Jin, Liang; Zheng, Rong; Yang, Ke; Su, QianyeLiu, C., N. Chen, J. Long, N. Cao, X. Liao, Y. Yang, N. Ou, L. Jin, R. Zheng, K. Yang, Q. Su, 2022: Review of the Observed Energy Flow in the Earth System. Atmosphere, 13(10), 1738. doi: 10.3390/atmos13101738. The energy budget imbalance at the top of the atmosphere (TOA) and the energy flow in the Earth’s system plays an essential role in climate change over the global and regional scales. Under the constraint of observations, the radiative fluxes at TOA have been reconstructed prior to CERES (Clouds and the Earth’s Radiant Energy System) between 1985 and 2000. The total atmospheric energy divergence has been mass corrected based on ERA5 (the fifth generation ECMWF ReAnalysis) atmospheric reanalysis by a newly developed method considering the enthalpy removing of the atmospheric water vapor, which avoids inconsistencies due to the residual lateral total mass flux divergence in the atmosphere, ensuring the balances of the freshwater fluxes at the surface. The net surface energy flux (Fs) has been estimated using the residual method based on energy conservation, which is the difference between the net TOA radiative flux and the atmospheric energy tendency and divergence. The Fs is then verified directly and indirectly with observations, and results show that the estimated Fs in North Atlantic is superior to those from model simulations. This paper gives a brief review of the progress in the estimation of the observed energy flow in the Earth system, discusses some caveats of the existing method, and provides some suggestions for the improvements of the aforementioned data sets. energy transport; mass corrected atmospheric energy divergence; net surface energy flux; TOA radiative flux
Liu, Chunlei; Yang, Yazhu; Liao, Xiaoqing; Cao, Ning; Liu, Jimmy; Ou, Niansen; Allan, Richard P.; Jin, Liang; Chen, Ni; Zheng, RongLiu, C., Y. Yang, X. Liao, N. Cao, J. Liu, N. Ou, R. P. Allan, L. Jin, N. Chen, R. Zheng, 2022: Discrepancies in Simulated Ocean Net Surface Heat Fluxes over the North Atlantic. Advances in Atmospheric Sciences. doi: 10.1007/s00376-022-1360-7. The change in ocean net surface heat flux plays an important role in the climate system. It is closely related to the ocean heat content change and ocean heat transport, particularly over the North Atlantic, where the ocean loses heat to the atmosphere, affecting the AMOC (Atlantic Meridional Overturning Circulation) variability and hence the global climate. However, the difference between simulated surface heat fluxes is still large due to poorly represented dynamical processes involving multiscale interactions in model simulations. In order to explain the discrepancy of the surface heat flux over the North Atlantic, datasets from nineteen AMIP6 and eight highresSST-present climate model simulations are analyzed and compared with the DEEPC (Diagnosing Earth’s Energy Pathways in the Climate system) product. As an indirect check of the ocean surface heat flux, the oceanic heat transport inferred from the combination of the ocean surface heat flux, sea ice, and ocean heat content tendency is compared with the RAPID (Rapid Climate Change-Meridional Overturning Circulation and Heat flux array) observations at 26°N in the Atlantic. The AMIP6 simulations show lower inferred heat transport due to less heat loss to the atmosphere. The heat loss from the AMIP6 ensemble mean north of 26°N in the Atlantic is about 10 W m−2 less than DEEPC, and the heat transport is about 0.30 PW (1 PW = 1015 W) lower than RAPID and DEEPC. The model horizontal resolution effect on the discrepancy is also investigated. Results show that by increasing the resolution, both surface heat flux north of 26°N and heat transport at 26°N in the Atlantic can be improved. observations; ocean heat transport; discrepancy; ocean net surface heat flux; simulations
Liu, Le; Wu, Bingyi; Ding, ShuoyiLiu, L., B. Wu, S. Ding, 2022: On the Association of the Summertime Shortwave Cloud Radiative Effect in Northern Russia With Atmospheric Circulation and Climate Over East Asia. Geophysical Research Letters, 49(2), e2021GL096606. doi: 10.1029/2021GL096606. This study employs ERA5 reanalysis and CERES/EBAF Ed4.1 data to evaluate the dominant features of summer shortwave cloud radiative effect (SWCRE) variability and associated atmospheric circulation anomalies. Our findings suggest that the greatest variability in summer SWCRE occurs over the Barents, Kara, and Laptev seas and northern Eurasia. We also observe a close relationship between summertime SWCRE, particularly in northern Russia, and atmospheric circulation variability over East Asia. Significant positive SWCRE anomalies over northern Russia favor the generation of the Ural blocking, and dynamically trigger the emergence of positive Eurasian (EU) pattern, resulting in positive (negative) precipitation anomalies in northern (southeastern) China and persistent East Asian heatwaves between 20°N and 40°N. In contrast to previous work, which has focused mainly on local atmospheric responses to SWCRE, this study provides a broader perspective, thereby helping bridge summertime circulation between high latitudes and East Asia. shortwave cloud radiative effect; East Asian atmospheric circulation variability; Eurasian teleconnection; Ural blocking
Liu, Xinyan; He, Tao; Sun, Lin; Xiao, Xiongxin; Liang, Shunlin; Li, SiweiLiu, X., T. He, L. Sun, X. Xiao, S. Liang, S. Li, 2022: Analysis of Daytime Cloud Fraction Spatiotemporal Variation over the Arctic from 2000 to 2019 from Multiple Satellite Products. J. Climate, 35(23), 3995-4023. doi: 10.1175/JCLI-D-22-0007.1. Abstract Insufficient understanding of complex Arctic cloud properties introduced large errors in estimating radiant energy balance parameters at the regional and global scales. Comprehensive and reliable cloud information is necessary for improving the accuracy of flux inversion. This study evaluated daytime cloud fraction (CF) uncertainties from 16 available satellite products and estimated the spatiotemporal distributions of Arctic daytime CF during 2000–19. Our results show that the differences among multiple products had significant temporal and spatial heterogeneities. Temporally, the maximum and minimum interproduct discrepancies occurred in April and the summer months, respectively. Spatially, the largest uncertainties were seen over Greenland. Substantial inconsistency also occurred on the central and Pacific sides of the Arctic Ocean. The active satellite product tended to capture more clouds in these two regions. We found that the inconsistencies caused by sensor differences were smaller than those caused by algorithm differences; that is, for MODIS based CF products, the inconsistencies caused by different sensors and different algorithms are ±2% and ±5%, while for AVHRR-based products, these inconsistencies are ±6% and ±15%, respectively. The annual average daytime CF in sunlit months was 70.9% ± 2.93% and increased over the Arctic during study periods. These upward trends might cool the Arctic by approximately 0.05–0.5 W m−2 decade−1. In terms of the spatiotemporal distributions, the CF over the ocean is higher than that over the land, and the former increased significantly while the latter decreased; the CF trends of most products are positive in June and July but are opposite in other months. From this study, the findings based on multiple products would be more robust than that based on a single or few datasets. Significance Statement This study aimed to comprehensively understand and obtain more robust general characteristics of the temporal and spatial distributions of Arctic daytime cloud fraction by comparing and analyzing the consistencies and discrepancies of multisource satellite products. It is important because the cloud fraction is a nonnegligible modulator of Earth’s energy budget and climate change. Although the Arctic is the most climate-sensitive region, existing studies lack a comprehensive assessment of the cloud fraction over the entire Arctic. We analyzed 16 different cloud products and found that although the inconsistencies were inevitable, most products showed similar spatiotemporal distribution and trend distribution of daytime CF. This study provided a new idea for Arctic CF research under the existing conditions.
Liu, Yansong; Ren, Qiang; Yu, Fei; Wang, Jianfeng; Wang, Ran; Nan, Feng; Ding, Yanan; Zheng, Tongtong; Zhang, Chuanzheng; Zhao, Ruixiang; Zheng, Hua; Zhu, Xiao-HuaLiu, Y., Q. Ren, F. Yu, J. Wang, R. Wang, F. Nan, Y. Ding, T. Zheng, C. Zhang, R. Zhao, H. Zheng, X. Zhu, 2022: Observed Taylor cap around a seamount intensified by a surface mesoscale eddy in the Northwest Pacific. Climate Dynamics. doi: 10.1007/s00382-022-06570-0. Observations from 4 current and pressure-recording inverted echo sounders (CPIESs) deployed in the northwest Pacific from 2018 to 2019 reveal an anticyclonic cap around a seamount. Significant increases in velocity can be found from mid-November 2018 to January 2019 and verified the coexistence with the “cold dome” combined with numerical model data. The Taylor cap induced by the impinging flow toward the seamount plays a primary role in the anticyclonic current structure compared with tide rectification. The relationship between the impinging flow and surface mesoscale eddy in the northwest Pacific was further analyzed by combining the satellite altimeter data. When the surface cyclonic eddy moved to the center of the seamount in November 2018, the absolute sea level anomaly (SLA) increased, the temperature at the summit decreased, and the deep velocity impinging toward the seamount decreased and then intensified the Taylor cap around the seamount. CPIES; Northwest Pacific; Seamount; Surface mesoscale eddy; Taylor cap
Liu, Yawen; Wang, Minghuai; Qian, Yun; Ding, AijunLiu, Y., M. Wang, Y. Qian, A. Ding, 2022: A Strong Anthropogenic Black Carbon Forcing Constrained by Pollution Trends Over China. Geophysical Research Letters, 49(10), e2022GL098965. doi: 10.1029/2022GL098965. Estimates of the effective radiative forcing from aerosol-radiation interaction (ERFari) of anthropogenic Black Carbon (BC) have been disputable and require better constraints. Here we find a substantial decline in atmospheric absorption of −5.79Wm−2decade−1 over eastern central China (ECC) responding to recent anthropogenic BC emission reductions. By combining the observational finding with advances from Coupled Model Intercomparison Project phase6 (CMIP6), we identify an emergent constraint on the ERFari of anthropogenic BC. We show that across CMIP6 models the simulated trends correlate well with simulated annual mean shortwave atmospheric absorption by anthropogenic BC over China. Making use of this emergent relationship allows us to constrain the aerosol absorption optical depth of anthropogenic BC and further provide a constrained range of 2.4–3.0 Wm−2 for its top-of-atmosphere ERFari over China, higher than existing estimates. Our work supports a strong warming effect of BC over China, and highlights the need to improve BC simulations over source regions. CMIP6 models; anthropogenic black carbon; effective radiative forcing from aerosol-radiation interaction; long-term trend; observational constraint
Liu, Yuzhi; Huang, Jianping; Wang, Tianhe; Li, Jiming; Yan, Hongru; He, YongliLiu, Y., J. Huang, T. Wang, J. Li, H. Yan, Y. He, 2022: Aerosol-cloud interactions over the Tibetan Plateau: An overview. Earth-Science Reviews, 234, 104216. doi: 10.1016/j.earscirev.2022.104216. This paper reviews progress in the study of aerosol-cloud interactions over the Tibetan Plateau (TP) in the past decade. Clarifying the aerosol-cloud-precipitation interactions over the TP is an important issue for both local and downstream precipitation forecasts. By exerting a “dynamic pump” effect due to the elevated heat source in summer, the TP acts as a “transfer station” for aerosols and water vapor, possessing abundant water vapor and enough cloud condensation nuclei (CCN) and ice nuclei (IN) in cloud physical processes. We found that mixtures of aerosols and clouds are frequently observed over the margin areas of the TP, especially the mixture between aerosols and ice clouds. The convective clouds over the TP could be affected by the Taklimakan dusts lifted from the north slope of the TP, inducing higher and more invigorated convective clouds locally. Furthermore, the dust-polluted convective clouds can continuously move eastward and merge with the convective cloud clusters along their motion paths, inducing more intensive rainfall over the downstream regions of the TP. Finally, challenges to further understanding aerosol-cloud interactions over the TP in the future are discussed. Precipitation; Tibetan Plateau; Cloud; Aerosol; Interaction
Loeb, Norman G.; Mayer, Michael; Kato, Seiji; Fasullo, John T.; Zuo, Hao; Senan, Retish; Lyman, John M.; Johnson, Gregory C.; Balmaseda, MagdalenaLoeb, N. G., M. Mayer, S. Kato, J. T. Fasullo, H. Zuo, R. Senan, J. M. Lyman, G. C. Johnson, M. Balmaseda, 2022: Evaluating Twenty-Year Trends in Earth's Energy Flows From Observations and Reanalyses. Journal of Geophysical Research: Atmospheres, 127(12), e2022JD036686. doi: 10.1029/2022JD036686. Satellite, reanalysis, and ocean in situ data are analyzed to evaluate regional, hemispheric and global mean trends in Earth's energy fluxes during the first 20 years of the twenty-first century. Regional trends in net top-of-atmosphere (TOA) radiation from the Clouds and the Earth's Radiant Energy System (CERES), ECMWF Reanalysis 5 (ERA5), and a model similar to ERA5 with prescribed sea surface temperature (SST) and sea ice differ markedly, particularly over the Eastern Pacific Ocean, where CERES observes large positive trends. Hemispheric and global mean net TOA flux trends for the two reanalyses are smaller than CERES, and their climatological means are half those of CERES in the southern hemisphere (SH) and more than nine times larger in the northern hemisphere (NH). The regional trend pattern of the divergence of total atmospheric energy transport (TEDIV) over ocean determined using ERA5 analyzed fields is similar to that inferred from the difference between TOA and surface fluxes from ERA5 short-term forecasts. There is also agreement in the trend pattern over ocean for surface fluxes inferred as a residual between CERES net TOA flux and ERA5 analysis TEDIV and surface fluxes obtained directly from ERA5 forecasts. Robust trends are observed over the Gulf Stream associated with enhanced surface-to-atmosphere transfer of heat. Within the ocean, larger trends in ocean heating rate are found in the NH than the SH after 2005, but the magnitude of the trend varies greatly among datasets.
Lv, Mingzhu; Song, Yan; Li, Xijia; Wang, Mengsi; Qu, YingLv, M., Y. Song, X. Li, M. Wang, Y. Qu, 2022: Spatiotemporal characteristics and driving factors of global planetary albedo: an analysis using the Geodetector method. Theoretical and Applied Climatology, 147(1), 737-752. doi: 10.1007/s00704-021-03858-9. As an important parameter of the Earth’s energy budget, the planetary albedo of Earth varies with the dynamics of atmospheric and surface variables. In this study, we investigated the spatiotemporal characteristics and driving factors of the global planetary albedo using the Clouds and the Earth’s Radiant Energy System (CERES) Energy Balanced and Filled (EBAF) dataset and the Geodetector method. The results revealed that the planetary albedo can be decomposed into atmospheric and surface contributions, and the planetary albedo in the middle and low latitudes was predominantly affected by the atmospheric contribution. The global planetary albedo and the atmospheric and surface contributions exhibited decreasing trends of − 0.0020, − 0.0015, and − 0.0004/decade from 2001 to 2018, respectively, which were closely related to the variations of atmospheric and surface variables. The cloud fraction was the driving factor of the atmospheric contribution in the middle and low latitudes, and its influence was further enhanced by the aerosol optical thickness (AOT), ice water path (IWP), and liquid water path (LWP). The snow/ice coverage and normalized difference vegetation index (NDVI) were the driving factors of the surface contribution in the snow/ice-covered and vegetated areas, respectively. The interaction relationships between the surface variables were mainly bi-enhanced and nonlinearly enhanced. These results provide useful information about the driving factors of the planetary albedo and are benefit for improving the parametrization of the planetary albedo.
Ma, Mengnan; Ou, Tinghai; Liu, Dongqing; Wang, Shuyu; Fang, Juan; Tang, JianpingMa, M., T. Ou, D. Liu, S. Wang, J. Fang, J. Tang, 2022: Summer regional climate simulations over Tibetan Plateau: from gray zone to convection permitting scale. Climate Dynamics. doi: 10.1007/s00382-022-06314-0. The Tibetan Plateau (TP) is often referred to as ‘the Third Pole’ and plays an essential role in the global climate. However, it remains challenging for most global and regional models to realistically simulate the characteristics of climate over the TP. In this study, two Weather Research and Forecasting model (WRF) experiments using spectral nudging with gray-zone (GZ9) and convection-permitting (CP3) resolution are conducted for summers from 2009 to 2018. The surface air temperature (T2m) and precipitation from the two simulations and the global reanalysis ERA5 are evaluated against in-situ observations. The results show that ERA5 has a general cold bias over southern TP, especially in maximum T2m (Tmax), and wet bias over whole TP. Both experiments can successfully capture the spatial pattern and daily variation of T2m and precipitation, though cold bias for temperature and dry bias for precipitation exist especially over the regions south of 35° N. Compared with ERA5, the added value of the two WRF experiments is mainly reflected in the reduced cold bias especially for Tmax with more improvement found in CP3 and the reduced wet bias. However, the ability of the convection-permitting WRF experiment in improving the simulation of precipitation seems limited when compared to the gray-zone WRF experiment, which may be related to the biases in physical parameterization and lack of representativeness of station observation. Further investigation into surface radiation budget reveals that the underestimation of net shortwave radiation contributes a lot to the cold bias of T2m over the southeastern TP in GZ9 which is improved in CP3. Compared with GZ9, CP3 shows that larger specific humidity at low-level (mid-high level) coexists with more precipitation (clouds) over the southern TP. This improvement is achieved by better depiction of topographic details, underlying surface and atmospheric processes, land–atmosphere interactions and so on, leading to stronger northward water vapor transport (WVT) in CP3, providing more water vapor for precipitation at surface and much wetter condition in the mid-high level. Tibetan Plateau; Convection permitting; Gray zone; Spectral nudging; Summer precipitation; Surface air temperature
Ma, Wen; Ding, Jianli; Wang, Jinlong; Zhang, JunyongMa, W., J. Ding, J. Wang, J. Zhang, 2022: Effects of aerosol on terrestrial gross primary productivity in Central Asia. Atmospheric Environment, 288, 119294. doi: 10.1016/j.atmosenv.2022.119294. Aerosols significantly contribute to global and regional climate change by altering the surface solar radiation, thereby affecting plant productivity. Central Asia is a primary source of global dust aerosols. However, the mechanisms of how aerosols affect terrestrial gross primary productivity (GPP), especially in Central Asia, are not clearly understood. In this study, we investigated the spatial variation in aerosol optical depth (AOD) and GPP and the relationship between them during the growing season (April–October) from 2001 to 2018 using remote sensing data from several sources. We created a GWR-SEM model consisting of a geographically weighted model (GWR) coupled with a structural equation model (SEM) to quantify and analyze the effects of AOD on GPP. The results show that AOD decreased slightly at a rate of −0.0002 y−1 during the study period and that there was a tendency towards spatial aggregation. The extent of AOD pollution in the northwest region (around the Aral Sea) was slightly greater than that in the southeast. GPP increased significantly at a rate of 7.2965 g C m−2 y−2, especially in the northern region. There were some differences in the effects of AOD on GPP between different vegetation types; the highest AOD–GPP correlation was found in shrublands and croplands. Analysis of the GWR-SEM model suggested that AOD and two forms of radiation (surface net radiation, SNR, and photosynthetically active radiation, PAR) explained 72.4% (63.4% for 2001, 66.8% for 2018) of the spatial variation in GPP. SNR had the greatest effect on GPP, followed by AOD. Diffuse PAR had the greatest indirect effect on GPP. The findings of this study highlight the importance of aerosol pollution on spatial variation in gross primary productivity, and they provide a methodological framework for investigating the relationship between AOD and GPP in arid areas. GPP; Aerosol optional depth; Central Asia; SEM
Maity, Suman; Nayak, Sridhara; Nayak, Hara Prasad; Bhatla, R.Maity, S., S. Nayak, H. P. Nayak, R. Bhatla, 2022: Comprehensive assessment of RegCM4 towards interannual variability of Indian Summer Monsoon using multi-year simulations. Theoretical and Applied Climatology. doi: 10.1007/s00704-022-03961-5. In this study, the interannual variability (IAV) of Indian Summer Monsoon (ISM) is investigated using multi-year (1982‒2016) seasonal scale simulations (May‒September) of the regional climate model RegCM4. Model-simulated fields such as surface temperature, wind and rainfall are validated initially to testify the climatological behaviour of ISM. Subsequently, different aspects of IAV associated with ISM are discussed primarily focusing on model simulated rainfall and are verified against high-resolution rainfall analysis from India Meteorological Department (IMD). Analysis indicated that RegCM4 shows reasonable accuracy in simulating major large-scale features, however, has cold bias over entire India and wet (dry) bias over northwest and peninsular (central) India. Easterly (westerly) bias is noticed in the model simulated low (upper) level wind that affects regional Hadley circulation. The cold bias is found to be associated with the feedback cycle of land–atmosphere interaction. Surface evaporative cooling likely affects the static instability in the atmospheric column, thereby limiting the convection and thus reducing rainfall. While categorizing, it is noticed that the efficacy of the model is found to be better in simulating normal monsoon as compared to contrasting monsoon (deficit and excess) year, thereby reducing the simulation skill for the entire period. EOF analysis revealed that first two leading modes of IMD rainfall are linked with large-scale variabilities, viz. El-Nino Southern Oscillation and Indian Ocean Dipole, respectively, but RegCM4 could not well reproduce these relationships. The spectral analysis showed 2–7 year periodicity in the model. However, the associated spectral peaks are close to the red noise spectrum due to their weak power suggesting limited model skill to capture large-scale variability. Overall, this study advocates that the RegCM4 could capture the climatological features of ISM fairly well, but needs further improvement in representing the IAV more accurately.
Maloney, Christopher; Toon, Brian; Bardeen, Charles; Yu, Pengfei; Froyd, Karl; Kay, Jennifer; Woods, SarahMaloney, C., B. Toon, C. Bardeen, P. Yu, K. Froyd, J. Kay, S. Woods, 2022: The balance between heterogeneous and homogeneous nucleation of ice clouds using CAM5/CARMA. Journal of Geophysical Research: Atmospheres, e2021JD035540. doi: 10.1029/2021JD035540. We present a modification to the Community Aerosol and Radiation model for Atmospheres (CARMA) sectional ice microphysical model where we have added interactive nucleation of sulfates and heterogeneous nucleation onto dust in order to create a more comprehensive representation of ice nucleation within the CARMA sectional ice model. The convective wet removal fix has also been added in order to correctly transport aerosol within the Community Atmosphere Model version 5 (CAM5) and the 3-mode Modal Aerosols Model (MAM3). In CARMA, the balance of homogeneous and heterogeneous nucleation is controlled by the presence of temperatures below 240 °K, supersaturation, and the availability of heterogeneous nuclei. Due to a paucity of dust at altitudes above about 7 km, where temperatures over most of the Earth fall below 240 °K, cirrus clouds above 7 km nucleate primarily via homogeneous nucleation on aqueous sulfate aerosols in our simulations. Over mid-latitudes of the Northern Hemisphere, dust is more common above 7 km during spring through fall, and both heterogeneous nucleation and homogenous freezing occur in our model. Below 7 km heterogeneous nucleation dominates in situ formation of ice. Furthermore, we find an improvement of the representation of in-cloud ice within mixed phase clouds in CAM5/CARMA when compared to simulations with only homogeneous ice nucleation. Other modes of nucleation such as contact nucleation of liquid cloud droplets or liquid cloud droplet freezing on immersion nuclei, were not directly compared with classical depositional heterogeneous nucleation in this study. Cloud modeling; Dust Aerosol; Heterogeneous nucleation; Homogeneous nucleation; Ice nucleation
Matthews, G.Matthews, G., 2022: Direct Solar Viewing Calibration Concept for Future CERES-, GERB-, or Libera-Type Earth Orbital Climate Missions. J. Atmos. Oceanic Technol., 39(7), 1085-1091. doi: 10.1175/JTECH-D-21-0002.1. Abstract Better predictions of global warming can be enabled by tuning legacy and current computer simulations to Earth radiation budget (ERB) measurements. Since the 1970s, such orbital results exist, and the next-generation instruments such as one called “Libera” are in production. Climate communities have requested that new ERB observing system missions like these have calibration accuracy obtaining significantly improved calibration SI traceability and stability. This is to prevent untracked instrument calibration drifts that could lead to false conclusions on climate change. Based on experience from previous ERB missions, the alternative concept presented here utilizes directly viewing solar calibration, for cloud-size Earth measurement resolution at
Matthews, GrantMatthews, G., 2022: Assessment of Terra/Aqua MODIS and Deep Convective Cloud Albedo Solar Calibration Accuracies and Stabilities Using Lunar Calibrated MERBE Results. Remote Sensing, 14(11), 2517. doi: 10.3390/rs14112517. Moon calibrated radiometrically stable and relatively accurate Earth reflected solar measurements from the Moon and Earth Radiation Budget Experiment (MERBE) are compared here to primary channels of coaligned Terra/Aqua MODIS instruments. A space-based climate observing system immune to untracked drifts due to varying instrument calibration is a key priority for climate science. Measuring these changes in radiometers such as MODIS and compensating for them is critical to such a system. The independent MERBE project using monthly lunar scans has made a proven factor of ten improvement in calibration stability and relative accuracy of measurements by all devices originally built for another project called ‘CERES’, also on the Terra and Aqua satellites. The MERBE comparison shown here uses spectrally invariant Deep Convective Cloud or DCC targets as a transfer, with the objective of detecting possible unknown MODIS calibration trends or errors. Most MODIS channel 1–3 collection 5 calibrations are shown to be correct and stable within stated accuracies of 3% relative to the Moon, much in line with changes made for MODIS collection 6. Stable lunar radiance standards are then separately compared to the sometimes used calibration metric of the coldest DCCs as standalone calibration targets, when also located by MODIS. The analysis overall for the first time finds such clouds can serve as an absolute solar target on the order of 1% accuracy and are stable to ±0.3% decade−1 with two sigma confidences, based on the Moon from 2000–2015. Finally, time series analysis is applied to potential DCC albedo corrected Terra data. This shows it is capable of beginning the narrowing of cloud climate forcing uncertainty before 2015; some twenty five years sooner than previously calculated elsewhere, for missions yet to launch. earth radiation budget; MODIS; earth observation; lunar calibration; MERBE; climate observing system; deep convective cloud (DCC) albedo; solar forcing
Mayer, Johannes; Mayer, Michael; Haimberger, Leopold; Liu, ChunleiMayer, J., M. Mayer, L. Haimberger, C. Liu, 2022: Comparison of Surface Energy Fluxes from Global to Local Scale. J. Climate, 35(14), 4551-4569. doi: 10.1175/JCLI-D-21-0598.1. Abstract This study uses the ECMWF ERA5 reanalysis and observationally constrained top-of-the-atmosphere radiative fluxes to infer net surface energy fluxes covering 1985–2018, which can be further adjusted to match the observed mean land heat uptake. Various diagnostics are applied to provide error estimates of inferred fluxes on different spatial scales. For this purpose, adjusted as well as unadjusted inferred surface fluxes are compared with other commonly used flux products. On a regional scale, the oceanic energy budget of the North Atlantic between the RAPID array at 26.5°N and moorings located farther north (e.g., at the Greenland–Scotland Ridge) is evaluated. On the station scale, a comprehensive comparison of inferred and buoy-based fluxes is presented. Results indicate that global land and ocean averages of unadjusted inferred surface fluxes agree with the observed heat uptake to within 1 W m−2, while satellite-derived and model-based fluxes show large global mean biases. Furthermore, the oceanic energy budget of the North Atlantic is closed to within 2.7 (−0.2) W m−2 for the period 2005–09 when unadjusted (adjusted) inferred surface fluxes are employed. Indirect estimates of the 2004–16 mean oceanic heat transport at 26.5°N are 1.09 PW (1.17 PW with adjusted fluxes), which agrees well with observed RAPID transports. On the station scale, inferred fluxes exhibit a mean bias of −20.1 W m−2 when using buoy-based fluxes as reference, which confirms expectations that biases increase from global to local scales. However, buoy-based fluxes as reference are debatable, and are likely positively biased, suggesting that the station-scale bias of inferred fluxes is more likely on the order of −10 W m−2.
Mazhar, Usman; Jin, Shuanggen; Hu, Ting; Bilal, Muhammad; Ali, MD Arfan; Atique, LuqmanMazhar, U., S. Jin, T. Hu, M. Bilal, M. A. Ali, L. Atique, 2022: Long-time Variation and Mechanism of Surface Energy Budget over Diverse Geographical Regions in Pakistan. IEEE Journal of Selected Topics in Applied Earth Observations and Remote Sensing, 1-13. doi: 10.1109/JSTARS.2022.3185177. Earth's Energy budget is a major force that drives global climate. The long-term pattern of land surface energy budget with pronounced biophysical effects on climate was normally ignored at a regional scale, particularly in Pakistan. In this paper, the land surface energy budget from 2001 to 2018 was estimated and analyzed from Moderate Resolution Imaging Spectroradiometer (MODIS) and Cloud and the Earth's Radiant Energy System (CERES) observations over three geographical regions (Northern highlands, Indus plains and Baluchistan plateau) in Pakistan. Biophysical and energy budget parameters such as Land Surface Temperature (LST), albedo, emissivity, and Normalized Difference Vegetation Index (NDVI) were obtained from MODIS, while the downward shortwave solar and longwave thermal radiation were obtained from CERES satellite data. Spatiotemporal trends of three energy budget parameters: net radiation, latent heat flux and sensible heat flux, and three biophysical parameters, albedo, NDVI and LST, were investigated from 2001 to 2018. The latent heat flux showed a significant increase with a trend of 0.24, while a decrease in sensible heat flux with a trend of−0.21 was observed over Pakistan. Net radiation showed an ignorable increase with a trend of 0.054 over whole Pakistan. A significant negative relation was found between net radiation and sensible heat flux with albedo while a significant positive relation was found between latent heat flux and NDVI. Biophysical parameters such as NDVI, albedo and LST successively explain the trends of radiative and non-radiative fluxes. This study comprehensively explains the mechanism and patterns of the regional energy budget. CERES; Land surface; Net radiation; Meteorology; MODIS; Land surface temperature; Heating systems; and Pakistan; IP networks; Land surface Energy budget; Spatiotemporal phenomena
McCoy, Daniel T.; Field, Paul; Frazer, Michelle E.; Zelinka, Mark D.; Elsaesser, Gregory S; Mülmenstädt, Johannes; Tan, Ivy; Myers, Timothy A.; Lebo, Zachary J.McCoy, D. T., P. Field, M. E. Frazer, M. D. Zelinka, G. S. Elsaesser, J. Mülmenstädt, I. Tan, T. A. Myers, Z. J. Lebo, 2022: Extratropical shortwave cloud feedbacks in the context of the global circulation and hydrological cycle. Geophysical Research Letters, n/a(n/a), e2021GL097154. doi: 10.1029/2021GL097154. Shortwave (SW) cloud feedback (SWFB) is the primary driver of uncertainty in the effective climate sensitivity (ECS) predicted by global climate models (GCMs). ECS for several GCMs participating in the sixth assessment report exceed 5K, above the fifth assessment report ‘likely’ maximum (4.5K) due to extratropical SWFB’s that are more positive than those simulated in the previous generation of GCMs. Here we show that across 57 GCMs Southern Ocean SWFB can be predicted from the sensitivity of column-integrated liquid water mass (LWP) to moisture convergence and to surface temperature. The response of LWP to moisture convergence and the response of albedo to LWP anti-correlate across GCMs. This is because GCMs that simulate a larger response of LWP to moisture convergence tend to have higher mean-state LWPs, which reduces the impact of additional LWP on albedo. Observational constraints suggest a modestly negative Southern Ocean SWFB— inconsistent with extreme ECS. Clouds; Feedback; Moisture; Climate; Simulations
Miyamoto, Ayumu; Nakamura, Hisashi; Miyasaka, Takafumi; Kosaka, YuMiyamoto, A., H. Nakamura, T. Miyasaka, Y. Kosaka, 2022: Wintertime Weakening of Low-Cloud Impacts on the Subtropical High in the South Indian Ocean. J. Climate, 35(1), 323-334. doi: 10.1175/JCLI-D-21-0178.1. Abstract To elucidate the unique seasonality in the coupled system of the subtropical Mascarene high and low-level clouds, the present study compares wintertime cloud radiative impacts on the high with their summertime counterpart through coupled and atmospheric general circulation model simulations. A comparison of a fully coupled control simulation with another simulation in which the radiative effects of low-level clouds are artificially switched off demonstrates that the low-cloud effect on the formation of the Mascarene high is much weaker in winter. Background climatology plays an important role in this seasonality of the Mascarene high reinforcement. Relative to summer, the suppression of deep convection due to low-level clouds that acts to reinforce the high is much weaker in winter. This arises from 1) seasonally lower sea surface temperature in concert with the smaller sea surface temperature reduction due to the deeper ocean mixed layer and the weaker cloud radiative effect under weaker insolation and 2) seasonally stronger subtropical subsidence associated with the Hadley circulation in winter. As verified through atmospheric dynamical model experiments, enhanced cloud-top radiative cooling by low-level clouds acts to reinforce the wintertime Mascarene high in comparable magnitude as in summer. The present study reveals that the self-sustaining feedback with low-level clouds alone is insufficient for replenishing the full strength of the wintertime Mascarene high. This implies that another internal feedback pathway and/or external driver must be operative in maintaining the wintertime high.
Nasihati Gourabi, Forough; Kiani, Maryam; Pourtakdoust, Seid H.Nasihati Gourabi, F., M. Kiani, S. H. Pourtakdoust, 2022: Satellite pose estimation using Earth radiation modeled by artificial neural networks. Advances in Space Research, 70(8), 2195-2207. doi: 10.1016/j.asr.2022.07.009. The thermal energy received by each surface of an Earth-orbiting satellite strongly depends on its position and orientation. In this sense, simultaneous orbit and attitude estimation (SOAE) using the surface temperature data has been focused in the present study. The Earth infrared (IR) radiation and the Earth’s top-of-atmosphere (TOA) albedo are two key sources of radiation affecting the satellite surface temperature rate. The Earth’s radiation information has been monitored for the past two decades by the Clouds and the Earth’s Radiant Energy System (CERES) project, producing a comprehensive set of Earth radiation budget (ERB) data for climate, weather and applied science research. The current study utilizes the ERB data to forecast the IR radiation flux (IRF) and the TOA albedo factor (AF) via an artificial neural network (ANN). In this respect, the satellite longitude, latitude and time constitute the input vector of the learning set, while the AF and IRF are considered as the output. The ANN is then employed to model the satellite surface temperature rate in the radiation-based SOAE process. The feasibility of the proposed pose estimation approach has been addressed and verified via Monte Carlo simulation. Obtained results demonstrate suitability of the algorithm in sunlight intervals with good accuracy. Artificial neural network; Albedo radiation; Attitude estimation; Infrared radiation; Orbit estimation
Niu, Xiaoying; Pu, Wei; Fu, Pingqing; Chen, Yang; Xing, Yuxuan; Wu, Dongyou; Chen, Ziqi; Shi, Tenglong; Zhou, Yue; Wen, Hui; Wang, XinNiu, X., W. Pu, P. Fu, Y. Chen, Y. Xing, D. Wu, Z. Chen, T. Shi, Y. Zhou, H. Wen, X. Wang, 2022: Fluorescence characteristics, absorption properties, and radiative effects of water-soluble organic carbon in seasonal snow across northeastern China. Atmospheric Chemistry and Physics, 22(21), 14075-14094. doi: 10.5194/acp-22-14075-2022. Water-soluble organic carbon (WSOC) in the cryosphere can significantly influence the global carbon cycle and radiation budget. However, WSOC in the snowpack has received little scientific attention to date. This study reports the fluorescence characteristics, absorption properties, and radiative effects of WSOC based on 34 snow samples collected from sites in northeastern China. A significant degree of regional WSOC variability is found, with concentrations ranging from 0.5±0.2 to 5.7±3.7 µg g−1 (average concentration: 3.6±3.2 µg g−1). The three principal fluorescent components of WSOC are identified as (1) the high-oxygenated humic-like substances (HULIS-1) of terrestrial origin, (2) the low-oxygenated humic-like substances (HULIS-2) of mixed origin, and (3) the protein-like substances (PRLIS) derived from autochthonous microbial activity. In southeastern Inner Mongolia (SEIM), a region dominated by desert and exposed soils, the WSOC exhibits the highest humification index (HIX) but the lowest fluorescence (FI) and biological (BIX) indices; the fluorescence signal is mainly attributed to HULIS-1 and thus implicates soil as the primary source. By contrast, the HIX (FI and BIX) value is the lowest (highest), and the percentage of PRLIS is the highest in the remote area of northeastern Inner Mongolia (NEIM), suggesting a primarily biological source. For south and north of northeastern China (SNC and NNC), both of which are characterized by intensive agriculture and industrial activity, the fluorescence signal is dominated by HULIS-2, and the HIX, FI, and BIX values are all moderate, indicating the mixed origins for WSOC (anthropogenic activity, microbial activity, and soil). We also observe that, throughout northeastern China, the light absorption of WSOC is dominated by HULIS-1, followed by HULIS-2 and PRLIS. The contribution of WSOC to albedo reduction (average concentration: 3.6 µg g−1) in the ultraviolet–visible (UV–Vis) band is approximately half that of black carbon (BC average concentration: 0.6 µg g−1). Radiative forcing is 3.8 (0.8) W m−2 in old (fresh) snow, equating to 19 % (17 %) of the radiative forcing of BC. These results indicate that WSOC has a profound impact on snow albedo and the solar radiation balance.
Nugent, J. M.; Turbeville, S. M.; Bretherton, C. S.; Blossey, P. N.; Ackerman, T. P.Nugent, J. M., S. M. Turbeville, C. S. Bretherton, P. N. Blossey, T. P. Ackerman, 2022: Tropical Cirrus in Global Storm-Resolving Models: 1. Role of Deep Convection. Earth and Space Science, 9(2), e2021EA001965. doi: 10.1029/2021EA001965. Pervasive cirrus clouds in the upper troposphere and tropical tropopause layer (TTL) influence the climate by altering the top-of-atmosphere radiation balance and stratospheric water vapor budget. These cirrus are often associated with deep convection, which global climate models must parameterize and struggle to accurately simulate. By comparing high-resolution global storm-resolving models from the Dynamics of the Atmospheric general circulation Modeled On Non-hydrostatic Domains (DYAMOND) intercomparison that explicitly simulate deep convection to satellite observations, we assess how well these models simulate deep convection, convectively generated cirrus, and deep convective injection of water into the TTL over representative tropical land and ocean regions. The DYAMOND models simulate deep convective precipitation, organization, and cloud structure fairly well over land and ocean regions, but with clear intermodel differences. All models produce frequent overshooting convection whose strongest updrafts humidify the TTL and are its main source of frozen water. Intermodel differences in cloud properties and convective injection exceed differences between land and ocean regions in each model. We argue that, with further improvements, global storm-resolving models can better represent tropical cirrus and deep convection in present and future climates than coarser-resolution climate models. To realize this potential, they must use available observations to perfect their ice microphysics and dynamical flow solvers. convection; microphysics; cirrus; tropical tropopause layer; DYAMOND; global storm-resolving models
Nuncio, M.; Satheesan, K.; Acharya, Asutosh; Chatterjee, Sourav; Subeesh, M. P.; Athulya, R.Nuncio, M., K. Satheesan, A. Acharya, S. Chatterjee, M. P. Subeesh, R. Athulya, 2022: A southerly wind event and precipitation in Ny Ålesund, Arctic. Journal of Atmospheric and Solar-Terrestrial Physics, 231, 105869. doi: 10.1016/j.jastp.2022.105869. Precipitation in the Arctic is expected to increase with implications to ecosystems and changes to atmospheric circulation. In the Arctic strong southerly wind, often known as atmospheric rivers, supply enormous moisture and heat into the Arctic and is expected to increase in future warming scenarios. The impact of these events on Arctic climate change is not yet understood fully. In this study precipitation associated with such an event is studied for Ny Ålesund, Svalbard for 2016 March. During the event, the high precipitation was noticed between 22 and 23 UTC and 6–9 UTC on 12th March and 13th March respectively. It has been shown that during these two time periods, downwelling longwave radiation increased due to clouds. The enhanced downwelling longwave radiation increased the surface temperature locally. Above the shallow planetary boundary, advection dominated the temperature changes and initiated a shallow convection in the atmosphere leading to intensified precipitation in the lower layers during the event. Enhanced vertical velocity in MRR could be a result of this convection. Thus, the largescale southerly winds, that developed into an atmospheric river has not only contributed to the supply of heat and moisture but also enhanced cloud radiative effects and resulted in local warming. The moisture sources for this event appears to be Norwegian Sea and the east coast of Greenland. The scenario we have investigated was characterised by a warm Arctic with southerly warm winds. Studies suggest that convective scale precipitation is increasing in Eurasia under warm conditions. Our study points to the change in precipitation regime that Arctic may characterise as the warming continues. Cloud radiative effects; Arctic precipitation; Atmospheric river
Ojo, Olusola SamuelOjo, O. S., 2022: Validation of net radiation from multi-models and satellite retrieval over Nigeria. Modeling Earth Systems and Environment. doi: 10.1007/s40808-022-01647-5. In this study, net radiation obtained from the three reanalysis models and a satellite product coded ERA-5, MERRA-2, NCAR/NCEP, and CERES were compared with ground measurement (in situ) from Nigerian Meteorological Agency (NIMET) using the comparative statistical analytic metrics. Atmospheric radiation data such as the shortwave and longwave radiative fluxes spanned a period of 13 years (2000–2013) across the four climatic regions viz the Sahel, Guinea savannah, Rainforest, and Coastal regions over Nigeria were used to evaluate net radiation. The correlation, similarity, and bias analyses between the in situ and the remote sensing net radiation were performed using the correlation coefficient (R) metric and Taylor Skill Scores. Analyses showed that net radiation from the National Centers for Environmental Prediction and the National Center for Atmospheric Research model (NCAR/NCEP) showed best agreement with the in situ net radiation across all the climatic zones in Nigeria. The correlations between NCAR/NCEP and in situ net radiation data have highest R-value of 0.8629 in the Sahel region, 0.6252 in the Guinea Savannah region, 0.7996 in the Rainforest region, and 0.7852 in the Coastal region for the annual timescale. Similar spatial patterns were observed from other analytical metrics for the dry and wet seasons across the four climatic zones. It can be concluded from the results that although all the four remote sensing data show similar patterns of variations but those of ERA-5 revealed significant departure to their in situ counterpart. Assessment; Net radiation; Nigeria; Reanalysis product; Satellite product
Oreopoulos, Lazaros; Cho, Nayeong; Lee, Dongmin; Lebsock, Matthew; Zhang, ZhiboOreopoulos, L., N. Cho, D. Lee, M. Lebsock, Z. Zhang, 2022: Assessment of Two Stochastic Cloud Subcolumn Generators Using Observed Fields of Vertically Resolved Cloud Extinction. J. Atmos. Oceanic Technol., 39(8), 1229-1244. doi: 10.1175/JTECH-D-21-0166.1. Abstract We evaluate two stochastic subcolumn generators used in GCMs to emulate subgrid cloud variability enabling comparisons with satellite observations and simulations of certain physical processes. Our evaluation necessitated the creation of a reference observational dataset that resolves horizontal and vertical cloud variability. The dataset combines two CloudSat cloud products that resolve two-dimensional cloud optical depth variability of liquid, ice, and mixed-phase clouds when blended at ∼200 m vertical and ∼2 km horizontal scales. Upon segmenting the dataset to individual “scenes,” mean profiles of the cloud fields are passed as input to generators that produce scene-level cloud subgrid variability. The assessment of generator performance at the scale of individual scenes and in a mean sense is largely based on inferred joint histograms that partition cloud fraction within predetermined combinations of cloud-top pressure–cloud optical thickness ranges. Our main finding is that both generators tend to underestimate optically thin clouds, while one of them also tends to overestimate some cloud types of moderate and high optical thickness. Associated radiative flux errors are also calculated by applying a simple transformation to the cloud fraction histogram errors, and are found to approach values almost as high as 3 W m−2 for the cloud radiative effect in the shortwave part of the spectrum. Significance Statement The purpose of the paper is to assess the realism of relatively simple ways of producing fine-scale cloud variability in global models from coarsely resolved cloud properties. The assessment is achieved via comparisons to observed cloud fields where the fine-scale variability is known in both the horizontal and vertical directions. Our results show that while the generators have considerable skill, they still suffer from consistent deficiencies that need to be addressed with further development guided by appropriate observations.
Paca, Victor Hugo da Motta; Espinoza-Dávalos, Gonzalo E.; da Silva, Rodrigo; Tapajós, Raphael; dos Santos Gaspar, Avner BrasileiroPaca, V. H. d. M., G. E. Espinoza-Dávalos, R. da Silva, R. Tapajós, A. B. dos Santos Gaspar, 2022: Remote Sensing Products Validated by Flux Tower Data in Amazon Rain Forest. Remote Sensing, 14(5), 1259. doi: 10.3390/rs14051259. This work compares methods of climate measurements, such as those used to measure evapotranspiration, precipitation, net radiation, and temperature. The satellite products used were compared and evaluated against flux tower data. Evapotranspiration was validated against the SSEBop monthly and GLEAM daily and monthly products, respectively, and the results were RMSE = 24.144 mm/month, NRMSE = 0.223, r2 = 0.163, slope = 0.411; RMSE = 1.781 mm/day, NRMSE = 0.599, r2 = 0.000, slope = 0.006; RMSE = 36.17 mm/month, NRMSE = 0.401, r2 = 0.002, and slope = 0.026. Precipitation was compared with the CHIRPS data, K67 was not part of the CHIRPS station correction. The results for both the daily and monthly comparisons were RMSE = 18.777 mm/day, NRMSE = 1.027, r2 = 0.086, slope = 0.238 and RMSE = 130.713 mm/month, NRMSE = 0.706, r2 = 0.402, and slope = 0.818. The net radiation validated monthly with CERES was RMSE = 75.357 W/m2, NRMSE = 0.383, r2 = 0.422, and slope = 0.867. The temperature results, as compared to MOD11C3, were RMSE = 2.829 °C, NRMSE = 0.116, r2 = 0.153, and slope = 0.580. Comparisons between the remote sensing products and validation against the ground data were performed on a monthly basis. GLEAM and CHIRPS daily were the data sets with considerable discrepancy. comparison and validation; hydro-meteorological variables; remote sensing products
Parkinson, Claire L.Parkinson, C. L., 2022: The Earth-Observing Aqua Satellite Mission: 20 Years and Counting. Earth and Space Science, n/a(n/a), e2022EA002481. doi: 10.1029/2022EA002481. The Earth-observing Aqua spacecraft was launched on May 4, 2002 and has now completed 20 years collecting and transmitting data regarding the Earth’s radiation budget, atmosphere, oceans, land, and ice. Although launched with a design life of 6 years, four of its instruments continue to operate and provide high-quality data streams more than 20 years after launch. The Aqua data are readily available to users worldwide and have been used in thousands of scientific publications and in numerous practical applications, including weather forecasting, air-quality assessments, and monitoring of forest fires, dust storms, volcanic ash plumes, oil spills, and crop yields. This article is protected by copyright. All rights reserved. Remote sensing; Earth Observing System; Aqua satellite; Satellite Earth observations
Peng, Liran; Pritchard, Michael; Hannah, Walter M.; Blossey, Peter N.; Worley, Patrick H; Bretherton, Christopher S.Peng, L., M. Pritchard, W. M. Hannah, P. N. Blossey, P. H. Worley, C. S. Bretherton, 2022: Load-balancing intense physics calculations to embed regionalized high-resolution cloud resolving models in the E3SM and CESM climate models. Journal of Advances in Modeling Earth Systems, n/a(n/a), e2021MS002841. doi: 10.1029/2021MS002841. We design a new strategy to load-balance high-intensity sub-grid atmospheric physics calculations restricted to a small fraction of a global climate simulation’s domain. We show why the current parallel load balancing infrastructure of CESM and E3SM cannot efficiently handle this scenario at large core counts. As an example, we study an unusual configuration of the E3SM Multiscale Modeling Framework (MMF) that embeds a binary mixture of two separate cloud-resolving model grid structures that is attractive for low cloud feedback studies. Less than a third of the planet uses high-resolution (MMF-HR; sub-km horizontal grid spacing) relative to standard low-resolution (MMF-LR) cloud superparameterization elsewhere. To enable MMF runs with Multi-Domain CRMs, our load balancing theory predicts the most efficient computational scale as a function of the high-intensity work’s relative overhead and its fractional coverage. The scheme successfully maximizes model throughput and minimizes model cost relative to precursor infrastructure, effectively by devoting the vast majority of the processor pool to operate on the few high-intensity (and rate-limiting) HR grid columns. Two examples prove the concept, showing that minor artifacts can be introduced near the HR/LR CRM grid transition boundary on idealized aquaplanets, but are minimal in operationally relevant real-geography settings. As intended, within the high (low) resolution area, our Multi-Domain CRM simulations exhibit cloud fraction and shortwave reflection convergent to standard baseline tests that use globally homogenous MMF-LR and MMF-HR. We suggest this approach can open up a range of creative multi-resolution climate experiments without requiring unduly large allocations of computational resources.
Quaas, Johannes; Jia, Hailing; Smith, Chris; Albright, Anna Lea; Aas, Wenche; Bellouin, Nicolas; Boucher, Olivier; Doutriaux-Boucher, Marie; Forster, Piers M.; Grosvenor, Daniel; Jenkins, Stuart; Klimont, Zig; Loeb, Norman G.; Ma, Xiaoyan; Naik, Vaishali; Paulot, Fabien; Stier, Philip; Wild, Martin; Myhre, Gunnar; Schulz, MichaelQuaas, J., H. Jia, C. Smith, A. L. Albright, W. Aas, N. Bellouin, O. Boucher, M. Doutriaux-Boucher, P. M. Forster, D. Grosvenor, S. Jenkins, Z. Klimont, N. G. Loeb, X. Ma, V. Naik, F. Paulot, P. Stier, M. Wild, G. Myhre, M. Schulz, 2022: Robust evidence for reversal in the aerosol effective climate forcing trend. Atmospheric Chemistry and Physics Discussions, 1-25. doi: 10.5194/acp-2022-295. Abstract. Anthropogenic aerosols exert a cooling influence that offsets part of the greenhouse gas warming. Due to their short tropospheric lifetime of only up to several days, the aerosol forcing responds quickly to emissions. Here we present and discuss the evolution of the aerosol forcing since 2000. There are multiple lines of evidence that allow to robustly conclude that the anthropogenic aerosol effective radiative forcing – both aerosol-radiation and aerosol-cloud interactions – has become globally less negative, i.e. that the trend in aerosol effective radiative forcing changed sign from negative to positive. Bottom-up inventories show that anthropogenic primary aerosol and aerosol precursor emissions declined in most regions of the world; observations related to aerosol burden show declining trends, in particular of the fine-mode particles that make up most of the anthropogenic aerosols; satellite retrievals of cloud droplet numbers show trends consistent in sign, as do observations of top-of-atmosphere radiation. Climate model results, including a revised set that is constrained by observations of the ocean heat content evolution show a consistent sign and magnitude for a positive forcing relative to 2000 due to reduced aerosol effects. This reduction leads to an acceleration of the forcing of climate change, i.e. an increase in forcing by 0.1 to 0.3 W m-2, up to 12 % of the total climate forcing in 2019 compared to 1750 according to IPCC.
Ramesh, Nandini; Boos, William R.Ramesh, N., W. R. Boos, 2022: The Unexpected Oceanic Peak in Energy Input to the Atmosphere and Its Consequences for Monsoon Rainfall. Geophysical Research Letters, 49(12), e2022GL099283. doi: 10.1029/2022GL099283. Monsoons have historically been understood to be caused by the low thermal inertia of land, allowing more energy from summer insolation to be transferred to the overlying atmosphere than over adjacent ocean. Here, we show that during boreal summer, the global maximum net energy input (NEI) to the atmosphere unexpectedly lies over the Indian Ocean, not over land. Observed radiative fluxes suggest that cloud-radiative effects (CRE) almost double the NEI over ocean, shifting the NEI peak from land to ocean. Global climate model experiments with both land and interactive sea surface temperatures confirm that CRE create the oceanic NEI maximum. Interactions between CRE, NEI, circulation, and land-sea contrast in surface heat capacity shift precipitation from Southeast to South Asia. CRE thus alter the global partitioning of precipitation between land and ocean and the spatial structure of Earth's strongest monsoon, in ways that can be understood through the NEI. monsoons; cloud radiative effects; atmospheric dynamics; land-sea contrast; tropical climate
Ramos, R. D.; LeGrande, A. N.; Griffiths, M. L.; Elsaesser, G. S.; Litchmore, D. T.; Tierney, J. E.; Pausata, F. S. R.; Nusbaumer, J.Ramos, R. D., A. N. LeGrande, M. L. Griffiths, G. S. Elsaesser, D. T. Litchmore, J. E. Tierney, F. S. R. Pausata, J. Nusbaumer, 2022: Constraining Clouds and Convective Parameterizations in a Climate Model Using Paleoclimate Data. Journal of Advances in Modeling Earth Systems, 14(8), e2021MS002893. doi: 10.1029/2021MS002893. Cloud and convective parameterizations strongly influence uncertainties in equilibrium climate sensitivity. We provide a proof-of-concept study to constrain these parameterizations in a perturbed parameter ensemble of the atmosphere-only version of the Goddard Institute for Space Studies Model E2.1 simulations by evaluating model biases in the present-day runs using multiple satellite climatologies and by comparing simulated δ18O of precipitation (δ18Op), known to be sensitive to parameterization schemes, with a global database of speleothem δ18O records covering the Last Glacial Maximum (LGM), mid-Holocene (MH) and pre-industrial (PI) periods. Relative to modern interannual variability, paleoclimate simulations show greater sensitivity to parameter changes, allowing for an evaluation of model uncertainties over a broader range of climate forcing and the identification of parts of the world that are parameter sensitive. Certain simulations reproduced absolute δ18Op values across all time periods, along with LGM and MH δ18Op anomalies relative to the PI, better than the default parameterization. No single set of parameterizations worked well in all climate states, likely due to the non-stationarity of cloud feedbacks under varying boundary conditions. Future work that involves varying multiple parameter sets simultaneously with coupled ocean feedbacks will likely provide improved constraints on cloud and convective parameterizations. PPE; cloud and convective parameterization; paleoclimate model; proxy-model comparison; speleothem; water isotopes
Ren, Tong; Yang, Ping; Wei, Jian; Huang, Xianglei; Sang, HuiyanRen, T., P. Yang, J. Wei, X. Huang, H. Sang, 2022: Performance of Cloud 3D Solvers in Ice Cloud Shortwave Radiation Closure Over the Equatorial Western Pacific Ocean. Journal of Advances in Modeling Earth Systems, 14(2), e2021MS002754. doi: 10.1029/2021MS002754. For retrieving cloud optical properties from satellite images or computing these properties from climate model output, computationally efficient treatments of cloud horizontal inhomogeneity include the Monte Carlo Independent Column Approximation (McICA) and the Tripleclouds method. Computationally efficient treatment of cloud horizontal radiation exchanges includes the SPeedy Algorithm for Radiative TrAnsfer through CloUd Sides (SPARTACUS). As a test to derive properties from satellite images, we collocate Moderate Resolution Imaging Spectroradiometer (MODIS) cloud retrievals with near-nadir Cloud and the Earth's Radiant Energy System (CERES) footprints in July 2008 over an equatorial western Pacific Ocean region to compare the performance of the McICA, Tripleclouds, and SPARTACUS solvers to the conventional plane-parallel homogeneous (PPH) treatment. PPH overestimates cloud albedo, and the three solvers effectively reduce overestimation with root mean square error of shortwave upwelling irradiance decreasing between 15.72 and 18.53 W m−2, or about 22%–25%. Although cloud top variability does not get fed into the simulations, all three solvers also reduce the effect of cloud top variability on cloud albedo. Entrapment (energy reflected downward from clouds) and horizontal radiation transfer have opposite effects on the SPARTACUS cloud albedo simulation. The net effect depends on the cloud vertical extent, the unawareness of which limits the performance of the SPARTACUS solver. cloud 3D effect; cloud top variability; cloud vertical extent
Rosário, Nilton Évora do; Sena, Elisa Thomé; Yamasoe, Marcia AkemiRosário, N. É. d., E. T. Sena, M. A. Yamasoe, 2022: South American 2020 regional smoke plume: intercomparison with previous years, impact on solar radiation, and the role of Pantanal biomass burning season. Atmospheric Chemistry and Physics, 22(22), 15021-15033. doi: 10.5194/acp-22-15021-2022. The 2020 biomass burning season in Brazil was marked by an atypical amount of fire across the Pantanal biome, which led to high levels of smoke within the biome and downwind areas. The present study analyzes fire counts and smoke over Pantanal in 2020, comparing this particular year's data with those from the previous 17 years (2003–2019). Taking as reference the most-polluted years in this period, the regional smoke plume and its impact on surface solar radiation were also evaluated. In 2020, the regional smoke plume core covered an area of ∼ 2.6×106 km2 at the peak of the burning season, an area well above that of the previous 6 years but smaller than areas observed in a more remote past, as in 2007 and 2010 (> 5.0×106 km2). The smoke loading was lower (mean aerosol optical depth, AOD, of 550 nm; ∼ 0.7) than that of 2007 and 2010 (mean AOD 550 nm; ∼ 1.0). The plume radiation absorption efficiency, when compared with the previous year's plumes, did not present significant differences. Regarding the Pantanal burning season, it revealed some atypical features. Fire counts were up to 3.0 times higher than for the years from 2003 to 2019. Smoke loading over Pantanal, which is typically a fraction of that over Amazonia, was higher in 2020 than that over Amazonia, an indication that local smoke surpassed the smoke advection from upwind regions. The observed intraseasonal variability in smoke over Pantanal revealed to be largely driven by the nature of the burned areas in the biome. From September on, there was a significant increase in fire count in conservation and indigenous areas, where higher biomass density is present, which would explain the larger smoke plumes over Pantanal, even during October when the fire count was reduced. In October, the biome was covered by a thick smoke layer, which resulted in a mean deficit of surface solar radiation up to 200 W m−2. Despite the Pantanal biomes' massive burning in 2020, the regional smoke plume was not far from its climatological features. Nevertheless, the Pantanal 2020 burning season represents the worst combination of a climate extreme applied to a fire-prone environment, coupled with inadequately enforced environmental regulations, from which there is much to be learned.
Russotto, Rick D.; Strong, Jeffrey D. O.; Camargo, Suzana J.; Sobel, Adam; Elsaesser, Gregory S.; Kelley, Maxwell; Del Genio, Anthony; Moon, Yumin; Kim, DaehyunRussotto, R. D., J. D. O. Strong, S. J. Camargo, A. Sobel, G. S. Elsaesser, M. Kelley, A. Del Genio, Y. Moon, D. Kim, 2022: Evolution of Tropical Cyclone Properties Across the Development Cycle of the GISS-E3 Global Climate Model. Journal of Advances in Modeling Earth Systems, 14(1), e2021MS002601. doi: 10.1029/2021MS002601. The next-generation global climate model from the NASA Goddard Institute for Space Studies, GISS-E3, contains many improvements to resolution and physics that allow for improved representation of tropical cyclones (TCs) in the model. This study examines the properties of TCs in two different versions of E3 at different points in its development cycle, run for 20 years at 0.5° resolution, and compares these TCs with observations, the previous generation GISS model, E2, and other climate models. E3 shares many TC biases common to global climate models, such as having too few tropical cyclones, but is much improved from E2. E3 produces strong enough TCs that observation-based wind speed thresholds can now be used to detect and track them, and some storms now reach hurricane intensity; neither of these was true of E2. Model development between the first and second versions of E3 further increased the number and intensity of TCs and reduced TC count biases globally and in most regions. One-year sensitivity tests to changes in various microphysical and dynamical tuning parameters are also examined. Increasing the entrainment rate for the more strongly entraining plume in the convection scheme increases the number of TCs (though also affecting other climate variables, and in some cases increasing biases). Variations in divergence damping did not have a strong effect on simulated TC properties, contrary to expectations based on previous studies. Overall, the improvements in E3 make it more credible for studies of TC activity and its relationship to climate. tropical meteorology; climate model; tropical cyclones; hurricanes
Săftoiu, G; Stefan, Sabina; Antonescu, B; Iorga, Gabriela; Belegante, LSăftoiu, G., S. Stefan, B. Antonescu, G. Iorga, L. Belegante, 2022: CHARACTERISTICS OF STRATOCUMULUS CLOUDS OVER BUCHAREST-MĂGURELE. Romanian Reports in Physics, 74. Stratocumulus clouds represent one of the key components of the Earth's radiative balance because it generally reflects incident solar radiation. The aim of the study is to understand the occurrence and characteristics of stratocumulus clouds using satellite data collected from Dec 2019 to Feb 2021. A series of macrophysically and microphysical cloud parameters (cloud cover fraction, cloud types, cloud geometrical depth, cloud top temperature, cloud top pressure, cloud height, cloud optical depth, liquid water path) were extracted from the Clouds and the Earth's Radiant Energy System (CERES) database for a region in south west Bucharest, were the Măgurele Center for Atmosphere and Radiation Studies (MARS) is located.
Salazar-Martínez, Diego; Holwerda, Friso; Holmes, Thomas R. H.; Yépez, Enrico A.; Hain, Christopher R.; Alvarado-Barrientos, Susana; Ángeles-Pérez, Gregorio; Arredondo-Moreno, Tulio; Delgado-Balbuena, Josué; Figueroa-Espinoza, Bernardo; Garatuza-Payán, Jaime; González del Castillo, Eugenia; Rodríguez, Julio C.; Rojas-Robles, Nidia E.; Uuh-Sonda, Jorge M.; Vivoni, Enrique R.Salazar-Martínez, D., F. Holwerda, T. R. H. Holmes, E. A. Yépez, C. R. Hain, S. Alvarado-Barrientos, G. Ángeles-Pérez, T. Arredondo-Moreno, J. Delgado-Balbuena, B. Figueroa-Espinoza, J. Garatuza-Payán, E. González del Castillo, J. C. Rodríguez, N. E. Rojas-Robles, J. M. Uuh-Sonda, E. R. Vivoni, 2022: Evaluation of remote sensing-based evapotranspiration products at low-latitude eddy covariance sites. Journal of Hydrology, 610, 127786. doi: 10.1016/j.jhydrol.2022.127786. Remote sensing-based evapotranspiration (ET) products have been evaluated primarily using data from northern middle latitudes; therefore, little is known about their performance at low latitudes. To address this bias, an evaluation dataset was compiled using eddy covariance data from 40 sites between latitudes 30° S and 30° N. The flux data were obtained from the emerging network in Mexico (MexFlux) and from openly available databases of FLUXNET, AsiaFlux, and OzFlux. This unique reference dataset was then used to evaluate remote sensing-based ET products in environments that have been underrepresented in earlier studies. The evaluated products were: MODIS ET (MOD16, both the discontinued collection 5 (C5) and the latest collection (C6)), Global Land Evaporation Amsterdam Model (GLEAM) ET, and Atmosphere-Land Exchange Inverse (ALEXI) ET. Products were compared with unadjusted fluxes (ETorig) and with fluxes corrected for the lack of energy balance closure (ETebc). Three common statistical metrics were used: coefficient of determination (R2), root mean square error (RMSE), and percent bias (PBIAS). The effect of a vegetation mismatch b