Skip to main content

Publications

No Results Found

2020

Abera, Temesgen Alemayehu; Heiskanen, Janne; Pellikka, Petri K. E.; Maeda, Eduardo EijiAbera, T. A., J. Heiskanen, P. K. E. Pellikka, E. E. Maeda, 2020: Impact of rainfall extremes on energy exchange and surface temperature anomalies across biomes in the Horn of Africa. Agricultural and Forest Meteorology, 280, 107779. doi: 10.1016/j.agrformet.2019.107779. Precipitation extremes have a strong influence on the exchange of energy and water between the land surface and the atmosphere. Although the Horn of Africa has faced recurrent drought and flood events in recent decades, it is still unclear how these events impact energy exchange and surface temperature across different ecosystems. Here, we analyzed the impact of precipitation extremes on spectral albedo (total shortwave, visible, and near-infrared (NIR) broadband albedos), energy balance, and surface temperature in four natural vegetation types: forest, savanna, grassland, and shrubland. We used remotely sensed observations of surface biophysical properties and climate from 2001 to 2016. Our results showed that, in forests and savannas, precipitation extremes led to divergent spectral changes in visible and NIR albedos, which cancelled each other limiting shortwave albedo changes. An exception to this pattern was observed in shrublands and grasslands, where both visible and NIR albedo increased during drought events. Given that shrublands and grasslands occupy a large fraction of the Horn of Africa (52%), our results unveil the importance of these ecosystems in driving the magnitude of shortwave radiative forcing in the region. The average regional shortwave radiative forcing during drought events (−0.64 W m−2, SD 0.11) was around twice that of the extreme wet events (0.33 W m−2, SD 0.09). Such shortwave forcing, however, was too small to influence the surface–atmosphere coupling. In contrast, the surface feedback through turbulent flux changes was strong across vegetation types and had a significant (P  CERES; MODIS; Land surface temperature; Albedo; Energy exchange; Precipitation extremes
Ajoku, Osinachi; Norris, Joel R.; Miller, Arthur J.Ajoku, O., J. R. Norris, A. J. Miller, 2020: Observed monsoon precipitation suppression caused by anomalous interhemispheric aerosol transport. Climate Dynamics, 54(1), 1077-1091. doi: 10.1007/s00382-019-05046-y. This study uses observations and atmospheric reanalysis products in order to understand the impacts of smoke aerosols advected from the Southern Hemisphere on the dynamics of the West African monsoon. Seasonal biomass burning and resulting aerosol emissions have been well documented to affect regional weather patterns, especially low-level convection. Out of all monsoon months, precipitation shows the most variability over land during August, in which anomalous smoke aerosol values can increase (decrease) by 33% (29%) in the Northern Gulf of Guinea and precipitation can decrease (increase) by up to ~ 2.5 mm day−1 (~ 3 mm day−1) along the West African monsoon region accounting for a 17% (18%) change in precipitation. Smoke aerosols produced by biomass burning occurring near Central Africa are advected towards the Gulf of Guinea at elevations around the 850 hPa level. Satellite observations show an increase (decrease) in cloud fraction and optical depth below (above) the 300-hPa level in the Gulf of Guinea and along the West African coastline along with concurrent decreases (increases) in cloud droplet radius during dirty (clean) aerosol episodes. Additional observations of shortwave radiation quantify changes in cloud coverage and monsoon dynamics. On average, reductions in surface shortwave radiation of ~ 10–15 W m−2 occur over the Gulf of Guinea during increased aerosol transport, with aerosols accounting for ~ 33–50% of that reduction. Reductions in shortwave radiation are associated with decreased convective available potential energy (CAPE). This demonstrates that increased transport of aerosols perturbs surface radiation, convection in the lower troposphere and eventually cloud coverage, potentially leading to the observed monsoon precipitation suppression. In a broader social context, this region houses 200 million people and thus understanding these climate patterns may carry great importance.
Akkermans, Tom; Clerbaux, NicolasAkkermans, T., N. Clerbaux, 2020: Narrowband-to-Broadband Conversions for Top-of-Atmosphere Reflectance from the Advanced Very High Resolution Radiometer (AVHRR). Remote Sensing, 12(2), 305. doi: 10.3390/rs12020305. The current lack of a long, 30+ year, global climate data record of reflected shortwave top-of-atmosphere (TOA) radiation could be tackled by relying on existing narrowband records from the Advanced Very High Resolution Radiometer (AVHRR) instruments, and transform these measurements into broadband quantities like provided by the Clouds and the Earth’s Radiant Energy System (CERES). This paper presents the methodology of an AVHRR-to-CERES narrowband-to-broadband conversion for shortwave TOA reflectance, including the ready-to-use results in the form of scene-type dependent regression coefficients, allowing a calculation of CERES-like shortwave broadband reflectance from AVHRR channels 1 and 2. The coefficients are obtained using empirical relations in a large data set of collocated, coangular and simultaneous AVHRR-CERES observations, requiring specific orbital conditions for the AVHRR- and CERES-carrying satellites, from which our data analysis uses all available data for an unprecedented observation matching between both instruments. The multivariate linear regressions were found to be robust and well-fitting, as demonstrated by the regression statistics on the calibration subset (80% of data): adjusted R 2 higher than 0.9 and relative RMS residual mostly below 3%, which is a significant improvement compared to previous regressions. Regression models are validated by applying them on a validation subset (20% of data), indicating a good performance overall, roughly similar to the calibration subset, and a negligible mean bias. A second validation approach uses an expanded data set with global coverage, allowing regional analyses. In the error analysis, instantaneous accuracy is quantified at regional scale between 1.8 Wm − 2 and 2.3 Wm − 2 (resp. clear-sky and overcast conditions) at 1 standard deviation (RMS bias). On daily and monthly time scales, these errors correspond to 0.7 and 0.9 Wm − 2 , which is compliant with the GCOS requirement of 1 Wm − 2 . CERES; radiation; shortwave; broadband; AVHRR; narrowband
Attada, Raju; Dasari, Hari Prasad; Kunchala, Ravi Kumar; Langodan, Sabique; Niranjan Kumar, Kondapalli; Knio, Omar; Hoteit, IbrahimAttada, R., H. P. Dasari, R. K. Kunchala, S. Langodan, K. Niranjan Kumar, O. Knio, I. Hoteit, 2020: Evaluating Cumulus Parameterization Schemes for the Simulation of Arabian Peninsula Winter Rainfall. J. Hydrometeor., 21(5), 1089-1114. doi: 10.1175/JHM-D-19-0114.1. This study investigates the sensitivity of winter seasonal rainfall over the Arabian Peninsula (AP) to different convective physical parameterization schemes using a high-resolution WRF Model. Three different parameterization schemes, Kain–Fritch (KF), Betts–Miller–Janjić (BMJ), and Grell–Freitas (GF), are used in winter simulations from 2001 to 2016. Results from seasonal simulations suggest that simulated AP winter rainfall with KF is in best agreement with observed rainfall in terms of spatial distribution and intensity. Higher spatial correlation coefficients and fewer biases with observations are also obtained with KF. In addition, the regional moisture transport, cloud distribution, and cloud microphysical responses are better simulated by KF. The AP low-level circulation, characterized by the Arabian anticyclone, is well captured by KF and BMJ, but its position is displaced in GF. KF is furthermore successful at simulating the moisture distribution in the lower atmosphere and atmospheric water plumes in the middle troposphere. The higher skill of rainfall simulation with the KF (and to some extent BMJ) is attributed to a better representation of the Arabian anticyclone and subtropical westerly jet, which guides the upper tropospheric synoptic transients and moisture. In addition, the vertical profile of diabatic heating from KF is in better agreement with the observations. Discrepancies in representing the diabatic heating profile by BMJ and GF show discrepancies in instability and in turn precipitation biases. Our results indicate that the selection of subgrid convective parameterization in a high-resolution atmospheric model over the AP is an important factor for accurate regional rainfall simulations.
Baba, YuyaBaba, Y., 2020: Shallow convective closure in a spectral cumulus parameterization. Atmospheric Research, 233, 104707. doi: 10.1016/j.atmosres.2019.104707. A shallow convective closure (shallow closure) was introduced in a spectral cumulus parameterization (spectral scheme), and the validity was evaluated using an atmospheric general circulation model (AGCM) and Atmospheric Model Intercomparison Project (AMIP) experiments. The spectral scheme with shallow closure improved model simulated climatology and variability as compared with the spectral scheme only. The shallow closure enhanced shallow convection, leading to an improvements in dry bias in the tropics and cold bias in the extratropics. The simulated interannual variabilities were comparable regardless of the shallow closure; however, intraseasonal variability was greatly improved with the shallow closure. This is because detrainment from shallow convection during development of the Madden-Julian oscillation (MJO) contributes to supplying moisture in organized convection, and the spectral scheme with shallow closure was able to simulate this contribution well. Climatology; Shallow convection; Atmospheric variability; Convection scheme; Convective closure
Baba, Yuya; Giorgetta, Marco A.Baba, Y., M. A. Giorgetta, 2020: Tropical Variability Simulated in ICON-A With a Spectral Cumulus Parameterization. Journal of Advances in Modeling Earth Systems, 12(1), e2019MS001732. doi: 10.1029/2019MS001732. We implemented a spectral cumulus parameterization based on a cloud-resolving model (SC scheme) in the icosahedral nonhydrostatic atmospheric model (ICON-A). We compared the resulting simulated climatology and tropical variability with results from the standard version of ICON-A using a variant of the Tiedtke-Nordeng scheme (TK scheme) using observational and reanalysis data. The climatological errors of the SC scheme were similar to those of the TK scheme, but several biases, such as properties of meridional winds and precipitation pattern in the western Pacific, were much improved. For tropical variability, we found that the SC scheme improved the interannual response of the precipitation in the western Pacific and was able to simulate Madden-Julian oscillation (MJO) features much better than the TK scheme. We investigated the reason for the better simulation of the MJO using composite analysis and column process analysis for moisture. Our results suggest that the entrainment parameterization of the SC scheme is necessary to reproduce the MJO; however, spectral representation and improved convective closure are also found to contribute for better MJO simulation. These parameterizations improved moisture supply from low-level clouds and cloud mass flux which were needed to sustain the MJO. convection scheme; atmospheric general circulation model; tropical variability
Bai, Heming; Wang, Minghuai; Zhang, Zhibo; Liu, YawenBai, H., M. Wang, Z. Zhang, Y. Liu, 2020: Synergetic Satellite Trend Analysis of Aerosol and Warm Cloud Properties ver Ocean and Its Implication for Aerosol-Cloud Interactions. Journal of Geophysical Research: Atmospheres, 125(6), e2019JD031598. doi: 10.1029/2019JD031598. Decadal-scale trends in aerosol and cloud properties provide important ways for understanding aerosol-cloud interactions. In this paper, by using MODIS products (2003–2017), we analyze synergetic trends in aerosol properties and warm cloud properties over global ocean. Cloud droplet number concentration (CDNC) and aerosol parameters (aerosol optical depth, angstrom exponent, and aerosol index) show consistent decreasing trend over East Coast of the United States (EUS), west coast of Europe (WEU), and east coast of China (EC), and no significant trend in liquid water path is found over these regions during the period 2003–2017. Over regions with significant long-term trends of aerosol loading and CDNC (e.g., EUS and WEU), the sensitivity of CDNC to aerosol loading based on the long-term trend is closer to those derived from ground and aircraft observations and larger than those derived from instantaneous satellite observations, providing an alternative way for quantifying aerosol-cloud interactions. A clear shift in the normalized probability density function of CDNC between the first 5 years (2003–2007) and the last 5 years (2013–2017) is found, with a decrease of around 50% in the occurrence frequency of high CDNC (>400 cm−3) over EUS and WEU. The relative variances of cloud droplet effective radius generally decrease with decreasing aerosol loading, providing large-scale evidence for the effects of anthropogenic aerosols on the dispersion of cloud droplet size distribution. The long-term satellite data sets provide great opportunities for quantifying aerosol-cloud interactions and further confronting these interactions in climate models in the future.
Bao, Shanhu; Letu, Husi; Zhao, Jun; Lei, Yonghui; Zhao, Chuanfeng; Li, Jiming; Tana, Gegen; Liu, Chao; Guo, Enliang; Zhang, Jie; He, Jie; Bao, YuhaiBao, S., H. Letu, J. Zhao, Y. Lei, C. Zhao, J. Li, G. Tana, C. Liu, E. Guo, J. Zhang, J. He, Y. Bao, 2020: Spatiotemporal distributions of cloud radiative forcing and response to cloud parameters over the Mongolian Plateau during 2003–2017. International Journal of Climatology, (In Press). doi: 10.1002/joc.6444. The Mongolian Plateau (MP) is among the most sensitive areas to global climate change, and the clouds over the MP have a greater impact on regional and global radiation budgets by altering the atmospheric and surface radiative forcing. In this study, daily Cloud and Earth Radiation Energy System data are used to investigate spatiotemporal variation of cloud radiative forcing (CRF) at the top of atmosphere (TOA), surface and atmosphere over the MP from 2003 to 2017 and then combined with Moderate Resolution Imaging Spectroradiometer level 2 atmospheric data during the same period to analyse the cloud parameter impacts on CRF over the MP. At the TOA and surface, net radiative forcing (NRF) and shortwave radiative forcing (SRF) have cooling effects and longwave radiative forcing (LRF) have heating effects in all four seasons, and the NRF cooling effect in most areas of the MP decreases in summer and autumn and increases in spring and winter. In the atmosphere, SRF in spring and summer and NRF in summer reach larger values and heat the atmosphere, and LRF plays a strong cooling role in winter. The NRF change trend in the atmosphere over Mongolia is noteworthy in spring, its reduction slope is large, and most areas of Mongolia passed a significance test. As expected, a significant negative correlation was observed between cloud cover and NRF (as well as SRF) at the TOA and surface and a positive correlation was observed with NRF/SRF in the atmosphere and all LRF. With the increase in cloud optical thickness and cloud water path, the NRF and SRF cooling effects at the TOA and surface, the LRF cooling effect in the atmosphere, the LRF heating effect at the surface, and the SRF heating effect in the atmosphere all become stronger. cloud classification; cloud radiative forcing; cloud parameters; Mongolian Plateau; radiation validation
Barpanda, Pragallva; Shaw, Tiffany A.Barpanda, P., T. A. Shaw, 2020: Surface fluxes modulate the seasonality of zonal-mean storm tracks. J. Atmos. Sci., 77(2), 753–779. doi: 10.1175/JAS-D-19-0139.1. The observed zonal-mean extratropical storm tracks exhibit distinct hemispheric seasonality. Previously, the moist static energy (MSE) framework was used diagnostically to show that shortwave absorption (insolation) dominates seasonality but surface heat fluxes damp seasonality in the Southern Hemisphere (SH) and amplify it in the Northern Hemisphere (NH). Here we establish the causal role of surface fluxes (ocean energy storage), which affect surface heat fluxes, by varying the mixed layer depth (d) in zonally-symmetric 1) slab-ocean aquaplanet simulations with zero ocean energy transport and 2) Energy Balance Model (EBM) simulations. Using a scaling analysis we define a critical mixed layer depth (dc) and hypothesize 1) large mixed layer depths (d > dc) produce surface heat fluxes that are out of phase with shortwave absorption resulting in small storm track seasonality and 2) small mixed layer depths (d < dc) produce surface heat fluxes that are in phase with shortwave absorption resulting in large storm track seasonality. The aquaplanet simulations confirm the large mixed layer depth hypothesis and yield a useful idealization of the SH storm track. However, the small mixed layer depth hypothesis fails to account for the large contribution of the Ferrel cell and atmospheric storage. The small mixed layer limit does not yield a useful idealization of the NH storm track because the seasonality of the Ferrel cell contribution is opposite to the stationary eddy contribution in the NH. Varying the mixed layer depth in an EBM qualitatively supports the aquaplanet results.
Bauer, Susanne E.; Tsigaridis, Kostas; Faluvegi, Greg; Kelley, Maxwell; Lo, Ken K.; Miller, Ron L.; Nazarenko, Larissa; Schmidt, Gavin A.; Wu, JingboBauer, S. E., K. Tsigaridis, G. Faluvegi, M. Kelley, K. K. Lo, R. L. Miller, L. Nazarenko, G. A. Schmidt, J. Wu, 2020: Historical (1850-2014) aerosol evolution and role on climate forcing using the GISS ModelE2.1 contribution to CMIP6. Journal of Advances in Modeling Earth Systems, (In Press). doi: 10.1029/2019MS001978. The Earth’s climate is rapidly changing. Over the past centuries, aerosols, via their ability to absorb or scatter solar radiation and alter clouds, played an important role in counterbalancing some of the greenhouse gas (GHG) caused global warming. The multi-century anthropogenic aerosol cooling effect prevented present-day climate from reaching even higher surface air temperatures and subsequent more dramatic climate impacts. Trends in aerosol concentrations and optical depth show that in many polluted regions such as Europe and the United States of America, aerosol precursor emissions decreased back to levels of the 1950s. More recent polluting countries such as China may have reached a turning point in recent years as well, while India still follows an upward trend. Here we study aerosol trends in the CMIP6 simulations of the GISS ModelE2.1 climate model using a fully coupled atmosphere composition configuration, including interactive gas-phase chemistry, and either an aerosol microphysical (MATRIX) or a mass-based (OMA) aerosol module. Results show that whether global aerosol radiative forcing is already declining depends on the aerosol scheme used. Using the aerosol microphysical scheme, where the aerosol system reacts more strongly to the trend in sulfur dioxide (SO2) emissions, global peak direct aerosol forcing was reached in the 1980’s, whereas the mass-based scheme simulates peak direct aerosol forcing around 2010. aerosol microphysics; Aerosol Forcing; CMIP6 historical simulation; GISS model
Bellouin, N.; Quaas, J.; Gryspeerdt, E.; Kinne, S.; Stier, P.; Watson‐Parris, D.; Boucher, O.; Carslaw, K. S.; Christensen, M.; Daniau, A.-L.; Dufresne, J.-L.; Feingold, G.; Fiedler, S.; Forster, P.; Gettelman, A.; Haywood, J. M.; Lohmann, U.; Malavelle, F.; Mauritsen, T.; McCoy, D. T.; Myhre, G.; Mülmenstädt, J.; Neubauer, D.; Possner, A.; Rugenstein, M.; Sato, Y.; Schulz, M.; Schwartz, S. E.; Sourdeval, O.; Storelvmo, T.; Toll, V.; Winker, D.; Stevens, B.Bellouin, N., J. Quaas, E. Gryspeerdt, S. Kinne, P. Stier, D. Watson‐Parris, O. Boucher, K. S. Carslaw, M. Christensen, A. Daniau, J. Dufresne, G. Feingold, S. Fiedler, P. Forster, A. Gettelman, J. M. Haywood, U. Lohmann, F. Malavelle, T. Mauritsen, D. T. McCoy, G. Myhre, J. Mülmenstädt, D. Neubauer, A. Possner, M. Rugenstein, Y. Sato, M. Schulz, S. E. Schwartz, O. Sourdeval, T. Storelvmo, V. Toll, D. Winker, B. Stevens, 2020: Bounding global aerosol radiative forcing of climate change. Reviews of Geophysics, 58(1), e2019RG000660. doi: 10.1029/2019RG000660. Aerosols interact with radiation and clouds. Substantial progress made over the past 40 years in observing, understanding, and modeling these processes helped quantify the imbalance in the Earth's radiation budget caused by anthropogenic aerosols, called aerosol radiative forcing, but uncertainties remain large. This review provides a new range of aerosol radiative forcing over the industrial era based on multiple, traceable and arguable lines of evidence, including modelling approaches, theoretical considerations, and observations. Improved understanding of aerosol absorption and the causes of trends in surface radiative fluxes constrain the forcing from aerosol-radiation interactions. A robust theoretical foundation and convincing evidence constrain the forcing caused by aerosol-driven increases in liquid cloud droplet number concentration. However, the influence of anthropogenic aerosols on cloud liquid water content and cloud fraction is less clear, and the influence on mixed-phase and ice clouds remains poorly constrained. Observed changes in surface temperature and radiative fluxes provide additional constraints. These multiple lines of evidence lead to a 68% confidence interval for the total aerosol effective radiative forcing of -1.60 to -0.65 W m-2, or -2.0 to -0.4 W m-2 with a 90% likelihood. Those intervals are of similar width to the last Intergovernmental Panel on Climate Change assessment but shifted towards more negative values. The uncertainty will narrow in the future by continuing to critically combine multiple lines of evidence, especially those addressing industrial-era changes in aerosol sources and aerosol effects on liquid cloud amount and on ice clouds. Aerosol; Climate change; Radiative forcing; Aerosol-cloud interaction; Aerosol-radiation interaction
Berry, Elizabeth; Mace, Gerald G.; Gettelman, AndrewBerry, E., G. G. Mace, A. Gettelman, 2020: Using A-Train Observations to Evaluate East Pacific Cloud Occurrence and Radiative Effects in the Community Atmosphere Model. J. Climate, (In Press). doi: 10.1175/JCLI-D-19-0870.1. Using information from the A-Train satellites, the properties and radiative effects of East Pacific boundary layer clouds are evaluated in the Community Atmosphere Model version 5 (CAM5) from the summer of 2007 and 2008. The cloud microphysical properties are inferred using measurements from CloudSat and CALIPSO (CC) that are then used to calculate the broadband radiative flux profiles. Accounting appropriately for sampling differences between the measurements and the simulation, evidence of the “too few, too bright” low cloud bias is found in CAM5. Single-layer low clouds have a frequency of occurrence of 42% from CC, compared to just 29% in CAM5, while the averaged cloud radiative kernel (CRK) for the model shows stronger cooling. For Stratocumulus in particular, the cooling in the model CRK is a factor of two larger than the observations, implying an overly sensitive tropical low cloud feedback.Differences in the day/night occurrence of Stratocumulus help explain some of the difference in the CRK. The cloud-type microphysics for liquid clouds are represented reasonably well by the model, with a tendency for smaller water paths and smaller effective radii. Overall, the occurrence and CRK have partially compensating errors such that the net cooling at the top of the atmosphere for East Pacific low clouds is -43W m-2 in CAM5, compared to -32 W m-2 from CC. The cooling effect in the model is accomplished by fewer low clouds with a narrower range of properties, compared to more clouds with a broader range of properties in the observation-based dataset.
Bhatt, Rajendra; Doelling, David R.; Angal, Amit; Xiong, Xiaoxiong; Haney, Conor; Scarino, Benjamin R.; Wu, Aisheng; Gopalan, ArunBhatt, R., D. R. Doelling, A. Angal, X. Xiong, C. Haney, B. R. Scarino, A. Wu, A. Gopalan, 2020: Response Versus Scan-Angle Assessment of MODIS Reflective Solar Bands in Collection 6.1 Calibration. IEEE Transactions on Geoscience and Remote Sensing, 58(4), 2276-2289. doi: 10.1109/TGRS.2019.2946963. The Moderate Resolution Imaging Spectroradiometer (MODIS) instruments onboard the Aqua and Terra satellites have been operated for nearly two decades, producing high-quality earth observation data sets suitable for a broad range of scientific studies regarding the earth's land, ocean, and atmospheric processes. The high radiometric accuracy of MODIS reflective solar band (RSB) calibration has also served as benchmark measurements for on-orbit cross-calibration studies. As the two MODIS instruments have operated well beyond their design lifespan of six years, the measurements from the onboard calibrators alone become inadequate to characterize the sensor's response at all scan angles, as evinced by long-term drifts observed at certain scan positions of the Aqua-MODIS 0.64- and 0.86-μm bands in Collection 6 (C6) data set. The latest MODIS Level 1B C6.1 data set incorporates earth-view response trending from invariant desert sites as supplemental inputs to characterize the scan-angle calibration dependencies for all RSB. This article presents a deep convective cloud (DCC)-based calibration approach for an independent evaluation of the MODIS RSB response versus scan-angle (RVS) performance in C6.1. The long-term calibration stability and RVS differences in C6.1 have been significantly improved for Aqua-MODIS RSB. The observed RVS differences of more than 2% in Aqua-MODIS C6 bands 1 and 2 have been reduced to within 1% in C6.1. Some RSBs of Terra-MODIS have suffered temporal drifts up to 2% and calibration shifts up to 3%, particularly around 2016 when the Terra satellite entered into safe mode. The DCC approach has been found very effective in tracking the on-orbit RVS changes over time. clouds; calibration; radiometry; VIIRS; Moderate Resolution Imaging Spectroradiometer; deep convective cloud; Moderate Resolution Imaging Spectroradiometer (MODIS); Terra satellite; Clouds and the Earth’s Radiant Energy System (CERES); remote sensing; deep convective cloud (DCC); Earth Polychromatic Imaging Camera (EPIC); radiometric calibration; response versus scan-angle (RVS); Aqua satellites; Aqua-MODIS RSB; high-quality earth observation datasets; MODIS instruments; MODIS level 1B C6.1 dataset; MODIS reflective solar band calibration; onboard calibrators; scan-angle calibration; Terra-MODIS
Bhatt, Rajendra; Doelling, David R.; Angal, Amit; Xiong, Xiaoxiong; Haney, Conor; Scarino, Benjamin R.; Wu, Aisheng; Gopalan, ArunBhatt, R., D. R. Doelling, A. Angal, X. Xiong, C. Haney, B. R. Scarino, A. Wu, A. Gopalan, 2020: Response Versus Scan-Angle Assessment of MODIS Reflective Solar Bands in Collection 6.1 Calibration. IEEE Transactions on Geoscience and Remote Sensing, 1-14. doi: 10.1109/TGRS.2019.2946963. The Moderate Resolution Imaging Spectroradiometer (MODIS) instruments onboard the Aqua and Terra satellites have been operated for nearly two decades, producing high-quality earth observation data sets suitable for a broad range of scientific studies regarding the earth's land, ocean, and atmospheric processes. The high radiometric accuracy of MODIS reflective solar band (RSB) calibration has also served as benchmark measurements for on-orbit cross-calibration studies. As the two MODIS instruments have operated well beyond their design lifespan of six years, the measurements from the onboard calibrators alone become inadequate to characterize the sensor's response at all scan angles, as evinced by long-term drifts observed at certain scan positions of the Aqua-MODIS 0.64- and 0.86-μm bands in Collection 6 (C6) data set. The latest MODIS Level 1B C6.1 data set incorporates earth-view response trending from invariant desert sites as supplemental inputs to characterize the scan-angle calibration dependencies for all RSB. This article presents a deep convective cloud (DCC)-based calibration approach for an independent evaluation of the MODIS RSB response versus scan-angle (RVS) performance in C6.1. The long-term calibration stability and RVS differences in C6.1 have been significantly improved for Aqua-MODIS RSB. The observed RVS differences of more than 2% in Aqua-MODIS C6 bands 1 and 2 have been reduced to within 1% in C6.1. Some RSBs of Terra-MODIS have suffered temporal drifts up to 2% and calibration shifts up to 3%, particularly around 2016 when the Terra satellite entered into safe mode. The DCC approach has been found very effective in tracking the on-orbit RVS changes over time. Clouds and the Earth's Radiant Energy System (CERES); Moderate Resolution Imaging Spectroradiometer (MODIS); deep convective cloud (DCC); Earth Polychromatic Imaging Camera (EPIC); radiometric calibration; response versus scan-angle (RVS); VIIRS.
Bony, Sandrine; Schulz, Hauke; Vial, Jessica; Stevens, BjornBony, S., H. Schulz, J. Vial, B. Stevens, 2020: Sugar, Gravel, Fish and Flowers: Dependence of Mesoscale Patterns of Trade-wind Clouds on Environmental Conditions. Geophysical Research Letters, 47(7), e2019GL085988. doi: 10.1029/2019GL085988. Trade-wind clouds exhibit a large diversity of spatial organizations at the mesoscale. Over the tropical western Atlantic, a recent study has visually identified four prominent mesoscale patterns of shallow convection, referred to as Flowers, Fish, Gravel and Sugar. We show that these four patterns can be identified objectively from satellite observations by analyzing the spatial distribution of infrared brightness temperatures. By applying this analysis to 19 years of data, we examine relationships between cloud patterns and large-scale environmental conditions. This investigation reveals that on daily and interannual timescales, the near-surface wind speed and the strength of the lower-tropospheric stability discriminate the occurrence of the different organization patterns. These results, combined with the tight relationship between cloud patterns, low-level cloud amount and cloud-radiative effects, suggest that the mesoscale organization of shallow clouds might change under global warming. The role of shallow convective organization in determining low-cloud feedback should thus be investigated. low-cloud feedback; shallow convection; mesoscale organization; tradewind clouds
Bosilovich, Michael G.; Robertson, Franklin R.; Stackhouse, Paul W.Bosilovich, M. G., F. R. Robertson, P. W. Stackhouse, 2020: El Niño–Related Tropical Land Surface Water and Energy Response in MERRA-2. J. Climate, 33(3), 1155-1176. doi: 10.1175/JCLI-D-19-0231.1. Although El Niño events each have distinct evolutionary character, they typically provide systematic large-scale forcing for warming and increased drought frequency across the tropical continents. We assess this response in the Modern-Era Retrospective Analysis for Research and Applications, version 2 (MERRA-2), reanalysis and in a 10-member-model Atmospheric Model Intercomparison Project (AMIP) ensemble. The lagged response (3–4 months) of mean tropical land temperature to El Niño warming in the Pacific Ocean is well represented. MERRA-2 reproduces the patterns of precipitation in the tropical regions, and the AMIP ensemble reproduces some regional responses that are similar to those observed and some regions that are not simulating the response well. Model skill is dependent on event forcing strength and temporal proximity to the peak of the sea surface warming. A composite approach centered on maximum Niño-3.4 SSTs and lag relationships to energy fluxes and transports is used to identify mechanisms supporting tropical land warming. The composite necessarily moderates weather-scale variability of the individual events while retaining the systematic features across all events. We find that reduced continental upward motions lead to reduced cloudiness and more shortwave radiation at the surface, as well as reduced precipitation. The increased shortwave heating at the land surface, along with reduced soil moisture, leads to warmer surface temperature, more sensible heating, and warming of the lower troposphere. The composite provides a broad picture of the mechanisms governing the hydrologic response to El Niño forcing, but the regional and temporal responses can vary substantially for any given event. The 2015/16 El Niño, one of the strongest events, demonstrates some of the forced response noted in the composite, but with shifts in the evolution that depart from the composite, demonstrating the limitations of the composite and individuality of El Niño.
Boucher, Olivier; Servonnat, Jérôme; Albright, Anna Lea; Aumont, Olivier; Balkanski, Yves; Bastrikov, Vladislav; Bekki, Slimane; Bonnet, Rémy; Bony, Sandrine; Bopp, Laurent; Braconnot, Pascale; Brockmann, Patrick; Cadule, Patricia; Caubel, Arnaud; Cheruy, Frédérique; Codron, Francis; Cozic, Anne; Cugnet, David; D'Andrea, Fabio; Davini, Paolo; Lavergne, Casimir de; Denvil, Sébastien; Deshayes, Julie; Devilliers, Marion; Ducharne, Agnès; Dufresne, Jean-Louis; Dupont, Eliott; Éthé, Christian; Fairhead, Laurent; Falletti, Lola; Flavoni, Simona; Foujols, Marie-Alice; Gardoll, Sébastien; Gastineau, Guillaume; Ghattas, Josefine; Grandpeix, Jean-Yves; Guenet, Bertrand; Guez, Lionel; Guilyardi, Éric; Guimberteau, Matthieu; Hauglustaine, Didier; Hourdin, Frédéric; Idelkadi, Abderrahmane; Joussaume, Sylvie; Kageyama, Masa; Khodri, Myriam; Krinner, Gerhard; Lebas, Nicolas; Levavasseur, Guillaume; Lévy, Claire; Li, Laurent; Lott, François; Lurton, Thibaut; Luyssaert, Sebastiaan; Madec, Gurvan; Madeleine, Jean-Baptiste; Maignan, Fabienne; Marchand, Marion; Marti, Olivier; Mellul, Lidia; Meurdesoif, Yann; Mignot, Juliette; Musat, Ionela; Ottlé, Catherine; Peylin, Philippe; Planton, Yann; Polcher, Jan; Rio, Catherine; Rochetin, Nicolas; Rousset, Clément; Sepulchre, Pierre; Sima, Adriana; Swingedouw, Didier; Thiéblemont, Rémi; Traore, Abdoul Khadre; Vancoppenolle, Martin; Vial, Jessica; Vialard, Jérôme; Viovy, Nicolas; Vuichard, NicolasBoucher, O., J. Servonnat, A. L. Albright, O. Aumont, Y. Balkanski, V. Bastrikov, S. Bekki, R. Bonnet, S. Bony, L. Bopp, P. Braconnot, P. Brockmann, P. Cadule, A. Caubel, F. Cheruy, F. Codron, A. Cozic, D. Cugnet, F. D'Andrea, P. Davini, C. d. Lavergne, S. Denvil, J. Deshayes, M. Devilliers, A. Ducharne, J. Dufresne, E. Dupont, C. Éthé, L. Fairhead, L. Falletti, S. Flavoni, M. Foujols, S. Gardoll, G. Gastineau, J. Ghattas, J. Grandpeix, B. Guenet, L. Guez, É. Guilyardi, M. Guimberteau, D. Hauglustaine, F. Hourdin, A. Idelkadi, S. Joussaume, M. Kageyama, M. Khodri, G. Krinner, N. Lebas, G. Levavasseur, C. Lévy, L. Li, F. Lott, T. Lurton, S. Luyssaert, G. Madec, J. Madeleine, F. Maignan, M. Marchand, O. Marti, L. Mellul, Y. Meurdesoif, J. Mignot, I. Musat, C. Ottlé, P. Peylin, Y. Planton, J. Polcher, C. Rio, N. Rochetin, C. Rousset, P. Sepulchre, A. Sima, D. Swingedouw, R. Thiéblemont, A. K. Traore, M. Vancoppenolle, J. Vial, J. Vialard, N. Viovy, N. Vuichard, 2020: Presentation and evaluation of the IPSL-CM6A-LR climate model. Journal of Advances in Modeling Earth Systems, (In Press). doi: 10.1029/2019MS002010. keypoints The IPSL-CM6A-LR model climatology is much improved over the previous version although some systematic biases and shortcomings persist. A long pre-industrial control and a large number of historical and scenario simulations have been performed as part of CMIP6. The effective climate sensitivity of the IPSL model increases from 4.1 to 4.8 K between IPSL-CM5A-LR and IPSL-CM6A-LR. climate model; CMIP6; climate sensitivity; climate metrics; IPSL-CM6A-LR
Brutsaert, Wilfried; Cheng, Lei; Zhang, Lu; Brutsaert, Wilfried; Cheng, Lei; Zhang, LuBrutsaert, W., L. Cheng, L. Zhang, W. Brutsaert, L. Cheng, L. Zhang, 2020: Spatial Distribution of Global Landscape Evaporation in the Early Twenty-First Century by Means of a Generalized Complementary Approach. J. Hydrometeor., 21(2), 551–581. doi: 10.1175/JHM-D-19-0208.1. AbstractA generalized implementation of the complementary principle was applied to estimate global land surface evaporation and its spatial distribution. The single parameter in the method was cali...
Burgdorf, Martin J.; Müller, Thomas G.; Buehler, Stefan A.; Prange, Marc; Brath, ManfredBurgdorf, M. J., T. G. Müller, S. A. Buehler, M. Prange, M. Brath, 2020: Characterization of the High-Resolution Infrared Radiation Sounder Using Lunar Observations. Remote Sensing, 12(9), 1488. doi: 10.3390/rs12091488. The High-Resolution Infrared Radiation Sounder (HIRS) has been operational since 1975 on different satellites. In spite of this long utilization period, the available information about some of its basic properties is incomplete or contradictory. We have approached this problem by analyzing intrusions of the Moon in the deep space view of HIRS/2 through HIRS/4. With this method we found: (1) The diameters of the field of view of HIRS/2, HIRS/3, and HIRS/4 have the relative proportions of 1.4 ° to 1.3 ° to 0.7 ° with all channels; (2) the co-registration differs by up to 0.031 ° among the long-wave and by up to 0.015 ° among the shortwave spectral channels in the along-track direction; (3) the photometric calibration is consistent within 0.7% or less for channels 2–7 (1.2% for HIRS/2), similar values were found for channels 13–16; (4) the non-linearity of the short-wavelength channels is negligible; and (5) the contribution of reflected sunlight to the flux in the short-wavelength channels can be determined in good approximation, if the emissivity of the surface is known. surface; calibration; infrared sounder; moon
Cao, Yunfeng; Liang, Shunlin; Yu, MengCao, Y., S. Liang, M. Yu, 2020: Observed low-frequency linkage between Northern Hemisphere tropical expansion and polar vortex weakening from 1979 to 2012. Atmospheric Research, 243, 105034. doi: 10.1016/j.atmosres.2020.105034. In recent decades, the northern hemisphere (NH) atmospheric meridional circulation has experienced unprecedented changes. The NH tropical belt is significantly expanding toward high latitudes, and the Arctic polar vortex is continually weakening. Both phenomena have led to severe consequences on the Earth's surface, such as more frequent droughts in the subtropics and accelerated sea ice loss in the Arctic. However, the potential linkage between these phenomena and the underlying mechanisms have rarely been discussed. In this study, we report strong observational evidence that the NH tropical boundary and tropospheric polar vortex are synchronously changing, based on analysis of long-term satellite records from 1979 to 2012. Our investigation suggests that both the variance of the NH tropical boundary and tropospheric polar vortex from 1979 to 2012 are associated to the natural anomaly of NH mid-latitude sea surface temperature. The low-frequency sea surface temperature anomalies over the North Pacific (i.e., the Pacific Decadal Oscillation, PDO) and Atlantic (i.e., the Atlantic Multidecadal Oscillation, AMO) could explain 61% of the NH tropical boundary variance and 56% of the polar vortex variance from 1979 to 2012. Atlantic Multidecadal Oscillation; Low-frequency linkage; NH tropical expansion; Pacific Decadal Oscillation; Polar vortex weakening
Chen, Jiang; He, Tao; Jiang, Bo; Liang, ShunlinChen, J., T. He, B. Jiang, S. Liang, 2020: Estimation of all-sky all-wave daily net radiation at high latitudes from MODIS data. Remote Sensing of Environment, 245, 111842. doi: 10.1016/j.rse.2020.111842. Surface all-wave net radiation (Rn) plays an important role in various land surface processes, such as agricultural, ecological, hydrological, and biogeochemical processes. Recently, remote sensing of Rn at regional and global scales has attracted considerable attention and has achieved significant advances. However, there are many issues in estimating all-sky daily average Rn at high latitudes, such as posing greater uncertainty by surface and atmosphere satellite products at high latitudes, and unavailability of real-time and accurate cloud base height and temperature parameters. In this study, we developed the LRD (length ratio of daytime) classification model using the genetic algorithm-artificial neural network (GA-ANN) to estimate all-sky daily average Rn at high latitudes. With a very high temporal repeating frequency (~6 to 20 times per day) at high latitudes, data from the Moderate Resolution Imaging Spectroradiometer (MODIS) were used to test the proposed method. Rn measurements at 82 sites and top-of-atmosphere (TOA) data of MODIS from 2000 to 2017 were matched for model training and validation. Two models for estimating daily average Rn were developed: model I based on instantaneous daytime MODIS observation and model II based on instantaneous nighttime MODIS observation. Validation results of model I showed an R2 of 0.85, an RMSE of 23.66 W/m2, and a bias of 0.27 W/m2, whereas these values were 0.51, 15.04 W/m2, and −0.08 W/m2 for model II, respectively. Overall, the proposed machine learning algorithm with the LRD classification can accurately estimate the all-sky daily average Rn at high latitudes. Mapping of Rn over the high latitudes at 1 km spatial resolution showed a similar spatial distribution to Rn estimates from the Clouds and the Earth's Radiant Energy System (CERES) product. This method has the potential for operational monitoring of spatio-temporal change of Rn at high latitudes with a long-term coverage of MODIS observations. MODIS; Net radiation; High latitudes; High spatial resolution; Length ratio of daytime
Chen, Liang; Dirmeyer, Paul A.Chen, L., P. A. Dirmeyer, 2020: Reconciling the disagreement between observed and simulated temperature responses to deforestation. Nature Communications, 11(1), 1-10. doi: 10.1038/s41467-019-14017-0. Models show a cooler surface temperature response to deforestation than observations which has been attributed to uncertainties in the models. A comparison of satellite observations and model experiments shows that the disagreement is due to the role of atmospheric feedbacks, which are not well captured in the observational space-for-time approach.
Cherian, Ribu; Quaas, JohannesCherian, R., J. Quaas, 2020: Trends in AOD, Clouds, and Cloud Radiative Effects in Satellite Data and CMIP5 and CMIP6 Model Simulations Over Aerosol Source Regions. Geophysical Research Letters, 47(9), e2020GL087132. doi: 10.1029/2020GL087132. Several regions worldwide have seen significant trends in anthropogenic aerosol emissions during the period of detailed satellite observations since 2001. Over Europe (EUR) and North America (NAM) there were strong declines, over China increases then declines and over India, strong increases. Regional trends in model-simulated aerosol optical depth (AOD) and cloud radiative effects in both the Fifth and Sixth Coupled Model Intercomparison Projects (CMIP5 and CMIP6) are broadly consistent with the ones from satellite retrievals in most parts of EUR, NAM and India. CMIP6 models better match satellite-derived AOD trend in western NAM (increasing) and eastern China (decreasing), where CMIP5 models failed, pointing to improved anthropogenic aerosol emissions. Drop concentration trends in both observations and models qualitatively match AOD trends. The result for solar cloud radiative effect in models, however, is due to compensating errors: Models fail to reproduce observed liquid water path trends and show, in turn, opposite trends in cloud fraction. climate models; aerosol optical depth; cloud radiative effects; aerosol emission trend; aerosol source regions; CDNC
Cho, Heeje; Jun, Sang-Yoon; Ho, Chang-Hoi; McFarquhar, GregCho, H., S. Jun, C. Ho, G. McFarquhar, 2020: Simulations of Winter Arctic Clouds and Associated Radiation Fluxes Using Different Cloud Microphysics Schemes in the Polar WRF: Comparisons With CloudSat, CALIPSO, and CERES. Journal of Geophysical Research: Atmospheres, 125(2), e2019JD031413. doi: 10.1029/2019JD031413. Key Points Winter Arctic clouds simulated by the polar version of the Weather Research and Forecasting model are compared with satellite retrievals The cloud amount and cloud top height of model simulations agree well with those of satellite retrievals The downward longwave radiation at the surface shows realistic temporal variations, but is sensitive to the cloud microphysics scheme choice satellite observation; surface radiation; Polar WRF; cloud microphysics; winter Arctic cloud
Choi, Yong-Sang; Hwang, Jiwon; Ok, Jung; Park, Doo-Sun R.; Su, Hui; Jiang, Jonathan H.; Huang, Lei; Limpasuvan, TyChoi, Y., J. Hwang, J. Ok, D. R. Park, H. Su, J. H. Jiang, L. Huang, T. Limpasuvan, 2020: Effect of Arctic clouds on the ice-albedo feedback in midsummer. International Journal of Climatology, (In Press). doi: 10.1002/joc.6469. The Arctic clouds should be an important factor that affects the summertime sea ice. By reflecting the incoming solar radiation before it reaches the surface, the Arctic clouds may prevent the surface from absorbing tremendous solar radiation due to the reduced sea ice. This cloud effect will lead to intervene the feedback relation between the solar radiation and the sea ice change. However, few studies have quantitatively investigated the Arctic cloud effect on the ice-albedo feedback. This study found that the Arctic clouds regulate the melting speed of sea ice in midsummer months (June to August) based on the data from multiple sources, that is, satellite, reanalysis, and climate models. During this period, the fraction of Arctic clouds with the net radiative cooling effect is almost invariable with sea ice reduction. However, despite of the steady cloud fraction in the midsummer months, the shortwave cloud radiative effect (total-sky minus clear-sky absorbed shortwave radiation) was found to significantly increase with the reduced sea ice concentration (0.64 W m−2%−1 in CERES, 0.73 W m−2%−1 in ERA5). This is because the clouds present more contrast of albedo with the sea ice-free ocean than the sea ice-covered ocean. Finally, our analyses show that the Arctic clouds are nearly halving the strength of the ice-albedo feedback in the midsummer months. These results imply that the sea ice reduction could have been much faster in the past decades in the absence of the cloud effect found here. Arctic clouds; ice-albedo feedback; Arctic Sea ice; cloud effect; midsummer
Clerbaux, Nicolas; Akkermans, Tom; Baudrez, Edward; Velazquez Blazquez, Almudena; Moutier, William; Moreels, Johan; Aebi, ChristineClerbaux, N., T. Akkermans, E. Baudrez, A. Velazquez Blazquez, W. Moutier, J. Moreels, C. Aebi, 2020: The Climate Monitoring SAF Outgoing Longwave Radiation from AVHRR. Remote Sensing, 12(6), 929. doi: 10.3390/rs12060929. Data from the Advanced Very High Resolution Radiometer (AVHRR) have been used to create several long-duration data records of geophysical variables describing the atmosphere and land and water surfaces. In the Climate Monitoring Satellite Application Facility (CM SAF) project, AVHRR data are used to derive the Cloud, Albedo, and Radiation (CLARA) climate data records of radiation components (i.a., surface albedo) and cloud properties (i.a., cloud cover). This work describes the methodology implemented for the additional estimation of the Outgoing Longwave Radiation (OLR), an important Earth radiation budget component, that is consistent with the other CLARA variables. A first step is the estimation of the instantaneous OLR from the AVHRR observations. This is done by regressions on a large database of collocated observations between AVHRR Channel 4 (10.8 µm) and 5 (12 µm) and the OLR from the Clouds and Earth’s Radiant Energy System (CERES) instruments. We investigate the applicability of this method to the first generation of AVHRR instrument (AVHRR/1) for which no Channel 5 observation is available. A second step concerns the estimation of daily and monthly OLR from the instantaneous AVHRR overpasses. This step is especially important given the changes in the local time of the observations due to the orbital drift of the NOAA satellites. We investigate the use of OLR in the ERA5 reanalysis to estimate the diurnal variation. The developed approach proves to be valuable to model the diurnal change in OLR due to day/night time warming/cooling over clear land. Finally, the resulting monthly mean AVHRR OLR product is intercompared with the CERES monthly mean product. For a typical configuration with one morning and one afternoon AVHRR observation, the Root Mean Square (RMS) difference with CERES monthly mean OLR is about 2 Wm−2 at 1° × 1° resolution. We quantify the degradation of the OLR product when only one AVHRR instrument is available (as is the case for some periods in the 1980s) and also the improvement when more instruments are available (e.g., using METOP-A, NOAA-15, NOAA-18, and NOAA-19 in 2012). The degradation of the OLR product from AVHRR/1 instruments is also quantified, which is done by “masking” the Channel 5 observations. CERES; outgoing longwave radiation; broadband; AVHRR; OLR; flux; TOA
Colón Robles, Marilé; Amos, Helen M.; Dodson, J. Brant; Bouwman, Jeffrey; Rogerson, Tina; Bombosch, Annette; Farmer, Lauren; Burdick, Autumn; Taylor, Jessica; Chambers, Lin H.Colón Robles, M., H. M. Amos, J. B. Dodson, J. Bouwman, T. Rogerson, A. Bombosch, L. Farmer, A. Burdick, J. Taylor, L. H. Chambers, 2020: Clouds Around the World: How a Simple Citizen Science Data Challenge Became a Worldwide Success. Bull. Amer. Meteor. Soc., (In Press). doi: 10.1175/BAMS-D-19-0295.1. GLOBE Spring Cloud Challenge, a citizen science engagement event, resulted in a global dataset of 55,000+ cloud observations with coincident-satellite data by volunteers across all continents and in hard-to-observe regions.
Danabasoglu, G.; Lamarque, J.-F.; Bacmeister, J.; Bailey, D. A.; DuVivier, A. K.; Edwards, J.; Emmons, L. K.; Fasullo, J.; Garcia, R.; Gettelman, A.; Hannay, C.; Holland, M. M.; Large, W. G.; Lauritzen, P. H.; Lawrence, D. M.; Lenaerts, J. T. M.; Lindsay, K.; Lipscomb, W. H.; Mills, M. J.; Neale, R.; Oleson, K. W.; Otto‐Bliesner, B.; Phillips, A. S.; Sacks, W.; Tilmes, S.; Kampenhout, L. van; Vertenstein, M.; Bertini, A.; Dennis, J.; Deser, C.; Fischer, C.; Fox‐Kemper, B.; Kay, J. E.; Kinnison, D.; Kushner, P. J.; Larson, V. E.; Long, M. C.; Mickelson, S.; Moore, J. K.; Nienhouse, E.; Polvani, L.; Rasch, P. J.; Strand, W. G.Danabasoglu, G., J. Lamarque, J. Bacmeister, D. A. Bailey, A. K. DuVivier, J. Edwards, L. K. Emmons, J. Fasullo, R. Garcia, A. Gettelman, C. Hannay, M. M. Holland, W. G. Large, P. H. Lauritzen, D. M. Lawrence, J. T. M. Lenaerts, K. Lindsay, W. H. Lipscomb, M. J. Mills, R. Neale, K. W. Oleson, B. Otto‐Bliesner, A. S. Phillips, W. Sacks, S. Tilmes, L. v. Kampenhout, M. Vertenstein, A. Bertini, J. Dennis, C. Deser, C. Fischer, B. Fox‐Kemper, J. E. Kay, D. Kinnison, P. J. Kushner, V. E. Larson, M. C. Long, S. Mickelson, J. K. Moore, E. Nienhouse, L. Polvani, P. J. Rasch, W. G. Strand, 2020: The Community Earth System Model Version 2 (CESM2). Journal of Advances in Modeling Earth Systems, 12(2), e2019MS001916. doi: 10.1029/2019MS001916. An overview of the Community Earth System Model Version 2 (CESM2) is provided, including a discussion of the challenges encountered during its development and how they were addressed. In addition, an evaluation of a pair of CESM2 long preindustrial control and historical ensemble simulations is presented. These simulations were performed using the nominal 1° horizontal resolution configuration of the coupled model with both the “low-top” (40 km, with limited chemistry) and “high-top” (130 km, with comprehensive chemistry) versions of the atmospheric component. CESM2 contains many substantial science and infrastructure improvements and new capabilities since its previous major release, CESM1, resulting in improved historical simulations in comparison to CESM1 and available observations. These include major reductions in low-latitude precipitation and shortwave cloud forcing biases; better representation of the Madden-Julian Oscillation; better El Niño-Southern Oscillation-related teleconnections; and a global land carbon accumulation trend that agrees well with observationally based estimates. Most tropospheric and surface features of the low- and high-top simulations are very similar to each other, so these improvements are present in both configurations. CESM2 has an equilibrium climate sensitivity of 5.1–5.3 °C, larger than in CESM1, primarily due to a combination of relatively small changes to cloud microphysics and boundary layer parameters. In contrast, CESM2's transient climate response of 1.9–2.0 °C is comparable to that of CESM1. The model outputs from these and many other simulations are available to the research community, and they represent CESM2's contributions to the Coupled Model Intercomparison Project Phase 6. Community Earth System Model (CESM); coupled model development and evaluation; global coupled Earth system modeling; preindustrial and historical simulations
Devasthale, Abhay; Sedlar, Joseph; Tjernström, Michael; Kokhanovsky, AlexanderDevasthale, A., J. Sedlar, M. Tjernström, A. Kokhanovsky, 2020: A Climatological Overview of Arctic Clouds. Physics and Chemistry of the Arctic Atmosphere, 331-360. The Arctic climate system is complex and clouds are one of its least understood components. Since cloud processes occur from micrometer to synoptic scales, their couplings with the other components of the Arctic climate system and their overall role in modulating the energy budget at different spatio-temporal scales is challenging to quantify. The in-situ measurements, as limited in space and time as they are, still reveal the complex nature of cloud microphysical and thermodynamical processes in the Arctic. However, the synoptic scale variability of cloud systems can only be obtained from the satellite observations. A considerable progress has been made in the last decade in understanding cloud processes in the Arctic due to the availability of valuable data from the multiple campaigns in the Central Arctic and due to the advances in the satellite remote sensing. This chapter provides an overview of this progress.First an overview of the lessons learned from the recent in-situ measurement campaigns in the Arctic is provided. In particular, the importance of supercooled liquid water clouds, their role in the radiation budget and their interaction with the vertical thermodynamical structure is discussed. In the second part of the chapter, a climatological overview of cloud properties using the state-of-the-art satellite based cloud climate datasets is provided. The agreements and disagreements in these datasets are highlighted. The third and the fourth parts of the chapter highlight two most important processes that are currently being researched, namely cloud response to the rapidly changing sea-ice extent and the role of moisture transport in to the Arctic in governing cloud variability. Both of these processes have implications for the cloud feedback in the Arctic. Arctic clouds; Satellite remote sensing; Cloud properties; Arctic sea-ice; Climate data records; Cloud variability; Moisture transport; Supercooled liquid clouds; Surface radiation budget; Thermodynamic structure
Diamond, Michael S.; Director, Hannah M.; Eastman, Ryan; Possner, Anna; Wood, RobertDiamond, M. S., H. M. Director, R. Eastman, A. Possner, R. Wood, 2020: Substantial Cloud Brightening From Shipping in Subtropical Low Clouds. AGU Advances, 1(1), e2019AV000111. doi: 10.1029/2019AV000111. The influence of aerosol particles on cloud reflectivity remains one of the largest sources of uncertainty in our understanding of anthropogenic climate change. Commercial shipping constitutes a large and concentrated aerosol perturbation in a meteorological regime where clouds have a disproportionally large effect on climate. Yet, to date, studies have been unable to detect climatologically relevant cloud radiative effects from shipping, despite models indicating that the cloud response should produce a sizable negative radiative forcing (perturbation to Earth's energy balance). We attribute a significant increase in cloud reflectivity to enhanced cloud droplet number concentrations within a major shipping corridor in the southeast Atlantic. Prevailing winds constrain emissions around the corridor, which cuts through a climatically important region of expansive low cloud cover. We use universal kriging, a classic geostatistical method, to estimate what cloud properties would have been in the absence of shipping. In the morning, cloud brightening is consistent with changes in microphysics alone, whereas in the afternoon, increases in cloud brightness from microphysical changes are offset by decreases in the total amount of cloud water. We calculate an effective radiative forcing within the southeast Atlantic shipping corridor of approximately −2 W/m2. Several years of data are required to identify a clear signal. Extrapolating our results globally, we calculate an effective radiative forcing due to aerosol-cloud interactions in low clouds of −1.0 W/m2 (95% confidence interval: −1.6 to −0.4 W/m2). The unique setup in the southeast Atlantic could be an ideal test for the representation of aerosol-cloud interactions in climate models. radiative forcing; climate; cloud; aerosol; shipping
Donohoe, Aaron; Armour, Kyle C.; Roe, Gerard H.; Battisti, David S.; Hahn, LilyDonohoe, A., K. C. Armour, G. H. Roe, D. S. Battisti, L. Hahn, 2020: The Partitioning of Meridional Heat Transport from the Last Glacial Maximum to CO2 Quadrupling in Coupled Climate Models. J. Climate, 33(10), 4141-4165. doi: 10.1175/JCLI-D-19-0797.1. Meridional heat transport (MHT) is analyzed in ensembles of coupled climate models simulating climate states ranging from the Last Glacial Maximum (LGM) to quadrupled CO2. MHT is partitioned here into atmospheric (AHT) and implied oceanic (OHT) heat transports. In turn, AHT is partitioned into dry and moist energy transport by the meridional overturning circulation (MOC), transient eddy energy transport (TE), and stationary eddy energy transport (SE) using only monthly averaged model output that is typically archived. In all climate models examined, the maximum total MHT (AHT + OHT) is nearly climate-state invariant, except for a modest (4%, 0.3 PW) enhancement of MHT in the Northern Hemisphere (NH) during the LGM. However, the partitioning of MHT depends markedly on the climate state, and the changes in partitioning differ considerably among different climate models. In response to CO2 quadrupling, poleward implied OHT decreases, while AHT increases by a nearly compensating amount. The increase in annual-mean AHT is a smooth function of latitude but is due to a spatially inhomogeneous blend of changes in SE and TE that vary by season. During the LGM, the increase in wintertime SE transport in the NH midlatitudes exceeds the decrease in TE resulting in enhanced total AHT. Total AHT changes in the Southern Hemisphere (SH) are not significant. These results suggest that the net top-of-atmosphere radiative constraints on total MHT are relatively invariant to climate forcing due to nearly compensating changes in absorbed solar radiation and outgoing longwave radiation. However, the partitioning of MHT depends on detailed regional and seasonal factors.
Donohoe, Aaron; Blanchard-Wrigglesworth, Ed; Schweiger, Axel; Rasch, Philip J.Donohoe, A., E. Blanchard-Wrigglesworth, A. Schweiger, P. J. Rasch, 2020: The effect of atmospheric transmissivity on model and observational estimates of the sea ice albedo feedback. J. Climate, (In Press). doi: 10.1175/JCLI-D-19-0674.1. The sea-ice-albedo feedback (SIAF) is the product of the ice sensitivity (IS) – how much the surface albedo in sea-ice regions changes as the planet warms– and the radiative sensitivity (RS) – how much the top of atmosphere radiation changes as the surface albedo changes. We demonstrate that the RS calculated from radiative kernels in climate models is reproduced from calculations using the “approximate partial radiative perturbation” method that uses the climatological radiative fluxes at the top of atmosphere and the assumption that the atmosphere is isotropic to shortwave radiation. This method facilitates the comparison of RS from satellite-based estimates of climatological radiative fluxes with RS estimates across a full suite of coupled climate models and, thus, allows model evaluation of a quantity important in characterizing the climate impact of sea ice concentration changes. The satellite based RS is within the model range of RS that differs by a factor of two across climate models in both the Arctic and Southern Ocean. Observed trends in Arctic sea ice are used to estimate IS which, in conjunction with the satellite-based RS yields an SIAF of 0.16 ± 0.04 W m−2 K−1. This Arctic SIAF estimate suggests a modest amplification of future global surface temperature change by approximately 14% relative to a climate system with no SIAF. We calculate the global albedo feedback in climate models using model specific RS and IS and find a model mean feedback parameter of 0.37 W m−2 K−1 which is 40% larger than the IPCC AR5 estimate based on using RS calculated from radiative kernel calculations in a single climate model.
Donohoe, Aaron; Dawson, Eliza; McMurdie, Lynn; Battisti, David S.; Rhines, AndyDonohoe, A., E. Dawson, L. McMurdie, D. S. Battisti, A. Rhines, 2020: Seasonal Asymmetries in the Lag between Insolation and Surface Temperature. J. Climate, 33(10), 3921-3945. doi: 10.1175/JCLI-D-19-0329.1. We analyze the temporal structure of the climatological seasonal cycle in surface air temperature across the globe. We find that, over large regions of Earth, the seasonal cycle of surface temperature departs from an annual harmonic: the duration of fall and spring differ by as much as 2 months. We characterize this asymmetry by the metric ASYM, defined as the phase lag of the seasonal maximum temperature relative to the summer solstice minus the phase lag of the seasonal minimum temperature relative to winter solstice. We present a global analysis of ASYM from weather station data and atmospheric reanalysis and find that ASYM is well represented in the reanalysis. ASYM generally features positive values over land and negative values over the ocean, indicating that spring has a longer duration over the land domain whereas fall has a longer duration over the ocean. However, ASYM also features more positive values over North America compared to Europe and negative values in the polar regions over ice sheets and sea ice. Understanding the root cause of the climatological ASYM will potentially further our understanding of controls on the seasonal cycle of temperature and its future/past changes. We explore several candidate mechanisms to explain the spatial structure of ASYM including 1) modification of the seasonal cycle of surface solar radiation by the seasonal evolution of cloud thickness, 2) differences in the seasonal cycle of the atmospheric boundary layer depth over ocean and over land, and 3) temperature advection by the seasonally evolving atmospheric circulation.
Duncan, Bryan N.; Ott, Lesley E.; Abshire, James B.; Brucker, Ludovic; Carroll, Mark L.; Carton, James; Comiso, Josefino C.; Dinnat, Emmanuel P.; Forbes, Bruce C.; Gonsamo, Alemu; Gregg, Watson W.; Hall, Dorothy K.; Ialongo, Iolanda; Jandt, Randi; Kahn, Ralph A.; Karpechko, Alexey; Kawa, Stephan R.; Kato, Seiji; Kumpula, Timo; Kyrölä, Erkki; Loboda, Tatiana V.; McDonald, Kyle C.; Montesano, Paul M.; Nassar, Ray; Neigh, Christopher S. R.; Parkinson, Claire L.; Poulter, Benjamin; Pulliainen, Jouni; Rautiainen, Kimmo; Rogers, Brendan M.; Rousseaux, Cecile S.; Soja, Amber J.; Steiner, Nicholas; Tamminen, Johanna; Taylor, Patrick C.; Tzortziou, Maria A.; Virta, Henrik; Wang, James S.; Watts, Jennifer D.; Winker, David M.; Wu, Dong L.Duncan, B. N., L. E. Ott, J. B. Abshire, L. Brucker, M. L. Carroll, J. Carton, J. C. Comiso, E. P. Dinnat, B. C. Forbes, A. Gonsamo, W. W. Gregg, D. K. Hall, I. Ialongo, R. Jandt, R. A. Kahn, A. Karpechko, S. R. Kawa, S. Kato, T. Kumpula, E. Kyrölä, T. V. Loboda, K. C. McDonald, P. M. Montesano, R. Nassar, C. S. R. Neigh, C. L. Parkinson, B. Poulter, J. Pulliainen, K. Rautiainen, B. M. Rogers, C. S. Rousseaux, A. J. Soja, N. Steiner, J. Tamminen, P. C. Taylor, M. A. Tzortziou, H. Virta, J. S. Wang, J. D. Watts, D. M. Winker, D. L. Wu, 2020: Space-Based Observations for Understanding Changes in the Arctic-Boreal Zone. Reviews of Geophysics, 58(1), e2019RG000652. doi: 10.1029/2019RG000652. Observations taken over the last few decades indicate that dramatic changes are occurring in the Arctic-Boreal Zone (ABZ), which are having significant impacts on ABZ inhabitants, infrastructure, flora and fauna, and economies. While suitable for detecting overall change, the current capability is inadequate for systematic monitoring and for improving process-based and large-scale understanding of the integrated components of the ABZ, which includes the cryosphere, biosphere, hydrosphere, and atmosphere. Such knowledge will lead to improvements in Earth system models, enabling more accurate prediction of future changes and development of informed adaptation and mitigation strategies. In this article, we review the strengths and limitations of current space-based observational capabilities for several important ABZ components and make recommendations for improving upon these current capabilities. We recommend an interdisciplinary and stepwise approach to develop a comprehensive ABZ Observing Network (ABZ-ON), beginning with an initial focus on observing networks designed to gain process-based understanding for individual ABZ components and systems that can then serve as the building blocks for a comprehensive ABZ-ON. Arctic; satellite; Arctic-Boreal Zone; Boreal; Observing Strategy
Feng, Huihui; Ye, Shuchao; Zou, BinFeng, H., S. Ye, B. Zou, 2020: Contribution of vegetation change to the surface radiation budget: A satellite perspective. Global and Planetary Change, 192, 103225. doi: 10.1016/j.gloplacha.2020.103225. The surface radiation budget is of crucial importance to ecosystem evolution but varies with complex atmospheric and surface conditions. Vegetation change alters the surface thermal properties and the subsequent radiation budget; however, the vegetation contribution is difficult to isolate from mixed influences. Based on satellite observations, we apply a novel trajectory-based approach to detect the impact of vegetation change on the global surface radiation variation in recent decades (2001–2016). Satellite data on radiation and vegetation available from the Clouds and the Earth's Radiant Energy System (CERES) and Moderate Resolution Imaging Spectroradiometer (MODIS) instruments are adopted for this investigation. Methodologically, the surface net radiation (Rn) in the nonchanged vegetation trajectory represents the synthetic result of atmospheric influences and serves as a reference for isolating Rn variations due to vegetation change. The results demonstrate that the multiyear mean of global Rn is 71.57 W·m−2 with an increasing trend of 0.053 W·m−2·yr−1. Vegetation change contributes an additional 0.047 W·m−2·yr−1 of radiation in greening regions, accounting for 53.36% of the total increase in Rn. Spatially, the contribution of vegetation presents significant variability, with positive contributions located mainly in western Europe and southern Africa and negative contributions located mainly in parts of Asia and eastern Australia. Physically, the influence of vegetation change on the surface radiation budget originates from its alteration of albedo and emissivity, particularly the former. Specifically, a 1% increase in the normalized difference vegetation index (NDVI) is expected to reduce albedo by −0.003 and increase surface net shortwave radiation by 0.86 W·m−2. It can be concluded that the change in albedo by vegetation change has a nonnegligible influence on the surface radiation budget in different regions. These results help capture the physical mechanism responsible for the evolution of Earth's radiation and support environmental management. Satellite; Climate; Surface radiation budget; Globe; Vegetation change
Fielding, Mark D.; Schäfer, Sophia A. K.; Hogan, Robin J.; Forbes, Richard M.Fielding, M. D., S. A. K. Schäfer, R. J. Hogan, R. M. Forbes, 2020: Parameterizing cloud geometry and its application in a subgrid cloud edge erosion scheme. Quarterly Journal of the Royal Meteorological Society, (In Press). doi: 10.1002/qj.3758. To represent the effects of unresolved cloud processes in numerical weather prediction and climate models, parameterizations of the subgrid properties of clouds are required. In this paper, we describe a method for specifying the ‘cloud edge length’ within a model grid-box, which is an important parameter for approximating the subgrid mixing of air at cloud boundaries. We begin by proposing three conceptual models that predict the cloud edge length using the grid-box cloud fraction and a length scale to be derived empirically. The conceptual models are then evaluated using a wide range of observations and cloud-resolving models. Based on the finding that the ‘effective cloud spacing’ approach fits both these data best, we parameterize the effective cloud spacing as a function of pressure and model resolution. An application of this parameterization to the cloud erosion scheme in the ECMWF forecast model is then demonstrated. The effective cloud spacing approach is compared to the ‘effective cloud scale’ approach and is shown to increase cloud fraction in stratocumulus regions, while decreasing cloud fraction in cumulus regions. These cloud changes have the overall effect of decreasing the error of the modelled top-of-atmosphere net shortwave irradiance when compared to CERES observations by around 3%. Additionally, the cloud edge length is an important parameter for approximating subgrid radiative transfer and it is hoped that this parameterization will be useful to quantify the effect of representing 3D cloud radiative transfer in global models. This article is protected by copyright. All rights reserved. cloud perimeter; cloud structure; subgrid parameterization; turbulent mixing
Fountoukis, Christos; Harshvardhan, Harshvardhan; Gladich, Ivan; Ackermann, Luis; Ayoub, Mohammed A.Fountoukis, C., H. Harshvardhan, I. Gladich, L. Ackermann, M. A. Ayoub, 2020: Anatomy of a severe dust storm in the middle east: Impacts on aerosol optical properties and radiation budget. Aerosol and Air Quality Research, 20(1), 155-165. doi: 10.4209/aaqr.2019.04.0165.
Gonçalves, Nathan Borges; Lopes, Aline Pontes; Dalagnol, Ricardo; Wu, Jin; Pinho, Davieliton Mesquita; Nelson, Bruce WalkerGonçalves, N. B., A. P. Lopes, R. Dalagnol, J. Wu, D. M. Pinho, B. W. Nelson, 2020: Both near-surface and satellite remote sensing confirm drought legacy effect on tropical forest leaf phenology after 2015/2016 ENSO drought. Remote Sensing of Environment, 237, 111489. doi: 10.1016/j.rse.2019.111489. Amazon forest leaf phenology patterns have often been inferred from the Moderate Resolution Imaging Spectroradiometer (MODIS) Enhanced Vegetation Index (EVI). But reliable MODIS detection of seasonal and interannual leaf phenology patterns has also been questioned and is generally not validated with field observation. Here we compare inter-annual patterns of local-scale upper canopy leaf phenology and demography derived from tower-mounted phenocams at two upland forest sites in the Central Amazon, to corresponding satellite vegetation indices retrieved from MODIS-MAIAC (Multi-Angle Implementation of Atmospheric Correction). We focus on forest response to an unprecedented drought caused by the El Niño of 2015-16. At both sites, multi-year phenocam data showed post-drought shifts in leaf demography. These were consistent with MODIS-MAIAC anomalies in two vegetation indices. Specifically, a precocious leaf flush at both sites during the first two post-drought months, Feb-Mar 2016, caused (1) an anomalous decrease in flushing trees in Jun–Jul of 2016 and (2) an increase of trees with early mature stage leaves (2-4 mo age) in Apr-May-Jun of 2016. At both sites, these two phenological anomalies showed up in MODIS-MAIAC as, respectively, (1) a strong negative anomaly in Gcc (Green chromatic coordinate), which prior work has shown to be sensitive to the abundance of leaves 0-1 mo old, and (2) a strong positive anomaly in EVI, which is sensitive to abundance of leaves 2-4 mo age. A shift to sub-optimal seasonal leaf age mix is expected to change the ecosystem-scale intrinsic photosynthetic capacity for ~18 month after the drought. El Niño; Amazon green-up; EVI seasonality; Leaf demography; MODIS-MAIAC; Phenocam
González-Bárcena, David; Fernández-Soler, Alejandro; Pérez-Grande, Isabel; Sanz-Andrés, ÁngelGonzález-Bárcena, D., A. Fernández-Soler, I. Pérez-Grande, Á. Sanz-Andrés, 2020: Real data-based thermal environment definition for the ascent phase of Polar-Summer Long Duration Balloon missions from Esrange (Sweden). Acta Astronautica, 170, 235-250. doi: 10.1016/j.actaastro.2020.01.024. Long Duration Balloon missions are key platforms for scientific research and space technology development. Thermal analyses of this kind of systems are crucial for the success of the mission. Even though the science is usually performed at float altitude, the ascent phase, usually non-operational, is where the extreme cold conditions occur, due to the convective effects caused by relative wind speed together with the low temperatures found in the tropopause, making this scenario a dimensioning case. In this paper, a thorough study of the thermal environmental conditions during the ascent is carried out, in particular winds, temperature, and radiative thermal loads have been obtained as a function of the altitude. The study is based on real data obtained from different sources, including atmospheric soundings, radar and satellite, and a meticulous statistical treatment. The study is focussed on one of the main stratospheric balloon launch sites in Europe, Esrange (Sweden), a center of the Swedish Space Corporation, and the analyses are performed for the summer period. However, the methodology can be extended to any other location and epoch. As an example, the convective effect of the horizontal winds on a plate has been studied, and the heat transfer during the ascent phase has been quantified. A subcooling of around 7 °C was found in this case, which make worth the dedicated analysis. Albedo; Convection; Ascent phase; Long duration balloon (LDB); Thermal environment; Winds
Hahn, L. C.; Storelvmo, T.; Hofer, S.; Parfitt, R.; Ummenhofer, C. C.Hahn, L. C., T. Storelvmo, S. Hofer, R. Parfitt, C. C. Ummenhofer, 2020: Importance of Orography for Greenland Cloud and Melt Response to Atmospheric Blocking. J. Climate, 33(10), 4187-4206. doi: 10.1175/JCLI-D-19-0527.1. More frequent high pressure conditions associated with atmospheric blocking episodes over Greenland in recent decades have been suggested to enhance melt through large-scale subsidence and cloud dissipation, which allows more solar radiation to reach the ice sheet surface. Here we investigate mechanisms linking high pressure circulation anomalies to Greenland cloud changes and resulting cloud radiative effects, with a focus on the previously neglected role of topography. Using reanalysis and satellite data in addition to a regional climate model, we show that anticyclonic circulation anomalies over Greenland during recent extreme blocking summers produce cloud changes dependent on orographic lift and descent. The resulting increased cloud cover over northern Greenland promotes surface longwave warming, while reduced cloud cover in southern and marginal Greenland favors surface shortwave warming. Comparison with an idealized model simulation with flattened topography reveals that orographic effects were necessary to produce area-averaged decreasing cloud cover since the mid-1990s and the extreme melt observed in the summer of 2012. This demonstrates a key role for Greenland topography in mediating the cloud and melt response to large-scale circulation variability. These results suggest that future melt will depend on the pattern of circulation anomalies as well as the shape of the Greenland Ice Sheet.
Ham, Seung-Hee; Kato, Seiji; Rose, Fred G.Ham, S., S. Kato, F. G. Rose, 2020: Examining Biases in Diurnally-Integrated Shortwave Irradiances due to Two- and Four-Stream Approximations in Cloudy Atmosphere. J. Atmos. Sci., 77(2), 551–581. doi: 10.1175/JAS-D-19-0215.1. Shortwave irradiance biases due to two- and four-stream approximations have been studied for the last couple of decades, but biases in estimating Earth’s radiation budget have not been examined in earlier studies. In order to quantify biases in diurnally-averaged irradiances, we integrate the two- and four-stream biases using realistic diurnal variations of cloud properties from Clouds and the Earth’s Radiant Energy System (CERES) synoptic (SYN) hourly product. Three approximations are examined in this study, delta-two-stream-Eddington (D2strEdd), delta-two-stream-quadrature (D2strQuad), and delta-four-stream-quadrature (D4strQuad). Irradiances computed by the Discrete Ordinates Radiative Transfer (DISORT) and Monte Carlo (MC) methods are used as references. The MC noises are further examined by comparing with DISORT results. When the biases are integrated with a one-day of solar zenith angle variation, regional biases of D2strEdd and D2strQuad reach up to 8 W m−2, while biases of D4strQuad reach up to 2 W m−2. When the biases are further averaged monthly or annually, regional biases of D2strEdd and D2strQuad can reach –1.5 W m−2 in SW top-of-atmosphere (TOA) upward irradiances and +3 W m−2 in surface downward irradiances. In contrast, regional biases of D4strQuad are within +0.9 for TOA irradiances and –1.2 W m−2 for surface irradiances. Except for polar regions, monthly and annual global mean biases are similar, suggesting that the biases are nearly independent to season. Biases in SW heating rate profiles are up to –0.008 Kd−1 for D2strEdd and –0.016 K d−1 for D2strQuad, while the biases of the D4strQuad method are negligible.
Han, Ji-Young; Hong, Song-You; Kwon, Young CheolHan, J., S. Hong, Y. C. Kwon, 2020: The Performance of a Revised Simplified Arakawa–Schubert (SAS) Convection Scheme in the Medium-Range Forecasts of the Korean Integrated Model (KIM). Wea. Forecasting, 35(3), 1113-1128. doi: 10.1175/WAF-D-19-0219.1. The Korea Institute of Atmospheric Prediction Systems (KIAPS) has developed a new global numerical weather prediction model, named the Korean Integrated Model (KIM). This paper presents the cumulus parameterization scheme (CPS) used in KIM, which originates from the simplified Arakawa–Schubert (SAS) convection scheme in the National Centers for Environmental Prediction (NCEP) Global Forecast System (GFS) and has undergone numerous modifications in an effort to improve the medium-range forecast skill for precipitation and large-scale fields. The modifications include the following: 1) the threshold of the trigger condition is updated to consider the dependency on the environmental relative humidity (RH) averaged over the subcloud layer in order to suppress the trigger of convection in dry low-level environments; 2) the entrainment rate is modified to increase the sensitivity to environmental humidity, so that enhanced entrainment under lower RH conditions leads to a greater decrease in the strength of the convection that develops in drier environments; 3) the autoconversion parameter from cloud condensate to convective precipitation is changed to have a temperature dependency above the freezing level; 4) the closure is modified to consider rapidly varying boundary layer forcing; 5) the effect of the convection-induced pressure gradient force in convective momentum transport is enhanced in the upper part of the convective updrafts; and 6) scale awareness that enables a mass-flux CPS to work seamlessly at various grid sizes across gray-zone resolutions is addressed. The evaluation of medium-range forecasts with the KIM CPS reveals higher forecast skill, especially over the tropics, in comparison with its original version.
Hobeichi, Sanaa; Abramowitz, Gab; Contractor, Steefan; Evans, JasonHobeichi, S., G. Abramowitz, S. Contractor, J. Evans, 2020: Evaluating precipitation datasets using surface water and energy budget closure. J. Hydrometeor., (In Press). doi: 10.1175/JHM-D-19-0255.1. Evaluation of global gridded precipitation datasets typically entails using the in-situ or satellite-based data used to derive them, so that out-of-sample testing is usually not possible. Here we detail a methodology that incorporates the physical balance constraints of the surface water and energy budgets to evaluate gridded precipitation estimates, providing the capacity for out-of-sample testing. Performance conclusions are determined by the ability of precipitation products to achieve closure of the linked budgets using adjustments that are within their prescribed uncertainty bounds. We evaluate and compare five global gridded precipitation datasets: IMERG, GPCP, GPCC, REGEN, MERRA2. At the spatial level, we show that precipitation is best estimated by GPCC over the high latitudes, by GPCP over the tropics and by REGEN over North Africa and the Middle East. IMERG and REGEN appear best over Australia and South Asia. Furthermore, our results give insight into the adequacy of prescribed uncertainties of these products and shows that MERRA2, while being less competent than the other four products in estimating precipitation, has the best representation of uncertainties in its precipitation estimates. The spatial extent of our results is not only limited to grid cells with in-situ observations. Therefore, the approach enables a robust evaluation of precipitation estimates and goes some way to addressing the challenge of validation over observation scarce regions.
Hobeichi, Sanaa; Abramowitz, Gab; Contractor, Steefan; Evans, JasonHobeichi, S., G. Abramowitz, S. Contractor, J. Evans, 2020: Evaluating Precipitation Datasets Using Surface Water and Energy Budget Closure. J. Hydrometeor., 21(5), 989-1009. doi: 10.1175/JHM-D-19-0255.1. Evaluation of global gridded precipitation datasets typically entails using the in situ or satellite-based data used to derive them, so that out-of-sample testing is usually not possible. Here we detail a methodology that incorporates the physical balance constraints of the surface water and energy budgets to evaluate gridded precipitation estimates, providing the capacity for out-of-sample testing. Performance conclusions are determined by the ability of precipitation products to achieve closure of the linked budgets using adjustments that are within their prescribed uncertainty bounds. We evaluate and compare five global gridded precipitation datasets: IMERG, GPCP, GPCC, REGEN, and MERRA-2. At the spatial level, we show that precipitation is best estimated by GPCC over the high latitudes, by GPCP over the tropics, and by REGEN over North Africa and the Middle East. IMERG and REGEN appear best over Australia and South Asia. Furthermore, our results give insight into the adequacy of prescribed uncertainties of these products and shows that MERRA-2, while being less competent than the other four products in estimating precipitation, has the best representation of uncertainties in its precipitation estimates. The spatial extent of our results is not only limited to grid cells with in situ observations. Therefore, the approach enables a robust evaluation of precipitation estimates and goes some way to addressing the challenge of validation over observation scarce regions.
Hobeichi, Sanaa; Abramowitz, Gab; Evans, JasonHobeichi, S., G. Abramowitz, J. Evans, 2020: Conserving Land–Atmosphere Synthesis Suite (CLASS). J. Climate, 33(5), 1821-1844. doi: 10.1175/JCLI-D-19-0036.1. Accurate estimates of terrestrial water and energy cycle components are needed to better understand climate processes and improve models’ ability to simulate future change. Various observational estimates are available for the individual budget terms; however, these typically show inconsistencies when combined in a budget. In this work, a Conserving Land–Atmosphere Synthesis Suite (CLASS) of estimates of simultaneously balanced surface water and energy budget components is developed. Individual CLASS variable datasets, where possible, 1) combine a range of existing variable product estimates, and hence overcome the limitations of estimates from a single source; 2) are observationally constrained with in situ measurements; 3) have uncertainty estimates that are consistent with their agreement with in situ observations; and 4) are consistent with each other by being able to solve the water and energy budgets simultaneously. First, available datasets of a budget variable are merged by implementing a weighting method that accounts both for the ability of datasets to match in situ measurements and the error covariance between datasets. Then, the budget terms are adjusted by applying an objective variational data assimilation technique (DAT) that enforces the simultaneous closure of the surface water and energy budgets linked through the equivalence of evapotranspiration and latent heat. Comparing component estimates before and after applying the DAT against in situ measurements of energy fluxes and streamflow showed that modified estimates agree better with in situ observations across various metrics, but also revealed some inconsistencies between water budget terms in June over the higher latitudes. CLASS variable estimates are freely available via https://doi.org/10.25914/5c872258dc183.
Hobeichi, Sanaa; Abramowitz, Gab; Evans, JasonHobeichi, S., G. Abramowitz, J. Evans, 2020: Conserving Land–Atmosphere Synthesis Suite (CLASS). J. Climate, 33(5), 1821-1844. doi: 10.1175/JCLI-D-19-0036.1. Accurate estimates of terrestrial water and energy cycle components are needed to better understand climate processes and improve models’ ability to simulate future change. Various observational estimates are available for the individual budget terms; however, these typically show inconsistencies when combined in a budget. In this work, a Conserving Land–Atmosphere Synthesis Suite (CLASS) of estimates of simultaneously balanced surface water and energy budget components is developed. Individual CLASS variable datasets, where possible, 1) combine a range of existing variable product estimates, and hence overcome the limitations of estimates from a single source; 2) are observationally constrained with in situ measurements; 3) have uncertainty estimates that are consistent with their agreement with in situ observations; and 4) are consistent with each other by being able to solve the water and energy budgets simultaneously. First, available datasets of a budget variable are merged by implementing a weighting method that accounts both for the ability of datasets to match in situ measurements and the error covariance between datasets. Then, the budget terms are adjusted by applying an objective variational data assimilation technique (DAT) that enforces the simultaneous closure of the surface water and energy budgets linked through the equivalence of evapotranspiration and latent heat. Comparing component estimates before and after applying the DAT against in situ measurements of energy fluxes and streamflow showed that modified estimates agree better with in situ observations across various metrics, but also revealed some inconsistencies between water budget terms in June over the higher latitudes. CLASS variable estimates are freely available via https://doi.org/10.25914/5c872258dc183.
Hogikyan, Allison; Cronin, Meghan F.; Zhang, Dongxiao; Kato, SeijiHogikyan, A., M. F. Cronin, D. Zhang, S. Kato, 2020: Uncertainty in Net Surface Heat Flux due to Differences in Commonly Used Albedo Products. J. Climate, 33(1), 303-315. doi: 10.1175/JCLI-D-18-0448.1. The ocean surface albedo is responsible for the distribution of solar (shortwave) radiant energy between the atmosphere and ocean and therefore is a key parameter in Earth’s surface energy budget. In situ ocean observations typically do not measure upward reflected solar radiation, which is necessary to compute net solar radiation into the ocean. Instead, the upward component is computed from the measured downward component using an albedo estimate. At two NOAA Ocean Climate Station buoy sites in the North Pacific, the International Satellite Cloud Climatology Project (ISCCP) monthly climatological albedo has been used, while for the NOAA Global Tropical Buoy Array a constant albedo is used. This constant albedo is also used in the Coupled Ocean–Atmosphere Response Experiment (COARE) bulk flux algorithm. This study considers the impacts of using the more recently available NASA Cloud and the Earth’s Radiant Energy System (CERES) albedo product for these ocean surface heat flux products. Differences between albedo estimates in global satellite products like these imply uncertainty in the net surface solar radiation heat flux estimates that locally exceed the target uncertainty of 1.0 W m−2 for the global mean, set by the Global Climate Observing System (GCOS) of the World Meteorological Organization (WMO). Albedo has large spatiotemporal variability on hourly, monthly, and interannual time scales. Biases in high-resolution SWnet (the difference between surface downwelling and upwelling shortwave radiation) can arise if the albedo diurnal cycle is unresolved. As a result, for periods when satellite albedo data are not available it is recommended that an hourly climatology be used when computing high-resolution net surface shortwave radiation.
Hotta, Haruka; Suzuki, Kentaroh; Goto, Daisuke; Lebsock, MatthewHotta, H., K. Suzuki, D. Goto, M. Lebsock, 2020: Climate impact of cloud water inhomogeneity through microphysical processes in a global climate model. J. Climate, (In Press). doi: 10.1175/JCLI-D-19-0772.1. This study investigates how sub-grid cloud water inhomogeneity within a grid spacing of a General Circulation Model (GCM) links to the global climate through precipitation processes. The effect of the cloud inhomogeneity on autoconversion rate is incorporated into the GCM as an enhancement factor using a prognostic cloud water probability density function (PDF), which is assumed to be a truncated skewed-triangle distribution based on the total water PDF originally implemented. The PDF assumption and the factor are evaluated against those obtained by global satellite observations and simulated by a global cloud-system resolving model (GCRM). Results show that the factor implemented exerts latitudinal variations, with higher values at low latitudes, qualitatively consistent with satellite observations and the GCRM. The GCM thus validated for the sub-grid cloud inhomogeneity is then used to investigate how the characteristics of the enhancement factor affect global climate through sensitivity experiments with and without the factor incorporated. The latitudinal variation of the factor is found to have a systematic impact that reduce the cloud water and the solar reflection at low latitudes in the manner that helps mitigate the too-reflective cloud bias common among GCMs over the tropical oceans. Due to the limitation of the factor arising from the PDF assumption, however, no significant impact is found in the warm rain formation process. Finally, it is shown that the functional form for the PDF in a GCM is crucial to properly characterize the observed cloud water inhomogeneity and its relationship with precipitation.
Hotta, Haruka; Suzuki, Kentaroh; Goto, Daisuke; Lebsock, MatthewHotta, H., K. Suzuki, D. Goto, M. Lebsock, 2020: Climate Impact of Cloud Water Inhomogeneity through Microphysical Processes in a Global Climate Model. J. Climate, 33(12), 5195-5212. doi: 10.1175/JCLI-D-19-0772.1. This study investigates how subgrid cloud water inhomogeneity within a grid spacing of a general circulation model (GCM) links to the global climate through precipitation processes. The effect of the cloud inhomogeneity on autoconversion rate is incorporated into the GCM as an enhancement factor using a prognostic cloud water probability density function (PDF), which is assumed to be a truncated skewed-triangle distribution based on the total water PDF originally implemented. The PDF assumption and the factor are evaluated against those obtained by global satellite observations and simulated by a global cloud-system-resolving model (GCRM). Results show that the factor implemented exerts latitudinal variations, with higher values at low latitudes, qualitatively consistent with satellite observations and the GCRM. The GCM thus validated for the subgrid cloud inhomogeneity is then used to investigate how the characteristics of the enhancement factor affect global climate through sensitivity experiments with and without the factor incorporated. The latitudinal variation of the factor is found to have a systematic impact that reduces the cloud water and the solar reflection at low latitudes in the manner that helps mitigate the too-reflective cloud bias common among GCMs over the tropical oceans. Due to the limitation of the factor arising from the PDF assumption, however, no significant impact is found in the warm rain formation process. Finally, it is shown that the functional form for the PDF in a GCM is crucial to properly characterize the observed cloud water inhomogeneity and its relationship with precipitation.
Hou, Ning; Zhang, Xiaotong; Zhang, Weiyu; Wei, Yu; Jia, Kun; Yao, Yunjun; Jiang, Bo; Cheng, JieHou, N., X. Zhang, W. Zhang, Y. Wei, K. Jia, Y. Yao, B. Jiang, J. Cheng, 2020: Estimation of Surface Downward Shortwave Radiation over China from Himawari-8 AHI Data Based on Random Forest. Remote Sensing, 12(1), 181. doi: 10.3390/rs12010181. Downward shortwave radiation (RS) drives many processes related to atmosphere–surface interactions and has great influence on the earth’s climate system. However, ground-measured RS is still insufficient to represent the land surface, so it is still critical to generate high accuracy and spatially continuous RS data. This study tries to apply the random forest (RF) method to estimate the RS from the Himawari-8 Advanced Himawari Imager (AHI) data from February to May 2016 with a two-km spatial resolution and a one-day temporal resolution. The ground-measured RS at 86 stations of the Climate Data Center of the Chinese Meteorological Administration (CDC/CMA) are collected to evaluate the estimated RS data from the RF method. The evaluation results indicate that the RF method is capable of estimating the RS well at both the daily and monthly time scales. For the daily time scale, the evaluation results based on validation data show an overall R value of 0.92, a root mean square error (RMSE) value of 35.38 (18.40%) Wm−2, and a mean bias error (MBE) value of 0.01 (0.01%) Wm−2. For the estimated monthly RS, the overall R was 0.99, the RMSE was 7.74 (4.09%) Wm−2, and the MBE was 0.03 (0.02%) Wm−2 at the selected stations. The comparison between the estimated RS data over China and the Clouds and Earth’s Radiant Energy System (CERES) Energy Balanced and Filled (EBAF) RS dataset was also conducted in this study. The comparison results indicate that the RS estimates from the RF method have comparable accuracy with the CERES-EBAF RS data over China but provide higher spatial and temporal resolution. downward shortwave radiation; Himawari-8 AHI; multi-channel; machine learning methods; Random Forest
Hourdin, Frédéric; Rio, Catherine; Grandpeix, Jean-Yves; Madeleine, Jean-Baptiste; Cheruy, Frédérique; Rochetin, Nicolas; Jam, Arnaud; Musat, Ionela; Idelkadi, Abderrahmane; Fairhead, Laurent; Foujols, Marie-Alice; Mellul, Lidia; Traore, Abdoul-Khadre; Dufresne, Jean-Louis; Boucher, Olivier; Lefebvre, Marie-Pierre; Millour, Ehouarn; Vignon, Etienne; Jouhaud, Jean; Diallo, F. Binta; Lott, François; Gastineau, Guillaume; Caubel, Arnaud; Meurdesoif, Yann; Ghattas, JosefineHourdin, F., C. Rio, J. Grandpeix, J. Madeleine, F. Cheruy, N. Rochetin, A. Jam, I. Musat, A. Idelkadi, L. Fairhead, M. Foujols, L. Mellul, A. Traore, J. Dufresne, O. Boucher, M. Lefebvre, E. Millour, E. Vignon, J. Jouhaud, F. B. Diallo, F. Lott, G. Gastineau, A. Caubel, Y. Meurdesoif, J. Ghattas, 2020: LMDZ6A: the atmospheric component of the IPSL climate model with improved and better tuned physics. Journal of Advances in Modeling Earth Systems, (In Press). doi: 10.1029/2019MS001892. This study presents the version of the LMDZ global atmospheric model used as the atmospheric component of the Institut Pierre Simon Laplace coupled model (IPSL-CM6A-LR) to contribute to the 6th phase of the international Coupled Model Intercomparison Project (CMIP6). This LMDZ6A version includes original convective parameterizations that define the LMDZ 'New Physics’: a mass flux parameterization of the organized structures of the convective boundary layer, the 'thermal plume model', and a parameterization of the cold pools created by reevaporation of convective rainfall. The vertical velocity associated with thermal plumes and gust fronts of cold pools are used to control the triggering and intensity of deep convection. Because of several shortcomings, the early version 5B of this ‘New Physics’ was worse than the previous 'Standard Physics' version 5A regarding several classical climate metrics. To overcome these deficiencies, version 6A includes new developments: a stochastic triggering of deep convection, a modification of the thermal plume model that allows the representation of stratocumulus and cumulus clouds in a unified framework, an improved parameterization of very stable boundary layers, and the modification of the gravity waves scheme targeting the quasi biennal oscillation in the stratosphere. These improvements to the physical content and a more well-defined tuning strategy led to major improvements in the LMDZ6A version model climatology. Beyond the presentation of this particular model version and documentation of its climatology, the present paper underlines possible methodological pathways toward model improvement that can be shared across modeling groups. Climate model development; tuning
Hourdin, Frédéric; Rio, Catherine; Grandpeix, Jean-Yves; Madeleine, Jean-Baptiste; Cheruy, Frédérique; Rochetin, Nicolas; Jam, Arnaud; Musat, Ionela; Idelkadi, Abderrahmane; Fairhead, Laurent; Foujols, Marie-Alice; Mellul, Lidia; Traore, Abdoul-Khadre; Dufresne, Jean-Louis; Boucher, Olivier; Lefebvre, Marie-Pierre; Millour, Ehouarn; Vignon, Etienne; Jouhaud, Jean; Diallo, F. Binta; Lott, François; Gastineau, Guillaume; Caubel, Arnaud; Meurdesoif, Yann; Ghattas, JosefineHourdin, F., C. Rio, J. Grandpeix, J. Madeleine, F. Cheruy, N. Rochetin, A. Jam, I. Musat, A. Idelkadi, L. Fairhead, M. Foujols, L. Mellul, A. Traore, J. Dufresne, O. Boucher, M. Lefebvre, E. Millour, E. Vignon, J. Jouhaud, F. B. Diallo, F. Lott, G. Gastineau, A. Caubel, Y. Meurdesoif, J. Ghattas, 2020: LMDZ6A: the atmospheric component of the IPSL climate model with improved and better tuned physics. Journal of Advances in Modeling Earth Systems, (In Press). doi: 10.1029/2019MS001892. This study presents the version of the LMDZ global atmospheric model used as the atmospheric component of the Institut Pierre Simon Laplace coupled model (IPSL-CM6A-LR) to contribute to the 6th phase of the international Coupled Model Intercomparison Project (CMIP6). This LMDZ6A version includes original convective parameterizations that define the LMDZ 'New Physics’: a mass flux parameterization of the organized structures of the convective boundary layer, the 'thermal plume model', and a parameterization of the cold pools created by reevaporation of convective rainfall. The vertical velocity associated with thermal plumes and gust fronts of cold pools are used to control the triggering and intensity of deep convection. Because of several shortcomings, the early version 5B of this ‘New Physics’ was worse than the previous 'Standard Physics' version 5A regarding several classical climate metrics. To overcome these deficiencies, version 6A includes new developments: a stochastic triggering of deep convection, a modification of the thermal plume model that allows the representation of stratocumulus and cumulus clouds in a unified framework, an improved parameterization of very stable boundary layers, and the modification of the gravity waves scheme targeting the quasi biennal oscillation in the stratosphere. These improvements to the physical content and a more well-defined tuning strategy led to major improvements in the LMDZ6A version model climatology. Beyond the presentation of this particular model version and documentation of its climatology, the present paper underlines possible methodological pathways toward model improvement that can be shared across modeling groups. Climate model development; tuning
Hourdin, Frédéric; Rio, Catherine; Jam, Arnaud; Traore, Abdoul-Khadre; Musat, IonelaHourdin, F., C. Rio, A. Jam, A. Traore, I. Musat, 2020: Convective boundary layer control of the sea surface temperature in the tropics. Journal of Advances in Modeling Earth Systems, (In Press). doi: 10.1029/2019MS001988. Using successive versions of a global climate model, we show how convective transport to the free troposphere of the humidity evaporated at the surface, or, reciprocally, entrainment of dry air from the free troposphere into the mixed layer, controls surface evaporative cooling and then sea surface temperature. This control is as important as the radiative effect of boundary layer clouds on radiation. Those aspects are shown to be improved when activating a mass-flux representation of the organized structures of the convective boundary layer coupled to eddy diffusion, the so-called 'thermal plume model', leading to an increased near-surface drying compared to the use of turbulent diffusion alone. Controlling detrainment by air properties from just above the boundary-layer allows the thermal plume model to be valid for both cumulus and stratocumulus regimes, improving the contrast in near surface humidity between the trade winds region and East Tropical oceans. Using pairs of stand-alone atmospheric simulations forced by sea-surface temperature and of coupled atmosphere-ocean simulations, we show how the improvement of the surface fluxes that arise from this improved physics, projects into an improvement of the representation of sea surface temperature patterns in the coupled model, and in particular into a reduction of the East Tropical Ocean warm bias. The work presented here led to the bias reduction in sea surface temperature in the Institute Pierre Simon Laplace coupled model, IPSL-CM6A, developed recently for the 6th phase of the Coupled Model Intercomparison Project, CMIP6. Convective boundary layer; SST warm biases; stratocumulus clouds
Hourdin, Frédéric; Rio, Catherine; Jam, Arnaud; Traore, Abdoul-Khadre; Musat, IonelaHourdin, F., C. Rio, A. Jam, A. Traore, I. Musat, 2020: Convective Boundary Layer Control of the Sea Surface Temperature in the Tropics. Journal of Advances in Modeling Earth Systems, 12(6), e2019MS001988. doi: 10.1029/2019MS001988. Using successive versions of a global climate model, we show how convective transport to the free troposphere of the humidity evaporated at the surface or, reciprocally, entrainment of dry air from the free troposphere into the mixed layer, controls surface evaporative cooling and then sea surface temperature. This control is as important as the radiative effect of boundary layer clouds on radiation. Those aspects are shown to be improved when activating a mass flux representation of the organized structures of the convective boundary layer coupled to eddy diffusion, the so-called “thermal plume model,” leading to an increased near-surface drying compared to the use of turbulent diffusion alone. Controlling detrainment by air properties from just above the boundary layer allows the thermal plume model to be valid for both cumulus and stratocumulus regimes, improving the contrast in near-surface humidity between the trade winds region and East Tropical oceans. Using pairs of stand-alone atmospheric simulations forced by sea surface temperature and of coupled atmosphere-ocean simulations, we show how the improvement of the surface fluxes that arise from this improved physics projects into an improvement of the representation of sea surface temperature patterns in the coupled model, and in particular into a reduction of the East Tropical Ocean warm bias. The work presented here led to the bias reduction in sea surface temperature in the Institute Pierre Simon Laplace coupled model, IPSL-CM6A, developed recently for the 6th phase of the Coupled Model Intercomparison Project, CMIP6. convective boundary layer; SST warm biases; stratocumulus clouds
Hulswar, Shrivardhan; Menon, Harilal B.; Anilkumar, N.Hulswar, S., H. B. Menon, N. Anilkumar, 2020: Physical-chemical characteristics of composite aerosols in the Indian Ocean sector of the Southern Ocean and its associated effect on insolation: A climate perspective. Deep Sea Research Part II: Topical Studies in Oceanography, 104801. doi: 10.1016/j.dsr2.2020.104801. Aerosol optical depth (AOD), black carbon (BC) mass concentration, aerosol size, along with wind parameters, were derived during Southern Ocean expeditions (SOE) 7 and 8 carried out in austral summer of 2013 and 2015, with an aim to analyse the effect of aerosol on incoming solar radiation. The data were complemented with trace metals from aerosol samples of SOE-6 conducted in 2012. The AOD spectra north of 40oS followed Angstrom turbidity formulae while those in the south deviated from it. A statistically significant correlation (R2) of 0.79 (P « 0.0001) between the differences of AOD440 estimated from an Optical Properties of Aerosol and Cloud (OPAC) model and measured in situ and chlorophyll-a concentration revealed phytoplankton as a significant source of fine mode aerosols. Analysis of ten years of MODIS derived fine mode particle concentration indicated an increase as season advanced from winter to summer and a subsequent decrease towards the following winter, clearly showing a contribution from phytoplankton. BC mass concentration was found to be around 80 ng m−3. Prevalence of trace metals such as Cu, Cd and Zn and the anions SO4−4-2 and NO3−3-1 were observed in this part of the world ocean. An inverse relation was observed between Cu and phytoplankton derived SO4−4-2, indicating the detrimental effect of Cu on fine mode sulphate aerosols which are as significant as cloud condensation nuclei (CCN). The aerosol radiative forcing was found to be between 25 and –28 W m−2 to the north of the ITCZ while it was around 2–6 W m−2 in the south. The associated heating rate was from 0.05 to –0.09 and from 0.01 to –0.02 K day−1, respectively. The study revealed an increase in black carbon due to ship emissions. An increase in BC over the Southern Ocean atmosphere may have a far-reaching effect on the cloud formation and regional albedo.
Ji, Peng; Yuan, Xing; Li, DanJi, P., X. Yuan, D. Li, 2020: Atmospheric Radiative Processes Accelerate Ground Surface Warming over the Southeastern Tibetan Plateau during 1998–2013. J. Climate, 33(5), 1881-1895. doi: 10.1175/JCLI-D-19-0410.1. The Tibetan Plateau (TP), known as the world’s “Third Pole,” plays a vital role in regulating the regional and global climate and provides freshwater for about 1.5 billion people. Observations show an accelerated ground surface warming trend over the southeastern TP during the global warming slowdown period of 1998–2013, especially in the summer and winter seasons. The processes responsible for such acceleration are under debate as contributions from different radiative processes are still unknown. Here we estimate for the first time the contributions of each radiative component to the ground surface warming trend before and after 1998 by analyzing multisource datasets under an energy balance framework. Results show that declining cloud cover caused by the weakening of both the South Asian summer monsoon and local-scale atmospheric upward motion mainly led to the accelerated ground surface warming during the summers of 1998–2013, whereas the decreased surface albedo caused by the snow melting was the major warming factor in winter. Moreover, increased clear-sky longwave radiation induced by the warming middle and upper troposphere was the second largest factor, contributing to about 21%–48% of the ground surface warming trend in both the summer and winter seasons. Our results unravel the key processes driving the ground surface warming over the southeastern TP and have implications for the development of climate and Earth system models in simulating ground surface temperature change and other related complex cryosphere–hydrosphere–atmosphere interactions over high-altitude land areas.
Jian, Bida; Li, Jiming; Zhao, Yuxin; He, Yongli; Wang, Jing; Huang, JianpingJian, B., J. Li, Y. Zhao, Y. He, J. Wang, J. Huang, 2020: Evaluation of the CMIP6 planetary albedo climatology using satellite observations. Climate Dynamics, 54(11), 5145-5161. doi: 10.1007/s00382-020-05277-4. The Earth’s planetary albedo (PA) has an essential impact on the global radiation budget. Based on 14 years of monthly data from the Clouds and the Earth’s Radiant Energy System energy balanced and filled (CERES-EBAF) Ed4.1 dataset and atmosphere-only simulations of the Coupled Model Intercomparison Project Phase6 (CMIP6/AMIP), this study investigates the ability of CMIP6/AMIP model in reproducing the observed inter-month changes, annual cycle and trend of PA at near-global and regional scales. Statistical results indicate that some persistent biases in the previous models continue to exist in the CMIP6 models; however, some progresses have been made. In CMIP6/AMIP, large negative correlations for PA between the model ensemble mean and observation are addressed over the subtropical stratocumulus regions. In addition, the simulation of PA in drylands and tropical oceans remains a challenge in CMIP6 models. Over the most regions, PA biases are governed by cloud albedo forcing biases. These results demonstrate the importance of improving cloud process simulations for accurately representing the PA in models. For the annual cycles, the model ensemble mean captures the difference in amplitude between the two peak values of PA (June and December), as well as the phase of the seasonal cycle, despite PA is systematically overestimated. The differences between different terrestrial climatic regions are also examined. Results indicate that the relative biases of PA are greatest in semi-arid (2.2%) and semi-humid (2.8%) regions, whereas the minimum relative bias occurs in arid regions (0.3%) due to compensating errors.
Jin, Qinjian; Pryor, S. C.Jin, Q., S. C. Pryor, 2020: Long-term trends of high aerosol pollution events and their climatic impacts in North America using multiple satellite retrievals and MERRA-2. Journal of Geophysical Research: Atmospheres, 125(4), e2019JD031137. doi: 10.1029/2019JD031137. Mean magnitudes and temporal trends in Aerosol Optical Depth (AOD) from satellite observations and an aerosol reanalysis exhibit a negative-positive east-northwest dipole across the contiguous US with large magnitude negative trends over the eastern US while small magnitude positive trends over the northwestern states. Based on analyses of MERRA-2, the AOD reduction over the eastern US appears to be largely attributable to reductions in aerosol-sulfate, while there have been marked increases in aerosol-organic and elemental carbon over almost all of the contiguous US and particularly the northwestern states. Long-term trends of high aerosol pollution events (HAPE; days with AOD over the long-term local 90th daily AOD percentile) during 2000-2017 also indicate that over the eastern US, both the frequency and spatial scale of summer HAPEs exhibit significant negative trends, while those of moderate aerosol events (days with AOD between the local 30th and 70th AOD percentiles) exhibit weak upward trends. Opposing trends, of smaller magnitude, are derived in the north-western US and southwestern Canada. Net and shortwave solar radiation show positive trends at the surface and top of atmosphere under clear-sky conditions over the eastern US consistent with the reduction in AOD. However, skin temperatures do not indicate significant trends during all days or HAPEs, indicating that the aerosol-induced radiation trends are not sufficient to manifest trends in surface temperature. Precipitation during HAPEs appears to have increased during 2000-2017 over the eastern and central US, indicating that the reduction in aerosol may already be enhancing the precipitation through aerosol-cloud interactions. CERES; North America; MERRA2; aerosol-precipitation interaction; extreme aerosol trend; satellite retrieval
Johnson, Richard H.; Ciesielski, Paul E.Johnson, R. H., P. E. Ciesielski, 2020: Potential Vorticity Generation by West African Squall Lines. Mon. Wea. Rev., 148(4), 1691-1715. doi: 10.1175/MWR-D-19-0342.1. The West African summer monsoon features multiple, complex interactions between African easterly waves (AEWs), moist convection, variable land surface properties, dust aerosols, and the diurnal cycle. One aspect of these interactions, the coupling between convection and AEWs, is explored using observations obtained during the 2006 African Monsoon Multidisciplinary Analyses (AMMA) field campaign. During AMMA, a research weather radar operated at Niamey, Niger, where it surveilled 28 squall-line systems characterized by leading convective lines and trailing stratiform regions. Nieto Ferreira et al. found that the squall lines were linked with the passage of AEWs and classified them into two tracks, northerly and southerly, based on the position of the African easterly jet (AEJ). Using AMMA sounding data, we create a composite of northerly squall lines that tracked on the cyclonic shear side of the AEJ. Latent heating within the trailing stratiform regions produced a midtropospheric positive potential vorticity (PV) anomaly centered at the melting level, as commonly observed in such systems. However, a unique aspect of these PV anomalies is that they combined with a 400–500-hPa positive PV anomaly extending southward from the Sahara. The latter feature is a consequence of the deep convective boundary layer over the hot Saharan Desert. Results provide evidence of a coupling and merging of two PV sources—one associated with the Saharan heat low and another with latent heating—that ends up creating a prominent midtropospheric positive PV maximum to the rear of West African squall lines.
Jung, Hyun-Seok; Lee, Kyu-Tae; Zo, Il-SungJung, H., K. Lee, I. Zo, 2020: Calculation Algorithm of Upward Longwave Radiation Based on Surface Types. Asia-Pacific Journal of Atmospheric Sciences. doi: 10.1007/s13143-020-00175-5. Upward longwave radiation (ULR) is an important element for climate change analysis. We calculated ULR using land surface temperature (LST), sea surface temperature (SST), and downward longwave radiation (DLR) data from the Moderate Resolution Imaging Spectroradiometer (MODIS) and Cloud and the Earth’s Radiant Energy System (CERES), along with broadband emissivity calculated using four multiple linear regression models designed to consider specific land-cover categories along with MODIS data and reflectivity data for 241 materials from the Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER). Our broadband emissivity values were compared with those of Wang et al. Journal of Geophysical Research: Atmospheres, 110(D11), (2005); all correlation coefficients were higher than 0.90 for the period from January to December 2016, and the root mean square error (RMSE) was 0.00750–0.00825. We then calculated ULR using the broadband emissivity and compared the results with CERES data, resulting in smaller errors relative to CERES than found by Wang et al. (2005). Furthermore, the calculated ULR compared with the observational data of Baseline Surface Radiation Network (BSRN) and the resultant statistical values of R(correlation coefficient), RMSE, and bias were 0.93, 21.22 W m−2, and 0.29 respectively.
Kang, Hyoji; Choi, Yong-Sang; Hwang, Jiwon; Kim, Hye-SilKang, H., Y. Choi, J. Hwang, H. Kim, 2020: On the cloud radiative effect for tropical high clouds overlying low clouds. Geoscience Letters, 7(1), 7. doi: 10.1186/s40562-020-00156-6. Since high and low clouds ubiquitously overlie the Tropical Western Pacific (TWP) region, the cloud radiative effect (CRE) cannot be influenced by either high or low clouds, but by combinations of the clouds. This study investigates the CRE of multi-layered clouds in TWP via a radiative transfer model, Streamer. We assumed that multi-layered clouds are composed of full coverage of high clouds overlying low clouds with fractional coverage. The simulation results show that low clouds readily change CREs from positive to negative in the case of optically thin high clouds, even if the fraction of low clouds takes 10% of that of high clouds. Also, various combinations of physical properties of multi-layered high and low clouds allow more CRE variability (− 253.76 to 93.10 W m−2) than single-layered clouds do (− 101.62 to 96.95 W m−2). Even in the same conditions (total column cloud optical thickness = 15 and high cloud top pressure = 200 hPa), the multi-layer clouds have various CREs from − 180.55 to 45.64 W m−2, while the single-layer high clouds − 2.00 W m−2. These findings are also comparable with satellite observations from CERES and CALIPSO. The present study suggests that considerable uncertainty of radiative effects of high clouds over TWP can attribute to low clouds below high clouds.
Kato, Seiji; Rose, Fred G.Kato, S., F. G. Rose, 2020: Global and Regional Entropy Production by Radiation Estimated from Satellite Observations. J. Climate, 33(8), 2985-3000. doi: 10.1175/JCLI-D-19-0596.1. Vertical profiles of shortwave and longwave irradiances computed with satellite-derived cloud properties and temperature and humidity profiles from reanalysis are used to estimate entropy production. Entropy production by shortwave radiation is computed by the absorbed irradiance within layers in the atmosphere and by the surface divided by their temperatures. Similarly, entropy production by longwave radiation is computed by emitted irradiance to space from layers in the atmosphere and surface divided by their temperatures. Global annual mean entropy production by shortwave absorption and longwave emission to space are, respectively, 0.852 and 0.928 W m−2 K−1. With a steady-state assumption, entropy production by irreversible processes within the Earth system is estimated to be 0.076 W m−2 K−1 and by nonradiative irreversible processes to be 0.049 W m−2 K−1. Both global annual mean entropy productions by shortwave absorption and longwave emission to space increase with increasing shortwave absorption (i.e., with decreasing the planetary albedo). The increase of entropy production by shortwave absorption is, however, larger than the increase of entropy production by longwave emission to space. The result implies that global annual mean entropy production by irreversible processes decreases with increasing shortwave absorption. Input and output temperatures derived by dividing the absorbed shortwave irradiance and emitted longwave irradiance to space by respective entropy production are, respectively, 282 and 259 K, which give the Carnot efficiency of the Earth system of 8.5%.
Kim, Siyun; Park, Sungsu; Shin, JihoonKim, S., S. Park, J. Shin, 2020: Impact of Subgrid Variation of Water Vapor on Longwave Radiation in a General Circulation Model. Journal of Advances in Modeling Earth Systems, 12(4), e2019MS001926. doi: 10.1029/2019MS001926. Most general circulation models compute radiation fluxes by assuming that water vapor is uniform within individual grid layers, which leads to an underestimation of satellite-observed longwave (LW) cloud radiative forcing (LWCF). To fix this problem, we calculated water vapor content separately for clear and cloudy portions and used them to compute LW radiation. The impacts of this modification were examined by comparing two global simulations with and without the modification (NEW and OLD, respectively). Global-annual mean LWCF from NEW was 1.8 W m−2 higher than that of OLD, thus remedying a long-standing negative bias of LWCF. This improvement is a combined result of more clear-sky and less all-sky upward LW flux at the top of the atmosphere than OLD. Large increases in LWCF and clear-sky LW flux occurred in the tropical deep convection and midlatitude storm track regions where upper- and middle-level clouds are abundant. Although only the LW radiation scheme was modified, global-annual mean shortwave cloud radiative forcing also increased, particularly in the vicinity of the eastern subtropical marine stratocumulus decks through radiative feedback processes. With this improved treatment, it may be possible to tune general circulation models in a more flexible and physical way without introducing compensating errors. GCM; longwave radiation; longwave cloud radiative forcing; water vapor inhomogeneity
Kotsuki, Shunji; Sato, Yousuke; Miyoshi, TakemasaKotsuki, S., Y. Sato, T. Miyoshi, 2020: Data Assimilation for Climate Research: Model Parameter Estimation of Large-Scale Condensation Scheme. Journal of Geophysical Research: Atmospheres, 125(1), e2019JD031304. doi: 10.1029/2019JD031304. This study proposes using data assimilation (DA) for climate research as a tool for optimizing model parameters objectively. Mitigating radiation bias is very important for climate change assessments with general circulation models. With the Nonhydrostatic ICosahedral Atmospheric Model (NICAM), this study estimated an autoconversion parameter in a large-scale condensation scheme. We investigated two approaches to reducing radiation bias: examining useful satellite observations for parameter estimation and exploring the advantages of estimating spatially varying parameters. The parameter estimation accelerated autoconversion speed when we used liquid water path, outgoing longwave radiation, or outgoing shortwave radiation (OSR). Accelerated autoconversion reduced clouds and mitigated overestimated OSR bias of the NICAM. An ensemble-based DA with horizontal localization can estimate spatially varying parameters. When liquid water path was used, the local parameter estimation resulted in better cloud representations and improved OSR bias in regions where shallow clouds are dominant. radiation; global climate model; data assimilation; large-scale condensation; liquid water path; parameter estimation
Kratz, David P.; Gupta, Shashi K.; Wilber, Anne C.; Sothcott, Victor E.Kratz, D. P., S. K. Gupta, A. C. Wilber, V. E. Sothcott, 2020: Validation of the CERES Edition-4A Surface-Only Flux Algorithms. J. Appl. Meteor. Climatol., 59(2), 281-295. doi: 10.1175/JAMC-D-19-0068.1. Surface radiative fluxes have been derived with the objective of supplementing top-of-atmosphere (TOA) radiative fluxes being measured under NASA’s Clouds and the Earth’s Radiant Energy System (CERES) project. This has been accomplished by using combinations of CERES TOA measurements, parameterized radiative transfer algorithms, and high-quality meteorological datasets available from reanalysis projects. Current CERES footprint-level products include surface fluxes derived from two shortwave (SW) and three longwave (LW) algorithms designated as SW models A and B and LW models A, B, and C. The SW and LW models A work for clear conditions only; the other models work for both clear and cloudy conditions. The current CERES Edition-4A computed surface fluxes from all models are validated against ground-based flux measurements from high-quality surface networks like the Baseline Surface Radiation Network and NOAA’s Surface Radiation Budget Network (SURFRAD). Validation results as systematic and random errors are provided for all models, separately for five different surface types and combined for all surface types as tables and scatterplots. Validation of surface fluxes is now a part of CERES processing and is used to continually improve the above algorithms. Since both models B work for clear and cloudy conditions alike and meet the accuracy requirement, their results are considered to be the most reliable and most likely to be retained for future work. Both models A have limited use given that they work for clear skies only. Models B will continue to undergo further improvement as more validation results become available.
Laszlo, Istvan; Liu, Hongqing; Kim, Hye-Yun; Pinker, Rachel T.Laszlo, I., H. Liu, H. Kim, R. T. Pinker, 2020: Chapter 15 - Shortwave Radiation from ABI on the GOES-R Series. The GOES-R Series, 179-191. Two components of SRB, solar radiation reflected to space and solar radiation reaching the surface, are retrieved from the Advanced Baseline Imager (ABI). Physical algorithms are used that combine forward and inverse methods to estimate reflection and transmission and account for all major interactions of the radiation with the atmosphere and the surface. Owing to the improved upstream ABI cloud and aerosol product inputs, and because of availability of calibrated solar reflective bands on ABI, the two products represent an improvement in quality over legacy radiation products. Preliminary evaluation of the two products with reference data indicates that they meet expectations. Satellite; Radiation budget; Advanced Baseline Imager (ABI); Clear-sky composite; Direct path; GOES (Geostationary Operational Environmental Satellite); Indirect path; Narrow-to-broadband transformation; Shortwave; Surface; Top of atmosphere
Lehmann, Peter; Bickel, Samuel; Wei, Zhongwang; Or, DaniLehmann, P., S. Bickel, Z. Wei, D. Or, 2020: Physical constraints for improved soil hydraulic parameter estimation by pedotransfer functions. Water Resources Research, (In Press). doi: 10.1029/2019WR025963. Global land surface models use spatially distributed soil information for the parameterization of soil hydraulic properties (SHP). Parameters of measured SHP are correlated with easy-to-measure soil properties to construct general pedotransfer functions (PTFs) used to predict SHP from spatial soil information. Global PTFs are based on a limited number of samples yielding highly variable and poorly constrained SHP. The study implements a physical constraint, soil specific capillary length, to reduce unphysical combinations of SHP. The procedure fits concurrently soil water retention (SWC) and capillary length using the same parameters. Results suggest that meeting the capillary length constraint has minor effects on the goodness of fit to SWC data. Constrained SHP (CSHP) were applied to represent 4 years of lysimeter fluxes yielding evapotranspiration (ET) values in close agreement with measurements relative to slight overestimation by unconstrained SHP (USHP). The procedure was applied for testing constraint SHP at a regional scale in New Zealand using the surface evaporation capacitance (SEC) model and Noah-MP for detailed simulations of land-surface processes. The use of CSHP in both models yields higher surface runoff in agreement with observations (USHP severely underestimated runoff generation). The concept of constrained SHP could be extended to include other physical constraints to improve PTFs, for example, by consideration of vegetation cover and soil structure effects on infiltration. characteristic length; pedotransfer function; soil hydraulic properties; soil water characteristics
Lehmann, Peter; Bickel, Samuel; Wei, Zhongwang; Or, DaniLehmann, P., S. Bickel, Z. Wei, D. Or, 2020: Physical Constraints for Improved Soil Hydraulic Parameter Estimation by Pedotransfer Functions. Water Resources Research, 56(4), e2019WR025963. doi: 10.1029/2019WR025963. Global land surface models use spatially distributed soil information for the parameterization of soil hydraulic properties (SHP). Parameters of measured SHP are correlated with easy-to-measure soil properties to construct general pedotransfer functions (PTFs) used to predict SHP from spatial soil information. Global PTFs are based on a limited number of samples yielding highly variable and poorly constrained SHP. The study implements a physical constraint, soil-specific capillary length, to reduce unphysical combinations of SHP. The procedure fits concurrently soil water retention and capillary length using the same parameters. Results suggest that meeting the capillary length constraint has minor effects on the goodness of fit to soil water retention data. Constrained SHP were applied to represent 4 years of lysimeter fluxes yielding evapotranspiration values in close agreement with measurements relative to slight overestimation by unconstrained SHP. The procedure was applied for testing constraint SHP at a regional scale in New Zealand using the surface evaporation capacitance model and Noah-MP for detailed simulations of land surface processes. The use of constrained SHP in both models yields higher surface runoff in agreement with observations (unconstrained SHP severely underestimated runoff generation). The concept of constrained SHP could be extended to include other physical constraints to improve PTFs, for example, by consideration of vegetation cover and soil structure effects on infiltration. characteristic length; pedotransfer function; soil hydraulic properties; soil water characteristics
León, José Andrés PérezLeón, J., . Andrés Pérez, 2020: Progress towards assimilating cloud radar and lidar observations. ECMWF. Successful weather forecasts start from accurate estimates of the current state of the Earth system. Such estimates are obtained by combining model information with Earth system observations in a process called data assimilation. Recent work at ECMWF has demonstrated for the first time that assimilating cloud observations from satellite radar and lidar instruments into a global, operational forecasting system using a 4D-Var data assimilation system is feasible and improves weather forecasts.
Letu, Husi; Shi, Jiancheng; Li, Ming; Wang, Tianxing; Shang, Huazhe; Lei, Yonghui; Ji, Dabin; Wen, Jianguang; Yang, Kun; Chen, LiangfuLetu, H., J. Shi, M. Li, T. Wang, H. Shang, Y. Lei, D. Ji, J. Wen, K. Yang, L. Chen, 2020: A review of the estimation of downward surface shortwave radiation based on satellite data: Methods, progress and problems. Science China Earth Sciences, 63(6), 774-789. doi: 10.1007/s11430-019-9589-0. The estimation of downward surface shortwave radiation (DSSR) is important for the Earth’s energy budget and climate change studies. This review was organised from the perspectives of satellite sensors, algorithms and future trends, retrospects and summaries of the satellite-based retrieval methods of DSSR that have been developed over the past 10 years. The shortwave radiation reaching the Earth’s surface is affected by both atmospheric and land surface parameters. In recent years, studies have given detailed considerations to the factors which affect DSSR. It is important to improve the retrieval accuracy of cloud microphysical parameters and aerosols and to reduce the uncertainties caused by complex topographies and high-albedo surfaces (such as snow-covered areas) on DSSR estimation. This review classified DSSR retrieval methods into four categories: empirical, parameterisation, look-up table and machine-learning methods, and evaluated their advantages, disadvantages and accuracy. Further efforts are needed to improve the calculation accuracy of atmospheric parameters such as cloud, haze, water vapor and other land surface parameters such as albedo of complex terrain and bright surface, organically combine machine learning and other methods, use the new-generation geostationary satellite and polar orbit satellite data to produce high-resolution DSSR products, and promote the application of radiation products in hydrological and climate models.
Li, Jiandong; You, Qinglong; He, BianLi, J., Q. You, B. He, 2020: Distinctive spring shortwave cloud radiative effect and its inter-annual variation over southeastern China. Atmospheric Science Letters, 21(6), e970. doi: 10.1002/asl.970. The shortwave cloud radiative effect (SWCRE) plays a critical role in the earth's radiation balance, and its global mean magnitude is much larger than the warming effect induced by greenhouse gases. This study investigates the SWCRE at the top of the atmosphere and its inter-annual variation over southeastern China (SEC) using satellite retrievals and ERA-Interim reanalysis data. The results show that in this region the largest SWCRE with the maximum intensity up to −120 W·m−2 occurs in spring and is also the strongest between 60°S and 60°N. The domain-averaged intensity of SWCRE is much larger than the longwave cloud radiative effect (LWCRE), suggesting the dominant cooling role of SWCRE in the regional atmosphere–surface system. The spring SWCRE over SEC shows a weak increasing trend and its anomalies in most years exceed those of LWCRE during 2000–2017. This means that SWCRE also plays a dominant role in the inter-annual variation of regional cloud radiative effects. Over SEC, low- to mid-level ascending motion and water vapor convergence during spring favor the generation and maintenance of cloud water, leading to strong SWCRE. Statistical analysis shows that the spatial pattern and intensity of the spring SWCRE are well correlated with the low- to mid-level ascending motion and water vapor convergence. The temporal correlation coefficient between domain-averaged spring SWCRE and 850–500-hPa vertical velocity is .76 during 2000–2017. The long-term variation in spring SWCRE over SEC can be inferred to some extent from regional ascending motion and associated large-scale circulations. southeastern China; ascending motion; inter-annual variation; shortwave cloud radiative effect; spring
Li, Zhujun; Xu, Kuan-ManLi, Z., K. Xu, 2020: Arctic Clouds Simulated by a Multiscale Modeling Framework and Comparisons With Observations and Conventional GCMs. Journal of Geophysical Research: Atmospheres, 125(1), e2019JD030522. doi: 10.1029/2019JD030522. Clouds are an important component of the Arctic climate system through their regulation of the surface energy budget; however, Arctic clouds are poorly simulated in global climate models (GCMs). In this study, we evaluate the Arctic clouds simulated by a multiscale modeling framework (MMF). The results are compared against a merged CloudSat-CALIPSO radar-lidar cloud product and contrasted with an atmospheric reanalysis and conventional GCMs. The comparisons focus on the annual cycle of cloud covers, vertical structures of cloud fraction, and condensate mixing ratio, as well as the relationships between low-cloud cover and atmospheric static stability. The MMF is found to represent Arctic boundary layer clouds slightly more realistically than the reanalysis and GCMs in both the annual cycle and vertical distribution except that middle- and high-cloud covers are underestimated and the amplitude of annual cycle of total cloud cover is larger. The relationship between low-cloud cover and near-surface atmospheric stability produced by MMF is remarkably similar to the satellite observation during autumn, winter, and early spring, as low-cloud cover decreases with colder surface and stronger stability. Such relationships over the annual cycle are not reproduced by other modeling approaches. Lastly, MMF yields a positive correlation between low-cloud cover and atmospheric stability over the Arctic ocean from May to August, opposite to the satellite observation, implying stronger control of horizontal advection on low-cloud formation. This modeled relationship is contributed by cloud fraction near the surface, which is known to be underestimated due to radar's surface clutter.
Loeb, Norman G.; Doelling, David R.Loeb, N. G., D. R. Doelling, 2020: CERES Energy Balanced and Filled (EBAF) from Afternoon-Only Satellite Orbits. Remote Sensing, 12(8), 1280. doi: 10.3390/rs12081280. The Clouds and the Earth’s Radiant Energy System (CERES) Energy Balanced and Filled (EBAF) data product uses a diurnal correction methodology to produce a shortwave (SW) top-of-atmosphere (TOA) radiative flux time series that accounts for diurnal cycle changes between CERES observation times while ensuring that the stability of the EBAF record is tied as closely as possible to CERES instrument calibration stability. The current EBAF Ed4.1 data product combines observations from Terra and Aqua after July 2002. However, the Terra satellite will start to drift in Mean Local Time (MLT) in early 2021, and Aqua’s MLT will start to drift in 2022. To ensure the EBAF record remains temporally stable, we explore the feasibility of using only CERES instruments from afternoon satellite orbits with a tight 1330 MLT after July 2002. We test this approach by directly comparing SW TOA fluxes generated after applying diurnal corrections to Aqua-only and to Terra + Aqua for 07/2002–06/2019. We find that global climatological mean SW TOA fluxes for these two cases are within 0.01 Wm−2 and the trend of the difference is < is 0.03 Wm−2 per decade. climate; radiation budget; diurnal
Loeb, Norman G.; Rose, Fred G.; Kato, Seiji; Rutan, David A.; Su, Wenying; Wang, Hailan; Doelling, David R.; Smith, William L.; Gettelman, AndrewLoeb, N. G., F. G. Rose, S. Kato, D. A. Rutan, W. Su, H. Wang, D. R. Doelling, W. L. Smith, A. Gettelman, 2020: Toward a Consistent Definition between Satellite and Model Clear-Sky Radiative Fluxes. J. Climate, 33(1), 61-75. doi: 10.1175/JCLI-D-19-0381.1. A new method of determining clear-sky radiative fluxes from satellite observations for climate model evaluation is presented. The method consists of applying adjustment factors to existing satellite clear-sky broadband radiative fluxes that make the observed and simulated clear-sky flux definitions more consistent. The adjustment factors are determined from the difference between observation-based radiative transfer model calculations of monthly mean clear-sky fluxes obtained by ignoring clouds in the atmospheric column and by weighting hourly mean clear-sky fluxes with imager-based clear-area fractions. The global mean longwave (LW) adjustment factor is −2.2 W m−2 at the top of the atmosphere and 2.7 W m−2 at the surface. The LW adjustment factors are pronounced at high latitudes during winter and in regions with high upper-tropospheric humidity and cirrus cloud cover, such as over the west tropical Pacific, and the South Pacific and intertropical convergence zones. In the shortwave (SW), global mean adjustment is 0.5 W m−2 at TOA and −1.9 W m−2 at the surface. It is most pronounced over sea ice off of Antarctica and over heavy aerosol regions, such as eastern China. However, interannual variations in the regional SW and LW adjustment factors are small compared to those in cloud radiative effect. After applying the LW adjustment factors, differences in zonal mean cloud radiative effect between observations and climate models decrease markedly between 60°S and 60°N and poleward of 65°N. The largest regional improvements occur over the west tropical Pacific and Indian Oceans. In contrast, the impact of the SW adjustment factors is much smaller.
Loeb, Norman G.; Wang, Hailan; Allan, Richard P.; Andrews, Timothy; Armour, Kyle; Cole, Jason N. S.; Dufresne, Jean-Louis; Forster, Piers; Gettelman, Andrew; Guo, Huan; Mauritsen, Thorsten; Ming, Yi; Paynter, David; Proistosescu, Cristian; Stuecker, Malte F.; Willén, Ulrika; Wyser, KlausLoeb, N. G., H. Wang, R. P. Allan, T. Andrews, K. Armour, J. N. S. Cole, J. Dufresne, P. Forster, A. Gettelman, H. Guo, T. Mauritsen, Y. Ming, D. Paynter, C. Proistosescu, M. F. Stuecker, U. Willén, K. Wyser, 2020: New Generation of Climate Models Track Recent Unprecedented Changes in Earth's Radiation Budget Observed by CERES. Geophysical Research Letters, 47(5), e2019GL086705. doi: 10.1029/2019GL086705. We compare top-of-atmosphere (TOA) radiative fluxes observed by the Clouds and the Earth's Radiant Energy System (CERES) and simulated by seven general circulation models forced with observed sea-surface temperature (SST) and sea-ice boundary conditions. In response to increased SSTs along the equator and over the eastern Pacific (EP) following the so-called global warming “hiatus” of the early 21st century, simulated TOA flux changes are remarkably similar to CERES. Both show outgoing shortwave and longwave TOA flux changes that largely cancel over the west and central tropical Pacific, and large reductions in shortwave flux for EP low-cloud regions. A model's ability to represent changes in the relationship between global mean net TOA flux and surface temperature depends upon how well it represents shortwave flux changes in low-cloud regions, with most showing too little sensitivity to EP SST changes, suggesting a “pattern effect” that may be too weak compared to observations.
Ma, Libin; Yang, ShuangyanMa, L., S. Yang, 2020: Impacts of the stochastic multicloud parameterization on the simulation of Western North Pacific summer rainfall. Atmospheric Research, 244, 105067. doi: 10.1016/j.atmosres.2020.105067. This study investigated the sensitivity of the western North Pacific (WNP) summer precipitation to the convection schemes and discussed the associated dynamical processes. Two convection schemes were compared: one is the default mass-flux convection scheme used in the state-of-the-art ECHAM6.3 atmosphere model and the other incorporates the Stochastic Multicloud Model (SMCM) into ECHAM6.3. Incorporation of the SMCM reduces the bias of cloud cover and shortwave and longwave radiation by regulating the shortwave and longwave cloud radiative forcing over the WNP. Compared to the default model, the modified model with the SMCM alleviates the dry bias in the WNP, which is associated with enhanced ascending motion. The moist static energy balance revealed that improved simulation of precipitation in the modified model is contributed by enhanced horizontal advection of moist enthalpy and increased net energy in the atmosphere, which is attributed to increased total cloud cover, over the WNP. Additionally, intensified latent energy advection over the WNP dominates enhanced horizontal advection of moist enthalpy in the modified model. On the other hand, the moisture budget analysis of the WNP demonstrated that strengthened convergence of moisture flux in the modified model plays the most influential role in reducing precipitation bias. Further analysis unraveled that enhanced zonal-mean moisture transported by the stationary eddy zonal flow convergence in the WNP dominates intensified zonal moisture convergence, thus increased horizontal convergence of moist flux in the modified model. ECHAM6.3 atmosphere model; Moist static energy balance; Moisture budget analysis; The Stochastic Multicloud Model; The western North Pacific precipitation
Mackie, Anna; Wild, Martin; Brindley, Helen; Folini, Doris; Palmer, Paul I.Mackie, A., M. Wild, H. Brindley, D. Folini, P. I. Palmer, 2020: Observed and CMIP5-Simulated Radiative Flux Variability Over West Africa. Earth and Space Science, 7(5), e2019EA001017. doi: 10.1029/2019EA001017. We explore the ability of general circulation models in the Coupled Model Intercomparison Project (CMIP5) to recreate observed seasonal variability in top-of-the-atmosphere and surface radiation fluxes over West Africa. This tests CMIP5 models' ability to describe the radiative energy partitioning, which is fundamental to our understanding of the current climate and its future changes. We use 15 years of the monthly Clouds and the Earth's Radiant Energy System Energy Balanced and Filled (EBAF) product, alongside other satellite, reanalysis, and surface station products. We find that the CMIP5 multimodel mean is generally within the reference product range, with annual mean CMIP5 multimodel mean—EBAF of −0.5 W m−2 for top-of-the-atmosphere reflected shortwave radiation, and 4.6 W m−2 in outgoing longwave radiation over West Africa. However, the range in annual mean of the model seasonal cycles is large (37.2 and 34.0 W m−2 for reflected shortwave radiation and outgoing longwave radiation, respectively). We use seasonal and regional contrasts in all-sky fluxes to infer that the representation of the West African monsoon in numerical models affects radiative energy partitioning. Using clear-sky surface fluxes, we find that the models tend to have more downwelling shortwave and less downwelling longwave radiation than EBAF, consistent with past research. We find models that are drier and have lower aerosol loading tend to show the largest differences. We find evidence that aerosol variability has a larger effect in modulating downwelling shortwave radiation than water vapor in EBAF, while the opposite effect is seen in the majority of CMIP5 models. CMIP5; aerosols; water vapor; TOA radiation flux; West African monsoon
Mantsis, Damianos F.; Sherwood, Steven; Dixit, Vishal; Morrison, Hugh; Thompson, GregMantsis, D. F., S. Sherwood, V. Dixit, H. Morrison, G. Thompson, 2020: Mid-level clouds over the Sahara in a convection-permitting regional model. Climate Dynamics, 54(7), 3425-3439. doi: 10.1007/s00382-020-05188-4. The simulation of Saharan mid tropospheric clouds is investigated with the weather research and forecasting (WRF) regional atmospheric model at convection permitting (4 km) horizontal grid-spacing. We identify two potential problems in such simulations: one that affects cloud cover, and another that affects the mean and geographic patterns of both cloud and precipitation. Our simulations show that using a vertical grid typical of GCMs (38 levels) inhibits the formation of Saharan mid-level clouds. In particular, it underestimates the supercooled water content that often resides at the top of these clouds, in favour of ice which falls out of the cloud quickly. When the vertical resolution becomes high enough to allow layers of supercooled water and ice to exist separately, the simulation of the Saharan mid-level clouds improves significantly. Additional improvement is achieved by using realistic high resolution surface albedo, which also shows that low albedo areas favour the formation of mid-level clouds much more than high albedo ones. The simulation of precipitation on the northern edge of the Sahel is also improved with the use of realistic surface albedo. Overall, despite the disagreement of the simulated and the observed clouds, our results show that using increased resolution and realistic surface albedo seems to fully reproduce their observed radiative effect.
Marchand, Roger T; Hinkelman, Laura M.Marchand, R. T., L. M. Hinkelman, 2020: Evaluation of CERES and CloudSat Surface Radiative Fluxes over the Southern Ocean. Earth and Space Science Open Archive, 32. doi: 10.1002/essoar.10502814.1. Many studies involving surface radiative fluxes rely on surface fluxes retrieved by the Clouds and the Earth&rsquo;s Radiant Energy System (CERES) project, or derived from spaceborne cloud radar and lidar observations (CloudSat-CALIPSO). In particular, most climate models that participated in the Coupled Model Intercomparison Project Phase 5 (CMIP5) were found to have too little shortwave radiation being reflected back to space and excessive shortwave radiation reaching the surface over the Southern Ocean &ndash; an error with significant consequences for predicting both regional and global climate. There have been few evaluations of CERES or CloudSat retrievals over the Southern Ocean. In this article, CERES and CloudSat retrieved surface shortwave (SW) and longwave (LW) downwelling fluxes are evaluated using surface observations collected over the Southern Ocean during the Macquarie Island Cloud and Radiation Experiment (MICRE). Overall, biases (CERES &ndash; surface observations) in the CERES- surface fluxes are found to be slightly larger over Macquarie Island than most other regions, approximately +10 Wm for the SW and -10 Wm for the LW in the annual mean, but with significant seasonal and diurnal variations. If the Macquarie observations are representative of the larger SO, these results imply that CMIP5 model errors in SW surface fluxes are (if anything) somewhat larger than previous evaluation studies suggest. The bias in LW surface flux shows a marked increase at night, which explains most of the total LW bias. The nighttime bias is due to poor representation of cloud base associated with low clouds.
Meftah, Mustapha; Damé, Luc; Keckhut, Philippe; Bekki, Slimane; Sarkissian, Alain; Hauchecorne, Alain; Bertran, Emmanuel; Carta, Jean-Paul; Rogers, David; Abbaki, Sadok; Dufour, Christophe; Gilbert, Pierre; Lapauw, Laurent; Vieau, André-Jean; Arrateig, Xavier; Muscat, Nicolas; Bove, Philippe; Sandana, Éric; Teherani, Ferechteh; Li, Tong; Pradel, Gilbert; Mahé, Michel; Mercier, Christophe; Paskeviciute, Agne; Segura, Kevin; Berciano Alba, Alicia; Aboulila, Ahmed; Chang, Loren; Chandran, Amal; Dahoo, Pierre-Richard; Bui, AlainMeftah, M., L. Damé, P. Keckhut, S. Bekki, A. Sarkissian, A. Hauchecorne, E. Bertran, J. Carta, D. Rogers, S. Abbaki, C. Dufour, P. Gilbert, L. Lapauw, A. Vieau, X. Arrateig, N. Muscat, P. Bove, É. Sandana, F. Teherani, T. Li, G. Pradel, M. Mahé, C. Mercier, A. Paskeviciute, K. Segura, A. Berciano Alba, A. Aboulila, L. Chang, A. Chandran, P. Dahoo, A. Bui, 2020: UVSQ-SAT, a Pathfinder CubeSat Mission for Observing Essential Climate Variables. Remote Sensing, 12(1), 92. doi: 10.3390/rs12010092. The UltraViolet and infrared Sensors at high Quantum efficiency onboard a small SATellite (UVSQ-SAT) mission aims to demonstrate pioneering technologies for broadband measurement of the Earth’s radiation budget (ERB) and solar spectral irradiance (SSI) in the Herzberg continuum (200–242 nm) using high quantum efficiency ultraviolet and infrared sensors. This research and innovation mission has been initiated by the University of Versailles Saint-Quentin-en-Yvelines (UVSQ) with the support of the International Satellite Program in Research and Education (INSPIRE). The motivation of the UVSQ-SAT mission is to experiment miniaturized remote sensing sensors that could be used in the multi-point observation of Essential Climate Variables (ECV) by a small satellite constellation. UVSQ-SAT represents the first step in this ambitious satellite constellation project which is currently under development under the responsibility of the Laboratory Atmospheres, Environments, Space Observations (LATMOS), with the UVSQ-SAT CubeSat launch planned for 2020/2021. The UVSQ-SAT scientific payload consists of twelve miniaturized thermopile-based radiation sensors for monitoring incoming solar radiation and outgoing terrestrial radiation, four photodiodes that benefit from the intrinsic advantages of Ga 2 O 3 alloy-based sensors made by pulsed laser deposition for measuring solar UV spectral irradiance, and a new three-axis accelerometer/gyroscope/compass for satellite attitude estimation. We present here the scientific objectives of the UVSQ-SAT mission along the concepts and properties of the CubeSat platform and its payload. We also present the results of a numerical simulation study on the spatial reconstruction of the Earth’s radiation budget, on a geographical grid of 1 ° × 1 ° degree latitude-longitude, that could be achieved with UVSQ-SAT for different observation periods. carbon nanotubes; earth’s radiation budget; Ga2O3; nanosatellite remote sensing; photodiodes; solar–terrestrial relations; thermopiles; UV solar spectral irradiance
Myers, Timothy A.; Mechoso, Carlos R.Myers, T. A., C. R. Mechoso, 2020: Relative Contributions of Atmospheric, Oceanic, and Coupled Processes to North Pacific and North Atlantic Variability. Geophysical Research Letters, 47(5), e2019GL086321. doi: 10.1029/2019GL086321. Patterns of sea surface temperature (SST) variability over the northern oceans arise from a combination of atmospheric, oceanic, and coupled processes. Here we use a novel methodology and a suite of observations to quantify the processes contributing to the dominant patterns of interannual SST variability over these regions. We decompose the upper ocean heat content tendency associated with such dominant patterns into contributions from different heat fluxes: (a) atmospherically driven, (b) surface feedbacks, and (c) oceanic. We find that in the subtropics, cloud radiative flux, turbulent heat flux, and residual oceanic processes each contributes substantially to North Pacific SST variability, whereas turbulent heat flux primarily induces North Atlantic SST variability. Cloud radiative fluxes therefore provide a major source of interannual SST variability in the North Pacific but not in the North Atlantic. In midlatitudes, SST fluctuations over the northern oceans are driven by the combination of turbulent and oceanic heat fluxes.
Obregón, Maria A.; Costa, Maria João; Silva, Ana Maria; Serrano, AntonioObregón, M. A., M. J. Costa, A. M. Silva, A. Serrano, 2020: Spatial and Temporal Variation of Aerosol and Water Vapour Effects on Solar Radiation in the Mediterranean Basin during the Last Two Decades. Remote Sensing, 12(8), 1316. doi: 10.3390/rs12081316. This study aims to calculate and analyse the spatial and temporal variation of aerosol optical thickness (AOT) and precipitable water vapour (PWV) and their effects on solar radiation at the surface in the Mediterranean basin, one of the maritime areas with the largest aerosol loads in the world. For the achievement of this objective, a novel and validated methodology was applied. Satellite data, specifically CERES (Clouds and the Earth’s Radiant Energy System) SYN1deg products during the period 2000–2018, were used. Results show that the spatial distribution of AOT and PWV are closely linked to the spatial distributions of its effects on solar radiation. These effects are negative, indicating a reduction of solar radiation reaching the surface due to aerosol and water vapour effects. This reduction ranges between 2% and 8% for AOT, 11.5% and 15% for PWV and 14% and 20% for the combined effect. The analysis of the temporal distribution has focused on the detection of trends from their anomalies. This study has contributed to a better understanding of AOT and PWV effects on solar radiation over the Mediterranean basin, one of the most climatically sensitive regions of the planet, and highlighted the importance of water vapour. CERES; radiative effects; aerosol optical depth; Mediterranean basin; precipitable water vapour
Ollila, AnteroOllila, A., 2020: The Pause End and Major Temperature Impacts during Super El Niños are Due to Shortwave Radiation Anomalies. Physical Science International Journal, 1-20. doi: 10.9734/psij/2020/v24i230174. ENSO; climate change; El Niño; hiatus; Pause; shortwave changes
Oreopoulos, Lazaros; Cho, Nayeong; Lee, DongminOreopoulos, L., N. Cho, D. Lee, 2020: A Global Survey of Apparent Aerosol-Cloud Interaction Signals. Journal of Geophysical Research: Atmospheres, 125(1), e2019JD031287. doi: 10.1029/2019JD031287. We update and expand analysis of the apparent responses to aerosol variations of the planet's cloud regimes seen by the Moderate Resolution Imaging Spectroradiometer (MODIS). We distinguish between morning aerosol loadings and afternoon clouds and consider local scales explicitly. Aerosol loading is represented by gridded aerosol optical depth (AOD) from either MODIS or a reanalysis data set, while cloud information comes exclusively from MODIS. The afternoon cloud affected quantities (CAQs) examined in conjunction with morning AOD include precipitation and cloud radiative effect, in addition to cloud properties. One analysis thrust focuses on calculating global means distinguished by morning cloud regime, of afternoon CAQs, for distinct percentiles of grid cell seasonal morning AOD distributions. When the dependence of these global means on AOD is examined, we find persistent increases in cloud radiative fluxes with AOD as predicted by classic aerosol-cloud interaction paradigms, and also deviations from expected cloud responses, especially for precipitation. The other analysis thrust involves calculations at 1° scales of logarithmic CAQ sensitivities to AOD perturbations, approximated by linear regression slopes for distinct morning cloud regime groups. While the calculations are fundamentally local, we concentrate on the prevailing sensitivity signs in statistics of the slopes at global scales. Results from this second analysis approach indicate CAQ directions of change with AOD that are largely consistent with the first approach. When using a rather simple methodology where meteorological variables are treated as if they were CAQs, no conclusive results on the potential influence of meteorology on our findings are inferred. clouds; MODIS; aerosol; indirect effects; MERRA; satellite
Pan, Fang; Kato, Seiji; Rose, Fred G.; Radkevich, Alexander; Liu, Xu; Huang, XiangleiPan, F., S. Kato, F. G. Rose, A. Radkevich, X. Liu, X. Huang, 2020: An algorithm to derive temperature and humidity profile changes using spatially and temporally averaged spectral radiance differences. J. Atmos. Oceanic Technol.. doi: 10.1175/JTECH-D-19-0143.1. A linear inversion algorithm to derive changes of surface skin temperature and atmospheric temperature and specific humidity vertical profiles using spatially and temporally averaged spectral radiance differences is developed. The algorithm uses spectral radiative kernels, which is the top-of-atmosphere spectral radiance change caused by perturbations of skin temperature and air temperature and specific humidity in the atmosphere, and is an improved version of the algorithm used in earlier studies. Two improvements are the inclusion of the residual and cloud spectral kernels in the form of eigenvectors of principal components. Three and six eigenvectors are used for, respectively, the residual and cloud spectral kernels. An underlying assumption is that the spectral shape of the principal components is constant and their magnitude varies temporally and spatially. The algorithm is tested using synthetic spectral radiances with the spectral range of the Atmospheric Infrared Sounder averaged over 16 days and over a 10° × 10° grid box. Changes of skin temperature, air temperature and specific humidity vertical profiles are derived from the difference of nadir view all-sky spectral radiances. The root-mean-square difference of retrieved and true skin temperature differences is 0.59 K. The median of absolute errors in the air temperature change is less than 0.5 K above 925 hPa. The median of absolute errors in the relative specific humidity changes is less than 10% above 825 hPa.
Pan, Zengxin; Mao, Feiyue; Lu, Xin; Gong, Wei; Shen, Huanfeng; Mao, QingzhouPan, Z., F. Mao, X. Lu, W. Gong, H. Shen, Q. Mao, 2020: Enhancement of vertical cloud-induced radiative heating in East Asian monsoon circulation derived from CloudSat-CALIPSO observations. International Journal of Remote Sensing, 41(2), 595-614. doi: 10.1080/01431161.2019.1646935. Improving the understanding of cloud–radiation–monsoon interactions is difficult due to the limited knowledge regarding the impacts of vertical cloud radiative forcing on monsoon circulation. Here, we focus on the annual cycle of the vertical structure of cloud-induced radiative heating (CRH) to evaluate further their impacts on the East Asian monsoon circulation (100°–140° E, 20°–45° N) derived from satellite observations and reanalysis datasets. Entire troposphere and lower stratosphere are heated by vertical CRH, with the peak reaching 1 K day−1 at the mid-level troposphere (4–10 km) during summer. Although radiative warming occurs below 3 km from the prevailing stratocumulus, widespread weak radiative cooling (approximately −0.2 K day−1) occurs at a wide vertical range above 3 km during winter. Consequently, the wind vector variations resulting from vertical CRH highly coincide with the monsoon circulation, leading to the increase in wind speeds by 1.8 and 0.5 m s−1 during summer and winter, respectively, while a weakly negative influence (about 0.3 m s−1) occurs at the low-level troposphere below 3 km during winter. Although high clouds, stratiform clouds, and stratocumulus dominate these wind vector variations, deep convective clouds generate the strongest updraft (up to 7 m s−1) amongst all cloud categories despite their low occurrence frequency. Results highlight the important enhancement of vertical CRH to East Asian monsoon circulation by perturbing the vertical structure of heating rate.
Pandey, Satyendra Kumar; Vinoj, V.; Panwar, AnnuPandey, S. K., V. Vinoj, A. Panwar, 2020: The short-term variability of aerosols and their impact on cloud properties and radiative effect over the Indo-Gangetic Plain. Atmospheric Pollution Research, 11(3), 630-638. doi: 10.1016/j.apr.2019.12.017. Anthropogenic activities have been shown to have a significant effect on weather and hence climate. However, discerning them from various observations over a certain region including India has been a challenge due to the large role played by natural variability. We show that anthropogenic signals in terms of sub-weekly scale are quite significant (of the order of 20%) in aerosol loading over the Indo-Gangetic Plains. These, in turn, clouds become thinner and less reflective with weekly variations of aerosol, which indicate the possible effect of aerosol on clouds. In terms of changes to Short Wave (SW) and Long Wave (LW) radiation fluxes, we find that change in aerosol direct effect is larger during cloudy sky conditions than clear sky conditions showing that aerosol induced changes to dynamics and hence clouds are dominant factors. This is also manifested in changes to cloud macro physical properties such as cloud optical depth (COD), cloud top temperature (CTT), cloud top pressure (CTP) and liquid water path (LWP). The changes in clear-sky and all-sky top of the atmosphere aerosol direct radiative effect (DRE) and cloud radiative effect (CRE) using CERES derived fluxes were found to be ~7–10% different during weekends with respect to weekly means. Similarly, the change in longwave cloud radiative effect is double that of the shortwave CRE. Aerosol direct effect; Anthropogenic aerosols; Cloud radiative effect; Indo-Gangetic plain
Papavasileiou, Georgios; Voigt, Aiko; Knippertz, PeterPapavasileiou, G., A. Voigt, P. Knippertz, 2020: The role of observed cloud-radiative anomalies for the dynamics of the North Atlantic Oscillation on synoptic time-scales. Quarterly Journal of the Royal Meteorological Society, (In Press). doi: 10.1002/qj.3768. Clouds shape weather and climate by regulating the latent and radiative heating in the atmosphere. Recent work has demonstrated the importance of cloud-radiative effects (CRE) for the mean circulation of the extratropical atmosphere and its response to global warming. In contrast, little research has been done regarding the impact of CRE on internal variability. Here, we study how clouds and the North Atlantic Oscillation (NAO) couple on synoptic time-scales during Northern Hemisphere winter via CRE within the atmosphere (ACRE). A regression analysis based on 5-day mean data from CloudSat/CALIPSO, CERES and GERB satellite observations and ERA-Interim short-term forecast data reveals a robust dipole of high-level and low-level cloud-incidence anomalies during a positive NAO, with increased high-level cloud incidence along the storm track (near 45°N) and the subpolar Atlantic, and decreased high-level cloud incidence poleward and equatorward of this track. Opposite changes occur for low-level cloud incidence. The cloud anomalies lead to an anomalous column-mean heating from ACRE over the region of the Iceland low, and to a cooling over the region of the Azores high. To quantify the impact of the ACRE anomalies on the NAO, and to thereby test the hypothesis of a cloud-radiative feedback on the NAO persistence, we apply the surface pressure tendency equation for ERA-Interim short-term forecast data. The NAO-generated ACRE anomalies amplify the NAO-related surface pressure anomalies over the Azores high but have no area-averaged impact on the Iceland low. In contrast, diabatic processes as a whole, including latent heating and clear-sky radiation, strongly amplify the NAO-related surface pressure anomalies over both the Azores high and the Iceland low, and their impact is much more spatially coherent. This suggests that, while atmospheric cloud-radiative effects lead to an increase in NAO persistence on synoptic time-scales, their impact is relatively minor and much smaller than other diabatic processes. atmospheric cloud-radiative effects (ACRE); cloud–circulation coupling; diabatic processes; latent heating; North Atlantic Oscillation (NAO)
Papavasileiou, Georgios; Voigt, Aiko; Knippertz, PeterPapavasileiou, G., A. Voigt, P. Knippertz, 2020: The role of observed cloud-radiative anomalies for the dynamics of the North Atlantic Oscillation on synoptic time-scales. Quarterly Journal of the Royal Meteorological Society, 146(729), 1822-1841. doi: 10.1002/qj.3768. Clouds shape weather and climate by regulating the latent and radiative heating in the atmosphere. Recent work has demonstrated the importance of cloud-radiative effects (CRE) for the mean circulation of the extratropical atmosphere and its response to global warming. In contrast, little research has been done regarding the impact of CRE on internal variability. Here, we study how clouds and the North Atlantic Oscillation (NAO) couple on synoptic time-scales during Northern Hemisphere winter via CRE within the atmosphere (ACRE). A regression analysis based on 5-day mean data from CloudSat/CALIPSO, CERES and GERB satellite observations and ERA-Interim short-term forecast data reveals a robust dipole of high-level and low-level cloud-incidence anomalies during a positive NAO, with increased high-level cloud incidence along the storm track (near 45°N) and the subpolar Atlantic, and decreased high-level cloud incidence poleward and equatorward of this track. Opposite changes occur for low-level cloud incidence. The cloud anomalies lead to an anomalous column-mean heating from ACRE over the region of the Iceland low, and to a cooling over the region of the Azores high. To quantify the impact of the ACRE anomalies on the NAO, and to thereby test the hypothesis of a cloud-radiative feedback on the NAO persistence, we apply the surface pressure tendency equation for ERA-Interim short-term forecast data. The NAO-generated ACRE anomalies amplify the NAO-related surface pressure anomalies over the Azores high but have no area-averaged impact on the Iceland low. In contrast, diabatic processes as a whole, including latent heating and clear-sky radiation, strongly amplify the NAO-related surface pressure anomalies over both the Azores high and the Iceland low, and their impact is much more spatially coherent. This suggests that, while atmospheric cloud-radiative effects lead to an increase in NAO persistence on synoptic time-scales, their impact is relatively minor and much smaller than other diabatic processes. atmospheric cloud-radiative effects (ACRE); cloud–circulation coupling; diabatic processes; latent heating; North Atlantic Oscillation (NAO)
Pasut, Chiara; Tang, Fiona H. M.; Maggi, FedericoPasut, C., F. H. M. Tang, F. Maggi, 2020: A mechanistic analysis of wetland biogeochemistry in response to temperature, vegetation, and nutrient input changes. Journal of Geophysical Research: Biogeosciences, (In Press). doi: 10.1029/2019JG005437. Wetlands represent the most significant natural greenhouse gas (GHG) source and their annual emissions tightly depend on climatic and anthropogenic factors. Biogeochemical processes occurring in wetlands are still poorly described by mechanistic models and hence their dynamic response to environmental changes are weakly predicted. We investigated wetland GHG emissions, relevant electron acceptors and donors concentrations, and microbial composition resulting from changes in temperature, CH4 plant uptake efficiency, and deposition using a mechanistic biogeochemical model (here called BAMS3) that integrates the carbon (C), nitrogen (N), and sulfur (S) cycles. Parameters constraining the coupled C-N-S cycles were retrieved from controlled experiments and were validated against independent field data of CH4 emissions, and CH4 (aq) and concentration profiles in a wetland in southern Michigan, USA (Shannon & White, 1994). We found that +1.75°C increase in temperature leads to 22% and 30% increment in CH4 and N2O emissions, respectively. A decrease in the CH4 plant uptake efficiency causes the prevalent CH4 emission pathway to become diffusion-mediated and resulted in 50% increase in the daily average CH4 emissions. Finally, a decreasing deposition rate can increase CH4 emissions up to 5%. We conclude that the increasing GHG emissions from wetlands is a result of both environmental and anthropogenic causes rather than global warming alone. An increase in model complexity does not necessary improve the estimation of GHG emissions but it aids interpretation of intermediate processes to a greater detail. Modeling; Nutrients; Wetland
Pasut, Chiara; Tang, Fiona H. M.; Maggi, FedericoPasut, C., F. H. M. Tang, F. Maggi, 2020: A Mechanistic Analysis of Wetland Biogeochemistry in Response to Temperature, Vegetation, and Nutrient Input Changes. Journal of Geophysical Research: Biogeosciences, 125(4), e2019JG005437. doi: 10.1029/2019JG005437. Wetlands represent the most significant natural greenhouse gas (GHG) source and their annual emissions tightly depend on climatic and anthropogenic factors. Biogeochemical processes occurring in wetlands are still poorly described by mechanistic models and hence their dynamic response to environmental changes are weakly predicted. We investigated wetland GHG emissions, relevant electron acceptors and donors concentrations, and microbial composition resulting from changes in temperature, CH4 plant uptake efficiency, and SO deposition using a mechanistic biogeochemical model (here called BAMS3) that integrates the carbon (C), nitrogen (N), and sulfur (S) cycles. Parameters constraining the coupled C-N-S cycles were retrieved from controlled experiments and were validated against independent field data of CH4 emissions, and CH4(aq) and SO concentration profiles in a wetland in southern Michigan, USA (Shannon & White, 1994, http://hdl.handle.net/102.100.100/236252?index=1). We found that +1.75 °C increase in temperature leads to 22% and 30% increment in CH4 and N2O emissions, respectively. A decrease in the CH4 plant uptake efficiency causes the prevalent CH4 emission pathway to become diffusion mediated and resulted in 50% increase in the daily average CH4 emissions. Finally, a decreasing SO deposition rate can increase CH4 emissions up to 5%. We conclude that the increasing GHG emissions from wetlands is a result of both environmental and anthropogenic causes rather than global warming alone. An increase in model complexity does not necessary improve the estimation of GHG emissions but it aids interpretation of intermediate processes to a greater detail. modeling; nutrients; wetland
Perdigão, João; Canhoto, Paulo; Salgado, Rui; Costa, Maria JoãoPerdigão, J., P. Canhoto, R. Salgado, M. J. Costa, 2020: Assessment of Direct Normal Irradiance Forecasts Based on IFS/ECMWF Data and Observations in the South of Portugal. Forecasting, 2(2), 130-150. doi: 10.3390/forecast2020007. Direct Normal Irradiance (DNI) predictions obtained from the Integrated Forecasting System of the European Centre for Medium-Range Weather Forecast (IFS/ECMWF) were compared against ground-based observational data for one location at the south of Portugal (Évora). Hourly and daily DNI values were analyzed for different temporal forecast horizons (1 to 3 days ahead) and results show that the IFS/ECMWF slightly overestimates DNI for the period of analysis (1 August 2018 until 31 July 2019) with a fairly good agreement between model and observations. Hourly basis evaluation shows relatively high errors, independently of the forecast day. Root mean square error increases as the forecast time increases with a relative error of ~45% between the first and the last forecast. Similar patterns are observed in the daily analysis with comparable magnitude errors. The correlation coefficients between forecast and observed data are above 0.7 for both hourly and daily data. A methodology based on a new DNI attenuation Index (DAI) was developed to estimate cloud fraction from hourly values integrated over a day and, with that, to correlate the accuracy of the forecast with sky conditions. This correlation with DAI reveals that in IFS/ECMWF model, the atmosphere as being more transparent than reality since cloud cover is underestimated in the majority of the months of the year, taking the ground-based measurements as a reference. The use of the DAI estimator confirms that the errors in IFS/ECMWF are larger under cloudy skies than under clear sky. The development and application of a post-processing methodology improves the DNI predictions from the IFS/ECMWF outputs, with a decrease of error of the order of ~30%, when compared with raw data. evaluation; bias correction; Direct Normal Irradiance (DNI); DNI attenuation Index (DAI); forecast; IFS/ECMWF
Rehbein, Amanda; Rugna, Martín; Hobouchian, M. Paula; Moral³, Anna del; Goodman, Steven J.; Lindsey, Daniel T.; Thomas, JanelRehbein, A., M. Rugna, M. P. Hobouchian, A. d. Moral³, S. J. Goodman, D. T. Lindsey, J. Thomas, 2020: A Workshop on the Next Generation Environmental Satellite Constellations. Bull. Amer. Meteor. Soc., (In Press). doi: 10.1175/BAMS-D-19-0349.1.
Ridout, James A.; Barton, Neil P.; Janiga, Matthew A.; Reynolds, Carolyn A.; May, Jackie C.; Rowley, Clark; Bishop, Craig H.Ridout, J. A., N. P. Barton, M. A. Janiga, C. A. Reynolds, J. C. May, C. Rowley, C. H. Bishop, 2020: Surface Radiative Flux Bias Reduction through Regionally Varying Cloud Fraction Parameter Nudging in a Global Coupled Forecast System. Journal of Advances in Modeling Earth Systems, (In Press). doi: 10.1029/2019MS002006. Key Points: A method is presented to nudge a cloud fraction parameter in a global coupled forecast system to reduce surface net shortwave flux biases. Results from a series of 45-day test forecasts are presented demonstrating the efficacy of the approach. Further tests are required to determine operational applicability using a suitable near real-time source of surface radiative flux data. cloud parameterization; coupled modelling; parameter adjustment; surface radiation budget
Righi, Mattia; Andela, Bouwe; Eyring, Veronika; Lauer, Axel; Predoi, Valeriu; Schlund, Manuel; Vegas-Regidor, Javier; Bock, Lisa; Brötz, Björn; Mora, Lee de; Diblen, Faruk; Dreyer, Laura; Drost, Niels; Earnshaw, Paul; Hassler, Birgit; Koldunov, Nikolay; Little, Bill; Loosveldt Tomas, Saskia; Zimmermann, KlausRighi, M., B. Andela, V. Eyring, A. Lauer, V. Predoi, M. Schlund, J. Vegas-Regidor, L. Bock, B. Brötz, L. d. Mora, F. Diblen, L. Dreyer, N. Drost, P. Earnshaw, B. Hassler, N. Koldunov, B. Little, S. Loosveldt Tomas, K. Zimmermann, 2020: Earth System Model Evaluation Tool (ESMValTool) v2.0 – technical overview. Geoscientific Model Development, 13(3), 1179-1199. doi: 10.5194/gmd-13-1179-2020. Abstract. This paper describes the second major release of the Earth System Model Evaluation Tool (ESMValTool), a community diagnostic and performance metrics tool for the evaluation of Earth system models (ESMs) participating in the Coupled Model Intercomparison Project (CMIP). Compared to version 1.0, released in 2016, ESMValTool version 2.0 (v2.0) features a brand new design, with an improved interface and a revised preprocessor. It also features a significantly enhanced diagnostic part that is described in three companion papers. The new version of ESMValTool has been specifically developed to target the increased data volume of CMIP Phase 6 (CMIP6) and the related challenges posed by the analysis and the evaluation of output from multiple high-resolution or complex ESMs. The new version takes advantage of state-of-the-art computational libraries and methods to deploy an efficient and user-friendly data processing. Common operations on the input data (such as regridding or computation of multi-model statistics) are centralized in a highly optimized preprocessor, which allows applying a series of preprocessing functions before diagnostics scripts are applied for in-depth scientific analysis of the model output. Performance tests conducted on a set of standard diagnostics show that the new version is faster than its predecessor by about a factor of 3. The performance can be further improved, up to a factor of more than 30, when the newly introduced task-based parallelization options are used, which enable the efficient exploitation of much larger computing infrastructures. ESMValTool v2.0 also includes a revised and simplified installation procedure, the setting of user-configurable options based on modern language formats, and high code quality standards following the best practices for software development.
Righi, Mattia; Hendricks, Johannes; Lohmann, Ulrike; Beer, Christof Gerhard; Hahn, Valerian; Heinold, Bernd; Heller, Romy; Krämer, Martina; Ponater, Michael; Rolf, Christian; Tegen, Ina; Voigt, ChristianeRighi, M., J. Hendricks, U. Lohmann, C. G. Beer, V. Hahn, B. Heinold, R. Heller, M. Krämer, M. Ponater, C. Rolf, I. Tegen, C. Voigt, 2020: Coupling aerosols to (cirrus) clouds in the global EMAC-MADE3 aerosol–climate model. Geoscientific Model Development, 13(3), 1635-1661. doi: 10.5194/gmd-13-1635-2020. Abstract. A new cloud microphysical scheme including a detailed parameterization for aerosol-driven ice formation in cirrus clouds is implemented in the global ECHAM/MESSy Atmospheric Chemistry (EMAC) chemistry–climate model and coupled to the third generation of the Modal Aerosol Dynamics model for Europe adapted for global applications (MADE3) aerosol submodel. The new scheme is able to consistently simulate three regimes of stratiform clouds – liquid, mixed-, and ice-phase (cirrus) clouds – considering the activation of aerosol particles to form cloud droplets and the nucleation of ice crystals. In the cirrus regime, it allows for the competition between homogeneous and heterogeneous freezing for the available supersaturated water vapor, taking into account different types of ice-nucleating particles, whose specific ice-nucleating properties can be flexibly varied in the model setup. The new model configuration is tuned to find the optimal set of parameters that minimizes the model deviations with respect to observations. A detailed evaluation is also performed comparing the model results for standard cloud and radiation variables with a comprehensive set of observations from satellite retrievals and in situ measurements. The performance of EMAC-MADE3 in this new coupled configuration is in line with similar global coupled models and with other global aerosol models featuring ice cloud parameterizations. Some remaining discrepancies, namely a high positive bias in liquid water path in the Northern Hemisphere and overestimated (underestimated) cloud droplet number concentrations over the tropical oceans (in the extratropical regions), which are both a common problem in these kinds of models, need to be taken into account in future applications of the model. To further demonstrate the readiness of the new model system for application studies, an estimate of the anthropogenic aerosol effective radiative forcing (ERF) is provided, showing that EMAC-MADE3 simulates a relatively strong aerosol-induced cooling but within the range reported in the Intergovernmental Panel on Climate Change (IPCC) assessments.
Rind, D.; Orbe, C.; Jonas, J.; Nazarenko, L.; Zhou, T.; Kelley, M.; Lacis, A.; Shindell, D.; Faluvegi, G.; Romanou, A.; Russell, G.; Tausnev, N.; Bauer, M.; Schmidt, G.Rind, D., C. Orbe, J. Jonas, L. Nazarenko, T. Zhou, M. Kelley, A. Lacis, D. Shindell, G. Faluvegi, A. Romanou, G. Russell, N. Tausnev, M. Bauer, G. Schmidt, 2020: GISS Model E2.2: A Climate Model Optimized for the Middle Atmosphere. Model Structure, Climatology, Variability and Climate Sensitivity. Journal of Geophysical Research: Atmospheres, (In Press). doi: 10.1029/2019JD032204. We introduce a new climate model (GISS E2.2) that has been specially optimized for the Middle Atmosphere, and whose output is being contributed to the CMIP6 archive. The top of the model is at a geopotential altitude of 89 km, and parameterizations of moist convection and various forms of gravity wave drag based on tropospheric processes are chosen specifically for this optimization. We first evaluate the model in its configuration as a coupled atmosphere-chemistry model with respect to its simulation of the mean state of the Middle Atmosphere, from the mesosphere down through the Upper Troposphere/Lower Stratosphere. Then we assess its use as a coupled atmosphere-ocean climate model by exploring its mean ocean climatology. To evaluate its variability, we report on its simulation of the primary modes in the troposphere, stratosphere and ocean. Two climate change simulations are presented, the responses to instantaneous increases of 2xCO2 and 4xCO2, run with two different ocean models. Sensitivity studies are performed to illustrate the effect of parameterizations on the model results. We compare these results to the lower vertical resolution/top GISS Model E2.1, whose output has also been submitted to CMIP6. The different choices made for these models are explored. It is shown that important improvements in the circulation above and below the tropopause can be obtained when attention is paid to representation of Middle Atmosphere processes in climate model development. Climate Model; Middle Atmosphere; Model Development
Rind, D.; Orbe, C.; Jonas, J.; Nazarenko, L.; Zhou, T.; Kelley, M.; Lacis, A.; Shindell, D.; Faluvegi, G.; Romanou, A.; Russell, G.; Tausnev, N.; Bauer, M.; Schmidt, G.Rind, D., C. Orbe, J. Jonas, L. Nazarenko, T. Zhou, M. Kelley, A. Lacis, D. Shindell, G. Faluvegi, A. Romanou, G. Russell, N. Tausnev, M. Bauer, G. Schmidt, 2020: GISS Model E2.2: A Climate Model Optimized for the Middle Atmosphere—Model Structure, Climatology, Variability, and Climate Sensitivity. Journal of Geophysical Research: Atmospheres, 125(10), e2019JD032204. doi: 10.1029/2019JD032204. We introduce a new climate model (GISS E2.2) that has been specially optimized for the middle atmosphere and whose output is being contributed to the CMIP6 archive. The top of the model is at a geopotential altitude of 89 km, and parameterizations of moist convection and various forms of gravity wave drag based on tropospheric processes are chosen specifically for this optimization. We first evaluate the model in its configuration as a coupled atmosphere-chemistry model with respect to its simulation of the mean state of the middle atmosphere, from the mesosphere down through the upper troposphere/lower stratosphere. Then we assess its use as a coupled atmosphere-ocean climate model by exploring its mean ocean climatology. To evaluate its variability, we report on its simulation of the primary modes in the troposphere, stratosphere, and ocean. Two climate change simulations are presented, the responses to instantaneous increases of 2xCO2 and 4xCO2, run with two different ocean models. Sensitivity studies are performed to illustrate the effect of parameterizations on the model results. We compare these results to the lower vertical resolution/top GISS Model E2.1, whose output has also been submitted to CMIP6. The different choices made for these models are explored. It is shown that important improvements in the circulation above and below the tropopause can be obtained when attention is paid to representation of middle atmosphere processes in climate model development. climate model; model development; middle atmosphere
Roehrig, Romain; Beau, Isabelle; Saint‐Martin, David; Alias, Antoinette; Decharme, Bertrand; Guérémy, Jean-Francois; Voldoire, Aurore; Younous, Abdel-Lathif Ahmat; Bazile, Eric; Belamari, Sophie; Blein, Sébastien; Bouniol, Dominique; Bouteloup, Yves; Cattiaux, Julien; Chauvin, Fabrice; Chevallier, Matthieu; Colin, Jeanne; Douville, Hervé; Marquet, Pascal; Michou, Martine; Nabat, Pierre; Oudar, Thomas; Peyrillé, Philippe; Piriou, Jean-Marcel; Melia, David Salas y; Séférian, Roland; Sénési, StéphaneRoehrig, R., I. Beau, D. Saint‐Martin, A. Alias, B. Decharme, J. Guérémy, A. Voldoire, A. A. Younous, E. Bazile, S. Belamari, S. Blein, D. Bouniol, Y. Bouteloup, J. Cattiaux, F. Chauvin, M. Chevallier, J. Colin, H. Douville, P. Marquet, M. Michou, P. Nabat, T. Oudar, P. Peyrillé, J. Piriou, D. S. y. Melia, R. Séférian, S. Sénési, 2020: The CNRM global atmosphere model ARPEGE-Climat 6.3: description and evaluation. Journal of Advances in Modeling Earth Systems, (In Press). doi: 10.1029/2020MS002075. keypoints The version 6.3 of the ARPEGE-Climat atmospheric model includes an increased vertical resolution and a major update of the moist physics Improvements include radiation, cloud and precipitation climatology, daily rainfall distribution and water discharge at major river outlets Weaknesses still include biases in low clouds and some dynamical fields, while the West African monsoon is a new model deficiency
Salazar, Germán; Gueymard, Christian; Galdino, Janis Bezerra; de Castro Vilela, Olga; Fraidenraich, NaumSalazar, G., C. Gueymard, J. B. Galdino, O. de Castro Vilela, N. Fraidenraich, 2020: Solar irradiance time series derived from high-quality measurements, satellite-based models, and reanalyses at a near-equatorial site in Brazil. Renewable and Sustainable Energy Reviews, 117, 109478. doi: 10.1016/j.rser.2019.109478. This study analyzes five years of 1-min solar global horizontal irradiance (GHI) and direct normal irradiance (DNI) observations obtained at Petrolina (northeast Brazil). Quality-assured hourly and daily averages are obtained after applying filters and methodologies based on a Baseline Solar Radiation Network (BSRN) quality-control procedure. To calculate correct hourly averages, a minimum fraction of 20% of valid GHI or DNI minutely data is needed, as well as at least 60% of valid days to calculate correct daily-mean monthly values. An asymmetric diurnal pattern is found in GHI and DNI during all months, attributed to consistently higher cloudiness in the morning. The quality-assured hourly and monthly-mean GHI and DNI time series are compared to estimates from 11 solar databases regularly used in solar resource assessment studies: CAMS, CERES, ERA5, INPE, MERRA-2, Meteonorm, NASA-POWER, NSRDB, SARAH, SWERA-BR, and SWERA-US. For hourly GHI values, a range of RMS differences is found between the best (CAMS, 17.3%) and the worst (MERRA-2, 38.9%) results. The latter database is also affected by a larger bias (18.7%) than CAMS (4%). Larger RMS differences are found with hourly DNI, in a range extending from 37% (CAMS) to 63.4% (ERA5). Biases are all above 12%, except for CERES (−1%). For long-term mean-monthly GHI results, low biases of less than 1% are obtained with CAMS, CERES and NASA-POWER, whereas MERRA-2 overestimates (13%). Larger biases are found for mean-monthly DNI, spanning between CAMS (3%) and Meteonorm (−18.4%). Overall, CAMS appears the most consistent solar database for long-term irradiance time series at Petrolina. The significant differences found here between modeled databases are larger than expected, and underline the importance of regional validation studies like this one to decrease the incidence of uncertainties in solar resource assessments on the design and performance of solar energy projects. Data quality control; Solar resource assessment; Validation; Solar irradiance; Data gaps
Sayago, Silvina; Ovando, Gustavo; Almorox, Javier; Bocco, MónicaSayago, S., G. Ovando, J. Almorox, M. Bocco, 2020: Daily solar radiation from NASA-POWER product: assessing its accuracy considering atmospheric transparency. International Journal of Remote Sensing, 41(3), 897-910. doi: 10.1080/01431161.2019.1650986. Satellite remote sensing in estimating solar energy budget components at the top of the atmosphere (TOA) level and at the terrestrial level plays a very important role in various types of applications. Solar radiation data are especially problematic because of a quite generalized lack of sufficient data in quantity and quality. Satellite images allow solving the problem of continuity or lack of solar radiation data. The objective of this work was to fit daily solar radiation from NASA-POWER (National Aeronautics and Space Administration – Prediction Of Worldwide Energy Resources), considering different intervals of atmospheric transparency index. The accuracy was assessed from the analysis of voluminous data-sets registered by meteorological ground stations, 31 in number, located in whole Spain, during the period from 2000 to 2017. Clearness index (KT) was calculated to define nine classes of cloud cover conditions. The study reveals that the degree of correlation between the satellite data and observatory data depends upon atmospheric conditions and the correlation accuracy improves for higher values of KT. The coefficients of determination (R2), considering all KT values, were between 0.85 and 0.96; particularly for clear days R2 = 0.96 and root-mean-square error equal to 1.78 MJ m−2 d−1 were obtained. Geographically, the better statistic values were located in the central region of the country. NASA-POWER shows potential to estimate solar radiation and that it is an important information resource for different applications.
Schifano, Luca; Smeesters, Lien; Geernaert, Thomas; Berghmans, Francis; Dewitte, StevenSchifano, L., L. Smeesters, T. Geernaert, F. Berghmans, S. Dewitte, 2020: Design and Analysis of a Next-Generation Wide Field-of-View Earth Radiation Budget Radiometer. Remote Sensing, 12(3), 425. doi: 10.3390/rs12030425. Climate on Earth is determined by the Earth Radiation Budget (ERB), which quantifies the incoming and outgoing radiative energy fluxes. The ERB can be monitored by non-scanning wide field-of-view radiometers, or by scanning narrow field-of-view radiometers. We propose an enhanced design for the wide field-of-view radiometer, with as key features the use of a near-spherical cavity to obtain a uniform angular sensitivity and the integration of the shuttered electrical substitution principle, eliminating long term drifts of the radiometer and improving its time response. The target absolute accuracy is 1 W/m 2 and the target stability is 0.1 W/m 2 per decade for the measurement of the total outgoing Earth’s radiation. In order to increase the spatial resolution and to separate the total outgoing radiation into reflected Solar and emitted thermal radiation, we propose the joint use of the radiometer with wide field-of-view Shortwave (400–900 nm) and Longwave (8–14 μm) cameras. This paper presents the concept and design of the novel wide field-of-view radiometer, including simulations and analyses of its expected performance. We focus on mechanical design and the measurement characteristics based on optical and thermal analyses. In combination with the cameras, we obtain an estimated accuracy of 0.44 W/m 2 . Earth Radiation Budget; radiometer; Earth Energy Imbalance; optical modelling; space instrumentation; thermal modelling
Schwarz, M.; Folini, D.; Yang, S.; Allan, R. P.; Wild, M.Schwarz, M., D. Folini, S. Yang, R. P. Allan, M. Wild, 2020: Changes in atmospheric shortwave absorption as important driver of dimming and brightening. Nature Geoscience, 13(2), 110-115. doi: 10.1038/s41561-019-0528-y. Changes in the atmospheric absorption of shortwave radiation, probably through cloud and aerosol effects, is the main reason for the dimming and brightening over China and Europe in past decades, according to co-located surface and space observations.
Shell, Karen M.; de Szoeke, Simon P.; Makiyama, Michael; Feng, ZheShell, K. M., S. P. de Szoeke, M. Makiyama, Z. Feng, 2020: Vertical Structure of Radiative Heating Rates of the MJO during DYNAMO. J. Climate, 33(12), 5317-5335. doi: 10.1175/JCLI-D-19-0519.1. The vertical structure of radiative heating rates over the region of the tropical Indian Ocean associated with the MJO during the DYNAMO/ARM MJO Investigation Experiment is presented. The mean and variability of heating rates during active, suppressed, and disturbed phases are determined from the Pacific Northwest National Laboratory Combined Remote Sensing Retrieval (CombRet) from Gan Island, Maldives (0.69°S, 73.15°E). TOA and surface fluxes from the CombRet product are compared with collocated 3-hourly CERES SYN1deg Ed4A satellite retrievals. The fluxes are correlated in time with correlation coefficients around 0.9, yet CombRet time-mean OLR is 15 W m−2 larger. Previous work has suggested that CombRet undersamples high clouds, due to signal attenuation by low-level clouds and reduced instrument sensitivity with altitude. However, mean OLR differs between CombRet and CERES for all values of OLR, not just the lowest values corresponding to widespread high clouds. The discrepancy peaks for midrange OLR, suggestive of precipitating, towering cumulus convective clouds, rather than stratiform cirrus clouds. Low biases in the cloud-top height of thick clouds substantially contribute to the overestimate of OLR by CombRet. CombRet data are used to generate composite shortwave and longwave atmospheric heating rate profiles as a function of the local OLR. Although there is considerable variability in CombRet not directly related to OLR, the time–height structure of mean heating rate composites generated using OLR as the interpolant is broadly representative of tropical convective variability on intraseasonal time scales.
Shell, Karen M.; de Szoeke, Simon P.; Makiyama, Michael; Feng, ZheShell, K. M., S. P. de Szoeke, M. Makiyama, Z. Feng, 2020: Vertical Structure of Radiative Heating Rates of the MJO during DYNAMO. J. Climate, (In Press). doi: 10.1175/JCLI-D-19-0519.1. The vertical structure of radiative heating rates over the region of the tropical Indian Ocean associated with the MJO during the DYNAMO/ARM MJO Investigation Experiment is presented. The mean and variability of heating rates during active, suppressed, and disturbed phases are determined from the Pacific Northwest National Laboratory combined remote sensing retrieval (CombRet) from Gan Island, Maldives (0.69° S, 73.15° E). TOA and surface fluxes from the CombRet product are compared with collocated three-hourly CERES SYN1deg Ed4A satellite retrievals. The fluxes are correlated in time with correlation coefficients around 0.9, yet CombRet time-mean OLR is 15 W m−2 larger. Previous work has suggested that CombRet under-samples high clouds, due to signal attenuation by low-level clouds and reduced instrument sensitivity with altitude. However, mean OLR differs between CombRet and CERES for all values of OLR, not just the lowest values corresponding to widespread high clouds. The discrepancy peaks for mid-range OLR, suggestive of precipitating, towering cumulus convective clouds, rather than stratiform cirrus clouds. Low biases in the cloud-top height of thick clouds substantially contribute to the overestimate of OLR by CombRet. CombRet data is used to generate composite shortwave and longwave atmospheric heating rate profiles as a function of the local OLR. Though there is considerable variability in CombRet not directly related to OLR, the time-height structure of mean heating rate composites generated using OLR as the interpolant is broadly representative of tropical convective variability on intraseasonal time scales.
Shi, Tenglong; Pu, Wei; Zhou, Yue; Cui, Jiecan; Zhang, Daizhou; Wang, XinShi, T., W. Pu, Y. Zhou, J. Cui, D. Zhang, X. Wang, 2020: Albedo of Black Carbon-contaminated Snow across Northwestern China and The Validation with Model Simulation. Journal of Geophysical Research: Atmospheres, (In Press). doi: 10.1029/2019JD032065. Light-absorbing particles (LAPs) in snow can significantly reduce the snow albedo. Quantification of the influence of black carbon (BC), one of the most important LAPs, on snow albedo is essential for understanding the budgets of solar radiation on snow-covered areas. We measured BC concentration in snow at 28 sites and snow albedo at 18 sites in a vast region across northwestern China in January 2018. The BC concentration was in a wide range of 40–1850 ng g–1. The presence of the BC reduced the snow albedo by 0.01–0.20 at the visible wavelength band (400–750 nm). The reduction differed from sites to sites with large values close to industrial areas that are characterized by high pollutants emission. Albedos simulated with a Snow, Ice, and Aerosol Radiation (SNICAR) model based on the measured BC agreed well with the measured albedos, with the deviation within ±0.03 and the average underestimation of
Shi, Tenglong; Pu, Wei; Zhou, Yue; Cui, Jiecan; Zhang, Daizhou; Wang, XinShi, T., W. Pu, Y. Zhou, J. Cui, D. Zhang, X. Wang, 2020: Albedo of Black Carbon-Contaminated Snow Across Northwestern China and the Validation With Model Simulation. Journal of Geophysical Research: Atmospheres, 125(9), e2019JD032065. doi: 10.1029/2019JD032065. Light-absorbing particles in snow can significantly reduce the snow albedo. Quantification of the influence of black carbon (BC), one of the most important light-absorbing particles, on snow albedo is essential for understanding the budgets of solar radiation on snow-covered areas. We measured BC concentration in snow at 28 sites and snow albedo at 18 sites in a vast region across northwestern China in January 2018. The BC concentration was in a wide range of 40–1,850 ng g−1. The presence of the BC reduced the snow albedo by 0.01–0.20 at the visible wavelength band (400–750 nm). The reduction differed from sites to sites with large values close to industrial areas that are characterized by high pollutants emission. Albedos simulated with a Snow, Ice, and Aerosol Radiation model based on the measured BC agreed well with the measured albedos, with the deviation within ±0.03 and the average underestimation of
Shukla, Ravi P.; Huang, BohuaShukla, R. P., B. Huang, 2020: Cumulative Influence of Summer Subsurface Soil Temperature on North America Surface Temperature in the CFSv2. Journal of Geophysical Research: Atmospheres, 125(6), e2019JD031899. doi: 10.1029/2019JD031899. Analyzing a long simulation and a set of seasonal reforecasts of the Climate Forecast System version 2 (CFSv2), this study demonstrates a large model cold bias in the deep soil layer (100–200 cm) over most of North America continent during summer due to weaker seasonal change in summer. The summer subsurface temperature (SUBT) cold bias influences the land surface temperature (LST) during the summer and subsequent seasons in different ways over different geographical regions in North America: West of the Rocky Mountains, the SUBT's effect on LST is largely overruled by the stronger upstream marine influence from the Pacific. Over the central Great Plains, however, it is a major cause for severe cold LST bias during summer in the model simulation and reforecasts. As a result, model underestimates sensible heat flux into the atmosphere but overestimates latent heat flux. The latter may contribute to an excessive summer rainfall in the region. Over the northeast region, the SUBT cold bias persists to August and September, which causes an additional surface cooling in the fall and helps to bring LST to the freezing point early. This sets up the stage for a prolonged snow-albedo feedback. In particular, the model long simulation that passes through previous summer and fall demonstrates longer persistence of snow cover over the northeast region than reforecasts initialized in late winter and spring do. A cold bias of the water temperature in the North Atlantic seems also to play a role to prolong cold bias in the northeast region. NCEP CFSv2; snow-albedo feedback; subsurface soil temperature; deep soil layer (100–200 cm); North America continent; simulation and seasonal reforecasts
Sorooshian, Armin; Corral, Andrea F.; Braun, Rachel A.; Cairns, Brian; Crosbie, Ewan; Ferrare, Richard; Hair, Johnathan; Kleb, Mary M.; Mardi, Ali Hossein; Maring, Hal; McComiskey, Allison; Moore, Richard; Painemal, David; Scarino, Amy Jo; Schlosser, Joseph; Shingler, Taylor; Shook, Michael; Wang, Hailong; Zeng, Xubin; Ziemba, Luke; Zuidema, PaquitaSorooshian, A., A. F. Corral, R. A. Braun, B. Cairns, E. Crosbie, R. Ferrare, J. Hair, M. M. Kleb, A. H. Mardi, H. Maring, A. McComiskey, R. Moore, D. Painemal, A. J. Scarino, J. Schlosser, T. Shingler, M. Shook, H. Wang, X. Zeng, L. Ziemba, P. Zuidema, 2020: Atmospheric Research Over the Western North Atlantic Ocean Region and North American East Coast: A Review of Past Work and Challenges Ahead. Journal of Geophysical Research: Atmospheres, 125(6), e2019JD031626. doi: 10.1029/2019JD031626. Decades of atmospheric research have focused on the Western North Atlantic Ocean (WNAO) region because of its unique location that offers accessibility for airborne and ship measurements, gradients in important atmospheric parameters, and a range of meteorological regimes leading to diverse conditions that are poorly understood. This work reviews these scientific investigations for the WNAO region, including the East Coast of North America and the island of Bermuda. Over 50 field campaigns and long-term monitoring programs, in addition to 715 peer-reviewed publications between 1946 and 2019 have provided a firm foundation of knowledge for these areas. Of particular importance in this region has been extensive work at the island of Bermuda that is host to important time series records of oceanic and atmospheric variables. Our review categorizes WNAO atmospheric research into eight major categories, with some studies fitting into multiple categories (relative %): Aerosols (25%), Gases (24%), Development/Validation of Techniques, Models, and Retrievals (18%), Meteorology and Transport (9%), Air-Sea Interactions (8%), Clouds/Storms (8%), Atmospheric Deposition (7%), and Aerosol-Cloud Interactions (2%). Recommendations for future research are provided in the categories highlighted above. Atlantic Ocean; Aerosol; Cloud; ACTIVATE; Deposition; Gas
Stengel, Martin; Stapelberg, Stefan; Sus, Oliver; Finkensieper, Stephan; Würzler, Benjamin; Philipp, Daniel; Hollmann, Rainer; Poulsen, Caroline; Christensen, Matthew; McGarragh, GregoryStengel, M., S. Stapelberg, O. Sus, S. Finkensieper, B. Würzler, D. Philipp, R. Hollmann, C. Poulsen, M. Christensen, G. McGarragh, 2020: Cloud_cci Advanced Very High Resolution Radiometer post meridiem (AVHRR-PM) dataset version 3: 35-year climatology of global cloud and radiation properties. Earth System Science Data, 12(1), 41-60. doi: 10.5194/essd-12-41-2020. Abstract. We present version 3 of the Cloud_cci Advanced Very High Resolution Radiometer post meridiem (AVHRR-PM) dataset, which contains a comprehensive set of cloud and radiative flux properties on a global scale covering the period of 1982 to 2016. The properties were retrieved from AVHRR measurements recorded by the afternoon (post meridiem – PM) satellites of the National Oceanic and Atmospheric Administration (NOAA) Polar Operational Environmental Satellite (POES) missions. The cloud properties in version 3 are of improved quality compared with the precursor dataset version 2, providing better global quality scores for cloud detection, cloud phase and ice water path based on validation results against A-Train sensors. Furthermore, the parameter set was extended by a suite of broadband radiative flux properties. They were calculated by combining the retrieved cloud properties with thermodynamic profiles from reanalysis and surface properties. The flux properties comprise upwelling and downwelling and shortwave and longwave broadband fluxes at the surface (bottom of atmosphere – BOA) and top of atmosphere (TOA). All fluxes were determined at the AVHRR pixel level for all-sky and clear-sky conditions, which will particularly facilitate the assessment of the cloud radiative effect at the BOA and TOA in future studies. Validation of the BOA downwelling fluxes against the Baseline Surface Radiation Network (BSRN) shows a very good agreement. This is supported by comparisons of multi-annual mean maps with NASA's Clouds and the Earth's Radiant Energy System (CERES) products for all fluxes at the BOA and TOA. The Cloud_cci AVHRR-PM version 3 (Cloud_cci AVHRR-PMv3) dataset allows for a large variety of climate applications that build on cloud properties, radiative flux properties and/or the link between them. For the presented Cloud_cci AVHRR-PMv3 dataset a digital object identifier has been issued: https://doi.org/10.5676/DWD/ESA_Cloud_cci/AVHRR-PM/V003 (Stengel et al., 2019).
Su, Wenying; Minnis, Patrick; Liang, Lusheng; Duda, David P.; Khlopenkov, Konstantin; Thieman, Mandana M.; Yu, Yinan; Smith, Allan; Lorentz, Steven; Feldman, Daniel; Valero, Francisco P. J.Su, W., P. Minnis, L. Liang, D. P. Duda, K. Khlopenkov, M. M. Thieman, Y. Yu, A. Smith, S. Lorentz, D. Feldman, F. P. J. Valero, 2020: Determining the daytime Earth radiative flux from National Institute of Standards and Technology Advanced Radiometer (NISTAR) measurements. Atmospheric Measurement Techniques, 13(2), 429-443. doi: https://doi.org/10.5194/amt-13-429-2020. Abstract. The National Institute of Standards and Technology Advanced Radiometer (NISTAR) onboard the Deep Space Climate Observatory (DSCOVR) provides continuous full-disk global broadband irradiance measurements over most of the sunlit side of the Earth. The three active cavity radiometers measure the total radiant energy from the sunlit side of the Earth in shortwave (SW; 0.2–4 µm), total (0.4–100 µm), and near-infrared (NIR; 0.7–4 µm) channels. The Level 1 NISTAR dataset provides the filtered radiances (the ratio between irradiance and solid angle). To determine the daytime top-of-atmosphere (TOA) shortwave and longwave radiative fluxes, the NISTAR-measured shortwave radiances must be unfiltered first. An unfiltering algorithm was developed for the NISTAR SW and NIR channels using a spectral radiance database calculated for typical Earth scenes. The resulting unfiltered NISTAR radiances are then converted to full-disk daytime SW and LW flux by accounting for the anisotropic characteristics of the Earth-reflected and emitted radiances. The anisotropy factors are determined using scene identifications determined from multiple low-Earth orbit and geostationary satellites as well as the angular distribution models (ADMs) developed using data collected by the Clouds and the Earth's Radiant Energy System (CERES). Global annual daytime mean SW fluxes from NISTAR are about 6 % greater than those from CERES, and both show strong diurnal variations with daily maximum–minimum differences as great as 20 Wm−2 depending on the conditions of the sunlit portion of the Earth. They are also highly correlated, having correlation coefficients of 0.89, indicating that they both capture the diurnal variation. Global annual daytime mean LW fluxes from NISTAR are 3 % greater than those from CERES, but the correlation between them is only about 0.38.
Subba, Tamanna; Gogoi, Mukunda M.; Pathak, Binita; Bhuyan, Pradip K.; Babu, S. SureshSubba, T., M. M. Gogoi, B. Pathak, P. K. Bhuyan, S. S. Babu, 2020: Recent trend in the global distribution of aerosol direct radiative forcing from satellite measurements. Atmospheric Science Letters, (In Press). doi: 10.1002/asl.975. Global distribution of aerosol direct radiative forcing (DRF) is estimated using Clouds and Earth's Radiant Energy System (CERES) synoptic (SYN) 1° datasets. During 2001–2017, a statistically significant change of global DRFs is revealed with a general decreasing trend (i.e., a reduced cooling effect) at the top of the atmosphere (DRFTOA 0.017 W⋅m−2⋅year−1) and at the surface (DRFSFC 0.033 W⋅m−2⋅year−1) with rapid change over the land compared to the global ocean. South Asia and Africa/Middle East regions depict significant increasing trend of atmospheric warming by 0.025 and 0.002 W·m−2⋅year−1 whereas, the rest of the regions show a decline. These regional variations significantly modulate the global mean DRF (−5.36 ± 0.04 W·m−2 at the TOA and − 9.64 ± 0.07 W·m−2 at the surface during the study period). The observed DRF trends are coincident with the change in the underlying aerosol properties, for example, aerosol optical depth, Ångström exponent and partly due to the increasing columnar burden of SO2 over some of the regions. This indicates that increasing industrialization and urbanization have caused prominent change in the DRF during recent decades. aerosol optical depth; angstrom exponent; global aerosol radiative forcing; trend
Suseno, Dwi Prabowo Yuga; Yamada, Tomohito J.Suseno, D. P. Y., T. J. Yamada, 2020: Simulating Flash Floods Using Geostationary Satellite-Based Rainfall Estimation Coupled with a Land Surface Model. Hydrology, 7(1), 9. doi: 10.3390/hydrology7010009. Clarifying hydrologic behavior, especially behavior related to extreme events such as flash floods, is vital for flood mitigation and management. However, discharge and rainfall measurement data are scarce, which is a major obstacle to flood mitigation. This study: (i) simulated flash floods on a regional scale using three types of rainfall forcing implemented in a land surface model; and (ii) evaluated and compared simulated flash floods with the observed discharge. The three types of rainfall forcing were those observed by the Automated Meteorological Data Acquisition System (AMeDAS) (Simulation I), the observed rainfall from the Ministry of Land, Infrastructure and Transportation (MLIT) (Simulation II), and the estimated rainfall from the Multi-purpose Transport Satellite (MTSAT), which was downscaled by AMeDAS rainfall (Simulation III). MLIT rainfall observations have a denser station network over the Ishikari River basin (spacing of approximately 10 km) compared with AMeDAS (spacing of approximately 20 km), so they are expected to capture the rainfall spatial distribution more accurately. A land surface model, the Minimal Advance Treatments of Surface Interaction and Runoff (MATSIRO), was implemented for the flash flood simulation. The river flow simulations were run over the Ishikari river basin at a 1-km grid resolution and a 1-h temporal resolution during August 2010. The statistical performance of the river flow simulations during a flash flood event on 23 and 24 August 2010 demonstrated that Simulation I was reasonable compared with Simulation III. The findings also suggest that the advantages of the MTSAT-based estimated rainfall (i.e., good spatial distribution) can be coupled with the benefit of direct AMeDAS observations (i.e., representation of the true rainfall). MTSAT; flash flood; heavy rainfall; LSM
Thomas, Christopher M.; Dong, Bo; Haines, KeithThomas, C. M., B. Dong, K. Haines, 2020: Inverse modelling of global and regional energy and water cycle fluxes using Earth observation data. J. Climate, 33(5), 1707–1723. doi: 10.1175/JCLI-D-19-0343.1. The NASA Energy and Water Cycle Study (NEWS) climatology is a self–consistent coupled annual and seasonal cycle solution for radiative, turbulent and water fluxes over the Earth’s surface using Earth observation data covering 2000–2009. Here we seek to improve the NEWS solution, particularly over the ocean basins, by considering spatial covariances in the observation errors (some evidence for which is found by comparing five turbulent flux products over the oceans) and by introducing additional horizontal transports from ocean reanalyses as weak constraints. By explicitly representing large error covariances between surface heat flux components over the major ocean basins we retain the flux contrasts present in the original data and infer additional heat losses over the North Atlantic, more consistent with a strong Atlantic overturning. This change does not alter the global flux balance but if only the errors in evaporation and precipitation are correlated then those fluxes experience larger adjustments (e.g. the surface latent heat flux increases to 85±2 Wm−2). Replacing SeaFlux v1 with J-OFURO v3 ocean fluxes also leads to a considerable increase in the global latent heat loss as well as a larger North Atlantic heat loss. Furthermore, including a weak constraint on the horizontal transports of heat and freshwater from high-resolution ocean reanalyses improves the net fluxes over the North Atlantic, Caribbean and Arctic Oceans, without any impact on the global flux balances. These results suggest that better characterised flux uncertainties can greatly improve the quality of the optimised flux solution.
Thorsen, Tyler J.; Ferrare, Richard A.; Kato, Seiji; Winker, David M.Thorsen, T. J., R. A. Ferrare, S. Kato, D. M. Winker, 2020: Aerosol direct radiative effect sensitivity analysis. J. Climate, (In Press). doi: 10.1175/JCLI-D-19-0669.1. To both reconcile the large range in satellite-based estimates of the aerosol direct radiative effect (DRE) and to optimize the design of future observing systems, this study builds a framework for assessing aerosol DRE uncertainty. Shortwave aerosol DRE radiative kernels (Jacobians) were derived using the MERRA-2 reanalysis data. These radiative kernels give the differential response of the aerosol DRE to perturbations in the aerosol extinction coefficient, aerosol single scattering albedo, aerosol asymmetry factor, surface albedo, cloud fraction, and cloud optical depth. This comprehensive set of kernels provides a convenient way to consistently and accurately assess the aerosol DRE uncertainties that result from observational or model-based uncertainties. The aerosol DRE kernels were used to test the effect of simplifying the full vertical profile of aerosol scattering properties into column-integrated quantities. This analysis showed that while the clear-sky aerosol DRE can be had fairly accurately, more significant errors occur in the all-sky. The sensitivity in determining the broadband spectral dependencies of the aerosol scattering properties directly from a limited set of wavelengths was quantified. These spectral dependencies can be reasonably constrained using column-integrated aerosol scattering properties in the mid-visible and near infrared. Separating the aerosol DRE and its kernels by scene type shows that accurate aerosol properties in the clear-sky are the most crucial component of the global aerosol DRE. In cloudy skies, determining aerosol properties in the presence of optically-thin cloud is more radiatively important than doing so when optically thick cloud is present.
Tian, Jingjing; Dong, Xiquan; Xi, Baike; Feng, ZheTian, J., X. Dong, B. Xi, Z. Feng, 2020: Characteristics of Ice Cloud–Precipitation of Warm Season Mesoscale Convective Systems over the Great Plains. J. Hydrometeor., 21(2), 317-334. doi: 10.1175/JHM-D-19-0176.1. In this study, the mesoscale convective systems (MCSs) are tracked using high-resolution radar and satellite observations over the U.S. Great Plains during April–August from 2010 to 2012. The spatiotemporal variability of MCS precipitation is then characterized using the Stage IV product. We found that the spatial variability and nocturnal peaks of MCS precipitation are primarily driven by the MCS occurrence rather than the precipitation intensity. The tracked MCSs are further classified into convective core (CC), stratiform rain (SR), and anvil clouds regions. The spatial variability and diurnal cycle of precipitation in the SR regions of MCSs are not as significant as those of MCS precipitation. In the SR regions, the high-resolution, long-term ice cloud microphysical properties [ice water content (IWC) and ice water paths (IWPs)] are provided. The IWCs generally decrease with height. Spatially, the IWC, IWP, and precipitation are all higher over the southern Great Plains than over the northern Great Plains. Seasonally, those ice and precipitation properties are all higher in summer than in spring. Comparing the peak timings of MCS precipitation and IWPs from the diurnal cycles and their composite evolutions, it is found that when using the peak timing of IWPSR as a reference, the heaviest precipitation in the MCS convective core occurs earlier, while the strongest SR precipitation occurs later. The shift of peak timings could be explained by the stratiform precipitation formation process. The IWP and precipitation relationships are different at MCS genesis, mature, and decay stages. The relationships and the transition processes from ice particles to precipitation also depend on the low-level humidity.
Tomasi, Claudio; Petkov, Boyan H.; Lupi, Angelo; Mazzola, Mauro; Lanconelli, Christian; Gultepe, IsmailTomasi, C., B. H. Petkov, A. Lupi, M. Mazzola, C. Lanconelli, I. Gultepe, 2020: Radiation in the Arctic Atmosphere and Atmosphere – Cryosphere Feedbacks. Physics and Chemistry of the Arctic Atmosphere, 591-672. Arctic surface temperature has been increasing at a rate 2–3 times that of the global average in the last half century. Enhanced warming of the Arctic, or Arctic Amplification, is a climatic response to external forcing. Despite good results obtained by climatic models for the globe, the largest intermodel differences in surface temperature warming are found in the Arctic. The magnitude of this warming drives many different processes and determines the evolution of many climatic parameters such as clouds, sea ice extent, and land ice sheet mass. The Arctic Amplification can be attributed to the peculiar feedback processes that are triggered in the Arctic. Most of these processes include radiation interaction with the atmosphere and with the surface, all of them contributing to the radiation budget. It is then mandatory to correctly evaluate this budget both at the surface and at the top of the atmosphere and in the solar and thermal spectra. This can be done using both direct observations, from ground and from space, and model simulation via radiation transfer codes. This last approach need many observed input parameters anyhow.In this contribution results on the evaluation of the radiation budget in the Arctic are first reviewed. Follows a detailed description of the effects of the most important atmospheric gases (carbon dioxide, methane, ozone etc.) on both shortwave and longwave radiation ranges. The same is illustrated for aerosol loading in the Arctic, based on a large dataset of aerosol radiative properties measured by means of sun-photometers in numerous Arctic stations. Finally, the effect of the surface reflectivity characteristics on the radiation budget is illustrated by means of albedo models specific for the Arctic. Aerosols; Arctic amplification; Albedo; Radiation budget; Feedback processes; Greenhouse gas; Reflectivity
Unglaub, Claudia; Block, Karoline (ORCID:0000000244582327); Mülmenstädt, Johannes (ORCID:0000000311056678); Sourdeval, Odran (ORCID:0000000228225303); Quaas, Johannes (ORCID:000000017057194X)Unglaub, C., K. Block, J. Mülmenstädt, O. Sourdeval, J. Quaas, 2020: A new classification of satellite-derived liquid water cloud regimes at cloud scale. Atmospheric Chemistry and Physics (Online), 20(4). doi: 10.5194/acp-20-2407-2020. The U.S. Department of Energy's Office of Scientific and Technical Information
Vargas Zeppetello, Lucas R.; Battisti, David S.; Baker, Marcia B.Vargas Zeppetello, L. R., D. S. Battisti, M. B. Baker, 2020: A New Look at the Variance of Summertime Temperatures Over Land. J. Climate, (In Press). doi: 10.1175/JCLI-D-19-0887.1. The increasing frequency of very high summertime temperatures has motivated growing interest in the processes determining the probability distribution of surface temperature over land. Here, we show that on monthly time scales, temperature anomalies can be modeled as linear responses to fluctuations in shortwave radiation and precipitation. Our model contains only three adjustable parameters, and, surprisingly, these can be taken as constant across the globe, notwithstanding large spatial variability in topography, vegetation, and hydrological processes. Using observations of shortwave radiation and precipitation from 2000-2017, the model accurately reproduces the observed pattern of temperature variance throughout the Northern Hemisphere midlatitudes. In addition, the variance in latent heat flux estimated by the model agrees well with the few long-term records that are available in the central U.S. As an application of the model, we investigate the changes in the variance of monthly averaged surface temperature that might be expected due to anthropogenic climate change. We find that a climatic warming of 4°C causes a 10% increase in temperature variance in parts of North America.
Vargas Zeppetello, Lucas R.; Battisti, David S.; Baker, Marcia B.Vargas Zeppetello, L. R., D. S. Battisti, M. B. Baker, 2020: A New Look at the Variance of Summertime Temperatures over Land. J. Climate, 33(13), 5465-5477. doi: 10.1175/JCLI-D-19-0887.1. The increasing frequency of very high summertime temperatures has motivated growing interest in the processes determining the probability distribution of surface temperature over land. Here, we show that on monthly time scales, temperature anomalies can be modeled as linear responses to fluctuations in shortwave radiation and precipitation. Our model contains only three adjustable parameters, and, surprisingly, these can be taken as constant across the globe, notwithstanding large spatial variability in topography, vegetation, and hydrological processes. Using observations of shortwave radiation and precipitation from 2000 to 2017, the model accurately reproduces the observed pattern of temperature variance throughout the Northern Hemisphere midlatitudes. In addition, the variance in latent heat flux estimated by the model agrees well with the few long-term records that are available in the central United States. As an application of the model, we investigate the changes in the variance of monthly averaged surface temperature that might be expected due to anthropogenic climate change. We find that a climatic warming of 4°C causes a 10% increase in temperature variance in parts of North America.
Vielberg, Kristin; Kusche, JürgenVielberg, K., J. Kusche, 2020: Extended forward and inverse modeling of radiation pressure accelerations for LEO satellites. Journal of Geodesy, 94(4), 43. doi: 10.1007/s00190-020-01368-6. For low Earth orbit (LEO) satellites, activities such as precise orbit determination, gravity field retrieval, and thermospheric density estimation from accelerometry require modeled accelerations due to radiation pressure. To overcome inconsistencies and better understand the propagation of modeling errors into estimates, we here suggest to extend the standard analytical LEO radiation pressure model with emphasis on removing systematic errors in time-dependent radiation data products for the Sun and the Earth. Our extended unified model of Earth radiation pressure accelerations is based on hourly CERES SYN1deg data of the Earth’s outgoing radiation combined with angular distribution models. We apply this approach to the GRACE (Gravity Recovery and Climate Experiment) data. Validations with 1 year of calibrated accelerometer measurements suggest that the proposed model extension reduces RMS fits between 5 and 27%, depending on how measurements were calibrated. In contrast, we find little changes when implementing, e.g., thermal reradiation or anisotropic reflection at the satellite’s surface. The refined model can be adopted to any satellite, but insufficient knowledge of geometry and in particular surface properties remains a limitation. In an inverse approach, we therefore parametrize various combinations of possible systematic errors to investigate estimability and understand correlations of remaining inconsistencies. Using GRACE-A accelerometry data, we solve for corrections of material coefficients and CERES fluxes separately over ocean and land. These results are encouraging and suggest that certain physical radiation pressure model parameters could indeed be determined from satellite accelerometry data.
Wang, Dongdong; Liang, Shunlin; Zhang, Yi; Gao, Xueyuan; Brown, Meredith G. L.; Jia, AolinWang, D., S. Liang, Y. Zhang, X. Gao, M. G. L. Brown, A. Jia, 2020: A New Set of MODIS Land Products (MCD18): Downward Shortwave Radiation and Photosynthetically Active Radiation. Remote Sensing, 12(1), 168. doi: 10.3390/rs12010168. Surface downward shortwave radiation (DSR) and photosynthetically active radiation (PAR), its visible component, are key parameters needed for many land process models and terrestrial applications. Most existing DSR and PAR products were developed for climate studies and therefore have coarse spatial resolutions, which cannot satisfy the requirements of many applications. This paper introduces a new global high-resolution product of DSR (MCD18A1) and PAR (MCD18A2) over land surfaces using the MODIS data. The current version is Collection 6.0 at the spatial resolution of 5 km and two temporal resolutions (instantaneous and three-hour). A look-up table (LUT) based retrieval approach was chosen as the main operational algorithm so as to generate the products from the MODIS top-of-atmosphere (TOA) reflectance and other ancillary data sets. The new MCD18 products are archived and distributed via NASA’s Land Processes Distributed Active Archive Center (LP DAAC). The products have been validated based on one year of ground radiation measurements at 33 Baseline Surface Radiation Network (BSRN) and 25 AmeriFlux stations. The instantaneous DSR has a bias of −15.4 W/m2 and root mean square error (RMSE) of 101.0 W/m2, while the instantaneous PAR has a bias of −0.6 W/m2 and RMSE of 45.7 W/m2. RMSE of daily DSR is 32.3 W/m2, and that of the daily PAR is 13.1 W/m2. The accuracy of the new MODIS daily DSR data is higher than the GLASS product and lower than the CERES product, while the latter incorporates additional geostationary data with better capturing DSR diurnal variability. MCD18 products are currently under reprocessing and the new version (Collection 6.1) will provide improved spatial resolution (1 km) and accuracy. validation; MODIS; downward shortwave radiation; satellite product; solar radiation; photosynthetically active radiation
Wang, Tianxing; Shi, Jiancheng; Ma, Ya; Letu, Husi; Li, XingcaiWang, T., J. Shi, Y. Ma, H. Letu, X. Li, 2020: All-sky longwave downward radiation from satellite measurements: General parameterizations based on LST, column water vapor and cloud top temperature. ISPRS Journal of Photogrammetry and Remote Sensing, 161, 52-60. doi: 10.1016/j.isprsjprs.2020.01.011. Remotely sensed surface longwave downward radiation (LWDR) plays an essential role in studying the surface energy budget and greenhouse effect. Most existing satellite-based methods or products depend on variables that are not readily available from space such as, liquid water path, air temperature, vapor pressure and/or cloud-base temperature etc., which seriously restrict the wide applications of satellite data. In this paper, new nonlinear parameterizations and a machine learning-based model for deriving all-sky LWDR are proposed based only on land surface temperature (LST), column water vapor and cloud-top temperature (CTT), that are relatively readily available day and night for most satellite missions. It is the first time to incorporate the CTT in the parameterizations for estimating LWDR under the cloudy-sky conditions. The results reveal that the new models work well and can derive all-sky global LWDR with reasonable accuracies (RMSE  CERES; Land surface temperature; Cloud-top temperature; Cloudy-sky; Column water vapor; Surface longwave downward radiation
Wang, Yanyu; Lyu, Rui; Xie, Xin; Meng, Ze; Huang, Meijin; Wu, Junshi; Mu, Haizhen; Yu, Qiu-Run; He, Qianshan; Cheng, TiantaoWang, Y., R. Lyu, X. Xie, Z. Meng, M. Huang, J. Wu, H. Mu, Q. Yu, Q. He, T. Cheng, 2020: Retrieval of gridded aerosol direct radiative forcing based on multiplatform datasets. Atmospheric Measurement Techniques, 13(2), 575-592. doi: 10.5194/amt-13-575-2020. Abstract. Atmospheric aerosols play a crucial role in regional radiative budgets. Previous studies on clear-sky aerosol direct radiative forcing (ADRF) have mainly been limited to site-scale observations or model simulations for short-term cases, and long-term distributions of ADRF in China have not been portrayed yet. In this study, an accurate fine-resolution ADRF estimate at the surface was proposed. Multiplatform datasets, including satellite (MODIS aboard Terra and Aqua) and reanalysis datasets, served as inputs to the Santa Barbara Discrete Atmospheric Radiative Transfer (SBDART) model for ADRF simulation with consideration of the aerosol vertical profile over eastern China during 2000–2016. Specifically, single-scattering albedo (SSA) from the Modern-Era Retrospective Analysis for Research and Application, Version 2 (MERRA-2) was validated with sun photometers over eastern China. The gridded asymmetry parameter (ASY) was then simulated by matching the calculated top-of-atmosphere (TOA) radiative fluxes from the radiative transfer model with satellite observations (Clouds and the Earth's Radiant Energy System, CERES). The high correlation and small discrepancy (6–8 W m−2) between simulated and observed radiative fluxes at three sites (Baoshan, Fuzhou, and Yong'an) indicated that ADRF retrieval is feasible and has high accuracy over eastern China. Then this method was applied in each grid of eastern China, and the overall picture of ADRF distributions over eastern China during 2000–2016 was displayed. ADRF ranges from −220 to −20 W m−2, and annual mean ADRF is −100.21 W m−2, implying that aerosols have a strong cooling effect at the surface in eastern China. With the economic development and rapid urbanization, the spatiotemporal changes of ADRF during the past 17 years are mainly attributed to the changes of anthropogenic emissions in eastern China. Our method provides the long-term ADRF distribution over eastern China for the first time, highlighting the importance of aerosol radiative impact under climate change.
Whitburn, Simon; Clarisse, Lieven; Bauduin, Sophie; George, Maya; Hurtmans, Daniel; Safieddine, Sarah; Coheur, Pierre François; Clerbaux, CathyWhitburn, S., L. Clarisse, S. Bauduin, M. George, D. Hurtmans, S. Safieddine, P. F. Coheur, C. Clerbaux, 2020: Spectrally resolved fluxes from IASI data: Retrieval algorithm for clear-sky measurements. J. Climate, (In Press). doi: 10.1175/JCLI-D-19-0523.1. Space-based measurements of the Outgoing Longwave Radiation (OLR) are essential for the study of the Earth’s climate system. While the CERES instrument provides accurate measurements of this quantity, its measurements are not spectrally resolved. Here we present a high-resolution OLR product (sampled at 0.25 cm-1), derived from measurements of the IASI satellite sounder. The applied methodology relies on pre-calculated Angular Dependent Models (ADMs). These are usually calculated for ten to hundreds of different scene types (characterized by surface and atmosphere parameters). To guarantee accurate results in the range 645-2300 cm-1 covered by IASI, we constructed ADMs for over 140,000 scenes. These were selected from one year of CAMS reanalysis data. A dissimilarity-based selection algorithm was applied to choose these scenes as different from each other as possible, thereby maximizing the performance on real data, whilst keeping the number of scenes manageable. A comparison of the IASI OLR integrated over the 645-2300 cm-1 range was performed with the longwave broadband OLR products from CERES and the AIRS instrument. The latter are systematically higher due to the contribution of the far infrared to the total IR spectral range, but as expected exhibit generally high spatial correlations with the IASI OLR, except for some areas in the tropical region. We also compared the IASI OLR against the spectrally resolved OLR derived from AIRS. A good agreement was found above 1200 cm-1 while AIRS OLR appeared to be systematically higher in the atmospheric window region, likely related to differences in overpass time or to the use of a different cloud detection algorithm.
Williams, K. D.; Hewitt, A. J.; Bodas‐Salcedo, A.Williams, K. D., A. J. Hewitt, A. Bodas‐Salcedo, 2020: Use of Short-Range Forecasts to Evaluate Fast Physics Processes Relevant for Climate Sensitivity. Journal of Advances in Modeling Earth Systems, 12(4), e2019MS001986. doi: 10.1029/2019MS001986. The configuration of the Met Office Unified Model being submitted to CMIP6 has a high climate sensitivity. Previous studies have suggested that the impact of model changes on initial tendencies in numerical weather prediction (NWP) should be used to guide their suitability for inclusion in climate models. In this study we assess, using NWP experiments, the atmospheric model changes which lead to the increased climate sensitivity in the CMIP6 configuration, namely, the replacement of the aerosol scheme with GLOMAP-mode and the introduction of a scheme for representing the turbulent production of liquid water within mixed-phase cloud. Overall, the changes included in this latest configuration were found to improve the initial tendencies of the model state variables over the first 6 hr of the forecast, this timescale being before significant dynamical feedbacks are likely to occur. The reduced model drift through the forecast appears to be the result of increased cloud liquid water, leading to enhanced radiative cooling from cloud top and contributing to a stronger shortwave cloud radiative effect. These changes improve the 5-day forecast in traditional metrics used for numerical weather prediction. This study was conducted after the model was frozen and the climate sensitivity of the model determined; hence, it provides an independent test of the model changes contributing to the higher climate sensitivity. The results, along with the large body process-orientated evaluation conducted during the model development process, provide reassurance that these changes are improving the physical processes simulated by the model.
Wu, Dong L.; Lee, Jae Nyung; Kim, Kyu-Myong; Lim, Young-KwonWu, D. L., J. N. Lee, K. Kim, Y. Lim, 2020: Interannual Variations of TOA Albedo over the Arctic, Antarctic and Tibetan Plateau in 2000–2019. Remote Sensing, 12(9), 1460. doi: 10.3390/rs12091460. Recent changes in Earth’s climate system have significantly affected the radiation budget and its year-to-year variations at top of the atmosphere (TOA). Observing high-latitude TOA fluxes is still challenging from space, because spatial inhomogeneity of surface/atmospheric radiative processes and spectral variability can reflect sunlight very differently. In this study we analyze the 20-year TOA flux and albedo data from CERES and MISR over the Arctic, the Antarctic, and Tibetan Plateau (TP), and found overall great consistency in the TOA albedo trend and interannual variations. The observations reveal a lagged correlation between the Arctic and subarctic albedo fluctuations. The observed year-to-year variations are further used to evaluate the reanalysis data, which exhibit substantial shortcomings in representing the polar TOA flux variability. The observed Arctic flux variations are highly correlated with cloud fraction (CF), except in the regions where CF > 90% or where the surface is covered by ice. An empirical orthogonal function (EOF) analysis shows that the first five EOFs can account for ~50% of the Arctic TOA variance, whereas the correlation with climate indices suggests that Sea Ice Extent (SIE), North Atlantic Oscillation (NAO) and 55°N–65°N cloudiness are the most influential processes in driving the TOA flux variabilities. albedo; shortwave radiation; 4-year oscillation; interannual variations; lagged correlation; top of the atmosphere
Yang, Dazhi; Bright, Jamie M.Yang, D., J. M. Bright, 2020: Worldwide validation of 8 satellite-derived and reanalysis solar radiation products: A preliminary evaluation and overall metrics for hourly data over 27 years. Solar Energy, (In Press). doi: 10.1016/j.solener.2020.04.016. Gridded solar radiation products, namely satellite-derived irradiance and reanalysis irradiance, are key to the next-generation solar resource assessment and forecasting. Since their accuracies are generally lower than that of the ground-based measurements, providing validation of the gridded solar radiation products is necessary in order to understand their qualities and characteristics. This article delivers a worldwide validation of hourly global horizontal irradiance derived from satellite imagery and reanalysis. The accuracies of 6 latest satellite-derived irradiance products (CAMS-RAD, NSRDB, SARAH-2, SARAH-E, CERES-SYN1deg, and Solcast) and 2 latest global reanalysis irradiance products (ERA5 and MERRA-2) are verified against the complete records from 57 BSRN stations, over 27 years (1992–2018). This scope of validation is unprecedented in the field of solar energy. Moreover, the importance of using distribution-oriented verification approaches is emphasized. Such approaches go beyond the traditional measure-oriented verification approach, and thus can offer additional insights and flexibility to the verification problem. Reanalysis; Satellite-derived irradiance; Solar resources; Verification; Worldwide validation
Yang, Quan; Zhang, Feng; Zhang, Hua; Wang, Zhili; Iwabuchi, Hironobu; Li, JiangnanYang, Q., F. Zhang, H. Zhang, Z. Wang, H. Iwabuchi, J. Li, 2020: Impact of δ-Four-Stream Radiative Transfer Scheme on global climate model simulation. Journal of Quantitative Spectroscopy and Radiative Transfer, 243, 106800. doi: 10.1016/j.jqsrt.2019.106800. The impact of radiative transfer scheme on global climate model (GCM) simulation is presented in this paper by comparing the difference between δ-two-stream adding method (δ-2DDA) and adding algorithm of the δ-four-stream discrete ordinates method (δ-4DDA) radiation schemes in the Atmospheric General Circulation Model of the Beijing Climate Center (BCC_AGCM). Only consider the effects of the calculation method itself, the δ-4DDA reduces the negative shortwave cloud radiative effect (CRE) in the areas with a significant fraction of low cloud, while enhances the negative shortwave CRE in the areas with the large fraction of high cloud. For the longwave CRE, the δ-4DDA enhances the longwave CRE drastically in the regions with a significant fraction of the high cloud. The feedback of clouds results in more interesting results. The δ-4DDA produces more accurate shortwave CRE in the region over the land and ocean in the middle and high latitude areas. The longwave CRE simulated by δ-4DDA is better than that affected by δ-2DDA over the ground in Africa, South America, and Atlantic. The change of radiation scheme affects the simulation of other meteorological variables. The simulation of global humidity by δ-4DDA is improved obviously. The δ-4DDA simulates more accurate temperature in continents of the northern hemisphere and precipitation in North America, Africa, northern Indian Ocean and western Pacific. Although the improvement of every physical process is required to develop the models, implementing δ-4DDA scheme into GCM and evaluating the effect of it are necessary and meaningful. Global climate model; Radiative transfer scheme; δ-4DDA
Yarahmadi, Mehran; Mahan, J. Robert; McFall, Kevin; Ashraf, Anum BarkiYarahmadi, M., J. R. Mahan, K. McFall, A. B. Ashraf, 2020: Numerical Focusing of a Wide-Field-Angle Earth Radiation Budget Imager Using an Artificial Neural Network. Remote Sensing, 12(1), 176. doi: 10.3390/rs12010176. Narrow field-of-view scanning thermistor bolometer radiometers have traditionally been used to monitor the earth’s radiant energy budget from low earth orbit (LEO). Such instruments use a combination of cross-path scanning and along-path spacecraft motion to obtain a patchwork of punctual observations which are ultimately assembled into a mosaic. Monitoring has also been achieved using non-scanning instruments operating in a push-broom mode in LOE and imagers operating in geostationary orbit. The current contribution considers a fourth possibility, that of an imager operating in LEO. The system under consideration consists of a Ritchey-Chrétien telescope illuminating a plane two-dimensional microbolometer array. At large field angles, the focal length of the candidate instrument is field-angle dependent, resulting in a blurred image in the readout plane. Presented is a full-field focusing algorithm based on an artificial neural network (ANN). Absorbed power distributions on the microbolometer array produced by discretized scenes are obtained using a high-fidelity Monte Carlo ray-trace (MCRT) model of the imager. The resulting readout array/scene pairs are then used to train an ANN. We demonstrate that a properly trained ANN can be used to convert the readout power distribution into an accurate image of the corresponding discretized scene. This opens the possibility of using an ANN based on a high-fidelity imager model for numerical focusing of an actual imager. artificial neural networks; earth radiation budget monitoring; image deblurring; numerical focusing
Yin, Jun; Porporato, AmilcareYin, J., A. Porporato, 2020: Radiative effects of daily cycle of cloud frequency in past and future climates. Climate Dynamics, 54(3), 1625-1637. doi: 10.1007/s00382-019-05077-5. The daily cloud cycle or diurnal cloud cycle (DCC) and its response to global warming are critical to the Earth’s energy budget, but their radiative effects have not been systematically quantified. Toward this goal, here we analyze the radiation at the top of the atmosphere and propose a measure of the DCC radiative effect (DCCRE) as the difference between the total radiative fluxes with the full cloud cycle and its uniformly distributed cloud counterpart. When applied to the frequency of cloud occurrence, DCCRE is linked to the covariance between DCC and cloud radiative effects. Satellite observations show that the daily cloud cycle is strongly linked to pacific decadal oscillation (PDO) and climate hiatus, revealing its potential role in controlling climate variability. Climate model outputs show large inter-model spreads of DCCRE, accounting for approximately 20% inter-model spread of the cloud radiative effects. Climate models also suggest that while DCCRE is not sensitive to rising temperatures at the global scale, it can be important in certain regions. Such a framework can be used to conduct a more systematic evaluation of the DCC in climate models and observations with the goal to understand climate variability and reduce uncertainty in climate projections.
Yu, Lan; Zhang, Ming; Wang, Lunche; Qin, Wenmin; Lu, Yunbo; Li, JunliYu, L., M. Zhang, L. Wang, W. Qin, Y. Lu, J. Li, 2020: Clear-sky solar radiation changes over arid and semi-arid areas in China and their determining factors during 2001–2015. Atmospheric Environment, 223, 117198. doi: 10.1016/j.atmosenv.2019.117198. In the study, we investigated the clear-sky solar radiation at the surface and their determining factors over the arid and semi-arid (ASA) areas in China using the simulations by Mesoscale Atmospheric Global Irradiance Code (MAGIC) radiation code with satellite remote sensing aerosol data and reanalysis data as input. The coefficient of determination (R2) between ground-based measurements and simulations was 0.959, and the average relative error was 6.33%. Stations with an average relative error of less than 10% accounted for 100%, confirming the reliability of simulations. The distribution of clear-sky solar radiation showed low values in regions with high latitudes and low altitudes, and high ones in regions with low latitudes and high altitudes. The monthly average of water vapour radiative effects (WVRE) was higher than the monthly average of aerosol direct radiative effects (ADRE) for each month. WVRE were even more than six times that of ADRE in July, August, September, indicating that water vapour has stronger weakening of clear-sky solar radiation than aerosols. The annual trend indicated increases in clear-sky solar radiation in most part of ASA areas. Central Inner Mongolia (0.389 W m−2 year−1) has the significant increase. There was an interesting finding that the area where the clear-sky solar radiation decreased/increased has a good match with the area where ADRE enhanced/weakened. The R2 between clear-sky solar radiation trend and ADRE trend was 0.957, indicating that the ADRE trends were the determining factor of the clear-sky solar radiation trends. Central Inner Mongolia (0.345 Wm-2 year−1) has the significant weakening of ADRE. Aerosol radiative effects; Arid and semi-arid areas; Clear-sky solar radiation at the surface; Liner trends; MAGIC; Water vapour radiative effects
Zapadka, Tomasz; Ostrowska, Mirosława; Stoltmann, Damian; Krężel, AdamZapadka, T., M. Ostrowska, D. Stoltmann, A. Krężel, 2020: A satellite system for monitoring the radiation budget at the Baltic Sea surface. Remote Sensing of Environment, 240, 111683. doi: 10.1016/j.rse.2020.111683. The paper discusses the possibilities and limitations of using satellite data to determine the radiation budget NET and its components at the Baltic Sea surface in near real time using a newly established SBRB system (SatBałtyk Radiation Budget). The system enables determination of daily radiation fluxes over the entire Baltic Sea employing data from satellites in combination with data from numerical prognostic models. Data from satellite radiometers like SEVIRI, AVHRR are used together with algorithms that take into account the specificity of this sea and are developed based on large empirical data sets collected in this region. A verification of the system has been carried out based on separate, empirical data collected in 2015 on the oil rig Plat placed on the Baltic Sea and Svenska Högarna station. The analysis showed that daily average NET had been calculated with RMSD of 15 Wm−2 and R2 = 0.95 for the South Baltic. For downward radiation fluxes in the solar wavelength range (SW) and the terrestrial, thermal wavelength range (LW) RMSD is respectively 11.9 Wm−2 and 9.6 Wm−2 and in both cases increase with latitude. The NET components estimated using SBRB were also compared with the corresponding magnitudes OSI -303-a and OSI 304-a from OSI SAF, EBAF surface Edition 4.0 from CERES and ERA-interim data from ECMWF systems. The main reasons for the discrepancies are discussed. The analyses confirmed the advisability of using local solutions which ensure high accuracy and spatial resolution. SBRB was developed and implemented as part of the comprehensive SatBałtyk System designed to monitor the Baltic Sea environment. The maps together with instantaneous values of the radiation components measured at actinometric stations employed at SatBałtyk System are accessible at www.satbaltyk.iopan.gda.pl. The scheme, algorithms and the way of the SBRB operation are described in detail.
Zhang, Baichao; Guo, Zhun; Zhang, Lixia; Zhou, Tianjun; Hayasaya, TadahiroZhang, B., Z. Guo, L. Zhang, T. Zhou, T. Hayasaya, 2020: Cloud Characteristics and Radiation Forcing in the Global Land Monsoon Region From Multisource Satellite Data Sets. Earth and Space Science, 7(3), e2019EA001027. doi: 10.1029/2019EA001027. The global land monsoon region has the highest land cloud amount in the world affecting two thirds of the world's population. Understanding the characteristics of cloud-radiation relies heavily on satellite data set, while few studies have addressed the advantages and weaknesses of current existing satellite data sets in estimating the cloud-radiation characteristics over global land monsoon regions. Multisource satellite data sets are used in this study to show the cloud characteristics in different monsoon regions. We find that all satellite data sets consistently show a peak of cloud fraction, cloud top height and cloud radiation forcing during summer over the global land monsoon regions. A regional difference in cloud characteristics is observed from multisource data sets. The seasonal cycle of cloud amount in the North American monsoon region is relatively smaller than that of the other monsoon regions. High-level clouds dominate the North African monsoon, while Low-level clouds dominate the Asian monsoon. The cloud properties and their radiative forcings revealed by four cloud-parameter data sets with multispectral imagers, that is, International Satellite Cloud Climatology Project (ISCCP)-D2, ISCCP-H, Moderate Resolution Imaging Spectroradiometer (MODIS)-MYD, and MODIS-MOD, are similar to one another, except stronger short-wave cloud radiative forcing in ISCCP-FD. Multidata comparison confirmed the climate and seasonal cycles of cloud characteristics in this study, demonstrating a better representation of cloud vertical structure in CloudSat over global land monsoon region. cloud; satellite data; global monsoon; multidata comparison
Zhang, Xingxing; Lu, Ning; Jiang, Hou; Yao, LingZhang, X., N. Lu, H. Jiang, L. Yao, 2020: Evaluation of Reanalysis Surface Incident Solar Radiation Data in China. Scientific Reports, 10(1), 1-20. doi: 10.1038/s41598-020-60460-1. Surface incident solar radiation (Rs) of reanalysis products is widely used in ecological conservation, agricultural production, civil engineering and various solar energy applications. It is of great importance to have a good knowledge of the uncertainty of reanalysis Rs products. In this study, we evaluated the Rs estimates from two representative global reanalysis (ERA-Interim and MERRA-2) using quality- controlled surface measurements from China Meteorological Administration (CMA) and Multi-layer Simulation and Data Assimilation Center of the Tibetan Plateau (DAM) from 2000 to 2009. Error causes are further analyzed in combination radiation products from the Earth’s Radiant Energy System (CERES) EBAF through time series estimation, hotspot selection and Geodetector methods. Both the ERA-Interim and MERRA-2 products overestimate the Rs in China, and the MERRA-2 overestimation is more pronounced. The errors of the ERA-Interim are greater in spring and winter, while that of the MERRA-2 are almost the same in all seasons. As more quality-controlled measurements were used for validation, the conclusions seem more reliable, thereby providing scientific reference for rational use of these datasets. It was also found that the main causes of errors are the cloud coverage in the southeast coastal area, aerosol optical depth (AOD) and water vapor content in the Sichuan Basin, and cloud coverage and AOD in the northeast and middle east of China.
Zhou, Zhigao; Lin, Aiwen; Wang, Lunche; Qin, Wenmin; Zhong, Yang; He, LijieZhou, Z., A. Lin, L. Wang, W. Qin, Y. Zhong, L. He, 2020: Trends in downward surface shortwave radiation from multi-source data over China during 1984–2015. International Journal of Climatology, (In Press). doi: 10.1002/joc.6408. The clear knowledge of decadal variability of surface solar radiation (SSR) is of vitally significant for understanding hydrological and biological processes and climate prediction. However, existing studies have shown observed SSR over China may have large discrepancies and inhomogeneity in decadal variability due to sensitivity drift, inaccurate calibrations and instrument replacement. Therefore, a new procedure of station selection was proposed to eliminate errors and to derive “true” SSR values in this study. Afterward, two satellite retrieves of SSR, including Clouds and the Earth's Radiant Energy System-energy balanced and filled product (CERES-EBAF) (edition 4) and Global Energy and Water Cycle Experiment-Surface Radiation Budget (GEWEX-SRB) (Version 3.0), and three reanalysis products, including National Centers for Environmental Prediction-National Center for Atmospheric Research (NCEP-NCAR), national centers for environmental prediction-/department of energy (NCEP-DOE) and Modern-Era Retrospective analysis for Research and Applications, version 2 (MERRA-2) were evaluated using “true” SSR values at 39 homogeneous stations from the China Meteorological Administration and it was found that although all five products overestimated SSR, two satellite retrieves showed better accuracy with an overall R of 0.95, an root mean squared error (RMSE) of 20.4 W m−2 and mean absolute bias error (MAE) of 14.9 W m−2 for CERES-EBAF and an overall R of 0.92, an RMSE of 27.7 W m−2 and MAE of 21.2 W m−2 for GEWEX-SRB across China. Meanwhile, inter-comparisons between trends of observations and trends of two satellite retrieves in this study showed that the new trends derived from two satellite retrieves (+0.78 W m−2 decade−1) were good agreement with trends of observation (+0.92 W m−2 decade−1) from 1994 to 2015. However, trends of SSR (+5.8 W m−2 decade−1) in situ measurements were still in disagreement with the trends of SSR (−3.7 W m−2 decade−1) derived from two satellite retrieves from 1984 to 1993 because of the sensitivity drift and instrument replacement in this period. The possible reasons for decadal variability of SSR in China were detected and it was found that variations in aerosol optical depth (AOD) and aerosol-cloud interaction, rather than cloud, were suggested to be likely the main influencing factor of decadal variability of SSR across China from 1984 to 2015. Aerosol optical depth; China; Decadal variability; Reanalyses; Satellite retrievals; Surface solar radiation

2019

Ackerman, S. A.; Platnick, S.; Bhartia, P. K.; Duncan, B.; L’Ecuyer, T.; Heidinger, A.; Skofronick-Jackson, G.; Loeb, N.; Schmit, T.; Smith, N.Ackerman, S. A., S. Platnick, P. K. Bhartia, B. Duncan, T. L’Ecuyer, A. Heidinger, G. Skofronick-Jackson, N. Loeb, T. Schmit, N. Smith, 2019: Satellites see the World’s Atmosphere. Meteorological Monographs, 59, 4.1–4.53. doi: 10.1175/AMSMONOGRAPHS-D-18-0009.1. Satellite meteorology is a relatively new branch of the atmospheric sciences. The field emerged in the late 1950’s during the Cold War and built on the advances in rocketry after World War II. In less than seventy years, satellite observations have transformed the way scientists observe and study Earth. This paper discusses some of the key advances in our understanding of the energy and water cycles, weather forecasting and atmospheric composition enabled by satellite observations. While progress truly has been an international achievement, in accord with a monograph observing the centennial of the American Meteorological Society, as well as limited space, the emphasis of this chapter is on the U.S. satellite effort.
Albrecht, Bruce; Ghate, Virendra; Mohrmann, Johannes; Wood, Robert; Zuidema, Paquita; Bretherton, Christopher; Schwartz, Christian; Eloranta, Edwin; Glienke, Susanne; Donaher, Shaunna; Sarkar, Mampi; McGibbon, Jeremy; Nugent, Alison D.; Shaw, Raymond A.; Fugal, Jacob; Minnis, Patrick; Paliknoda, Robindra; Lussier, Louis; Jensen, Jorgen; Vivekanandan, J.; Ellis, Scott; Tsai, Peisang; Rilling, Robert; Haggerty, Julie; Campos, Teresa; Stell, Meghan; Reeves, Michael; Beaton, Stuart; Allison, John; Stossmeister, Gregory; Hall, Samuel; Schmidt, SebastianAlbrecht, B., V. Ghate, J. Mohrmann, R. Wood, P. Zuidema, C. Bretherton, C. Schwartz, E. Eloranta, S. Glienke, S. Donaher, M. Sarkar, J. McGibbon, A. D. Nugent, R. A. Shaw, J. Fugal, P. Minnis, R. Paliknoda, L. Lussier, J. Jensen, J. Vivekanandan, S. Ellis, P. Tsai, R. Rilling, J. Haggerty, T. Campos, M. Stell, M. Reeves, S. Beaton, J. Allison, G. Stossmeister, S. Hall, S. Schmidt, 2019: Cloud System Evolution in the Trades—CSET Following the Evolution of Boundary Layer Cloud Systems with the NSF/NCAR GV. Bull. Amer. Meteor. Soc., 100(1), 93–12. doi: 10.1175/BAMS-D-17-0180.1. The evolution of the boundary layer aerosol, cloud, precipitation, and thermodynamic structures along trajectories within the north-Pacific trade-winds was investigated using the NSF NCAR Gulfstream V.
Ali, Md. Arfan; Islam, Md. Monirul; Islam, Md. Nazrul; Almazroui, MansourAli, M. A., M. M. Islam, M. N. Islam, M. Almazroui, 2019: Investigations of MODIS AOD and cloud properties with CERES sensor based net cloud radiative effect and a NOAA HYSPLIT Model over Bangladesh for the period 2001–2016. Atmospheric Research, 215, 268-283. doi: 10.1016/j.atmosres.2018.09.001. The present study investigates the spatiotemporal characteristics of aerosol optical depth (AOD), cloud properties, and TOA (Top Of Atmosphere) Net Cloud Radiative Effect (Net CRE) using MODIS (Moderate Resolution Imaging Spectroradiometer) Terra and CERES (Clouds and the Earth's Radiant Energy System) products over Bangladesh for the period 2001–2016. This study also explores the backward trajectory using a HYSPLIT (Hybrid Single Particle Lagrangian Integrated Trajectory) model from the National Oceanic and Atmospheric Administration (NOAA) to discover the origins of air masses. Results show annual values of AOD (0.55), Cloud Fraction (CF, 0.66), CER (Cloud Effective Radius, 14.89), COT (Cloud Optical Thickness, 15.25), CTP (Cloud Top Pressure, 639.17), CTT (Cloud Top Temperature, 262.52), WV (Water Vapor, 4.48), and Net CRE (−13.06) over Bangladesh. A seasonally peak is recorded for AOD (0.64) in MAM while for CF (0.96), CER (17.24), COT (21.12), WV (6.86), and Net CRE (−34.44) the peak is in JJA, and for CTP (884.06) and CTT (284.17) it is in DJF. By monthly the peak is recorded in June for AOD (0.73) and COT (24.86); for CER (17.87), WV (7.26), and Net CRE (−45.38) it is in July; for CF (0.97) it is in July/August; CTP (900.89) and for CTT (285.75) it is in February. Regression analysis shows annual increasing trends for AOD, CF, WV, COT, CTP, and CTT with negative trends for CER and Net CRE. AOD shows increasing trends in all seasons, whereas CF, CER and COT show increasing trends in DJF and MAM only. CTP and CTT show increasing trends in JJA and SON. WV shows an increasing trend in MAM, JJA, and DJF, whereas Net CRE shows an increasing trend in MAM and SON. Relationship study provides a better conclusion of AOD and cloud interaction based on the analysis of positive and negative correlation values over the study region. The backward trajectory indicated that the air masses originated from the Bay of Bengal, India, Nepal, Pakistan, and Iran. This study may be considered as a base document for further study on aerosols over Bangladesh using climate model simulation for the projection period. CERES; MODIS; AOD; Bangladesh; A HYSPLIT Model
Anderson, Martha; Diak, George; Gao, Feng; Knipper, Kyle; Hain, Christopher; Eichelmann, Elke; Hemes, Kyle S.; Baldocchi, Dennis; Kustas, William; Yang, YunAnderson, M., G. Diak, F. Gao, K. Knipper, C. Hain, E. Eichelmann, K. S. Hemes, D. Baldocchi, W. Kustas, Y. Yang, 2019: Impact of Insolation Data Source on Remote Sensing Retrievals of Evapotranspiration over the California Delta. Remote Sensing, 11(3), 216. doi: 10.3390/rs11030216. The energy delivered to the land surface via insolation is a primary driver of evapotranspiration (ET)—the exchange of water vapor between the land and atmosphere. Spatially distributed ET products are in great demand in the water resource management community for real-time operations and sustainable water use planning. The accuracy and deliverability of these products are determined in part by the characteristics and quality of the insolation data sources used as input to the ET models. This paper investigates the practical utility of three different insolation datasets within the context of a satellite-based remote sensing framework for mapping ET at high spatiotemporal resolution, in an application over the Sacramento–San Joaquin Delta region in California. The datasets tested included one reanalysis product: The Climate System Forecast Reanalysis (CFSR) at 0.25° spatial resolution, and two remote sensing insolation products generated with geostationary satellite imagery: a product for the continental United States at 0.2°, developed by the University of Wisconsin Space Sciences and Engineering Center (SSEC) and a coarser resolution (1°) global Clouds and the Earth’s Radiant Energy System (CERES) product. The three insolation data sources were compared to pyranometer data collected at flux towers within the Delta region to establish relative accuracy. The satellite products significantly outperformed CFSR, with root-mean square errors (RMSE) of 2.7, 1.5, and 1.4 MJ·m−2·d−1 for CFSR, CERES, and SSEC, respectively, at daily timesteps. The satellite-based products provided more accurate estimates of cloud occurrence and radiation transmission, while the reanalysis tended to underestimate solar radiation under cloudy-sky conditions. However, this difference in insolation performance did not translate into comparable improvement in the ET retrieval accuracy, where the RMSE in daily ET was 0.98 and 0.94 mm d−1 using the CFSR and SSEC insolation data sources, respectively, for all the flux sites combined. The lack of a notable impact on the aggregate ET performance may be due in part to the predominantly clear-sky conditions prevalent in central California, under which the reanalysis and satellite-based insolation data sources have comparable accuracy. While satellite-based insolation data could improve ET retrieval in more humid regions with greater cloud-cover frequency, over the California Delta and climatologically similar regions in the western U.S., the CFSR data may suffice for real-time ET modeling efforts. data fusion; evapotranspiration; California Delta; insolation; surface energy balance; water resource management
Armour, Kyle C.; Siler, Nicholas; Donohoe, Aaron; Roe, Gerard H.Armour, K. C., N. Siler, A. Donohoe, G. H. Roe, 2019: Meridional Atmospheric Heat Transport Constrained by Energetics and Mediated by Large-Scale Diffusion. J. Climate, 32(12), 3655–3680. doi: 10.1175/JCLI-D-18-0563.1. Meridional atmospheric heat transport (AHT) has been investigated through three broad perspectives: a dynamic perspective, linking AHT to the poleward flux of moist static energy (MSE) by atmospheric motions; an energetic perspective, linking AHT to energy input to the atmosphere by top-of-atmosphere radiation and surface heat fluxes; and a diffusive perspective, representing AHT in terms down-gradient energy transport. It is shown here that the three perspectives provide complementary diagnostics of meridional AHT and its changes under greenhouse-gas forcing. When combined, the energetic and diffusive perspectives offer prognostic insights: anomalous AHT is constrained to satisfy the net energetic demands of radiative forcing, radiative feedbacks, and ocean heat uptake; in turn, the meridional pattern of warming must adjust to produce those AHT changes, and does so approximately according to diffusion of anomalous MSE. The relationship between temperature and MSE exerts strong constraints on the warming pattern, favoring polar amplification. These conclusions are supported by use of a diffusive moist energy balance model (EBM) that accurately predicts zonal-mean warming and AHT changes within comprehensive general circulation models (GCMs). A dry diffusive EBM predicts similar AHT changes in order to satisfy the same energetic constraints, but does so through tropically-amplified warming – at odds with the GCMs’ polar-amplified warming pattern. The results suggest that polar-amplified warming is a near-inevitable consequence of a moist, diffusive atmosphere’s response to greenhouse-gas forcing. In this view, atmospheric circulations must act to satisfy net AHT as constrained by energetics.
Bae, S. Y.; Park, R.-S.Bae, S. Y., R. Park, 2019: Consistency between the cloud and radiation processes in a numerical forecasting model. Meteorology and Atmospheric Physics, 131(5), 1429-1436. doi: 10.1007/s00703-018-0647-9. In this study, the radiation process in the Korean Integrated Model (KIM) is modified to calculate the cloud radiative forcing keeping a physical consistency with the microphysics, convection, and cloudiness schemes in an aspect of hydrometeor. A formula to calculate effective radii of cloud water in radiation scheme of the KIM is modified to be consistent with that in the microphysics scheme and the radiative effect of a subgrid-scale hydrometeor is considered along with convective parameterization and cloudiness schemes. The impacts of these modifications on radiation and precipitation are diagnosed via an observation comparison, and a detailed analysis of these impacts is conducted. Especially, the contrasting feedback of the subgrid-scale hydrometeor on precipitation over the land and the ocean is separately discussed.
Beucler, Tom; Abbott, Tristan H.; Cronin, Timothy W.; Pritchard, Michael S.Beucler, T., T. H. Abbott, T. W. Cronin, M. S. Pritchard, 2019: Comparing Convective Self-Aggregation in Idealized Models to Observed Moist Static Energy Variability Near the Equator. Geophysical Research Letters, 46(17-18), 10589-10598. doi: 10.1029/2019GL084130. Idealized convection-permitting simulations of radiative-convective equilibrium have become a popular tool for understanding the physical processes leading to horizontal variability of tropical water vapor and rainfall. However, the applicability of idealized simulations to nature is still unclear given that important processes are typically neglected, such as lateral water vapor advection by extratropical intrusions, or interactive ocean coupling. Here, we exploit spectral analysis to compactly summarize the multiscale processes supporting convective aggregation. By applying this framework to high-resolution reanalysis data and satellite observations in addition to idealized simulations, we compare convective-aggregation processes across horizontal scales and data sets. The results affirm the validity of the radiative-convective equilibrium simulations as an analogy to the real world. Column moist static energy tendencies share similar signs and scale selectivity in convection-permitting models and observations: Radiation increases variance at wavelengths above 1,000 km, while advection damps variance across wavelengths, and surface fluxes mostly reduce variance between 1,000 and 10,000 km. radiation; convection; water vapor; cloud physics; aggregation; spectral analysis
Blunden, Jessica; Arndt, Derek S.Blunden, J., D. S. Arndt, 2019: State of the Climate in 2018. Bull. Amer. Meteor. Soc., 100(9), Si-S306. doi: 10.1175/2019BAMSStateoftheClimate.1. Editor’s note: For easy download the posted pdf of the State of the Climate for 2019 is a low-resolution file. A high-resolution copy of the report is available by clicking here. Please be patient as it may take a few minutes for the high-resolution file to download.
Bodas‐Salcedo, A.; Mulcahy, J. P.; Andrews, T.; Williams, K. D.; Ringer, M. A.; Field, P. R.; Elsaesser, G. S.Bodas‐Salcedo, A., J. P. Mulcahy, T. Andrews, K. D. Williams, M. A. Ringer, P. R. Field, G. S. Elsaesser, 2019: Strong Dependence of Atmospheric Feedbacks on Mixed-Phase Microphysics and Aerosol-Cloud Interactions in HadGEM3. Journal of Advances in Modeling Earth Systems, 11(6), 1735-1758. doi: 10.1029/2019MS001688. We analyze the atmospheric processes that explain the large changes in radiative feedbacks between the two latest climate configurations of the Hadley Centre Global Environmental model. We use a large set of atmosphere-only climate change simulations (amip and amip-p4K) to separate the contributions to the differences in feedback parameter from all the atmospheric model developments between the two latest model configurations. We show that the differences are mostly driven by changes in the shortwave cloud radiative feedback in the midlatitudes, mainly over the Southern Ocean. Two new schemes explain most of the differences: the introduction of a new aerosol scheme and the development of a new mixed-phase cloud scheme. Both schemes reduce the strength of the preexisting shortwave negative cloud feedback in the midlatitudes. The new aerosol scheme dampens a strong aerosol-cloud interaction, and it also suppresses a negative clear-sky shortwave feedback. The mixed-phase scheme increases the amount of cloud liquid water path (LWP) in the present day and reduces the increase in LWP with warming. Both changes contribute to reducing the negative radiative feedback of the increase of LWP in the warmer climate. The mixed-phase scheme also enhances a strong, preexisting, positive cloud fraction feedback. We assess the realism of the changes by comparing present-day simulations against observations and discuss avenues that could help constrain the relevant processes. cloud feedbacks; HadGEM3
Bright, Jamie M.; Gueymard, Christian A.Bright, J. M., C. A. Gueymard, 2019: Climate-specific and global validation of MODIS Aqua and Terra aerosol optical depth at 452 AERONET stations. Solar Energy, 183, 594-605. doi: 10.1016/j.solener.2019.03.043. Aerosol optical depth (AOD) is a highly influential variable in solar resource assessment and clear-sky radiation modelling. Hence, the accuracy of solar energy estimates ultimately depends on the accuracy of the measured or assumed AOD. Gridded satellite information is often used for solar modelling due to its geographical coverage, and so a global validation of commonly utilised AOD products is imperative. Here, all Level-3 Moderate Resolution Imaging Spectroradiometer (MODIS) daily observations of AOD (at 470, 550 and 660 nm, noted AOD470, AOD550 and AOD660, respectively) from the Aqua and Terra satellites (of 1° × 1° spatial resolution) from 2000 to 02/2018 are compared and validated against all of NASA’s ground sensing Aerosol Robotic NETwork (AERONET) V3 Level 2 AOD daily averages from sites that reported at least one year of observations during 2000–2018 (452 sites representing at least 653,000 observations per variable). Furthermore, sub-categorisation by Köppen-Geiger climate regions enables a novel climate-specific validation to ascertain any distinct climatic influence. The results demonstrate significant climatological influences that impact the derived AOD product at all three wavelengths. It is found that blending the two Aqua and Terra products results in a higher accuracy of daily estimates of all AOD products. Each AOD product is validated similarly and separately. AOD550, which is most commonly used in solar resource assessment, is found worst in the equatorial climate (absolute root mean square error (RMSE) of 0.194) and best in the temperate climate (RMSE of 0.126). Globally, the combined Aqua + Terra AOD550 experiences an absolute RMSE of 0.106 and a mean absolute error of 0.109. The most common MODIS AOD retrievals are between 0.01 and 0.25, suggesting that the MODIS daily AOD products may introduce a significant source of uncertainty in modelled irradiance estimates, and that other sources of input data should be used instead whenever their applications demand high accuracy. MODIS; AERONET; Aerosol optical depth; Global validation; Irradiance modelling
Bright, Ryan M.; O'Halloran, Thomas L.Bright, R. M., T. L. O'Halloran, 2019: Developing a monthly radiative kernel for surface albedo change from satellite climatologies of Earth's shortwave radiation budget: CACK v1.0. Geoscientific Model Development, 12(9), 3975-3990. doi: https://doi.org/10.5194/gmd-12-3975-2019. Abstract. Due to the potential for land-use–land-cover change (LULCC) to alter surface albedo, there is need within the LULCC science community for simple and transparent tools for predicting radiative forcings (ΔF) from surface albedo changes (Δαs). To that end, the radiative kernel technique – developed by the climate modeling community to diagnose internal feedbacks within general circulation models (GCMs) – has been adopted by the LULCC science community as a tool to perform offline ΔF calculations for Δαs. However, the codes and data behind the GCM kernels are not readily transparent, and the climatologies of the atmospheric state variables used to derive them vary widely both in time period and duration. Observation-based kernels offer an attractive alternative to GCM-based kernels and could be updated annually at relatively low costs. Here, we present a radiative kernel for surface albedo change founded on a novel, simplified parameterization of shortwave radiative transfer driven with inputs from the Clouds and the Earth's Radiant Energy System (CERES) Energy Balance and Filled (EBAF) products. When constructed on a 16-year climatology (2001–2016), we find that the CERES-based albedo change kernel – or CACK – agrees remarkably well with the mean kernel of four GCMs (rRMSE = 14 %). When the novel parameterization underlying CACK is applied to emulate two of the GCM kernels using their own boundary fluxes as input, we find even greater agreement (mean rRMSE = 7.4 %), suggesting that this simple and transparent parameterization represents a credible candidate for a satellite-based alternative to GCM kernels. We document and compute the various sources of uncertainty underlying CACK and include them as part of a more extensive dataset (CACK v1.0) while providing examples showcasing its application.
Caldwell, Peter M.; Mametjanov, Azamat; Tang, Qi; Roekel, Luke P. Van; Golaz, Jean-Christophe; Lin, Wuyin; Bader, David C.; Keen, Noel D.; Feng, Yan; Jacob, Robert; Maltrud, Mathew E.; Roberts, Andrew F.; Taylor, Mark A.; Veneziani, Milena; Wang, Hailong; Wolfe, Jonathan D.; Balaguru, Karthik; Cameron‐Smith, Philip; Dong, Lu; Klein, Stephen A.; Leung, L. Ruby; Li, Hong-Yi; Li, Qing; Liu, Xiaohong; Neale, Richard B.; Pinheiro, Marielle; Qian, Yun; Ullrich, Paul A.; Xie, Shaocheng; Yang, Yang; Zhang, Yuying; Zhang, Kai; Zhou, TianCaldwell, P. M., A. Mametjanov, Q. Tang, L. P. V. Roekel, J. Golaz, W. Lin, D. C. Bader, N. D. Keen, Y. Feng, R. Jacob, M. E. Maltrud, A. F. Roberts, M. A. Taylor, M. Veneziani, H. Wang, J. D. Wolfe, K. Balaguru, P. Cameron‐Smith, L. Dong, S. A. Klein, L. R. Leung, H. Li, Q. Li, X. Liu, R. B. Neale, M. Pinheiro, Y. Qian, P. A. Ullrich, S. Xie, Y. Yang, Y. Zhang, K. Zhang, T. Zhou, 2019: The DOE E3SM Coupled Model Version 1: Description and Results at High Resolution. Journal of Advances in Modeling Earth Systems, 11(12), 4095-4146. doi: 10.1029/2019MS001870. This study provides an overview of the coupled high-resolution Version 1 of the Energy Exascale Earth System Model (E3SMv1) and documents the characteristics of a 50-year-long high-resolution control simulation with time-invariant 1950 forcings following the HighResMIP protocol. In terms of global root-mean-squared error metrics, this high-resolution simulation is generally superior to results from the low-resolution configuration of E3SMv1 (due to resolution, tuning changes, and possibly initialization procedure) and compares favorably to models in the CMIP5 ensemble. Ocean and sea ice simulation is particularly improved, due to better resolution of bathymetry, the ability to capture more variability and extremes in winds and currents, and the ability to resolve mesoscale ocean eddies. The largest improvement in this regard is an ice-free Labrador Sea, which is a major problem at low resolution. Interestingly, several features found to improve with resolution in previous studies are insensitive to resolution or even degrade in E3SMv1. Most notable in this regard are warm bias and associated stratocumulus deficiency in eastern subtropical oceans and lack of improvement in El Niño. Another major finding of this study is that resolution increase had negligible impact on climate sensitivity (measured by net feedback determined through uniform +4K prescribed sea surface temperature increase) and aerosol sensitivity. Cloud response to resolution increase consisted of very minor decrease at all levels. Large-scale patterns of precipitation bias were also relatively unaffected by grid spacing.
Carlson, Barbara; Lacis, Andrew; Colose, Christopher; Marshak, Alexander; Su, Wenying; Lorentz, StevenCarlson, B., A. Lacis, C. Colose, A. Marshak, W. Su, S. Lorentz, 2019: Spectral Signature of the Biosphere: NISTAR Finds It in Our Solar System From the Lagrangian L-1 Point. Geophysical Research Letters, 46(17-18), 10679-10686. doi: 10.1029/2019GL083736. NISTAR, aboard the DSCOVR spacecraft, is one of the National Aeronautics and Space Administration's energy budget instruments designed to measure the seasonal changes in Earth's total outgoing radiation from a unique vantage point at the Lagrangian L-1 point a million miles from Earth. Global radiation energy balance measurements are important constraints for climate models, but are difficult measurements to quantify. CERES data offer the best current observational constraints, but need extensive modeling to get global energy. NISTAR observes the entire dayside hemisphere of the Earth as a single pixel, splitting the shortwave radiation into broadband visible and near-infrared components (analogous to the narrowband spectral ratios used to define vegetation indices). This spectral partitioning at the 0.7-μm vegetation red edge offers unique constraints on climate model spectral treatment of cloud and surface albedos. Moreover, NISTAR's unique viewing geometry amounts to observing the Earth as an exoplanet, which opens a new perspective on exoplanet observations. diurnal cycle; satellite data; global energy budget; remote sensing; climate model validation; exoplanet studies
Carrer, Dominique; Ceamanos, Xavier; Moparthy, Suman; Vincent, Chloé; C. Freitas, Sandra; Trigo, Isabel F.Carrer, D., X. Ceamanos, S. Moparthy, C. Vincent, S. C. Freitas, I. F. Trigo, 2019: Satellite Retrieval of Downwelling Shortwave Surface Flux and Diffuse Fraction under All Sky Conditions in the Framework of the LSA SAF Program (Part 1: Methodology). Remote Sensing, 11(21), 2532. doi: 10.3390/rs11212532. Several studies have shown that changes in incoming solar radiation and variations of the diffuse fraction can significantly modify the vegetation carbon uptake. Hence, monitoring the incoming solar radiation at large scale and with high temporal frequency is crucial for this reason along with many others. The European Organization for the Exploitation of Meteorological Satellites (EUMETSAT) Satellite Application Facility for Land Surface Analysis (LSA SAF) has operationally disseminated in near real time estimates of the downwelling shortwave radiation at the surface since 2005. This product is derived from observations provided by the SEVIRI instrument onboard the Meteosat Second Generation series of geostationary satellites, which covers Europe, Africa, the Middle East, and part of South America. However, near real time generation of the diffuse fraction at the surface level has only recently been initiated. The main difficulty towards achieving this goal was the general lack of accurate information on the aerosol particles in the atmosphere. This limitation is less important nowadays thanks to the improvements in atmospheric numerical models. This study presents an upgrade of the LSA SAF operational retrieval method, which provides the simultaneous estimation of the incoming solar radiation and its diffuse fraction from the satellite every 15 min. The upgrade includes a comprehensive representation of the influence of aerosols based on physical approximations of the radiative transfer within an atmosphere-surface associated medium. This article explains the retrieval method, discusses its limitations and differences with the previous method, and details the characteristics of the output products. A companion article will focus on the evaluation of the products against independent measurements of solar radiation. Finally, the access to the source code is provided through an open access platform in order to share the expertise on the satellite retrieval of this variable with the community. aerosols; diffuse; solar radiation; LSA SAF; MSG SEVIRI; open source code
Cesana, G.; Waliser, D. E.; Henderson, D.; L’Ecuyer, T. S.; Jiang, X.; Li, J-L. F.Cesana, G., D. E. Waliser, D. Henderson, T. S. L’Ecuyer, X. Jiang, J. F. Li, 2019: The Vertical Structure Of Radiative Heating Rates: A Multimodel Evaluation Using A-Train Satellite Observations. J. Climate, 32, 1573–1590. doi: 10.1175/JCLI-D-17-0136.1. We assess the vertical distribution of radiative heating rates (RHR) in climate models using a model experiment and A-train satellite observations, for the first time. As RHR relies on the representation of cloud amount and properties, we first compare the modeled vertical distribution of clouds directly against lidar-radar combined cloud observations (i.e., without simulator). On a near-global scale (50°S/N), two systematic differences arise: an excess of high-level clouds around 200hPa in the tropics, and a general lack of middle- and low-level clouds compared to the observations. Then, using RHR profiles calculated with constraints from A-train and reanalysis data, along with their associated maximum uncertainty estimates, we show that the excess clouds and ice water content in the upper troposphere results in excess infrared heating in the vicinity and below the clouds as well as a lack of solar heating below the clouds. In the lower troposphere, the smaller cloud amount and the underestimation of cloud-top height is coincident with a shift of the infrared cooling to lower levels, substantially reducing the greenhouse effect, that is slightly compensated for by an erroneous excess absorption of solar radiation. Clear sky RHR differences between the observations and the models mitigate cloudy RHR biases in the low levels while they enhance them in the high levels. Finally, our results indicate that a better agreement between observed and modeled cloud profiles could substantially improve the RHR profiles. However, more work is needed to precisely quantify modeled cloud errors and their subsequent effect on RHR.
Cesana, Grégory; Genio, Anthony D. Del; Ackerman, Andrew S.; Kelley, Maxwell; Elsaesser, Gregory; Fridlind, Ann M.; Cheng, Ye; Yao, Mao-SungCesana, G., A. D. D. Genio, A. S. Ackerman, M. Kelley, G. Elsaesser, A. M. Fridlind, Y. Cheng, M. Yao, 2019: Evaluating models' response of tropical low clouds to SST forcings using CALIPSO observations. Atmospheric Chemistry and Physics, 19(5), 2813-2832. doi: 10.5194/acp-19-2813-2019. Abstract. Recent studies have shown that, in response to a surface warming, the marine tropical low-cloud cover (LCC) as observed by passive-sensor satellites substantially decreases, therefore generating a smaller negative value of the top-of-the-atmosphere (TOA) cloud radiative effect (CRE). Here we study the LCC and CRE interannual changes in response to sea surface temperature (SST) forcings in the GISS model E2 climate model, a developmental version of the GISS model E3 climate model, and in 12 other climate models, as a function of their ability to represent the vertical structure of the cloud response to SST change against 10 years of CALIPSO (Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observations) observations. The more realistic models (those that satisfy the observational constraint) capture the observed interannual LCC change quite well (ΔLCC/ΔSST=-3.49±1.01 % K−1 vs. ΔLCC/ΔSSTobs=-3.59±0.28 % K−1) while the others largely underestimate it (ΔLCC/ΔSST=-1.32±1.28 % K−1). Consequently, the more realistic models simulate more positive shortwave (SW) feedback (ΔCRE/ΔSST=2.60±1.13 W m−2 K−1) than the less realistic models (ΔCRE/ΔSST=0.87±2.63
Chang, Kai-Wei; L'Ecuyer, Tristan S.Chang, K., T. S. L'Ecuyer, 2019: Role of Latent Heating Vertical Distribution in the Formation of the Tropical Cold Trap. Journal of Geophysical Research: Atmospheres, 124(14), 7836-7851. doi: 10.1029/2018JD030194. This study examines the role of latent heating (LH) vertical distribution in tropical tropopause layer (TTL) cooling and upper-tropospheric warming associated with equatorial wave responses using LH from the Tropical Rainfall Measurement Mission and temperature from radio occultation observations. We distinguish the effects of convective and stratiform LH in tropical convection on temperature in the upper troposphere and lower stratosphere. Cross-spectral analysis of time series of temperature and LH shows that stratiform LH exhibits higher coherence with temperature throughout most of the upper troposphere and lower stratosphere, especially in the equatorial Rossby wave response. Coherence between total LH and temperature tends to increase with the altitude of heating. Highest coherences occur almost exclusively at time scales of the Madden-Julian Oscillation, suggesting the importance of mesoscale convective activity in TTL cooling and subsequent dehydration processes. These results demonstrate that TTL and upper-tropospheric temperature perturbations depend on the vertical distribution of LH and that stratiform LH release has strong relationship with the formation of the horseshoe-shaped cold trap over the Maritime Continent and West Pacific. Madden-Julian Oscillation; equatorial waves; latent heating; stratosphere-troposphere coupling; tropical tropopause layer
Chen, Gengxin; Han, Weiqing; Li, Yuanlong; Yao, Jinglong; Wang, DongxiaoChen, G., W. Han, Y. Li, J. Yao, D. Wang, 2019: Intraseasonal Variability of the Equatorial Undercurrent in the Indian Ocean. J. Phys. Oceanogr., 49(1), 85-101. doi: 10.1175/JPO-D-18-0151.1. By analyzing in situ observations and conducting a series of ocean general circulation model experiments, this study investigates the physical processes controlling intraseasonal variability (ISV) of the Equatorial Undercurrent (EUC) of the Indian Ocean. ISV of the EUC leads to time-varying water exchanges between the western and eastern equatorial Indian Ocean. For the 2001–14 period, standard deviations of the EUC transport variability are 1.92 and 1.77 Sv (1 Sv ≡ 106 m3 s−1) in the eastern and western basins, respectively. The ISV of the EUC is predominantly caused by the wind forcing effect of atmospheric intraseasonal oscillations (ISOs) but through dramatically different ocean dynamical processes in the eastern and western basins. The stronger ISV in the eastern basin is dominated by the reflected Rossby waves associated with intraseasonal equatorial zonal wind forcing. It takes 20–30 days to set up an intraseasonal EUC anomaly through the Kelvin and Rossby waves associated with the first and second baroclinic modes. In the western basin, the peak intraseasonal EUC anomaly is generated by the zonal pressure gradient force, which is set up by radiating equatorial Kelvin and Rossby waves induced by the equatorial wind stress. Directly forced and reflected Rossby waves from the eastern basin propagate westward, contributing to intraseasonal zonal current near the surface but having weak impact on the peak ISV of the EUC.
Chen, Jinghua; Wu, Xiaoqing; Yin, Yan; Lu, Chunsong; Xiao, Hui; Huang, Qian; Deng, LipingChen, J., X. Wu, Y. Yin, C. Lu, H. Xiao, Q. Huang, L. Deng, 2019: Thermal Effects of the Surface Heat Flux on Cloud Systems over the Tibetan Plateau in Boreal Summer. J. Climate, 32(15), 4699-4714. doi: 10.1175/JCLI-D-18-0604.1. The influence of surface heat fluxes on the generation and development of cloud and precipitation and its relative importance to the large-scale circulation patterns are investigated via cloud-resolving model (CRM) simulations over the Tibetan Plateau (TP) during boreal summer. Over the lowland (e.g., along the middle and lower reaches of the Yangtze River), the dynamical and thermal properties of the atmosphere take more responsibility than the surface heat fluxes for the triggering of heavy rainfall events. However, the surface thermal driving force is a necessary criterion for the triggering of heavy rainfall in the eastern and western TP (ETP and WTP). Strong surface heat fluxes can trigger shallow convections in the TP. Furthermore, moisture that is mainly transported from the southern tropical ocean has a greater influence on the heavy rainfall events of the WTP than those of the ETP. Cloud microphysical processes are substantially less active and heavy rainfall cannot be produced when surface heat fluxes are weakened by half in magnitude over the TP. In addition, surface heating effects are largely responsible for the high occurrence frequency of convection during the afternoon, and the cloud tops of convective systems show a positive relationship with the intensity of surface heat fluxes.
Chen, Yi-Hsuan; Huang, Xianglei; Chen, Xiuhong; Flanner, MarkChen, Y., X. Huang, X. Chen, M. Flanner, 2019: The Effects of Surface Longwave Spectral Emissivity on Atmospheric Circulation and Convection over the Sahara and Sahel. J. Climate, 32(15), 4873-4890. doi: 10.1175/JCLI-D-18-0615.1. This study quantifies the impact of the inclusion of realistic surface spectral emissivity in the Sahara and Sahel on the simulated local climate and beyond. The surface emissivity in these regions can be as low as 0.6–0.7 over the infrared window band while close to unity in other spectral bands, but such spectral dependence has been ignored in current climate models. Realistic surface spectral emissivities over the Sahara and Sahel are incorporated into the Community Earth System Model (CESM) version 1.1.1, while treatments of surface emissivity for the rest of the globe remain unchanged. Both the modified and standard CESM are then forced with prescribed climatological SSTs and fixed present-day forcings for 35-yr simulations. The outputs from the last 30 years are analyzed. Compared to the standard CESM, the modified CESM has warmer surface air temperature, as well as a warmer and wetter planetary boundary layer over the Sahara and Sahel. The modified CESM thus favors more convection in these regions and has more convective rainfall, especially in the Sahara. The moisture convergence induced by such inclusion of surface spectral emissivity also contributes to the differences in simulated precipitation in the Sahel and the region south to it. Compared to observations, inclusion of surface spectral emissivity reduces surface temperature biases in the Sahara and precipitation biases in the Gulf of Guinea but exacerbates the wet biases in the Sahara. Such realistic representation of surface spectral emissivity can help unmask other factors contributing to regional biases in the original CESM.
Chen, Yilun; Chong, Kezhen; Fu, YunfeiChen, Y., K. Chong, Y. Fu, 2019: Impacts of distribution patterns of cloud optical depth on the calculation of radiative forcing. Atmospheric Research, 218, 70-77. doi: 10.1016/j.atmosres.2018.11.007. The gridding process applied to satellite-retrieved cloud properties results in the loss of certain information. In this study, we analyzed the error associated with using gridded cloud optical depth (τ) in calculating radiative forcing from the perspective of the distribution pattern of τ. Utilizing the simulated results from SBDART (Santa Babara DISORT Atmospheric Radiative Transfer), we calculated this error in ideal probability distribution functions (PDFs) of τ while keeping the average τ constant, and then used the τ retrieved from MODIS (Moderate Resolution Imaging Spectroradiometer) pixel-level observations to simulate real case studies. The results from both the ideal experiments and real case studies indicate that there is a large dependence of the error caused by gridding process on the PDF of τ. The greatest relative error occurs in the cases when τ fits a two-point or uniform distribution, reaching 10–20%, while this error is below 5% when τ follows a binomial distribution. From the analysis of MODIS pixel-level data from June 2016, we found that the PDFs of τ within one grid point (1° × 1°) could not be simply described by a normal distribution. Although using the logarithmic mean of τ controls the error effectively, the error can still be up to 4%. Our study suggests that using gridded data (especially the arithmetic mean) to calculate radiative forcing may result in uncertainty to a certain extent, which depends strongly on the distribution pattern of cloud properties within the grid point. The PDF of cloud properties should be comprehensively considered in the gridding process in the future. MODIS; Cloud optical depth; Distribution pattern; Grid; Radiative forcing
Choi, In-Jin; Park, Rae-Seol; Lee, JoonsukChoi, I., R. Park, J. Lee, 2019: Impacts of a newly-developed aerosol climatology on numerical weather prediction using a global atmospheric forecasting model. Atmospheric Environment, 197, 77-91. doi: 10.1016/j.atmosenv.2018.10.019. New four-dimensional aerosol climatology for global weather forecasting model is developed to take aerosol direct effect into account and its impacts on numerical weather prediction are investigated. The proposed aerosol climatology provides the global distribution of monthly-varying species-wise aerosol optical depths with more realistic aerosol vertical profiles. Including aerosol climatology enhances vertical stratification by surface cooling and atmospheric heating through the lower atmosphere by affecting radiation budget. Weakened vertical mixing and reduced surface fluxes related to aerosol loading result in decreased cloud fraction, particularly in the lower atmosphere. Evaluation of medium-range forecasts using the proposed aerosol climatology shows the overall improvement statistically for large-scale variable with reducing their biases, and the alleviation of systematic biases of overestimated light precipitation over the northern hemisphere. Aerosol climatology; Forecast skill; Global NWP; MACC; MOZART
Cronin, Meghan F.; Gentemann, Chelle L.; Edson, James; Ueki, Iwao; Bourassa, Mark; Brown, Shannon; Clayson, Carol Anne; Fairall, Chris W.; Farrar, J. Thomas; Gille, Sarah T.; Gulev, Sergey; Josey, Simon A.; Kato, Seiji; Katsumata, Masaki; Kent, Elizabeth; Krug, Marjolaine; Minnett, Peter J.; Parfitt, Rhys; Pinker, Rachel T.; Stackhouse, Paul W.; Swart, Sebastiaan; Tomita, Hiroyuki; Vandemark, Douglas; Weller, A. Robert; Yoneyama, Kunio; Yu, Lisan; Zhang, DongxiaoCronin, M. F., C. L. Gentemann, J. Edson, I. Ueki, M. Bourassa, S. Brown, C. A. Clayson, C. W. Fairall, J. T. Farrar, S. T. Gille, S. Gulev, S. A. Josey, S. Kato, M. Katsumata, E. Kent, M. Krug, P. J. Minnett, R. Parfitt, R. T. Pinker, P. W. Stackhouse, S. Swart, H. Tomita, D. Vandemark, A. R. Weller, K. Yoneyama, L. Yu, D. Zhang, 2019: Air-Sea Fluxes With a Focus on Heat and Momentum. Frontiers in Marine Science, 6, 430. doi: 10.3389/fmars.2019.00430. Turbulent and radiative exchanges of heat between the ocean and atmosphere (hereafter heat fluxes), ocean surface wind stress, and state variables used to estimate them, are Essential Ocean Variables (EOVs) and Essential Climate Variables (ECVs) influencing weather and climate. This paper describes an observational strategy for producing 3-hourly, 25-km (and an aspirational goal of hourly at 10-km) heat flux and wind stress fields over the global, ice-free ocean with breakthrough 1-day random uncertainty of 15 W m–2 and a bias of less than 5 W m–2. At present this accuracy target is met only for OceanSITES reference station moorings and research vessels (RVs) that follow best practices. To meet these targets globally, in the next decade, satellite-based observations must be optimized for boundary layer measurements of air temperature, humidity, sea surface temperature, and ocean wind stress. In order to tune and validate these satellite measurements, a complementary global in situ flux array, built around an expanded OceanSITES network of time series reference station moorings, is also needed. The array would include 500–1000 measurement platforms, including autonomous surface vehicles, moored and drifting buoys, RVs, the existing OceanSITES network of 22 flux sites, and new OceanSITES expanded in 19 key regions. This array would be globally distributed, with 1–3 measurement platforms in each nominal 10° by 10° box. These improved moisture and temperature profiles and surface data, if assimilated into Numerical Weather Prediction (NWP) models, would lead to better representation of cloud formation processes, improving state variables and surface radiative and turbulent fluxes from these models. The in situ flux array provides globally distributed measurements and metrics for satellite algorithm development, product validation, and for improving satellite-based, NWP and blended flux products. In addition, some of these flux platforms will also measure direct turbulent fluxes, which can be used to improve algorithms for computation of air-sea exchange of heat and momentum in flux products and models. With these improved air-sea fluxes, the ocean’s influence on the atmosphere will be better quantified and lead to improved long-term weather forecasts, seasonal-interannual-decadal climate predictions, and regional climate projections.
Cui, Wenjun; Dong, Xiquan; Xi, Baike; Fan, Jiwen; Tian, Jingjing; Wang, Jingyu; McHardy, Theodore M.Cui, W., X. Dong, B. Xi, J. Fan, J. Tian, J. Wang, T. M. McHardy, 2019: Understanding Ice Cloud-Precipitation Properties of Three Modes of Mesoscale Convective Systems During PECAN. Journal of Geophysical Research: Atmospheres, 124(7), 4121-4140. doi: 10.1029/2019JD030330. This study analyzes the precipitation and ice cloud microphysical features of three common modes of linear mesoscale convective systems during the Plains Elevated Convection at Night (PECAN) campaign. Three cases, one for each linear mesoscale convective system archetype (trailing stratiform, leading stratiform, and parallel stratiform precipitation), are selected. We focus primarily on analyzing ice cloud microphysical properties and precipitation rates (PRs) over the classified convective core (CC) and stratiform rain (SR) regions, as well as the two stratiform regions that developed behind (SR1) and ahead (SR2) of the convective line relative to the storm motion. In the three selected cases, the ice water path (IWP) and PR have strong correlations in the CC, but not in the SR. In terms of the temporal evolution of the mean IWPs and PRs, both CC and SR IWPs, as well as CC PRs, reach peaks quickly but take a longer time to dissipate than the increase period. For all the three cases, both SR1 and SR2 IWPs are 20–70% of their corresponding CC values in both the leading stratiform and parallel stratiform cases and up to 95% for the trailing stratiform case, while all of their PRs are only 7–25% of their CC values. These values suggest not only that the SR PRs may depend on IWPs but also that the microphysical properties of ice particles such as habit and size distribution may play an important role. Utilizing cloud-resolving simulations of these systems may provide better understanding of the physical meanings behind the results in the future.
Danso, Derrick Kwadwo; Anquetin, Sandrine; Diedhiou, Arona; Lavaysse, Christophe; Kobea, Arsène; Touré, N'Datchoh EvelyneDanso, D. K., S. Anquetin, A. Diedhiou, C. Lavaysse, A. Kobea, N. E. Touré, 2019: Spatio-temporal variability of cloud cover types in West Africa with satellite-based and reanalysis data. Quarterly Journal of the Royal Meteorological Society, 145(725), 3715-3731. doi: 10.1002/qj.3651. This study aims to understand and document the occurrence and variability of cloud cover types in West Africa (WA). Investigations are carried out with a 10-year hourly record of two cloud data products: CERES passive satellite observations and ERA5 reanalysis. The seasonal evolutions of high (HCC), middle (MCC), low (LCC) and total (TCC) cloud cover are examined. Both products agree on the seasonal and spatial occurrence of cloud cover, although CERES presents lower values of cloud fraction than ERA5 which is partly attributed to the inability of the satellite sensor to detect optically thin clouds in the atmosphere. Southern WA is found to be cloudier than other parts of the region in all seasons with mean TCC fractions of 70 and 80% for CERES and ERA5 respectively during the monsoon season. In all seasons, the presence of LCC over large areas of the Sahel/Sahara region is noted in the CERES product. This could be due to a possible misinterpretation of Saharan dust as low clouds which may have thus, caused it to overestimate the occurrences and fractions of LCC over this region. Northern WA is associated with higher frequencies of no cloud occurrence events, unlike the south where cloudless skies are rarely observed. Furthermore, in southern WA, overcast conditions of LCC are observed for a significant number of times (up to 20% of the time during the rainy season in CERES and 40% in ERA5). The climatology of cloud cover presented in this study could be useful for the planning of solar energy projects. CERES; West Africa; cloud cover; variability; ERA5; occurrence frequency
Dewitte, Steven; Clerbaux, Nicolas; Cornelis, JanDewitte, S., N. Clerbaux, J. Cornelis, 2019: Decadal Changes of the Reflected Solar Radiation and the Earth Energy Imbalance. Remote Sensing, 11(6), 663. doi: 10.3390/rs11060663. Decadal changes of the Reflected Solar Radiation (RSR) as measured by CERES from 2000 to 2018 are analysed. For both polar regions, changes of the clear-sky RSR correlate well with changes of the Sea Ice Extent. In the Arctic, sea ice is clearly melting, and as a result the earth is becoming darker under clear-sky conditions. However, the correlation between the global all-sky RSR and the polar clear-sky RSR changes is low. Moreover, the RSR and the Outgoing Longwave Radiation (OLR) changes are negatively correlated, so they partly cancel each other. The increase of the OLR is higher then the decrease of the RSR. Also the incoming solar radiation is decreasing. As a result, over the 2000–2018 period the Earth Energy Imbalance (EEI) appears to have a downward trend of −0.16 ± 0.11 W/m2dec. The EEI trend agrees with a trend of the Ocean Heat Content Time Derivative of −0.26 ± 0.06 (1 σ ) W/m2dec. Earth Radiation Budget; Earth Energy Imbalance; Reflected Solar Radiation
Dolinar, Erica K.; Dong, Xiquan; Xi, Baike; Jiang, Jonathan H.; Loeb, Norman G.; Campbell, James R.; Su, HuiDolinar, E. K., X. Dong, B. Xi, J. H. Jiang, N. G. Loeb, J. R. Campbell, H. Su, 2019: A global record of single-layered ice cloud properties and associated radiative heating rate profiles from an A-Train perspective. Climate Dynamics, 1-20. doi: 10.1007/s00382-019-04682-8. A record of global single-layered ice cloud properties has been generated using the CloudSat and CALIPSO Ice Cloud Property Product (2C-ICE) during the period 2007–2010. These ice cloud properties are used as inputs for the NASA Langley modified Fu–Liou radiative transfer model to calculate cloud radiative heating rate profiles and are compared with the NASA CERES observed top-of-atmosphere fluxes. The radiative heating rate profiles calculated in the CloudSat/CALIPSO 2B-FLXHR-LIDAR and CCCM_CC products are also examined to assess consistency and uncertainty of their properties using independent methods. Based on the methods and definitions used herein, single-layered ice clouds have a global occurrence frequency of ~ 18%, with most of them occurring in the tropics above 12 km. Zonal mean cloud radiative heating rate profiles from the three datasets are similar in their patterns of SW warming and LW cooling with small differences in magnitude; nevertheless, all three datasets show that the strongest net heating (> + 1.0 K day−1) occurs in the tropics (latitude < 30°) near the cloud-base while cooling occurs at higher latitudes (> ~ 50°). Differences in radiative heating rates are also assessed based on composites of the 2C-ICE ice water path (IWP) and total column water vapor (TCWV) mixing ratio to facilitate model evaluation and guide ice cloud parameterization improvement. Positive net cloud radiative heating rates are maximized in the upper troposphere for large IWPs and large TCWV, with an uncertainty of 10–25% in the magnitude and vertical structure of this heating. Satellite remote sensing; Radiative heating rate profiles; Single-layered ice cloud properties
Douglas, Alyson; L'Ecuyer, TristanDouglas, A., T. L'Ecuyer, 2019: Quantifying variations in shortwave aerosol–cloud–radiation interactions using local meteorology and cloud state constraints. Atmospheric Chemistry and Physics, 19(9), 6251-6268. doi: 10.5194/acp-19-6251-2019. Abstract. While many studies have tried to quantify the sign and the magnitude of the warm marine cloud response to aerosol loading, both remain uncertain, owing to the multitude of factors that modulate microphysical and thermodynamic processes within the cloud. Constraining aerosol–cloud interactions using the local meteorology and cloud liquid water may offer a way to account for covarying influences, potentially increasing our confidence in observational estimates of warm cloud indirect effects. A total of 4 years of collocated satellite observations from the NASA A-Train constellation, combined with reanalysis from MERRA-2, are used to partition marine warm clouds into regimes based on stability, the free atmospheric relative humidity, and liquid water path. Organizing the sizable number of satellite observations into regimes is shown to minimize the covariance between the environment or liquid water path and the indirect effect. Controlling for local meteorology and cloud state mitigates artificial signals and reveals substantial variance in both the sign and magnitude of the cloud radiative response, including regions where clouds become systematically darker with increased aerosol concentration in dry, unstable environments. A darkening effect is evident even under the most stringent of constraints. These results suggest it is not meaningful to report a single global sensitivity of cloud radiative effect to aerosol. To the contrary, we find the sensitivity can range from −0.46 to 0.11 Wm−2 ln(AI)−1 regionally.
Duan, Wentao; Huang, Shaopeng; Nie, ChenweiDuan, W., S. Huang, C. Nie, 2019: Entrance Pupil Irradiance Estimating Model for a Moon-Based Earth Radiation Observatory Instrument. Remote Sensing, 11(5), 583. doi: 10.3390/rs11050583. A Moon-based Earth radiation observatory (MERO) could provide a longer-term continuous measurement of radiation exiting the Earth system compared to current satellite-based observatories. In order to parameterize the detector for such a newly-proposed MERO, the evaluation of the instrument’s entrance pupil irradiance (EPI) is of great importance. The motivation of this work is to build an EPI estimating model for a simplified single-pixel MERO instrument. The rationale of this model is to sum the contributions of every location in the MERO-viewed region on the Earth’s top of atmosphere (TOA) to the MERO sensor’s EPI, taking into account the anisotropy in the longwave radiance at the Earth TOA. Such anisotropy could be characterized by the TOA anisotropic factors, which can be derived from the Clouds and the Earth’s Radiant Energy System (CERES) angular distribution models (ADMs). As an application, we estimated the shortwave (SW) (0.3–5 µm) and longwave (LW) (5–200 µm) EPIs for a hypothetic MERO instrument located at the Apollo 15 landing site. Results show that the SW EPI varied from 0 to 0.065 W/m2, while the LW EPI ranged between 0.061 and 0.075 W/m2 from 1 to 29 October, 2017. We also utilized this model to predict the SW and LW EPIs for any given location within the MERO-deployable region (region of 80.5°W–80.5°E and 81.5°S–81.5°N on the nearside of the Moon) for the future 18.6 years from October 2017 to June 2036. Results suggest that the SW EPI will vary between 0 and 0.118 W/m2, while the LW EPI will range from 0.056 to 0.081 W/m2. Though the EPI estimating model in this study was built for a simplistic single-pixel instrument, it could eventually be extended and improved in order to estimate the EPI for a multi-pixel MERO sensor. CERES; ADMs; Earth radiation; entrance pupil irradiance; MERO; TOA anisotropy
Duda, David P.; Bedka, Sarah T.; Minnis, Patrick; Spangenberg, Douglas; Khlopenkov, Konstantin; Chee, Thad; Smith Jr., William L.Duda, D. P., S. T. Bedka, P. Minnis, D. Spangenberg, K. Khlopenkov, T. Chee, W. L. Smith Jr., 2019: Northern Hemisphere contrail properties derived from Terra and Aqua MODIS data for 2006 and 2012. Atmospheric Chemistry and Physics, 19(8), 5313-5330. doi: 10.5194/acp-19-5313-2019. Abstract. Linear contrail coverage, optical property, and radiative forcing data over the Northern Hemisphere (NH) are derived from a year (2012) of Terra and Aqua Moderate-resolution Imaging Spectroradiometer (MODIS) imagery and compared with previously published 2006 results (Duda et al., 2013; Bedka et al., 2013; Spangenberg et al., 2013) using a consistent retrieval methodology. Differences in the observed Terra-minus-Aqua screened contrail coverage and patterns in the 2012 annual-mean air traffic estimated with respect to satellite overpass time suggest that most contrails detected by the contrail detection algorithm (CDA) form approximately 2 h before overpass time. The 2012 screened NH contrail coverage (Mask B) shows a relative 3 % increase compared to 2006 data for Terra and increases by almost 7 % for Aqua, although the differences are not expected to be statistically significant. A new post-processing algorithm added to the contrail mask processing estimated that the total contrail cirrus coverage visible in the MODIS imagery may be 3 to 4 times larger than the linear contrail coverage detected by the CDA. This estimate is similar in magnitude to the spreading factor estimated by Minnis et al. (2013). Contrail property retrievals of the 2012 data indicate that both contrail optical depth and contrail effective diameter decreased approximately 10 % between 2006 and 2012. The decreases may be attributed to better background cloudiness characterization, changes in the waypoint screening, or changes in contrail temperature. The total mean contrail radiative forcings (TCRFs) for all 2012 Terra observations were −6.3, 14.3, and 8.0 mW m−2 for the shortwave (SWCRF), longwave (LWCRF), and net forcings, respectively. These values are approximately 20 % less than the corresponding 2006 Terra estimates. The decline in TCRF results from the decrease in normalized CRF, partially offset by the 3 % increase in overall contrail coverage in 2012. The TCRFs for 2012 Aqua are similar, −6.4, 15.5, and 9.0 mW m−2 for shortwave, longwave, and net radiative forcing. The strong correlation between the relative changes in both total SWCRF and LWCRF between 2006 and 2012 and the corresponding relative changes in screened contrail coverage over each air traffic region suggests that regional changes in TCRF from year to year are dominated by year-to-year changes in contrail coverage over each area.
El Masri, Bassil; Rahman, Abdullah F.; Dragoni, DaniloEl Masri, B., A. F. Rahman, D. Dragoni, 2019: Evaluating a new algorithm for satellite-based evapotranspiration for North American ecosystems: Model development and validation. Agricultural and Forest Meteorology, 268, 234-248. doi: 10.1016/j.agrformet.2019.01.025. We introduce a different operational approach to estimate 8-day average daily evapotranspiration (ET) using both routinely available data and the Penman-Monteith (P-M) equation for canopy transpiration and evaporation of intercepted water and Priestley and Taylor for soil evaporation. Our algorithm considered the environmental constraints on canopy resistance and ET by (1) including vapor pressure deficit (VPD), incoming solar radiation, soil moisture, and temperature constraints on stomatal conductance; (2) using leaf area index (LAI) to scale from the leaf to canopy conductance; and (3) calculating canopy resistance as a function of environmental variables such as net radiation and VPD. Remote sensing data from the Moderate Resolution Spectroradiometer (MODIS) and satellite soil moisture data were used to derive the ET model. The algorithm was calibrated and evaluated using measured ET data from 20 AmeriFlux Eddy covariance flux sites for the period of 2003–2012. We found good agreements between our 8-day ET estimates and observations with mean absolute error (MAE) ranges from 0.17 mm/day to 0.94 mm/day compared with MAE ranging from 0.28 mm/day to 1.50 mm/day for MODIS ET. Compared to MODIS ET, our proposed algorithm has higher correlations and higher Willmott’s index of agreement with observations for the majority of the Ameriflux sites. The strong relationship between the model estimated ET and the flux tower observations implies that our model has the potential to be applied to different ecosystems and at different temporal scales. Remote sensing; MODIS; Evapotranspiration; Eddy covariance flux; Penman-Monteith
Feng, Fei; Wang, KaicunFeng, F., K. Wang, 2019: Does the modern-era retrospective analysis for research and applications-2 aerosol reanalysis introduce an improvement in the simulation of surface solar radiation over China?. International Journal of Climatology, 39(3), 1305-1318. doi: 10.1002/joc.5881. Surface incident solar radiation (Rs) is a key parameter of energy and water cycles of the Earth. Reanalyses represent important sources of information on Rs. However, reanalyses Rs may have important bias due to their imperfect parameterizations and input errors of cloud and aerosol. NASA's Global Modelling and Assimilation Office has recently released Version 2 of the Modern-Era Retrospective Analysis for Research and Applications (MERRA2), which incorporates a reanalysis of atmospheric optical depth for the first time. In this study, we evaluate Rs from MERRA2 and its predecessor (MERRA) in China from 1980 to 2014. We first compare three possible reference data sources: (a) observed Rs at 122 stations, (b) satellite retrievals of Rs and (c) Rs values derived from sunshine durations measured at 2,400 weather stations. We find sunshine duration derived Rs is a reliable reference and use it to evaluate MERRA and MERRA2. Our results show that both MERRA and MERRA2 have a high mean bias of 38.63 and 43.86 W/m2 over China due to their underestimation of cloud fraction, which is greater in southern China. MERRA2 displays improved capability in reproducing monthly and annual variability, and national mean trend of Rs. MERRA overestimates the trend of Rs by 3.23 W/m2 in eastern China. MERRA2 reduced this trend bias over the North China Plain likely due to its aerosol assimilation. However, MERRA2 show a negative bias in trend of Rs (?3.44 W/m2) in the south China likely due to its overestimation of atmospheric aerosols loading and aerosol-cloud interaction. The results provide guidance for future development of reanalysis and its scientific applications for ecological and hydrological models. cloud; aerosol; surface incident solar radiation; MERRA2
Feng, Fei; Wang, KaicunFeng, F., K. Wang, 2019: Determining Factors of Monthly to Decadal Variability in Surface Solar Radiation in China: Evidences From Current Reanalyses. Journal of Geophysical Research: Atmospheres, 124(16), 9161-9182. doi: 10.1029/2018JD030214. Clouds and aerosols play essential roles in regulating surface incident solar radiation (Rs). It has been suggested that the increased aerosol loading over China is a key factor for the decadal variability in Rs and can explain the bias in its trend from reanalyses because the reanalyses do not include the interannual variability of aerosols. In this study, we compare the Rs derived from sunshine duration at 2,400 weather stations in China and that from five reanalyses from 1980 to 2014. The determining factors for the biases in the mean values and trends of Rs from the reanalyses are examined, with the help of Rs and the cloud fraction (CF), from satellite and 2,400 weather stations. Our results show that all reanalyses overestimate the multiyear Rs by 24.10–40.00 W/m2 due to their underestimations of CF, which is more obvious in southern China. The biases in the simulated CF in the reanalyses can explain the biases in Rs by 55–41%, and the bias in clear-sky surface solar radiation (Rc), which is primarily due to biases in aerosol loading, can explain 32–9% of the bias in Rs. The errors in the trend of the simulated CF can explain the errors in the Rs trends in the reanalyses by 73–12%, and the trend errors in the Rc can explain 43–30% of the trend error in Rs. Our study suggests that more work is needed to improve the simulation of aerosols, clouds, and aerosol-cloud-radiation interactions in the reanalyses. radiation; surface; solar
Feng, Huihui; Zou, BinFeng, H., B. Zou, 2019: Satellite-based estimation of the aerosol forcing contribution to the global land surface temperature in the recent decade. Remote Sensing of Environment, 232, 111299. doi: 10.1016/j.rse.2019.111299. The aerosol forcing is an essential factor of global climate change, which can be estimated by various models. However, the model results ranging from −2.8 to 2.2 K remain controversial because of unavoidable uncertainty, leaving a great gap for global change prediction. This study aims to evaluate the forcing on the land surface temperature (Ts) using satellite-based observations. Based on the Blackbody radiation and surface radiation budget, first, a semi-physical framework is developed to estimate the Ts. Subsequently, the aerosol forcing is calculated by measuring the Ts difference between the changing aerosol scenario and baseline scenario with a fixed aerosol amount. Results show that the framework simulates Ts with acceptable accuracy (R = 0.62 and RMSE = 1.48 K), which supports the estimation of aerosol forcing. Generally, the change in the aerosol contributes 0.005 ± 0.237 K to the global Ts, which presents significant temporal and spatial variabilities. Temporally, the forcing shows a decreasing trend of −0.0006 K/year (R2 = 0.29, p = 0.031). Spatially, the forcing tends to warm the surface in regions with arid climate, low-cloud fraction, and moderate vapor or in sparsely vegetated and cool regions because of the potential interactions with climatic and environmental factors. The result of this study helps to reduce the uncertainty and validate the model results, which further supports the research on global climatic and environmental change. Satellite; Aerosol forcing; Land surface temperature; Radiation budget; Global change
Feng, Jiaojiao; Wang, Weizhen; Li, JingFeng, J., W. Wang, J. Li, 2019: An LM-BP Neural Network Approach to Estimate Monthly-Mean Daily Global Solar Radiation Using MODIS Atmospheric Products. Energies, 11(12), 3510. doi: 10.3390/en11123510. Solar energy is one of the most widely used renewable energy sources in the world and its development and utilization are being integrated into people’s lives. Therefore, accurate solar radiation data are of great significance for site-selection of photovoltaic (PV) power generation, design of solar furnaces and energy-efficient buildings. Practically, it is challenging to get accurate solar radiation data because of scarce and uneven distribution of ground-based observation sites throughout the country. Many artificial neural network (ANN) estimation models are therefore developed to estimate solar radiation, but the existing ANN models are mostly based on conventional meteorological data; clouds, aerosols, and water vapor are rarely considered because of a lack of instrumental observations at the conventional meteorological stations. Based on clouds, aerosols, and precipitable water-vapor data from Moderate Resolution Imaging Spectroradiometer (MODIS), along with conventional meteorological data, back-propagation (BP) neural network method was developed in this work with Levenberg-Marquardt (LM) algorithm (referred to as LM-BP) to simulate monthly-mean daily global solar radiation (M-GSR). Comparisons were carried out among three M-GSR estimates, including the one presented in this study, the multiple linear regression (MLR) model, and remotely-sensed radiation products by Cloud and the Earth’s radiation energy system (CERES). The validation results indicate that the accuracy of the ANN model is better than that of the MLR model and CERES radiation products, with a root mean squared error (RMSE) of 1.34 MJ·m−2 (ANN), 2.46 MJ·m−2 (MLR), 2.11 MJ·m−2 (CERES), respectively. Finally, according to the established ANN-based method, the M-GSR of 36 conventional meteorological stations for 12 months was estimated in 2012 in the study area. Solar radiation data based on the LM-BP method of this study can provide some reference for the utilization of solar and heat energy. clouds; aerosols; precipitable water vapor; solar radiation; LM-BP neural network
Fueglistaler, S.Fueglistaler, S., 2019: Observational Evidence for Two Modes of Coupling Between Sea Surface Temperatures, Tropospheric Temperature Profile, and Shortwave Cloud Radiative Effect in the Tropics. Geophysical Research Letters, 46(16), 9890-9898. doi: 10.1029/2019GL083990. Tropical average shortwave cloud radiative effect (SWCRE) anomalies observed by CERES/EBAF v4 are explained by observed average sea surface temperature ( ) and the difference between the warmest 30% where deep convection occurs and ). Observed tropospheric temperatures show variations in boundary layer capping strength over time consistent with the evolution of SST#. The CERES/EBAF v4 data confirm that associated cloud fraction changes over the colder waters dominate SWCRE. This observational evidence for the “pattern effect” noted in General Circulation Model simulations suggests that SST# captures much of this effect. The observed sensitivities (dSWCRE/d W·m−2·K−1, dSWCRE/dSST#≈−4.8W·m−2·K−1) largely reflect El Niño–Southern Oscillation. As El Niño develops, increases and SST# decreases (both increasing SWCRE). Only after the El Niño peak, SST# increases and SWCRE decreases. SST# is also relevant for the tropical temperature trend profile controversy and the discrepancy between observed and modeled equatorial Pacific SST trends. Causality and implications for future climates are discussed. ENSO; cloud albedo; tropical convection; climate sensitivity; sea surface temperatures
Furtado, Kalli; Field, Paul; Luo, Yali; Zhou, Tianjun; Hill, AdrianFurtado, K., P. Field, Y. Luo, T. Zhou, A. Hill, 2019: The effects of cloud-aerosol-interaction complexity on simulations of presummer rainfall over southern China. Atmospheric Chemistry and Physics Discussions, 1-19. doi: https://doi.org/10.5194/acp-2019-596. Abstract. Convection-permitting simulations are used to understand the effects of cloud-aerosol interactions on a case of heavy rainfall over south China. The simulations are evaluated using radar observations from the South China Monsoon Rainfall Experiment and remotely sensed estimates of precipitation, clouds and radiation. We focus on the effects of complexity in cloud-aerosol interactions, especially processing and transport of dissolved material inside clouds. In particular, simulations with aerosol concentrations held constant are compared with a fully coupled cloud-aerosol-interacting system to isolate the effects of processing on a line of organised-deep convection. It is shown that in-cloud processing of aerosols can change the vertical structure of squall lines thereby inducing changes in the statistics of surface rainfall. These effects are shown to be consistent with a modulation by aerosol of the timescale of the converting cloud-droplets to rain.
Gasparini, Blaž; Blossey, Peter N.; Hartmann, Dennis L.; Lin, Guangxing; Fan, JiwenGasparini, B., P. N. Blossey, D. L. Hartmann, G. Lin, J. Fan, 2019: What Drives the Life Cycle of Tropical Anvil Clouds?. Journal of Advances in Modeling Earth Systems, 11(8), 2586-2605. doi: 10.1029/2019MS001736. The net radiative effects of tropical clouds are determined by the evolution of thick, freshly detrained anvil clouds into thin anvil clouds. Thick anvil clouds reduce Earth's energy balance and cool the climate, while thin anvil clouds warm the climate. To determine role of these clouds in climate change we need to understand how interactions of their microphysical and macrophysical properties control their radiative properties. We explore anvil cloud evolution using a cloud-resolving model in three-simulation setups of increasing complexity to disentangle the impacts of the various components of diabatic heating and their interaction with cloud-scale motions. The first phase of evolution and rapid cloud spreading is dominated by latent heating within convective updrafts. After the convective detrainment stops, most of the spreading and thinning of the anvil cloud is driven by cloud radiative processes and latent heating. The combination of radiative cooling at cloud top, latent cooling due to sublimation at cloud base, latent heating due to deposition and radiative heating in between leads to a sandwich-like, cooling-heating-cooling structure. The heating sandwich promotes the development of two within-anvil convective layers and a double cell circulation, dominated by strong outflow at 12-km altitude with inflow above and below. Our study reveals how small-scale processes including convective, microphysical processes, latent and radiative heating interact within the anvil cloud system. The absence or a different representation of only one component results in a significantly different cloud evolution with large impacts on cloud radiative effects. radiative effects; circulation; anvil cloud; convective life cycle; high clouds; tropical cirrus
Ge, Jinming; Wang, Zhenquan; Liu, Yuanyong; Su, Jing; Wang, Chen; Dong, ZixiangGe, J., Z. Wang, Y. Liu, J. Su, C. Wang, Z. Dong, 2019: Linkages between mid-latitude cirrus cloud properties and large-scale meteorology at the SACOL site. Climate Dynamics, 53(7), 5035-5046. doi: 10.1007/s00382-019-04843-9. The linkages between midlatitude cirrus properties and large-scale meteorology are investigated in this study by using 2-year observations from a ground Ka-band Zenith Radar (KAZR) and the Earth’s Radiant Energy System (CERES) SYN1deg satellite product over the Semi-Arid Climate and Environment Observatory of Lanzhou University (SACOL). Four atmospheric parameters (i.e. upward motion, relative humidity, stability and temperature at upper atmosphere) are used to examine the cirrus dependence on these factors. It is found that cirrus properties significantly depend on the changes of the four parameters and are most linearly correlated with upper atmosphere temperature. Cirrus infrared (IR) emissivity and ice water path (IWP) are sensitive to the strength of upward motions (ω), while cirrus thickness and albedo are more sensitive to relative humidity. An Empirical Orthogonal Function (EOF) is used to combine the four meteorological factors into a single variable and isolate the irrelevant synoptic noise to cirrus development and dissipation from the structure strongly associated with cirrus variations. The first leading principle component (PC1) is much better correlated with cirrus properties than any one of the four parameters. We further apply the EOF analysis to all 37 vertical levels of the four parameters. It is found that a negative area of the main structure between 6 and 10 km above ground level (AGL) is well collocated with the cirrus distribution from the KAZR observations on a diurnal time scale, indicating a robust relationship between cirrus and the combined meteorological fields.
Gettelman, A.; Mills, M. J.; Kinnison, D. E.; Garcia, R. R.; Smith, A. K.; Marsh, D. R.; Tilmes, S.; Vitt, F.; Bardeen, C. G.; McInerny, J.; Liu, H.-L.; Solomon, S. C.; Polvani, L. M.; Emmons, L. K.; Lamarque, J.-F.; Richter, J. H.; Glanville, A. S.; Bacmeister, J. T.; Phillips, A. S.; Neale, R. B.; Simpson, I. R.; DuVivier, A. K.; Hodzic, A.; Randel, W. J.Gettelman, A., M. J. Mills, D. E. Kinnison, R. R. Garcia, A. K. Smith, D. R. Marsh, S. Tilmes, F. Vitt, C. G. Bardeen, J. McInerny, H. Liu, S. C. Solomon, L. M. Polvani, L. K. Emmons, J. Lamarque, J. H. Richter, A. S. Glanville, J. T. Bacmeister, A. S. Phillips, R. B. Neale, I. R. Simpson, A. K. DuVivier, A. Hodzic, W. J. Randel, 2019: The Whole Atmosphere Community Climate Model Version 6 (WACCM6). Journal of Geophysical Research: Atmospheres, 124(23), 12380-12403. doi: 10.1029/2019JD030943. The Whole Atmosphere Community Climate Model version 6 (WACCM6) is a major update of the whole atmosphere modeling capability in the Community Earth System Model (CESM), featuring enhanced physical, chemical and aerosol parameterizations. This work describes WACCM6 and some of the important features of the model. WACCM6 can reproduce many modes of variability and trends in the middle atmosphere, including the quasi-biennial oscillation, stratospheric sudden warmings, and the evolution of Southern Hemisphere springtime ozone depletion over the twentieth century. WACCM6 can also reproduce the climate and temperature trends of the 20th century throughout the atmospheric column. The representation of the climate has improved in WACCM6, relative to WACCM4. In addition, there are improvements in high-latitude climate variability at the surface and sea ice extent in WACCM6 over the lower top version of the model (CAM6) that comes from the extended vertical domain and expanded aerosol chemistry in WACCM6, highlighting the importance of the stratosphere and tropospheric chemistry for high-latitude climate variability.
Golaz, Jean-Christophe; Caldwell, Peter M.; Roekel, Luke P. Van; Petersen, Mark R.; Tang, Qi; Wolfe, Jonathan D.; Abeshu, Guta; Anantharaj, Valentine; Asay‐Davis, Xylar S.; Bader, David C.; Baldwin, Sterling A.; Bisht, Gautam; Bogenschutz, Peter A.; Branstetter, Marcia; Brunke, Michael A.; Brus, Steven R.; Burrows, Susannah M.; Cameron‐Smith, Philip J.; Donahue, Aaron S.; Deakin, Michael; Easter, Richard C.; Evans, Katherine J.; Feng, Yan; Flanner, Mark; Foucar, James G.; Fyke, Jeremy G.; Griffin, Brian M.; Hannay, Cécile; Harrop, Bryce E.; Hoffman, Mattthew J.; Hunke, Elizabeth C.; Jacob, Robert L.; Jacobsen, Douglas W.; Jeffery, Nicole; Jones, Philip W.; Keen, Noel D.; Klein, Stephen A.; Larson, Vincent E.; Leung, L. Ruby; Li, Hong-Yi; Lin, Wuyin; Lipscomb, William H.; Ma, Po-Lun; Mahajan, Salil; Maltrud, Mathew E.; Mametjanov, Azamat; McClean, Julie L.; McCoy, Renata B.; Neale, Richard B.; Price, Stephen F.; Qian, Yun; Rasch, Philip J.; Eyre, J. E. Jack Reeves; Riley, William J.; Ringler, Todd D.; Roberts, Andrew F.; Roesler, Erika L.; Salinger, Andrew G.; Shaheen, Zeshawn; Shi, Xiaoying; Singh, Balwinder; Tang, Jinyun; Taylor, Mark A.; Thornton, Peter E.; Turner, Adrian K.; Veneziani, Milena; Wan, Hui; Wang, Hailong; Wang, Shanlin; Williams, Dean N.; Wolfram, Phillip J.; Worley, Patrick H.; Xie, Shaocheng; Yang, Yang; Yoon, Jin-Ho; Zelinka, Mark D.; Zender, Charles S.; Zeng, Xubin; Zhang, Chengzhu; Zhang, Kai; Zhang, Yuying; Zheng, Xue; Zhou, Tian; Zhu, QingGolaz, J., P. M. Caldwell, L. P. V. Roekel, M. R. Petersen, Q. Tang, J. D. Wolfe, G. Abeshu, V. Anantharaj, X. S. Asay‐Davis, D. C. Bader, S. A. Baldwin, G. Bisht, P. A. Bogenschutz, M. Branstetter, M. A. Brunke, S. R. Brus, S. M. Burrows, P. J. Cameron‐Smith, A. S. Donahue, M. Deakin, R. C. Easter, K. J. Evans, Y. Feng, M. Flanner, J. G. Foucar, J. G. Fyke, B. M. Griffin, C. Hannay, B. E. Harrop, M. J. Hoffman, E. C. Hunke, R. L. Jacob, D. W. Jacobsen, N. Jeffery, P. W. Jones, N. D. Keen, S. A. Klein, V. E. Larson, L. R. Leung, H. Li, W. Lin, W. H. Lipscomb, P. Ma, S. Mahajan, M. E. Maltrud, A. Mametjanov, J. L. McClean, R. B. McCoy, R. B. Neale, S. F. Price, Y. Qian, P. J. Rasch, J. E. J. R. Eyre, W. J. Riley, T. D. Ringler, A. F. Roberts, E. L. Roesler, A. G. Salinger, Z. Shaheen, X. Shi, B. Singh, J. Tang, M. A. Taylor, P. E. Thornton, A. K. Turner, M. Veneziani, H. Wan, H. Wang, S. Wang, D. N. Williams, P. J. Wolfram, P. H. Worley, S. Xie, Y. Yang, J. Yoon, M. D. Zelinka, C. S. Zender, X. Zeng, C. Zhang, K. Zhang, Y. Zhang, X. Zheng, T. Zhou, Q. Zhu, 2019: The DOE E3SM Coupled Model Version 1: Overview and Evaluation at Standard Resolution. Journal of Advances in Modeling Earth Systems, 11(7), 2089-2129. doi: 10.1029/2018MS001603. This work documents the first version of the U.S. Department of Energy (DOE) new Energy Exascale Earth System Model (E3SMv1). We focus on the standard resolution of the fully coupled physical model designed to address DOE mission-relevant water cycle questions. Its components include atmosphere and land (110-km grid spacing), ocean and sea ice (60 km in the midlatitudes and 30 km at the equator and poles), and river transport (55 km) models. This base configuration will also serve as a foundation for additional configurations exploring higher horizontal resolution as well as augmented capabilities in the form of biogeochemistry and cryosphere configurations. The performance of E3SMv1 is evaluated by means of a standard set of Coupled Model Intercomparison Project Phase 6 (CMIP6) Diagnosis, Evaluation, and Characterization of Klima simulations consisting of a long preindustrial control, historical simulations (ensembles of fully coupled and prescribed SSTs) as well as idealized CO2 forcing simulations. The model performs well overall with biases typical of other CMIP-class models, although the simulated Atlantic Meridional Overturning Circulation is weaker than many CMIP-class models. While the E3SMv1 historical ensemble captures the bulk of the observed warming between preindustrial (1850) and present day, the trajectory of the warming diverges from observations in the second half of the twentieth century with a period of delayed warming followed by an excessive warming trend. Using a two-layer energy balance model, we attribute this divergence to the model's strong aerosol-related effective radiative forcing (ERFari+aci = −1.65 W/m2) and high equilibrium climate sensitivity (ECS = 5.3 K).
Granados-Muñoz, Maria José; Sicard, Michaël; Papagiannopoulos, Nikolaos; Barragán, Rubén; Bravo-Aranda, Juan Antonio; Nicolae, DoinaGranados-Muñoz, M. J., M. Sicard, N. Papagiannopoulos, R. Barragán, J. A. Bravo-Aranda, D. Nicolae, 2019: 2-D mineral dust radiative forcing calculations from CALIPSO observations over Europe. Atmospheric Chemistry and Physics Discussions, 1-40. doi: 10.5194/acp-2019-440. Abstract. A demonstration study to examine the feasibility to retrieve dust radiative effects based on combined satellite data from MODIS (Moderate Resolution Imaging Spectroradiometer), CERES (Clouds and the Earth’s Radiant Energy System) and CALIOP (Cloud-Aerosol Lidar with Orthogonal Polarization) li-dar vertical profiles along their orbit is presented. The radiative transfer model GAME (Global Atmos-pheric Model) is used to estimate the shortwave and longwave dust radiative effects below the CALIP-SO (Cloud-Aerosol Lidar and Infrared Pathfinder Satellite) orbit assuming an aerosol parameterization based on CALIOP vertical distribution at a horizontal resolution of 5 km and additional AERONET (Aerosol Robotic Network) data. Two study cases are analysed; a strong long-range transport mineral dust event (AOD = 0.52) originated in the Sahara Desert and reaching the United Kingdom and a weaker event (AOD = 0.16) affecting Eastern Europe. The obtained radiative fluxes are first validated in terms of radiative forcing efficiency at a single point with space-time co-located lidar ground-based measurements from EARLINET (European Aerosol Research Lidar Network) stations below the orbit. The methodology is then applied to the full orbit. The obtained results indicate that the radiative effects show a strong dependence on the aerosol load, highlighting the need of accurate AOD measurements for forcing studies, and on the surface albedo. The calculated dust radiative effects and heating rates below the orbits are in good agreement with previous studies of mineral dust, with the forcing efficiency obtained at the surface ranging between −80.3 and −63.0 W m−2 for the weaker event and −119.1 and −79.3 W m−2 for the strong one. Results thus demonstrate the validity of the presented method to retrieve 2-D accurate radiative properties with large spatial and temporal coverage.
Granados-Muñoz, María José; Sicard, Michael; Román, Roberto; Benavent-Oltra, Jose Antonio; Barragán, Rubén; Brogniez, Gerard; Denjean, Cyrielle; Mallet, Marc; Formenti, Paola; Torres, Benjamín; Alados-Arboledas, LucasGranados-Muñoz, M. J., M. Sicard, R. Román, J. A. Benavent-Oltra, R. Barragán, G. Brogniez, C. Denjean, M. Mallet, P. Formenti, B. Torres, L. Alados-Arboledas, 2019: Impact of mineral dust on shortwave and longwave radiation: evaluation of different vertically resolved parameterizations in 1-D radiative transfer computations. Atmospheric Chemistry and Physics, 19(1), 523-542. doi: 10.5194/acp-19-523-2019. Abstract. Aerosol radiative properties are investigated in southeastern Spain during a dust event on 16–17 June 2013 in the framework of the ChArMEx/ADRIMED (Chemistry-Aerosol Mediterranean Experiment/Aerosol Direct Radiative Impact on the regional climate in the MEDiterranean region) campaign. Particle optical and microphysical properties from ground-based sun/sky photometer and lidar measurements, as well as in situ measurements on board the SAFIRE ATR 42 French research aircraft, are used to create a set of different levels of input parameterizations, which feed the 1-D radiative transfer model (RTM) GAME (Global Atmospheric ModEl). We consider three datasets: (1) a first parameterization based on the retrievals by an advanced aerosol inversion code (GRASP; Generalized Retrieval of Aerosol and Surface Properties) applied to combined photometer and lidar data, (2) a parameterization based on the photometer columnar optical properties and vertically resolved lidar retrievals with the two-component Klett–Fernald algorithm, and (3) a parameterization based on vertically resolved optical and microphysical aerosol properties measured in situ by the aircraft instrumentation. Once retrieved, the outputs of the RTM in terms of both shortwave and longwave radiative fluxes are compared against ground and in situ airborne measurements. In addition, the outputs of the model in terms of the aerosol direct radiative effect are discussed with respect to the different input parameterizations. Results show that calculated atmospheric radiative fluxes differ no more than 7% from the measured ones. The three parameterization datasets produce a cooling effect due to mineral dust both at the surface and the top of the atmosphere. Aerosol radiative effects with differences of up to 10Wm−2 in the shortwave spectral range (mostly due to differences in the aerosol optical depth) and 2Wm−2 for the longwave spectral range (mainly due to differences in the aerosol optical depth but also to the coarse mode radius used to calculate the radiative properties) are obtained when comparing the three parameterizations. The study reveals the complexity of parameterizing 1-D RTMs as sizing and characterizing the optical properties of mineral dust is challenging. The use of advanced remote sensing data and processing, in combination with closure studies on the optical and microphysical properties from in situ aircraft measurements when available, is recommended.
Gristey, Jake J.; Chiu, J. Christine; Gurney, Robert J.; Shine, Keith P.; Havemann, Stephan; Thelen, Jean-Claude; Hill, Peter G.Gristey, J. J., J. C. Chiu, R. J. Gurney, K. P. Shine, S. Havemann, J. Thelen, P. G. Hill, 2019: Shortwave Spectral Radiative Signatures and Their Physical Controls. J. Climate, 32(15), 4805-4828. doi: 10.1175/JCLI-D-18-0815.1. The spectrum of reflected solar radiation emerging at the top of the atmosphere is rich with Earth system information. To identify spectral signatures in the reflected solar radiation and directly relate them to the underlying physical properties controlling their structure, over 90 000 solar reflectance spectra are computed over West Africa in 2010 using a fast radiation code employing the spectral characteristics of the Scanning Imaging Absorption Spectrometer for Atmospheric Chartography (SCIAMACHY). Cluster analysis applied to the computed spectra reveals spectral signatures related to distinct surface properties, and cloud regimes distinguished by their spectral shortwave cloud radiative effect (SWCRE). The cloud regimes exhibit a diverse variety of mean broadband SWCREs, and offer an alternative approach to define cloud type for SWCRE applications that does not require any prior assumptions. The direct link between spectral signatures and distinct physical properties extracted from clustering remains robust between spatial scales of 1, 20, and 240 km, and presents an excellent opportunity to understand the underlying properties controlling real spectral reflectance observations. Observed SCIAMACHY spectra are assigned to the calculated spectral clusters, showing that cloud regimes are most frequent during the active West African monsoon season of June–October in 2010, and all cloud regimes have a higher frequency of occurrence during the active monsoon season of 2003 compared with the inactive monsoon season of 2004. Overall, the distinct underlying physical properties controlling spectral signatures show great promise for monitoring evolution of the Earth system directly from solar spectral reflectance observations.
Guo, Zhun; Wang, Minghuai; Larson, Vincent E.; Zhou, TianjunGuo, Z., M. Wang, V. E. Larson, T. Zhou, 2019: A Cloud Top Radiative Cooling Model Coupled With CLUBB in the Community Atmosphere Model: Description and Simulation of Low Clouds. Journal of Advances in Modeling Earth Systems, 11(4), 979-997. doi: 10.1029/2018MS001505. In this study, a higher-order closure scheme known as Cloud Layers Unified By Binormals (CLUBB) is coupled with a cloud top radiative cooling scheme (RAD). The cloud top radiative cooling scheme treats the buoyancy flux generated near the top of the boundary layer which helps the CLUBB scheme to better represent the radiation-turbulence interaction on the condition of coarse vertical resolution. CLUBB with RAD is found to improve subtropical low-cloud simulations, and the improvement is particularly evident for nocturnal stratocumulus. The improvements are caused by the stronger and more symmetric vertical turbulent mixing in the boundary layer, as CLUBB with RAD increases the variance of vertical velocity and vertical turbulent transports and reduces the skewness of vertical velocity by enhancing the radiative cooling effects and buoyancy fluxes at the cloud layer. The pumping effect related to the stronger vertical turbulent transports further cools and dries the lower boundary layer, which increases the local surface heating fluxes and further improves the low-cloud simulations. buoyancy flux; low cloud; cloud top radiative cooling; higher-order closure scheme
Hahn, Gregory G.; Adoram-Kershner, Lauren Andrea; Cantin, Heather P.; Shafer, Michael W.Hahn, G. G., L. A. Adoram-Kershner, H. P. Cantin, M. W. Shafer, 2019: Assessing Solar Power for Globally Migrating Marine and Submarine Systems. IEEE Journal of Oceanic Engineering, 44(3), 693-706. doi: 10.1109/JOE.2018.2835178. Remote marine sensing systems, such as autonomous underwater vehicles or telemetry tags, can be limited in data collection and deployment duration due to the finite energy of the onboard battery. With these technologies migrating vast distances over long-term deployments, maintaining high data resolution is difficult and often yields nonideal data sets. Furthermore, electronics systems used in telemetry tags are often potted in epoxy, which makes replacing or recharging the battery impractical. The implementation of solar energy harvesting on these technologies could increase the fidelity of collected data and/or tag longevity. This paper presents an assessment model that estimates the energy output of a stationary or migrating solar cell above or below the ocean's surface. The theory and assumptions behind the model are explained, including a review of established concepts for the purpose of consolidation and variable consistency. The model is then compared to benchmark data for verification. Finally, a preliminary analysis is conducted on the previously collected time, depth, and global location data from a northern elephant seal deployment to demonstrate the resulting model outputs and how they can be used for analysis in future works. oceanographic equipment; oceanographic techniques; solar energy; Sea surface; Ocean temperature; solar power; assessing solar power; assessment model; autonomous underwater vehicles; benchmark data; collected time; data collection; deployment duration; electronics systems; energy harvesting; energy output; global location data; globally migrating marine; high data resolution; long-term deployments; Marine technology; migrating solar cell; model outputs; nonideal data sets; northern elephant seal deployment; onboard battery; Photovoltaic cells; predictive models; radiotelemetry; remote marine sensing systems; remotely operated vehicles; Solar energy; solar energy harvesting; stationary cell; submarine systems; Sun; tag longevity; telemetry; Telemetry; telemetry tags; underwater equipment; underwater vehicles; Underwater vehicles; wireless sensor networks
Hakuba, Maria Z.; Stephens, Graeme L.; Christophe, Bruno; Nash, Alfred E.; Foulon, Bernard; Bettadpur, Srinivas V.; Tapley, Byron D.; Webb, Frank H.Hakuba, M. Z., G. L. Stephens, B. Christophe, A. E. Nash, B. Foulon, S. V. Bettadpur, B. D. Tapley, F. H. Webb, 2019: Earth’s Energy Imbalance Measured From Space. IEEE Transactions on Geoscience and Remote Sensing, 57(1), 32-45. doi: 10.1109/TGRS.2018.2851976. The direct measurement of earth's energy imbalance (EEI) is one of the greatest challenges in climate research. The global mean EEI represents the integrated value of global warming and is tightly linked to changes in hydrological cycle and the habitability of our planet. Current space-born radiometers measure the individual radiative components of the energy balance with unprecedented stability, but with calibration errors too large to determine the absolute magnitude of global mean EEI as the components' residual. Best estimates of the long-term EEI are currently derived from temporal changes in ocean heat content at 0.7 Wm-2. To monitor EEI directly from space, we propose an independent approach based on accelerometry that measures nongravitational forces, such as radiation pressure, acting on earth-orbiting spacecrafts. The concept of deriving EEI from radiation pressure has been considered in the past, and we provide analysis that shows today's capabilities are sufficiently accurate to answer the question: At what rate is our planet warming? To measure global mean EEI to within at least ±0.3 Wm-2 requires spacecraft(s) of near-spherical shape and well-characterized surface properties to reduce confounding effects. The proposed concept may provide the basis for a data record of global and zonal mean EEI on annual and potentially monthly timescales. It is not meant to replace the existing concepts designed to measure energy balance components or ocean heat storage, but to complement these by providing an independent estimate of EEI for comparison and to anchor data products and climate models that lack energy balance closure. atmospheric radiation; Earth; Extraterrestrial measurements; Space vehicles; radiometry; Sea measurements; Oceans; hydrology; hydrological cycle; global warming; atmospheric temperature; remote sensing; climatology; Accelerometer; climate research; current space-born radiometers; earth-orbiting spacecrafts; earth’s energy imbalance; energy balance closure; energy balance components; global EEI; global mean EEI; Heating systems; individual radiative components; long-term EEI; low earth orbit satellites; Pressure measurement; radiation pressure; space vehicles; zonal mean EEI
Ham, Seung-Hee; Kato, Seiji; Rose, Fred G.Ham, S., S. Kato, F. G. Rose, 2019: Impacts of Partly Cloudy Pixels on Shortwave Broadband Irradiance Computations. J. Atmos. Oceanic Technol., 36(3), 369-386. doi: 10.1175/JTECH-D-18-0153.1. Because of the limitation of the spatial resolution of satellite sensors, satellite pixels identified as cloudy are often partly cloudy. For the first time, this study demonstrates the bias in shortwave (SW) broadband irradiances for partly cloudy pixels when the cloud optical depths are retrieved with an overcast and homogeneous assumption, and subsequently, the retrieved values are used for the irradiance computations. The sign of the SW irradiance bias is mainly a function of viewing geometry of the cloud retrieval. The bias in top-of-atmosphere (TOA) upward SW irradiances is positive for small viewing zenith angles (VZAs) ~60°. For a given solar zenith angle and viewing geometry, the magnitude of the bias increases with the cloud optical depth and reaches a maximum at the cloud fraction between 0.2 and 0.8. The sign of the SW surface net irradiance bias is opposite of the sign of TOA upward irradiance bias, with a similar magnitude. As a result, the bias in absorbed SW irradiances by the atmosphere is smaller than the biases in both TOA and surface irradiances. The monthly mean biases in SW irradiances due to partly cloudy pixels are
Hang, Yun; L’Ecuyer, Tristan S.; Henderson, David S.; Matus, Alexander V.; Wang, ZhienHang, Y., T. S. L’Ecuyer, D. S. Henderson, A. V. Matus, Z. Wang, 2019: Reassessing the Effect of Cloud Type on Earth’s Energy Balance in the Age of Active Spaceborne Observations. Part II: Atmospheric Heating. J. Climate, 32(19), 6219-6236. doi: 10.1175/JCLI-D-18-0754.1. The role of clouds in modulating vertically integrated atmospheric heating is investigated using CloudSat’s multisensor radiative flux dataset. On the global mean, clouds are found to induce a net atmospheric heating of 0.07 ± 0.08 K day−1 that derives largely from 0.06 ± 0.07 K day−1 of enhanced shortwave absorption and a small, 0.01 ± 0.04 K day−1 reduction of longwave cooling. However, this small global average longwave effect results from the near cancellation of much larger regional warming by multilayered cloud systems in the tropics and cooling from stratocumulus clouds in subtropical oceans. Clouds are observed to warm the tropical atmosphere by 0.23 K day−1 and cool the polar atmosphere by −0.13 K day−1 enhancing required zonal heat redistribution by the meridional overturning circulation. Zonal asymmetries in the occurrence of multilayered clouds that are more frequent in the Northern Hemisphere and stratocumulus that occur more frequently over the southern oceans also leads to 3 times as much cloud heating in the Northern Hemisphere (0.1 K day−1) than the Southern Hemisphere (0.04 K day−1). These findings suggest that clouds very likely make the strongest contribution to the annual mean atmospheric energy imbalance between the hemispheres (2.0 ± 3.5 PW).
Hao, Dalei; Asrar, Ghassem R.; Zeng, Yelu; Zhu, Qing; Wen, Jianguang; Xiao, Qing; Chen, MinHao, D., G. R. Asrar, Y. Zeng, Q. Zhu, J. Wen, Q. Xiao, M. Chen, 2019: Estimating hourly land surface downward shortwave and photosynthetically active radiation from DSCOVR/EPIC observations. Remote Sensing of Environment, 232, 111320. doi: 10.1016/j.rse.2019.111320. The direct and diffuse components of downward shortwave radiation (SW), and photosynthetically active radiation (PAR) at the Earth surface play an essential role in biochemical (e.g. photosynthesis) and physical (e.g. energy balance) processes that control weather and climate conditions, and many ecological processes. Space-based observations have the unique advantage of providing reliable estimates of SW and PAR globally with sufficient accuracy for constructing Earth's radiation budget and estimating land-surface fluxes that control these processes. However, most existing space-based SW and PAR estimations from sensors onboard polar-orbiting and geostationary satellites have inherently low temporal resolution and/or limited spatial coverage of the entire Earth surface. The unique location/orbit of Earth Polychromatic Imaging Camera (EPIC) onboard the Deep Space Climate Observatory (DSCOVR) provides an unprecedented opportunity to obtain global estimates of SW and PAR accurately at a high temporal resolution of about 1–2 h. In this study, we developed and used a model (random forest, RF) to estimate global hourly SW and PAR at 0.1° × 0.1° (about 10 km at equator) spatial resolution based on EPIC measurements. We used a combination of EPIC Level-2 products, including solar zenith angle, aerosol optical depth, cloud optical thickness, cloud fraction, total column ozone and surface pressure with their associated quality flags to drive the RF model for estimating SW and PAR. We evaluated the model results against in situ observations from the Baseline Surface Radiation Network (BSRN) and Surface Radiation Budget Network (SURFRAD). We found the EPIC SW and PAR estimates at both hourly and daily time scales to be highly correlated and consistent with these independently obtained in situ measurements. The RMSEs for estimated daily diffuse SW, direct SW, total SW, and total PAR were 19.10, 38.47, 33.52, and 14.09 W/m2, respectively, and the biases for these estimates were 1.71, −0.77, 1.04 and 4.11 W/m2, respectively. We further compared the estimated SW and PAR with the Clouds and the Earth's Radiant Energy System Synoptic 1° × 1° (CERES SYN1deg) products and found a good correlation and consistency in their accuracy, spatial patterns and latitudinal gradient. The EPIC SW and PAR estimates provide a unique dataset (i.e. observations from single instrument from pole-to-pole for the entire sunlit portion of Earth) for characterizing their diurnal cycles and their potential impact on photosynthesis and evapotranspiration processes. BSRN; Shortwave radiation; PAR; SURFRAD; DSCOVR; EPIC; Diffuse PAR
Hayatbini, Negin; Hsu, Kuo-lin; Sorooshian, Soroosh; Zhang, Yunji; Zhang, FuqingHayatbini, N., K. Hsu, S. Sorooshian, Y. Zhang, F. Zhang, 2019: Effective Cloud Detection and Segmentation Using a Gradient-Based Algorithm for Satellite Imagery: Application to Improve PERSIANN-CCS. J. Hydrometeor., 20(5), 901-913. doi: 10.1175/JHM-D-18-0197.1. The effective identification of clouds and monitoring of their evolution are important toward more accurate quantitative precipitation estimation and forecast. In this study, a new gradient-based cloud-image segmentation algorithm is developed using image processing techniques. This method integrates morphological image gradient magnitudes to separate cloud systems and patches boundaries. A varying scale kernel is implemented to reduce the sensitivity of image segmentation to noise and to capture objects with various finenesses of the edges in remote sensing images. The proposed method is flexible and extendable from single to multispectral imagery. Case studies were carried out to validate the algorithm by applying the proposed segmentation algorithm to synthetic radiances for channels of the Geostationary Operational Environmental Satellite (GOES-16) simulated by a high-resolution weather prediction model. The proposed method compares favorably with the existing cloud-patch-based segmentation technique implemented in the Precipitation Estimation from Remotely Sensed Information Using Artificial Neural Networks–Cloud Classification System (PERSIANN-CCS) rainfall retrieval algorithm. Evaluation of event-based images indicates that the proposed algorithm has potentials comparing to the conventional segmentation technique used in PERSIANN-CCS to improve rain detection and estimation skills with an accuracy rate of up to 98% in identifying cloud regions.
He, Min; Hu, Yongxiang; Chen, Nan; Wang, Donghai; Huang, Jianping; Stamnes, KnutHe, M., Y. Hu, N. Chen, D. Wang, J. Huang, K. Stamnes, 2019: High cloud coverage over melted areas dominates the impact of clouds on the albedo feedback in the Arctic. Scientific Reports, 9(1), 1-11. doi: 10.1038/s41598-019-44155-w. Warming in the Arctic is larger than the global average. A primary reason for this Arctic Amplification is the albedo feedback. The contrasting albedo of sea ice and dark melted surface areas is the key component of albedo feedback. Cloud coverage over the changing surface and the response of the clouds to the changing surface conditions will modify the change in planetary albedo when sea ice melts. Space-based lidar measurements provide a unique opportunity for cloud measurements in the Arctic. The response of clouds to the changing sea ice concentration was directly observed. Based on CALIPSO satellite observations of cloud properties, this study found that cloud coverage in ice-free regions in the Arctic linearly increased with the area of ice-free water during the melt seasons in the past 10 years, while sea ice coverage varies significantly year-to-year. The observations suggest that when sea-ice retreats, cloud fraction of the ice-free region remains fixed at nearly 81%. The high cloud coverage over melted areas significantly reduces the albedo feedback. These results indicate that space-based lidar cloud and surface observations of the Arctic can help constrain and improve climate models.
Hecht, Matthew; Veneziani, Milena; Weijer, Wilbert; Kravitz, Ben; Burrows, Susannah; Comeau, Darin; Hunke, Elizabeth; Jeffery, Nicole; Urrego‐Blanco, Jorge; Wang, Hailong; Wang, Shanlin; Zhang, Jiaxu; Bailey, David; Mills, Catrin; Rasch, Philip; Urban, NathanHecht, M., M. Veneziani, W. Weijer, B. Kravitz, S. Burrows, D. Comeau, E. Hunke, N. Jeffery, J. Urrego‐Blanco, H. Wang, S. Wang, J. Zhang, D. Bailey, C. Mills, P. Rasch, N. Urban, 2019: E3SMv0-HiLAT: A Modified Climate System Model Targeted for the Study of High-Latitude Processes. Journal of Advances in Modeling Earth Systems, 11(8), 2814-2843. doi: 10.1029/2018MS001524. We document the configuration, tuning, and evaluation of a modified version of the Community Earth System Model version 1 (Hurrell et al., 2013, https://doi.org/10.1175/BAMS-D-12), introduced here as E3SMv0-HiLAT, intended for study of high-latitude processes. E3SMv0-HiLAT incorporates changes to the atmospheric model affecting aerosol transport to high northern latitudes and to reduce shortwave cloud bias over the Southern Ocean. An updated sea ice model includes biogeochemistry that is coupled to an extended version of the ocean model's biogechemistry. This enables cloud nucleation to depend on the changing marine emissions of aerosol precursors, which may be expected in scenarios with strongly changing sea ice extent, oceanic stratification and associated nutrient availability, and atmospheric state. An evaluation of the basic preindustrial state of E3SMv0-HiLAT is presented in order to ensure that its climate is adequate to support future experimentation. Additional capability is not achieved without some cost, relative to the extraordinarily well-tuned model from which it was derived. In particular, a reduction of bias in cloud forcing achieved over the Southern Hemisphere also allows for greater Southern Ocean sea ice extent, a tendency that has been partially but not fully alleviated through experimentation and tuning. The most interesting change in the behavior of the model may be its response to greenhouse gas forcing: While the climate sensitivity is found to be essentially unchanged from that of Community Earth System Model version 1, the adjusted radiative forcing has increased from within one standard deviation above that of Coupled Model Intercomparison Project Phase 5 models to nearly two standard deviations. clouds; CESM; Earth System Model; high latitudes
Held, I. M.; Guo, H.; Adcroft, A.; Dunne, J. P.; Horowitz, L. W.; Krasting, J.; Shevliakova, E.; Winton, M.; Zhao, M.; Bushuk, M.; Wittenberg, A. T.; Wyman, B.; Xiang, B.; Zhang, R.; Anderson, W.; Balaji, V.; Donner, L.; Dunne, K.; Durachta, J.; Gauthier, P. P. G.; Ginoux, P.; Golaz, J.-C.; Griffies, S. M.; Hallberg, R.; Harris, L.; Harrison, M.; Hurlin, W.; John, J.; Lin, P.; Lin, S.-J.; Malyshev, S.; Menzel, R.; Milly, P. C. D.; Ming, Y.; Naik, V.; Paynter, D.; Paulot, F.; Rammaswamy, V.; Reichl, B.; Robinson, T.; Rosati, A.; Seman, C.; Silvers, L. G.; Underwood, S.; Zadeh, N.Held, I. M., H. Guo, A. Adcroft, J. P. Dunne, L. W. Horowitz, J. Krasting, E. Shevliakova, M. Winton, M. Zhao, M. Bushuk, A. T. Wittenberg, B. Wyman, B. Xiang, R. Zhang, W. Anderson, V. Balaji, L. Donner, K. Dunne, J. Durachta, P. P. G. Gauthier, P. Ginoux, J. Golaz, S. M. Griffies, R. Hallberg, L. Harris, M. Harrison, W. Hurlin, J. John, P. Lin, S. Lin, S. Malyshev, R. Menzel, P. C. D. Milly, Y. Ming, V. Naik, D. Paynter, F. Paulot, V. Rammaswamy, B. Reichl, T. Robinson, A. Rosati, C. Seman, L. G. Silvers, S. Underwood, N. Zadeh, 2019: Structure and Performance of GFDL's CM4.0 Climate Model. Journal of Advances in Modeling Earth Systems, 11(11), 3691-3727. doi: 10.1029/2019MS001829. We describe the Geophysical Fluid Dynamics Laboratory's CM4.0 physical climate model, with emphasis on those aspects that may be of particular importance to users of this model and its simulations. The model is built with the AM4.0/LM4.0 atmosphere/land model and OM4.0 ocean model. Topics include the rationale for key choices made in the model formulation, the stability as well as drift of the preindustrial control simulation, and comparison of key aspects of the historical simulations with observations from recent decades. Notable achievements include the relatively small biases in seasonal spatial patterns of top-of-atmosphere fluxes, surface temperature, and precipitation; reduced double Intertropical Convergence Zone bias; dramatically improved representation of ocean boundary currents; a high-quality simulation of climatological Arctic sea ice extent and its recent decline; and excellent simulation of the El Niño-Southern Oscillation spectrum and structure. Areas of concern include inadequate deep convection in the Nordic Seas; an inaccurate Antarctic sea ice simulation; precipitation and wind composites still affected by the equatorial cold tongue bias; muted variability in the Atlantic Meridional Overturning Circulation; strong 100 year quasiperiodicity in Southern Ocean ventilation; and a lack of historical warming before 1990 and too rapid warming thereafter due to high climate sensitivity and strong aerosol forcing, in contrast to the observational record. Overall, CM4.0 scores very well in its fidelity against observations compared to the Coupled Model Intercomparison Project Phase 5 generation in terms of both mean state and modes of variability and should prove a valuable new addition for analysis across a broad array of applications. climate; model; CMIP6; CM4; coupled; GFDL
Hinkelman, Laura M.Hinkelman, L. M., 2019: The global radiative energy budget in MERRA Version 1 and Version 2: Evaluation with respect to CERES EBAF data. J. Climate, 32(6), 1973–1994. doi: 10.1175/JCLI-D-18-0445.1. The representation of the long-term radiative energy budgets in NASA’s MERRA and MERRA-2 reanalyses has been evaluated, emphasizing changes associated with the reanalysis system update. Data from the CERES EBAF Edition 2.8 satellite product over 2001-2015 were used as a reference. For both MERRA and MERRA-2, the climatological global means of most TOA radiative flux terms agree to within ∼3 Wm-2 of EBAF. However, MERRA-2’s all-sky reflected shortwave flux is ∼7 Wm-2 higher than either MERRA or EBAF’s, resulting in a net TOA flux imbalance of -4 Wm-2. At the surface, all-sky downward longwave fluxes are problematic for both reanalyses while high clear-sky downward shortwave fluxes indicate that their atmospheres are too transmissive. Although MERRA-2’s individual all-sky flux terms agree better with EBAF, its net flux agreement is worse (-8.3 Wm-2 vs -3.3 Wm-2 for MERRA) because MERRA benefits from cancellation of errors. Analysis by region and surface type gives mixed outcomes. The results consistently indicate that clouds are over-represented over the tropical oceans in both reanalyses, particularly MERRA-2, and somewhat under-represented in marine stratocumulus areas. MERRA-2 also exhibits signs of excess cloudiness in the Southern Ocean. Notable discrepancies occur in the polar regions, where the effects of snow and ice cover are important. In most cases, MERRA-2 better represents variability and trends in the global mean radiative fluxes over the period of analysis. Overall, the performance of MERRA-2 relative to MERRA is mixed; there is still room for improvement in the radiative fluxes in this family of reanalysis products.
Hogikyan, Allison; Cronin, Meghan F.; Zhang, Dongxiao; Kato, SeijiHogikyan, A., M. F. Cronin, D. Zhang, S. Kato, 2019: Uncertainty in Net Surface Heat Flux due to Differences in Commonly Used Albedo Products. J. Climate, 33(1), 303-315. doi: 10.1175/JCLI-D-18-0448.1. The ocean surface albedo is responsible for the distribution of solar (shortwave) radiant energy between the atmosphere and ocean and therefore is a key parameter in Earth’s surface energy budget. In situ ocean observations typically do not measure upward reflected solar radiation, which is necessary to compute net solar radiation into the ocean. Instead, the upward component is computed from the measured downward component using an albedo estimate. At two NOAA Ocean Climate Station buoy sites in the North Pacific, the International Satellite Cloud Climatology Project (ISCCP) monthly climatological albedo has been used, while for the NOAA Global Tropical Buoy Array a constant albedo is used. This constant albedo is also used in the Coupled Ocean–Atmosphere Response Experiment (COARE) bulk flux algorithm. This study considers the impacts of using the more recently available NASA Cloud and the Earth’s Radiant Energy System (CERES) albedo product for these ocean surface heat flux products. Differences between albedo estimates in global satellite products like these imply uncertainty in the net surface solar radiation heat flux estimates that locally exceed the target uncertainty of 1.0 W m−2 for the global mean, set by the Global Climate Observing System (GCOS) of the World Meteorological Organization (WMO). Albedo has large spatiotemporal variability on hourly, monthly, and interannual time scales. Biases in high-resolution SWnet (the difference between surface downwelling and upwelling shortwave radiation) can arise if the albedo diurnal cycle is unresolved. As a result, for periods when satellite albedo data are not available it is recommended that an hourly climatology be used when computing high-resolution net surface shortwave radiation.
Hourdin, Frédéric; Jam, Arnaud; Rio, Catherine; Couvreux, Fleur; Sandu, Irina; Lefebvre, Marie-Pierre; Brient, Florent; Idelkadi, AbderrahmaneHourdin, F., A. Jam, C. Rio, F. Couvreux, I. Sandu, M. Lefebvre, F. Brient, A. Idelkadi, 2019: Unified Parameterization of Convective Boundary Layer Transport and Clouds With the Thermal Plume Model. Journal of Advances in Modeling Earth Systems, 11(9), 2910-2933. doi: 10.1029/2019MS001666. The representation of stratocumulus clouds, and of the stratocumulus to cumulus transitions which are ubiquitous features of marine boundary layer clouds, remains a challenge for climate models. We show how a mass flux representation of boundary layer convective structures combined with an eddy diffusivity scheme, the “thermal plume model,” first developed to represent cumulus clouds, can also adequately simulate stratocumulus and the stratocumulus to cumulus transition in a climate model. To achieve this, the detrainment formulation, in which detrainment increases for increasing negative buoyancy, has to be slightly modified: the buoyancy of a thermal plume parcel of air is computed by comparing the virtual potential temperature θv,th of the parcel with that of the surrounding environment θv,env at a given distance above instead of at the same level. This is consistent with the picture of detrained air parcels that experience some overshoot and reach a final destination at a level lower than the one at which they effectively leave the cloud or organized convective plume. The impacts of this modification are documented both for selected cases of stratocumulus, in comparison with large-eddy simulations, and in full 3-D climate simulations, in comparison with satellite observations of cloud cover. The modified scheme provides a uniform treatment of the dry convective boundary layer, of cumulus clouds, of stratocumulus, and of the transition from stratocumulus to cumulus. It is included in the most recent version of the LMDZ atmospheric general circulation model. global climate model; stratocumulus; convective boundary layer; mass flux scheme
Huang, Guanghui; Li, Zhanqing; Li, Xin; Liang, Shunlin; Yang, Kun; Wang, Dongdong; Zhang, YiHuang, G., Z. Li, X. Li, S. Liang, K. Yang, D. Wang, Y. Zhang, 2019: Estimating surface solar irradiance from satellites: Past, present, and future perspectives. Remote Sensing of Environment, 233, 111371. doi: 10.1016/j.rse.2019.111371. Surface Solar Irradiance (SSI) is a key parameter dictating surface-atmosphere interactions, driving radiative, hydrological, and land surface processes, and can thus impinge greatly upon weather and climate. It is thereby a prerequisite of many studies and applications. Estimating SSI from satellites began in the 1960s, and is currently the principal way to map SSI spatiotemporal distributions from regional to global scales. Starting from an overview of historical studies carried out in the past several decades, this paper reviews the progresses made in methodology, validation, and products over these years. First, the requirements of SSI in various studies or applications are presented along with the theoretical background of SSI satellite estimation. Methods to estimate SSI from satellites are then summarized as well as their advantages and limitations. Validations of satellite-based SSI on two typical spatial scales are discussed followed by a brief description of existing products and their accuracies. Finally, the challenges faced by current SSI satellite estimation are analyzed, and possible improvements to implement in the future are suggested. This review not only updates the review paper by Pinker et al. (1995) on satellite methods to derive SSI but also offers a more comprehensive summary of the related studies and applications. Remote sensing; Satellites; Radiation budget; Review; Surface solar irradiance
Huang, Xianglei; Chen, Xiuhong; Yue, QingHuang, X., X. Chen, Q. Yue, 2019: Band-by-Band Contributions to the Longwave Cloud Radiative Feedbacks. Geophysical Research Letters, 46(12), 6998-7006. doi: 10.1029/2019GL083466. Cloud radiative feedback is central to our projection of future climate change. It can be estimated using the cloud radiative kernel (CRK) method or adjustment method. This study, for the first time, examines the contributions of each spectral band to the longwave (LW) cloud radiative feedbacks (CRFs). Simulations of three warming scenarios are analyzed, including +2 K sea surface temperature, 2 × CO2, and 4 × CO2 experiments. While the LW broadband CRFs derived from the CRK and adjustment methods agree with each other, they disagree on the relative contributions from the far-infrared and window bands. The CRK method provides a consistent band-by-band decomposition of LW CRF for different warming scenarios. The simulated and observed short-term broadband CRFs for the 2003–2013 period are similar to the long-term counterparts, but their band-by-band decompositions are different, which can be further related to the cloud fraction changes in respective simulations and observation. climate model; cloud radiative feedback; radiative kernel; spectral longwave radiation
Huang, Yi; Chou, Gina; Xie, Yan; Soulard, NicholasHuang, Y., G. Chou, Y. Xie, N. Soulard, 2019: Radiative Control of the Interannual Variability of Arctic Sea Ice. Geophysical Research Letters, 46(16), 9899-9908. doi: 10.1029/2019GL084204. On top of a declining trend driven by global warming, the Arctic sea ice extent (SIE) exhibits considerable interannual variations. In this study, we analyze the interannual anomalies of September SIE in relation to the surface radiation anomalies. We find that the accumulation of radiation energy in the early months (June, July, and August) very well explains the September SIE variability (R2 = 0.81). In Particular, strong correlations are found between September SIE and June radiation anomalies, which in the shortwave is due to cloud and surface albedo changes and in the longwave due to atmospheric warming. The results show that monitoring the radiation anomalies affords a potential means to improve the prediction of the late summer sea ice. radiative forcing; cloud; sea ice; Arctic; interannual variability; NAO
Huang, Yiyi; Dong, Xiquan; Bailey, David A.; Holland, Marika M.; Xi, Baike; DuVivier, Alice K.; Kay, Jennifer E.; Landrum, Laura L.; Deng, YiHuang, Y., X. Dong, D. A. Bailey, M. M. Holland, B. Xi, A. K. DuVivier, J. E. Kay, L. L. Landrum, Y. Deng, 2019: Thicker Clouds and Accelerated Arctic Sea Ice Decline: The Atmosphere-Sea Ice Interactions in Spring. Geophysical Research Letters, 46(12), 6980-6989. doi: 10.1029/2019GL082791. Observations show that increased Arctic cloud cover in the spring is linked with sea ice decline. As the atmosphere and sea ice can influence each other, which one plays the leading role in spring remains unclear. Here we demonstrate, through observational data diagnosis and numerical modeling, that there is active coupling between the atmosphere and sea ice in early spring. Sea ice melting and thus the presence of more open water lead to stronger evaporation and promote cloud formation that increases downward longwave flux, leading to even more ice melt. Spring clouds are a driving force in the disappearance of sea ice and displacing the mechanism of atmosphere-sea ice coupling from April to June. These results suggest the need to accurately model interactions of Arctic clouds and radiation in Earth System Models in order to improve projections of the future of the Arctic. Arctic sea ice retreat; atmosphere-sea ice coupling; atmospheric physical processes; cloud and radiation impact
Huang, Yiyi; Dong, Xiquan; Xi, Baike; Deng, YiHuang, Y., X. Dong, B. Xi, Y. Deng, 2019: A survey of the atmospheric physical processes key to the onset of Arctic sea ice melt in spring. Climate Dynamics, 52(7), 4907-4922. doi: 10.1007/s00382-018-4422-x. September sea ice concentration (SIC) is found to be most sensitive to the early melt onset over the East Siberian Sea and Laptev Sea (73°–84°N, 90°–155°) in the Arctic, a region defined here as the area of focus (AOF). The areal initial melt date for a given year is marked when sea ice melting extends beyond 10% of the AOF size. With this definition, four early melting years (1990, 2012, 2003, 1991) and four late melting years (1996, 1984, 1983, 1982) were selected. The impacts and feedbacks of atmospheric physical and dynamical variables on the Arctic SIC variations were investigated for the selected early and late melting years based on the NASA MERRA-2 reanalysis. The sea ice melting tends to happen in a shorter period of time with larger magnitude in late melting years, while the melting lasts longer and tends to be more temporally smooth in early melting years. The first major melting event in each year has been further investigated and compared. In the early melting years, the positive Arctic Oscillation (AO) phase is dominant during springtime, which is accompanied by intensified atmospheric transient eddy activities in the Arctic and enhanced moisture flux convergence in the AOF and consequently enhanced northward transport of moist and warm air. As a result, positive anomalies of air temperature, precipitable water vapor (PWV) and/or cloud fraction and cloud water path were found over the AOF, increasing downward longwave radiative flux at the surface. The associated warming effect further contributes to the initial melt of sea ice. In contrast, the late melt onset is usually linked to the negative AO phase in spring accompanied with negative anomalies of PWV and downward longwave flux at the surface. The increased downward shortwave radiation during middle to late June plays a more important role in triggering the melting, aided further by the stronger than normal cloud warming effects. Arctic sea ice melt onset; Arctic September sea ice minimum retreat; Atmospheric physical processes; Cloud and radiation impact; Moisture and heat transport
Hwang, Jiwon; Choi, Yong-Sang; Yoo, Changhyun; Wang, Yuan; Su, Hui; Jiang, Jonathan H.Hwang, J., Y. Choi, C. Yoo, Y. Wang, H. Su, J. H. Jiang, 2019: Interpretation of the Top-of-Atmosphere Energy Flux for Future Arctic Warming. Scientific Reports, 9(1), 1-10. doi: 10.1038/s41598-019-49218-6. With the trend of amplified warming in the Arctic, we examine the observed and modeled top-of-atmosphere (TOA) radiative responses to surface air-temperature changes over the Arctic by using TOA energy fluxes from NASA’s CERES observations and those from twelve climate models in CMIP5. Considerable inter-model spreads in the radiative responses suggest that future Arctic warming may be determined by the compensation between the radiative imbalance and poleward energy transport (mainly via transient eddy activities). The poleward energy transport tends to prevent excessive Arctic warming: the transient eddy activities are weakened because of the reduced meridional temperature gradient under polar amplification. However, the models that predict rapid Arctic warming do not realistically simulate the compensation effect. This role of energy compensation in future Arctic warming is found only when the inter-model differences in cloud radiative effects are considered. Thus, the dynamical response can act as a buffer to prevent excessive Arctic warming against the radiative response of 0.11 W m−2 K−1 as measured from satellites, which helps the Arctic climate system retain an Arctic climate sensitivity of 4.61 K. Therefore, if quantitative analyses of the observations identify contribution of atmospheric dynamics and cloud effects to radiative imbalance, the satellite-measured radiative response will be a crucial indicator of future Arctic warming.
Jakob, C.; Singh, M. S.; Jungandreas, L.Jakob, C., M. S. Singh, L. Jungandreas, 2019: Radiative Convective Equilibrium and Organized Convection: An Observational Perspective. Journal of Geophysical Research: Atmospheres, 124(10), 5418-5430. doi: 10.1029/2018JD030092. Radiative convective equilibrium (RCE) describes a balance between the cooling of the atmosphere by radiation and the heating through latent heat release and surface heat fluxes. While RCE is known to provide an energetic constraint on the atmosphere at the global scale, little is known about the proximity of the atmosphere to RCE at smaller spatial and temporal scales, despite the common use of RCE in idealized modeling studies. Here we provide the first observational evaluation of the scales at which the atmosphere is near RCE. We further use observations of cloud characteristics to investigate the role played by organized convection in the RCE state. While the tropical atmosphere as a whole is near RCE on daily time scales and longer, this is not the case for any given location. Rather, areas in excess of 5,000 × 5,000 km2 must be considered to ensure the atmosphere remains near RCE at least 80% of the time, even for monthly averaged conditions. We confirm that RCE is established through the interplay of regions of active deep convection with high precipitation and weak radiative cooling and regions of subsiding motions leading to shallow cloud states that allow strong radiative cooling with no precipitation. The asymmetry in the maximum amount of radiative cooling and latent heating leads to the well-known ratio of small areas of precipitation and large regions of subsidence observed in the tropics. Finally, we show that organized deep convection does not occur when regions smaller than 1,000 × 1,000 km2 are near RCE. radiation; convection; tropics; climate
Jia, Hailing; Ma, Xiaoyan; Quaas, Johannes; Yin, Yan; Qiu, TomJia, H., X. Ma, J. Quaas, Y. Yin, T. Qiu, 2019: Is positive correlation between cloud droplet effective radius and aerosol optical depth over land due to retrieval artifacts or real physical processes?. Atmospheric Chemistry and Physics, 19(13), 8879-8896. doi: https://doi.org/10.5194/acp-19-8879-2019. Abstract. The Moderate Resolution Imaging Spectroradiometer (MODIS) C6 L3, Clouds and the Earth's Radiant Energy System (CERES) Edition-4 L3 products, and the European Centre for Medium-Range Weather Forecasts (ECMWF) ERA-Interim reanalysis data are employed to systematically study aerosol–cloud correlations over three anthropogenic aerosol regions and their adjacent oceans, as well as explore the effect of retrieval artifacts and underlying physical mechanisms. This study is confined to warm phase and single-layer clouds without precipitation during the summertime (June, July, and August). Our analysis suggests that cloud effective radius (CER) is positively correlated with aerosol optical depth (AOD) over land (positive slopes), but negatively correlated with aerosol index (AI) over oceans (negative slopes) even with small ranges of liquid water path (quasi-constant). The changes in albedo at the top of the atmosphere (TOA) corresponding to aerosol-induced changes in CER also lend credence to the authenticity of this opposite aerosol–cloud correlation between land and ocean. It is noted that potential artifacts, such as the retrieval biases of both cloud (partially cloudy and 3-D-shaped clouds) and aerosol, can result in a serious overestimation of the slope of CER–AOD/AI. Our results show that collision–coalescence seems not to be the dominant cause for positive slope over land, but the increased CER caused by increased aerosol might further increase CER by initializing collision–coalescence, generating a positive feedback. By stratifying data according to the lower tropospheric stability and relative humidity near cloud top, it is found that the positive correlations more likely occur in the case of drier cloud top and stronger turbulence in clouds, while negative correlations occur in the case of moister cloud top and weaker turbulence in clouds, which implies entrainment mixing might be a possible physical interpretation for such a positive CER–AOD slope.
Jiang, Bo; Liang, Shunlin; Jia, Aolin; Xu, Jianglei; Zhang, Xiaotong; Xiao, Zhiqiang; Zhao, Xiang; Jia, Kun; Yao, YunjunJiang, B., S. Liang, A. Jia, J. Xu, X. Zhang, Z. Xiao, X. Zhao, K. Jia, Y. Yao, 2019: Validation of the Surface Daytime Net Radiation Product From Version 4.0 GLASS Product Suite. IEEE Geoscience and Remote Sensing Letters, 16(4), 509-513. doi: 10.1109/LGRS.2018.2877625. The daytime surface net radiation (Rn) product from version 4.0 Global LAnd Surface Satellite (GLASS) product suite was recently generated from Moderate Resolution Imaging Spectroradiometer data. It is the daytime average product of Rn derived from 2000 to 2015 at a spatial resolution of 0.05°. This letter describes the results of validation of this new Rn product using ground measurements collected from 142 sites distributed worldwide. The overall accuracy of the GLASS daytime Rn product was satisfactory, with an R2 of 0.80, root-mean-square error of 51.35 Wm-2, and mean bias error of 0.11 Wm-2. Its accuracy and quality were highly consistent for different land cover classes and elevation zones. atmospheric techniques; atmospheric radiation; Satellites; Land surface; Atmospheric modeling; mean square error methods; spatial resolution; Clouds; net radiation; remote sensing; Spatial resolution; Ice; 4.0 Global LAnd Surface Satellite product suite; daytime average product; daytime surface net radiation; Glass; GLASS daytime R; Global LAnd Surface Satellite (GLASS); Moderate Resolution Imaging Spectroradiometer data; product; Rn; Rn product; Surface daytime net radiation product; version 4.0 GLASS product
Jing, Xianwen; Suzuki, Kentaroh; Michibata, TakuroJing, X., K. Suzuki, T. Michibata, 2019: The Key Role of Warm Rain Parameterization in Determining the Aerosol Indirect Effect in a Global Climate Model. J. Climate, 32(14), 4409-4430. doi: 10.1175/JCLI-D-18-0789.1. Global climate models (GCMs) have been found to share the common too-frequent bias in the warm rain formation process. In this study, five different autoconversion schemes are incorporated into a single GCM, to systematically evaluate the warm rain formation processes in comparison with satellite observations and investigate their effects on aerosol indirect effect (AIE). It is found that some schemes generate warm rain less efficiently under polluted conditions in the manner closer to satellite observations, while the others generate warm rain too frequently. Large differences in AIE are found among these schemes. It is remarkable that the schemes with more observation-like warm rain formation processes exhibit larger AIEs that far exceed the uncertainty range reported in IPCC AR5, to an extent that can cancel much of the warming trend in the past century, whereas schemes with too-frequent rain formations yield AIEs that are well bounded by the reported range. The power-law dependence of autoconversion rate on cloud droplet number concentration (β) is found to affect substantially the susceptibility of rain formation to aerosols: the more negative β is, the more difficult for rain to be triggered in polluted clouds, leading to larger AIE through substantial contributions from the wet scavenging feedback. The appropriate use of droplet size threshold can mitigate the effect of a less negative β. The role of the warm rain formation process on AIE in this particular model has broad implications for others that share the too-frequent rain-formation bias.
Joos, HannaJoos, H., 2019: Warm Conveyor Belts and Their Role for Cloud Radiative Forcing in the Extratropical Storm Tracks. J. Climate, 32(16), 5325-5343. doi: 10.1175/JCLI-D-18-0802.1. The link between cloud radiative forcing (CRF) and warm conveyor belts (WCBs), which are strongly ascending airstreams in extratropical cyclones, is investigated based on ERA-Interim reanalysis from 1979 to 2011. Clouds associated with WCBs can be liquid, mixed phase, or ice clouds. They interact with the longwave and shortwave radiation in different ways and thus strongly influence Earth’s radiative budget in the extratropical storm tracks in a complex way. In this study, WCBs are identified with a Lagrangian method, where WCBs are represented by trajectories that rise at least 600 hPa in 48 h in the vicinity of an extratropical cyclone, and CRF is traced along all WCB trajectories during the considered 30-yr period. The results show that due to the poleward ascent of WCBs, they exhibit negative net cloud forcing (NetCRF) in the southern part of the associated cloud band, whereas in their northern part, NetCRF gets positive due to the lack of sunlight in the winter months. This nonuniform CRF along WCBs from low to high latitudes increases the meridional NetCRF gradient. Furthermore, in their outflow regions in the North Atlantic, where WCBs are mainly associated with ice clouds, WCBs contribute up to 10 W m−2 to the global climatological NetCRF maximum in winter. The results highlight the importance of WCBs in modulating the radiative budget in the extratropics. Furthermore, the results emphasize the need for a correct representation of WCBs in climate models to correctly simulate the cloud–circulation coupling.
Kant, Sunny; Panda, Jagabandhu; Gautam, RiteshKant, S., J. Panda, R. Gautam, 2019: A seasonal analysis of aerosol-cloud-radiation interaction over Indian region during 2000–2017. Atmospheric Environment, 201, 212-222. doi: 10.1016/j.atmosenv.2018.12.044. The present study uses 18 years (March 2000–May 2017) of satellite–derived relevant parameters to examine the impact of aerosols on cloud properties, radiative fluxes and ACI (aerosol-cloud interaction) over Indian region. The study includes consideration of shortwave cloud radiative forcing (SWCRF), longwave cloud radiative forcing (LWCRF) and net cloud radiative forcing (NetCRF) from CERES (Clouds and Earth's Radiant Energy System). Also, aerosol optical depth (AOD) and cloud properties such as ice/liquid CER (Cloud Effective Radius), CF (Cloud Fraction), COD (Cloud Optical Depth), CTP (Cloud Top Pressure) and ice/liquid CWP (Cloud Water Path; i.e., ICWP and LCWP) are also considered. Moderate to high aerosol loading and the significant increasing trend of AOD is observed over several parts of Indian region depending upon the seasons. CF is found to be moderate to higher during monsoon months with increasing trend over several parts of the country. Optically thicker high-level clouds have low SWCRF value; whereas, middle-level and low-level clouds have low to moderate SWCRF value. In the majority of cases, Twomey effect is observed whereas in some scenarios Anti-Twomey effect is seen. Aerosol; Cloud; Cloud properties; Cloud radiative forcing
Kato, Seiji; Rose, Fred G.; Ham, Seung Hee; Rutan, David A.; Radkevich, Alexander; Caldwell, Thomas E.; Sun‐Mack, Sunny; Miller, Walter F.; Chen, YanKato, S., F. G. Rose, S. H. Ham, D. A. Rutan, A. Radkevich, T. E. Caldwell, S. Sun‐Mack, W. F. Miller, Y. Chen, 2019: Radiative Heating Rates Computed with Clouds Derived from Satellite-based Passive and Active Sensors and their Effects on Generation of Available Potential Energy. Journal of Geophysical Research: Atmospheres, 124(3), 1720-1740. doi: 10.1029/2018JD028878. Radiative heating rates computed with cloud properties derived from passive and active sensors are investigated. Zonal monthly radiative heating rate anomalies computed using both active and passive sensors show that larger variability in longwave cooling exists near the tropical tropopause and near the top of the boundary layer between 50°N to 50°S. Aerosol variability contributes to increases in shortwave heating rate variability. When zonal monthly mean cloud effects on the radiative heating rate computed with both active and passive sensors and those computed with passive sensor only are compared, the latter shows cooling and heating peaks corresponding to cloud top and base height ranges used for separating cloud types. The difference of these two sets of cloud radiative effect on heating rates in the middle to upper troposphere is larger than the radiative heating rate uncertainty estimated based on the difference of two active sensor radiative heating rate profile data products. In addition, radiative heating rate contribution to generation of eddy available potential energy is also investigated. Although radiation contribution to generation of eddy available potential energy averaged over a year and the entire globe is small, radiation increases the eddy available potential energy in the northern hemisphere during summer. Two key elements that longwave radiation contribute to the generation of eddy potential energy are 1) longitudinal temperature gradient in the atmosphere associated with land and ocean surface temperatures contrasts and absorption of longwave radiation emitted by the surface and 2) cooling near the cloud top of stratocumulus clouds. clouds; Heating rate; Radiation; Available potential energy
Kelleher, Mitchell K.; Grise, Kevin M.Kelleher, M. K., K. M. Grise, 2019: Examining Southern Ocean cloud controlling factors on daily timescales and their connections to midlatitude weather systems. J. Climate, 32(16), 5145–5160. doi: 10.1175/JCLI-D-18-0840.1. Clouds and their associated radiative effects are a large source of uncertainty in global climate models. One region with particularly large model biases in shortwave cloud radiative effects (CRE) is the Southern Ocean. Previous research has shown that many dynamical “cloud controlling factors” influence shortwave CRE on monthly timescales, and that two important cloud controlling factors over the Southern Ocean are mid-tropospheric vertical velocity and estimated inversion strength (EIS). Model errors may thus arise from biases in representing cloud controlling factors (atmospheric dynamics), representing how clouds respond to those cloud controlling factors (cloud parametrizations), or some combination thereof.This study extends previous work by examining cloud controlling factors over the Southern Ocean on daily timescales in both observations and global climate models. This allows the cloud controlling factors to be examined in the context of transient weather systems. Composites of EIS and mid-tropospheric vertical velocity are constructed around extratropical cyclones and anticyclones to examine how the different dynamical cloud controlling factors influence shortwave CRE around midlatitude weather systems and to assess how models compare to observations. On average, models tend to produce a realistic cyclone and anticyclone, when compared to observations, in terms of the dynamical cloud controlling factors. The difference between observations and models instead lies in how the models’ shortwave CRE respond to the dynamics. In particular, the models’ shortwave CRE are too sensitive to perturbations in mid-tropospheric vertical velocity and, thus, they tend to produce clouds that excessively brighten in the frontal region of the cyclone and excessively dim in the center of the anticyclone.
Khazaei, Bahram; Khatami, Sina; Alemohammad, Seyed Hamed; Rashidi, Lida; Wu, Changshan; Madani, Kaveh; Kalantari, Zahra; Destouni, Georgia; Aghakouchak, AmirKhazaei, B., S. Khatami, S. H. Alemohammad, L. Rashidi, C. Wu, K. Madani, Z. Kalantari, G. Destouni, A. Aghakouchak, 2019: Climatic or regionally induced by humans? Tracing hydro-climatic and land-use changes to better understand the Lake Urmia tragedy. Journal of Hydrology, 569, 203-217. doi: 10.1016/j.jhydrol.2018.12.004. Lake Urmia—a shallow endemic hypersaline lake in northwest Iran—has undergone a dramatic decline in its water level (WL), by about 8 m, since 1995. The primary cause of the WL decline in Lake Urmia has been debated in the scientific literature, regarding whether it has been predominantly driven by atmospheric climate change or by human activities in the watershed landscape. Using available climate, hydrological, and vegetation data for the period 1981–2015, this study analyzes and aims to explain the lake desiccation based on other observed hydro-climatic and vegetation changes in the Lake Urmia watershed and classical exploratory statistical methods. The analysis accounts for the relationships between atmospheric climate change (precipitation P, temperature T), and hydrological (soil moisture SM, and WL) and vegetation cover (VC; including agricultural crops and other vegetation) changes in the landscape. Results show that P, T, and SM changes cannot explain the sharp decline in lake WL since 2000. Instead, the agricultural increase of VC in the watershed correlates well with the lake WL change, indicating this human-driven VC and associated irrigation expansion as the dominant human driver of the Lake Urmia desiccation. Specifically, the greater transpiration from the expanded and increasingly irrigated agricultural crops implies increased total evapotranspiration and associated consumptive use of water (inherently related to the irrigation and water diversion and storage developments in the watershed). Thereby the runoff from the watershed into the lake has decreased, and the remaining smaller inflow to the lake has been insufficient for keeping up the previous lake WL, causing the observed WL drop to current conditions. Climate change; Vegetation; Anthropogenic change; Lake Urmia; Land-use change; Water resources management
Kim, Bu-Yo; Lee, Kyu-TaeKim, B., K. Lee, 2019: Using the Himawari-8 AHI Multi-Channel to Improve the Calculation Accuracy of Outgoing Longwave Radiation at the Top of the Atmosphere. Remote Sensing, 11(5), 589. doi: 10.3390/rs11050589. In this study, Himawari-8 Advanced Himawari Imager (AHI) longwave channel data that is sensitive to clouds and absorption gas were used to improve the accuracy of the algorithm used to calculate outgoing longwave radiation (OLR) at the top of the atmosphere. A radiative transfer model with a variety of atmospheric conditions was run using Garand vertical profile data as input data. The results of the simulation showed that changes in AHI channels 8, 12, 15, and 16, which were used to calculate OLR, were sensitive to changes in cloud characteristics (cloud optical thickness and cloud height) and absorption gases (water vapor, O3, CO2, aerosol optical thickness) in the atmosphere. When compared to long-term analysis OLR data from 2017, as recorded by the Cloud and Earth’s Radiant Energy System (CERES), the OLR calculated in this study had an annual mean bias of 2.28 Wm−2 and a root mean square error (RMSE) of 11.03 Wm−2. The new calculation method mitigated the problem of overestimations in OLR in mostly cloudy and overcast regions and underestimated OLR in cloud-free desert regions. It is also an improvement over the result from the existing OLR calculation algorithm, which uses window and water vapor channels. algorithm improvement; Cloud and Earth’s Radiant Energy System (CERES); Himawari-8 Advanced Himawari Imager (AHI); multi-channel; outgoing longwave radiation at the top of the atmosphere (TOA OLR); radiative transfer model
Kim, Jiwon; Kim, Kwangjin; Cho, Jaeil; Kang, Yong Q.; Yoon, Hong-Joo; Lee, Yang-WonKim, J., K. Kim, J. Cho, Y. Q. Kang, H. Yoon, Y. Lee, 2019: Satellite-Based Prediction of Arctic Sea Ice Concentration Using a Deep Neural Network with Multi-Model Ensemble. Remote Sensing, 11(1), 19. doi: 10.3390/rs11010019. Warming of the Arctic leads to a decrease in sea ice, and the decrease of sea ice, in turn, results in warming of the Arctic again. Several microwave sensors have provided continuously updated sea ice data for over 30 years. Many studies have been conducted to investigate the relationships between the satellite-derived sea ice concentration (SIC) of the Arctic and climatic factors associated with the accelerated warming. However, linear equations using the general circulation model (GCM) data, with low spatial resolution, cannot sufficiently cope with the problem of complexity or non-linearity. Time-series techniques are effective for one-step-ahead forecasting, but are not appropriate for future prediction for about ten or twenty years because of increasing uncertainty when forecasting multiple steps ahead. This paper describes a new approach to near-future prediction of Arctic SIC by employing a deep learning method with multi-model ensemble. We used the regional climate model (RCM) data provided in higher resolution, instead of GCM. The RCM ensemble was produced by Bayesian model averaging (BMA) to minimize the uncertainty which can arise from a single RCM. The accuracies of RCM variables were much improved by the BMA2 method, which took into consideration temporal and spatial variations to minimize the uncertainty of individual RCMs. A deep neural network (DNN) method was used to deal with the non-linear relationships between SIC and climate variables, and to provide a near-future prediction for the forthcoming 10 to 20 years. We adjusted the DNN model for optimized SIC prediction by adopting best-fitted layer structure, loss function, optimizer algorithm, and activation function. The accuracy was much improved when the DNN model was combined with BMA2 ensemble, showing the correlation coefficient of 0.888. This study provides a viable option for monitoring Arctic sea ice change of the near future. regional climate model; Bayesian model averaging; deep neural network; sea ice concentration
Kim, So-Young; Bae, Soo Ya; Park, Rae-Seol; Hong, Song-YouKim, S., S. Y. Bae, R. Park, S. Hong, 2019: Effects of Partial Cloudiness in a Cloud Microphysics Scheme on Simulated Precipitation Processes During a Boreal Summer. Journal of Geophysical Research: Atmospheres, 124(6), 3476-3491. doi: 10.1029/2018JD029519. The effect of partial cloudiness is included in a cloud microphysics scheme, and its impact on precipitation processes is examined through global-model simulations for a boreal summer. An excessive precipitation rate in the simulations is reduced by considering the partial cloudiness effect in microphysical processes, especially in the tropical western Pacific region where convective activity is strong. The reduction of the precipitation rate in this region is mainly due to a decrease in convective precipitation, as the partial cloudiness effect in cloud microphysical processes modulates the convective activity by interacting with radiative processes. Cloud radiative forcings are weaker in the simulations including the partial cloudiness effect, as more cloud water and ice are converted to rain and snow mainly due to enhanced accretion rates. This leads to a decrease in cloud radiative forcing for both shortwave and longwave fluxes, which is overestimated overall over the ocean in the simulations. Temperature is lowered overall as increased longwave radiative cooling overcompensates increased shortwave radiative heating. This reduces the convective available potential energy and results in a decrease in convective precipitation. The weakened instability and upward motion over the tropical western Pacific region due to the partial cloudiness effect not only affect the local precipitation processes in this region but also suppress the downward motion over the tropical eastern Pacific regions by modulating the large-scale zonal circulation over the tropical Pacific ocean.
Kniffka, Anke; Knippertz, Peter; Fink, Andreas H.Kniffka, A., P. Knippertz, A. H. Fink, 2019: The role of low-level clouds in the West African monsoon system. Atmospheric Chemistry and Physics, 19(3), 1623-1647. doi: 10.5194/acp-19-1623-2019. Abstract. Realistically simulating the West African monsoon system still poses a substantial challenge to state-of-the-art weather and climate models. One particular issue is the representation of the extensive and persistent low-level clouds over southern West Africa (SWA) during boreal summer. These clouds are important in regulating the amount of solar radiation reaching the surface, but their role in the local energy balance and the overall monsoon system has never been assessed. Based on sensitivity experiments using the ICON model for July 2006, we show for the first time that rainfall over SWA depends logarithmically on the optical thickness of low clouds, as these control the diurnal evolution of the planetary boundary layer, vertical stability and finally convection. In our experiments, the increased precipitation over SWA has a small direct effect on the downstream Sahel, as higher temperatures due to increased surface radiation are accompanied by decreases in low-level moisture due to changes in advection, leading to almost unchanged equivalent potential temperatures in the Sahel. A systematic comparison of simulations with and without convective parameterization reveals agreement in the direction of the precipitation signal but larger sensitivity for explicit convection. For parameterized convection the main rainband is too far south and the diurnal cycle shows signs of unrealistic vertical mixing, leading to a positive feedback on low clouds. The results demonstrate that relatively minor errors, variations or trends in low-level cloudiness over SWA can have substantial impacts on precipitation. Similarly, they suggest that the dimming likely associated with an increase in anthropogenic emissions in the future would lead to a decrease in summer rainfall in the densely populated Guinea coastal area. Future work should investigate longer-term effects of the misrepresentation of low clouds in climate models, e.g. moderated through effects on rainfall, soil moisture and evaporation.
Kramer, Ryan J.; Matus, Alexander V.; Soden, Brian J.; L'Ecuyer, Tristan S.Kramer, R. J., A. V. Matus, B. J. Soden, T. S. L'Ecuyer, 2019: Observation-Based Radiative Kernels From CloudSat/CALIPSO. Journal of Geophysical Research: Atmospheres, 124(10), 5431-5444. doi: 10.1029/2018JD029021. Radiative kernels describe the differential response of radiative fluxes to small perturbations in state variables and are widely used to quantify radiative feedbacks on the climate system. Radiative kernels have traditionally been generated using simulated data from a global climate model, typically sourced from the model's base climate. Consequently, these radiative kernels are subject to model bias from the climatological fields used to produce them. Here, we introduce the first observation-based temperature, water vapor, and surface albedo radiative kernels, developed from CloudSat's fluxes and heating rates data set, 2B-FLXHR-LIDAR, which is supplemented with cloud information from the Cloud–Aerosol Lidar and Infrared Pathfinder Satellite Observations (CALIPSO). We compare the radiative kernels to a previously published set generated from the Geophysical Fluid Dynamics Laboratory (GFDL) model and find general agreement in magnitude and structure. However, several key differences illustrate the sensitivity of radiative kernels to the distribution of clouds. The radiative kernels are used to quantify top-of-atmosphere and surface cloud feedbacks in an ensemble of global climate models from the Climate Model Intercomparison Project Phase 5, showing that biases in the GFDL low clouds likely cause the GFDL kernel to underestimate longwave surface cloud feedback. Since the CloudSat kernels are free of model bias in the base state, they will be ideal for future analysis of radiative feedbacks and forcing in both models and observations and for evaluating biases in model-derived radiative kernels. cloud feedback; remote sensing; cloud distribution; cloud masking; radiative kernel
Kubar, Terence L.; Jiang, Jonathan H.Kubar, T. L., J. H. Jiang, 2019: Net Cloud Thinning, Low-Level Cloud Diminishment, and Hadley Circulation Weakening of Precipitating Clouds with Tropical West Pacific SST Using MISR and Other Satellite and Reanalysis Data. Remote Sensing, 11(10), 1250. doi: 10.3390/rs11101250. Daily gridded Multi-Angle Imaging Spectroradiometer (MISR) satellite data are used in conjunction with CERES, TRMM, and ERA-Interim reanalysis data to investigate horizontal and vertical high cloud structure, top-of-atmosphere (TOA) net cloud forcing and albedo, and dynamics relationships against local SST and precipitation as a function of the mean Tropical West Pacific (TWP; 120°E to 155°W; 30°S–30°N) SST. As the TWP warms, the SST mode (~29.5 °C) is constant, but the area of the mode grows, indicating increased kurtosis of SSTs and decreased SST gradients overall. This is associated with weaker low-level convergence and mid-tropospheric ascent (ω500) over the highest SSTs as the TWP warms, but also a broader area of weak ascent away from the deepest convection, albeit stronger when compared to when the mean TWP is cooler. These associated dynamics changes are collocated with less anvil and thick cloud cover over the highest SSTs and similar thin cold cloud fraction when the TWP is warmer, but broadly more anvil and cirrus clouds over lower local SSTs (SST < 27 °C). For all TWP SST quintiles, anvil cloud fraction, defined as clouds with tops > 9 km and TOA albedos between 0.3–0.6, is closely associated with rain rate, making it an excellent proxy for precipitation; but for a given heavier rain rate, cirrus clouds are more abundant with increasing domain-mean TWP SST. Clouds locally over SSTs between 29–30 °C have a much less negative net cloud forcing, up to 25 W m−2 greater, when the TWP is warm versus cool. When the local rain rate increases, while the net cloud fraction with tops < 9 km decreases, mid-level clouds (4 km < Ztop < 9 km) modestly increase. In contrast, combined low-level and mid-level clouds decrease as the domain-wide SST increases (−10% deg−1). More cirrus clouds for heavily precipitating systems exert a stronger positive TOA effect when the TWP is warmer, and anvil clouds over a higher TWP SST are less reflective and have a weaker cooling effect. For all precipitating systems, total high cloud cover increases modestly with higher TWP SST quintiles, and anvil + cirrus clouds are more expansive, suggesting more detrainment when TWP SSTs are higher. Total-domain anvil cloud fraction scales mostly with domain-mean ω500, but cirrus clouds mostly increase with domain-mean SST, invoking an explanation other than circulation. The overall thinning and greater top-heaviness of clouds over the TWP with warming are possible TWP positive feedbacks not previously identified. cloud fraction; cloud radiative forcing; cloud feedbacks; tropical convection; remote sensing; precipitation
Kumar, Amit; Singh, Virendra; Mukherjee, Sunil; Singh, RandhirKumar, A., V. Singh, S. Mukherjee, R. Singh, 2019: Quality assessment of Outgoing Longwave Radiation (OLR) derived from INSAT-3D Imager: Impact of GSICS correction. Mausam, 70(2), 309-320. The INSAT-3D Outgoing longwave radiation (OLR), a fast-delivery level-2 product at pixel resolution, is being generated operationally from every half hourly acquisition of Imager Payload of INSAT-3D. In addition to this, binned daily and monthly OLR products are also generated. The OLR is estimated from the radiance observations in the infrared windows (TIR1: 10.3-11.3 mu m, TIR2: 11.5-12.5 mu m) and water vapor (WV: 6.5-7.1 mu m) channels of INSAT-3D Imager. In the present study, OLR estimated using the INSAT-3D Imager radiance observation is validated with the CERES (Cloud and Earth's Radiant Energy System; on board NPP satellite) from February, 2014 to December, 2017. For the uniform scenes, OLR estimated using INSAT-3D Imager radiance is of good quality with mean CC 0.93, bias -5.03 Wm(-2) & RMSD 10.39 Wm(-)(2) and it could be used in the various applications studies. validation; assimilation; ceres; Validation; diurnal-variation; erbe; insat-3d; olr
Lee, Wei-Liang; Li, Jui-Lin Frank; Xu, Kuan-Man; Suhas, Ettamal; Jiang, Jonathan H.; Wang, Yi-Hui; Stephens, Graeme; Fetzer, Eric; Yu, Jia-YuhLee, W., J. F. Li, K. Xu, E. Suhas, J. H. Jiang, Y. Wang, G. Stephens, E. Fetzer, J. Yu, 2019: Relating Precipitating Ice Radiative Effects to Surface Energy Balance and Temperature Biases Over the Tibetan Plateau in Winter. Journal of Geophysical Research: Atmospheres, 124(23), 12455-12467. doi: 10.1029/2018JD030204. Key Points Surface temperature bias is primarily determined by biases of surface radiative fluxes Underestimated ice water path in models is related to radiation deficiency and cold bias over the Tibetan Plateau in winter Precipitating ice radiative effects are responsible for some reduction of biases in surface radiative fluxes and temperature CMIP5; Tibetan Plateau; snow radiative effect
Lee, Wei-Liang; Liou, Kuo-Nan; Wang, Chia-chi; Gu, Yu; Hsu, Huang-Hsiung; Li, Jui-Lin F.Lee, W., K. Liou, C. Wang, Y. Gu, H. Hsu, J. F. Li, 2019: Impact of 3-D Radiation-Topography Interactions on Surface Temperature and Energy Budget Over the Tibetan Plateau in Winter. Journal of Geophysical Research: Atmospheres, 24(3), 1537-1549. doi: 10.1029/2018JD029592. We incorporate a parameterization to quantify the effect of three-dimensional (3-D) radiation-topography interactions on the solar flux absorbed by the surfaces, including multiple reflections between surfaces and differences in sunward/shaded slopes, in the Community Climate System Model version 4 (CCSM4). A sensitivity experiment is carried out using CCSM4 with the prescribed sea surface temperature for year 2000 to investigate its impact on energy budget and surface temperature over the Tibetan Plateau (TP). The results show that the topographic effect reduces the upward surface shortwave flux and, at the same time, enhance snowmelt rate over the central and southern parts of TP. Comparing to observations and the ensemble of Coupled Model Intercomparison Project Phase 5 (CMIP5), we found that CMIP5 models have a strong cold bias of 3.9 K over TP, partially induced by the strong reflection of shortwave fluxes. We show that the inclusion of topographic effect reduces the substantial biases of upward shortwave fluxes and surface air temperatures over TP by 13% in the CCSM4 model. CMIP5; Tibetan Plateau; 3-D radiative transfer; topographic effect
Lehmann, Peter; Berli, Markus; Koonce, Jeremy E.; Or, DaniLehmann, P., M. Berli, J. E. Koonce, D. Or, 2019: Surface Evaporation in Arid Regions: Insights From Lysimeter Decadal Record and Global Application of a Surface Evaporation Capacitor (SEC) Model. Geophysical Research Letters, 46(16), 9648-9657. doi: 10.1029/2019GL083932. Surface evaporation in arid regions determines the fraction of rainfall that remains to support vegetation and recharge. The surface evaporation capacitor approach was used to estimate rainfall partitioning to surface evaporation and leakage into deeper layers. The surface evaporation capacitor estimates a soil-specific surface evaporation depth and critical storage capacitance that defines rainfall events that exceed local capacitance and result in leakage into deeper layers protected from surface evaporation. A decade-long record of hydrologic observations in deep and barren lysimeters near Las Vegas revealed the dominance of a few large rainfall events in generating leakage and increasing interannual soil water storage. The surface evaporation capacitor was used to estimate mean annual surface evaporation and leakage protected from surface evaporation in all arid regions globally. About 13% of arid region rainfall contributes to soil water storage (in the absence of vegetation), similar to 11% found in the lysimeter study. water balance; evaporation; aridity; redistribution
Lemburg, Alexander; Bader, Jürgen; Claussen, MartinLemburg, A., J. Bader, M. Claussen, 2019: Sahel rainfall – Tropical Easterly Jet relationship on synoptic to intraseasonal time scales. Mon. Wea. Rev., 147, 1733–1752. doi: 10.1175/MWR-D-18-0254.1. The Tropical Easterly Jet (TEJ) is a characteristic upper-level feature of the West African Monsoon (WAM) circulation. Moreover, the TEJ over West Africa is significantly correlated with summer Sahel rainfall on interannual and decadal time scales. In contrast, the relationship between Sahel rainfall and the regional TEJ on synoptic to intraseasonal time scales is unclear. Therefore, this relationship is investigated by means of multiple statistical analyses using temporally highly resolved measurement and reanalysis data. It is shown that average correlations between convective activity and regional TEJ intensity remain below 0.3 for all synoptic to intraseasonal time scales. Especially on the synoptic time scale, the TEJ significantly lags anomalies in convective activity by one or two days which indicates that convection anomalies are more likely to drive changes in the regional TEJ than vice versa. To further shed light on the role of the TEJ for rainfall over West Africa, a previously proposed effect of TEJ-induced upper-level divergence on the development of mesoscale convective systems (MCS) is examined more closely. An analysis of nearly 300 Sahelian MCSs shows that their initiation is generally not associated with significant TEJ anomalies or jet-induced upper-level divergence. Furthermore, no statistically significant evidence is found that preexisting TEJ-related upper-level divergence anomalies affect intensity, size and lifetime of MCSs. A limiting factor of this study is the focus on TEJinduced upper-level divergence. Therefore, a possible effect of the TEJ on Sahel rainfall via other mechanisms cannot be ruled out and should be subject to future studies.
Li, Jiandong; Wang, Wei-Chyung; Mao, Jiangyu; Wang, Ziqian; Zeng, Gang; Chen, GuoxingLi, J., W. Wang, J. Mao, Z. Wang, G. Zeng, G. Chen, 2019: Persistent Spring Shortwave Cloud Radiative Effect and the Associated Circulations over Southeastern China. J. Climate, 32(11), 3069-3087. doi: 10.1175/JCLI-D-18-0385.1. Clouds strongly modulate regional radiation balance and their evolution is profoundly influenced by circulations. This study uses 2001–16 satellite and reanalysis data together with regional model simulations to investigate the spring shortwave cloud radiative effect (SWCRE) and the associated circulations over southeastern China (SEC). Strong SWCRE, up to −110 W m−2, persists throughout springtime in this region and its spring mean is the largest among the same latitudes of the Northern Hemisphere. SWCRE exhibits pronounced subseasonal variation and is closely associated with persistent regional ascending motion and moisture convergence, which favor large amounts of cloud liquid water and resultant strong SWCRE. Around pentad 12 (late February), SWCRE abruptly increases and afterward remains stable between 22° and 32°N. The thermal and dynamic effects of Tibetan Plateau and westerly jet provide appropriate settings for the maintenance of ascending motion, while water vapor, as cloud water supply, stably comes from the southern flank of the Tibetan Plateau and South China Sea. During pentads 25–36 (early May to late June), SWCRE is further enhanced by the increased water vapor transport caused by the march of East Asian monsoon systems, particularly after the onset of the South China Sea monsoon. After pentad 36, these circulations quickly weaken and the SWCRE decreases accordingly. Individual years with spring strong and weak rainfall are chosen to highlight the importance of the strength of the ascending motion. The simulation broadly reproduced the observed results, although biases exist. Finally, the model biases in SWCRE–circulation associations are discussed.
Li, Jui-Lin Frank; Richardson, Mark; Lee, Wei-Liang; Fetzer, Eric; Stephens, Graeme; Jiang, Jonathan; Hong, Yulan; Wang, Yi-Hui; Yu, Jia-Yuh; Liu, YinghuiLi, J. F., M. Richardson, W. Lee, E. Fetzer, G. Stephens, J. Jiang, Y. Hong, Y. Wang, J. Yu, Y. Liu, 2019: Potential faster Arctic sea ice retreat triggered by snowflakes' greenhouse effect. The Cryosphere, 13(3), 969-980. doi: https://doi.org/10.5194/tc-13-969-2019. Abstract. Recent Arctic sea ice retreat has been quicker than in most general circulation model (GCM) simulations. Internal variability may have amplified the observed retreat in recent years, but reliable attribution and projection requires accurate representation of relevant physics. Most current GCMs do not fully represent falling ice radiative effects (FIREs), and here we show that the small set of Coupled Model Intercomparison Project Phase 5 (CMIP5) models that include FIREs tend to show faster observed retreat. We investigate this using controlled simulations with the CESM1-CAM5 model. Under 1pctCO2 simulations, including FIREs results in the first occurrence of an “ice-free” Arctic (monthly mean extent <1×106 km2) at 550 ppm CO2, compared with 680 ppm otherwise. Over 60–90∘ N oceans, snowflakes reduce downward surface shortwave radiation and increase downward surface longwave radiation, improving agreement with the satellite-based CERES EBAF-Surface dataset. We propose that snowflakes' equivalent greenhouse effect reduces the mean sea ice thickness, resulting in a thinner pack whose retreat is more easily triggered by global warming. This is supported by the CESM1-CAM5 surface fluxes and a reduced initial thickness in perennial sea ice regions by approximately 0.3 m when FIREs are included. This explanation does not apply across the CMIP5 ensemble in which inter-model variation in the simulation of other processes likely dominates. Regardless, we show that FIRE can substantially change Arctic sea ice projections and propose that better including falling ice radiative effects in models is a high priority.
Li, R. L.; Storelvmo, T.; Fedorov, A. V.; Choi, Y.-S.Li, R. L., T. Storelvmo, A. V. Fedorov, Y. Choi, 2019: A Positive Iris Feedback: Insights from Climate Simulations with Temperature-Sensitive Cloud–Rain Conversion. J. Climate, 32(16), 5305-5324. doi: 10.1175/JCLI-D-18-0845.1. Estimates for equilibrium climate sensitivity from current climate models continue to exhibit a large spread, from 2.1 to 4.7 K per carbon dioxide doubling. Recent studies have found that the treatment of precipitation efficiency in deep convective clouds—specifically the conversion rate from cloud condensate to rain Cp—may contribute to the large intermodel spread. It is common for convective parameterization in climate models to carry a constant Cp, although its values are model and resolution dependent. In this study, we investigate how introducing a potential iris feedback, the cloud–climate feedback introduced by parameterizing Cp to increase with surface temperature, affects future climate simulations within a slab ocean configuration of the Community Earth System Model. Progressively stronger dependencies of Cp on temperature unexpectedly increase the equilibrium climate sensitivity monotonically from 3.8 to up to 4.6 K. This positive iris feedback puzzle, in which a reduction in cirrus clouds increases surface temperature, is attributed to changes in the opacity of convectively detrained cirrus. Cirrus clouds reduced largely in ice content and marginally in horizontal coverage, and thus the positive shortwave cloud radiative feedback dominates. The sign of the iris feedback is robust across different cloud macrophysics schemes, which control horizontal cloud cover associated with detrained ice. These results suggest a potentially strong but highly uncertain connection among convective precipitation, detrained anvil cirrus, and the high cloud feedback in a climate forced by increased atmospheric carbon dioxide concentrations.
Liu, Yuzhi; Hua, Shan; Jia, Rui; Huang, JianpingLiu, Y., S. Hua, R. Jia, J. Huang, 2019: Effect of Aerosols on the Ice Cloud Properties Over the Tibetan Plateau. Journal of Geophysical Research: Atmospheres, 124(16), 9594-9608. doi: 10.1029/2019JD030463. With the highlight of environmental problems over the Tibetan Plateau (TP), aerosol pollution and the influence of this pollution on cloud properties are becoming a new area of research. Based on the aerosol index and cloud property parameters derived from satellite observations, in this study, the inconsistent effects of aerosols on ice cloud properties between daytime and nighttime over the TP are investigated. The results indicate that ice clouds are mainly distributed over the TP margin area, especially over the north slope, during both daytime and nighttime. The occurrence frequency of ice cloud is higher during the daytime than during the nighttime over the margin areas of the TP. Similarly, aerosols are mainly concentrated over the northern margin of the TP. A potential relationship may exist between the aerosol index and ice cloud properties. When the aerosol index increases from 0.05 to 0.17, the ice cloud droplet radius (ICDR) during the daytime decreases from 32.1 to 27.9 μm, while the ICDR during the nighttime remains almost constant (approximately 25 μm); furthermore, the ice water path (IWP) during the daytime decreases slightly due to the saturation effect, while the nocturnal IWP increases significantly. The changes in ice cloud optical depth (ICOD) during daytime and nighttime show significant and completely opposite trends. The removal of the influence of meteorological factors showed that aerosols have a more dominant influence than meteorological conditions on ice cloud properties (except for the nocturnal ICDR and IWP during the daytime). Tibetan Plateau; aerosol; ice cloud; cloud droplet radius; cloud optical property
Liu, Yuzhi; Tang, Yuhan; Hua, Shan; Luo, Run; Zhu, QingzheLiu, Y., Y. Tang, S. Hua, R. Luo, Q. Zhu, 2019: Features of the Cloud Base Height and Determining the Threshold of Relative Humidity over Southeast China. Remote Sensing, 11(24), 2900. doi: 10.3390/rs11242900. Clouds play a critical role in adjusting the global radiation budget and hydrological cycle; however, obtaining accurate information on the cloud base height (CBH) is still challenging. In this study, based on Lidar and aircraft soundings, we investigated the features of the CBH and determined the thresholds of the environmental relative humidity (RH) corresponding to the observed CBHs over Southeast China from October 2017 to September 2018. During the observational period, the CBHs detected by Lidar/aircraft were commonly higher in cold months and lower in warm months; in the latter, 75.91% of the CBHs were below 2000 m. Overall, the RHs at the cloud base were mainly distributed between 70 and 90% for the clouds lower than 1000 m, in which the most concentrated RH was approximately 80%. In addition, for the clouds with a cloud base higher than 1000 m, the RH thresholds decreased dramatically with increasing CBH, where the RH thresholds at cloud bases higher than 2000 m could be lower than 60%. On average, the RH thresholds for determining the CBHs were the highest (72.39%) and lowest (63.56%) in the summer and winter, respectively, over Southeast China. Therefore, to determine the CBH, a specific threshold of RH is needed. Although the time period covered by the collected CBH data from Lidar/aircraft is short, the above analyses can provide some verification and evidence for using the RH threshold to determine the CBH. cloud base height; ground-based observations; relative humidity profile; threshold
Liu, Yuzhi; Zhu, Qingzhe; Huang, Jianping; Hua, Shan; Jia, RuiLiu, Y., Q. Zhu, J. Huang, S. Hua, R. Jia, 2019: Impact of dust-polluted convective clouds over the Tibetan Plateau on downstream precipitation. Atmospheric Environment, 209, 67-77. doi: 10.1016/j.atmosenv.2019.04.001. Based on satellite observations and reanalysis datasets, this study focuses on the effect of aerosols on clouds over the Tibetan Plateau (TP) and the impact of dust-polluted convective clouds on precipitation over downstream regions. A heavy dust event is detected by Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observations (CALIPSO) over the northern slope of the TP on 16 July and 17 July 2016. The high aerosol optical depth (AOD) values are mainly distributed over the northern slope of the TP. Simultaneously, the CloudSat satellite observes deep convective clouds over the northern slope area of the TP, in which convective clouds and dust mix at the same height. With the AOD increasing from 16 July to its peak on 17 July, the ice particle size decreases to a minimum, and convective clouds develop at higher heights because of the prolonged cloud life. Accordingly, a larger ice water path (IWP) is induced by the development of convective clouds that move eastwardly from 16 to 17 July. In the following days, under favorable meteorological conditions, some of the developed convective clouds continuously move eastward and merge with the convective cloud clusters along the motion path, which induces significant precipitation over the Yangtze River basin on 17 July. Furthermore, driven by the northward wind, some developed convective cloud clusters move northward and induce strong precipitation over North China on 19 July. The indirect effect of dust aerosols over the TP could enhance the plateau's cloud development and potentially contribute to downstream precipitation, which is a meaningful factor for weather forecasting. Precipitation; Aerosols; Tibetan plateau; Convective clouds
Loeb, Norman G.; Wang, Hailan; Rose, Fred G.; Kato, Seiji; Smith, William L.; Sun-Mack, SunnyLoeb, N. G., H. Wang, F. G. Rose, S. Kato, W. L. Smith, S. Sun-Mack, 2019: Decomposing Shortwave Top-of-Atmosphere and Surface Radiative Flux Variations in Terms of Surface and Atmospheric Contributions. J. Climate, 32(16), 5003–501. doi: 10.1175/JCLI-D-18-0826.1. A diagnostic tool for determining surface and atmospheric contributions to interannual variations in top-of-atmosphere (TOA) reflected shortwave (SW) and net downward SW surface radiative fluxes is introduced. The method requires only upward and downward radiative fluxes at the TOA and surface as input and therefore can readily be applied to both satellite-derived and model-generated radiative fluxes. Observations from the Clouds and the Earth’s Radiant Energy System (CERES) Energy Balanced and Filled (EBAF) Ed4.0 product show that 81% of the monthly variability in global mean reflected SW TOA flux anomalies is associated with atmospheric variations (mainly clouds), 6% is from surface variations, and 13% is from atmosphere-surface covariability. Over the Arctic Ocean, most of the variability in both reflected SW TOA flux and net downward SW surface flux anomalies is explained by variations in sea-ice and cloud fraction alone (r2=0.94). Compared to CERES, variability in two reanalyses—ECMWF Interim Reanalysis (ERA-Interim) and NASA’s Modern-Era Retrospective analysis for Research and Applications, Version 2 (MERRA-2)—show large differences in the regional distribution of variance for both the atmospheric and surface contributions to anomalies in net downward SW surface flux. For MERRA-2 the atmospheric contribution is 17% too large compared to CERES while ERA-Interim underestimates the variance by 15%. The difference is mainly due to how cloud variations are represented in the reanalyses. The overall surface contribution in both ERA-Interim and MERRA- 2 is smaller than CERES EBAF by 15% for ERA-Interim and 58% for MERRA-2, highlighting limitations of the reanalyses in representing surface albedo variations and their influence on SW radiative fluxes.
L’Ecuyer, Tristan S.; Hang, Yun; Matus, Alexander V.; Wang, ZhienL’Ecuyer, T. S., Y. Hang, A. V. Matus, Z. Wang, 2019: Reassessing the Effect of Cloud Type on Earth’s Energy Balance in the Age of Active Spaceborne Observations. Part I: Top of Atmosphere and Surface. J. Climate, 32(19), 6197-6217. doi: 10.1175/JCLI-D-18-0753.1. This study revisits the classical problem of quantifying the radiative effects of unique cloud types in the era of spaceborne active observations. The radiative effects of nine cloud types, distinguished based on their vertical structure defined by CloudSat and CALIPSO observations, are assessed at both the top of the atmosphere and the surface. The contributions from single- and multilayered clouds are explicitly diagnosed. The global, annual mean net cloud radiative effect at the top of the atmosphere is found to be −17.1 ± 4.2 W m−2 owing to −44.2 ± 2 W m−2 of shortwave cooling and 27.1 ± 3.7 W m−2 of longwave heating. Leveraging explicit cloud base and vertical structure information, we further estimate the annual mean net cloud radiative effect at the surface to be −24.8 ± 8.7 W m−2 (−51.1 ± 7.8 W m−2 in the shortwave and 26.3 ± 3.8 W m−2 in the longwave). Multilayered clouds are found to exert the strongest influence on the top-of-atmosphere energy balance. However, a strong asymmetry in net cloud radiative cooling between the hemispheres (8.6 W m−2) is dominated by enhanced cooling from stratocumulus over the southern oceans. It is found that there is no corresponding asymmetry at the surface owing to enhanced longwave emission by southern ocean clouds in winter, which offsets a substantial fraction of their impact on solar absorption in summer. Thus the asymmetry in cloud radiative effects is entirely realized as an atmosphere heating imbalance between the hemispheres.
Maher, Nicola; Milinski, Sebastian; Suarez‐Gutierrez, Laura; Botzet, Michael; Dobrynin, Mikhail; Kornblueh, Luis; Kröger, Jürgen; Takano, Yohei; Ghosh, Rohit; Hedemann, Christopher; Li, Chao; Li, Hongmei; Manzini, Elisa; Notz, Dirk; Putrasahan, Dian; Boysen, Lena; Claussen, Martin; Ilyina, Tatiana; Olonscheck, Dirk; Raddatz, Thomas; Stevens, Bjorn; Marotzke, JochemMaher, N., S. Milinski, L. Suarez‐Gutierrez, M. Botzet, M. Dobrynin, L. Kornblueh, J. Kröger, Y. Takano, R. Ghosh, C. Hedemann, C. Li, H. Li, E. Manzini, D. Notz, D. Putrasahan, L. Boysen, M. Claussen, T. Ilyina, D. Olonscheck, T. Raddatz, B. Stevens, J. Marotzke, 2019: The Max Planck Institute Grand Ensemble: Enabling the Exploration of Climate System Variability. Journal of Advances in Modeling Earth Systems, 11(7), 2050-2069. doi: 10.1029/2019MS001639. The Max Planck Institute Grand Ensemble (MPI-GE) is the largest ensemble of a single comprehensive climate model currently available, with 100 members for the historical simulations (1850–2005) and four forcing scenarios. It is currently the only large ensemble available that includes scenario representative concentration pathway (RCP) 2.6 and a 1% CO2 scenario. These advantages make MPI-GE a powerful tool. We present an overview of MPI-GE, its components, and detail the experiments completed. We demonstrate how to separate the forced response from internal variability in a large ensemble. This separation allows the quantification of both the forced signal under climate change and the internal variability to unprecedented precision. We then demonstrate multiple ways to evaluate MPI-GE and put observations in the context of a large ensemble, including a novel approach for comparing model internal variability with estimated observed variability. Finally, we present four novel analyses, which can only be completed using a large ensemble. First, we address whether temperature and precipitation have a pathway dependence using the forcing scenarios. Second, the forced signal of the highly noisy atmospheric circulation is computed, and different drivers are identified to be important for the North Pacific and North Atlantic regions. Third, we use the ensemble dimension to investigate the time dependency of Atlantic Meridional Overturning Circulation variability changes under global warming. Last, sea level pressure is used as an example to demonstrate how MPI-GE can be utilized to estimate the ensemble size needed for a given scientific problem and provide insights for future ensemble projects. internal variability; forced response; large ensemble; MPI-GE
Maldonado, Walter; Valeriano, Taynara Tuany Borges; de Souza Rolim, GlaucoMaldonado, W., T. T. B. Valeriano, G. de Souza Rolim, 2019: EVAPO: A smartphone application to estimate potential evapotranspiration using cloud gridded meteorological data from NASA-POWER system. Computers and Electronics in Agriculture, 156, 187-192. doi: 10.1016/j.compag.2018.10.032. In this study a new android app for smartphones to estimate potential evapotranspuration (PET) in real time, using gridded data from NASA-POWER, to any location in the world, would result in a more efficient irrigation and increase irrigation water conservation. The smartphone app called EVAPO uses meteorological data to calculate PET using the Penman–Monteith (FAO56) method. To evaluate performance of the proposed method, we compared PET estimated by the EVAPO with that estimated from climatic data from conventional surface meteorological stations. The accuracy, tendency and precision of the models were determined using the Willmott et al. (1985) concordance index (d), systematic root mean square error (RMSEs) and determination index (R2), respectively. The results obtained were satisfactory for all studied locations whit mean values of 0.67, 0.95 (mm) and 0.72 for d, RMSEs and R2, respectively. The app can be accessed in the Play Store (free): https://play.google.com/store/apps/details?id=br.com.maldonado.instantet0. Big data; Internet of things; Irrigation; Rational use of water
Maloney, Christopher; Bardeen, Charles; Toon, Owen Brian; Jensen, Eric; Woods, Sarah; Thornberry, Troy; Pfister, Leonhard; Diskin, Glenn; Bui, Thao PaulMaloney, C., C. Bardeen, O. B. Toon, E. Jensen, S. Woods, T. Thornberry, L. Pfister, G. Diskin, T. P. Bui, 2019: An Evaluation of the Representation of Tropical Tropopause Cirrus in the CESM/CARMA Model Using Satellite and Aircraft Observations. Journal of Geophysical Research: Atmospheres, 124(15), 8659-8687. doi: 10.1029/2018JD029720. Observations from the third campaign of the National Aeronautics and Space Administration Airborne Tropical Tropopause Experiment (ATTREX 3) field mission and Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observations satellite mission are used to evaluate simulations of tropical tropopause layer (TTL) cirrus clouds in the Community Earth System Model's (CESM) Community Atmosphere Model, CAM5. In this study, CAM5 is coupled with a sectional ice cloud model, the Community Aerosol and Radiation Model for Atmospheres (CARMA). We find that both model variants underrepresent cloud frequency along the ATTREX 3 flight path and both poorly represent relative humidity in the TTL. Furthermore, simulated in-cloud ice size distributions contained erroneous amounts of ice crystals throughout the distribution. In response, we present a modified ice cloud fraction scheme that boosts the cloud fraction within the TTL. Due to coarse vertical model resolution in the TTL, we also prescribe a 2-K decrease in cold point tropopause temperatures to better align with observed temperatures. Our modifications improve both CAM5 and CAM5/CARMA's in-cloud ice size and mass distributions. However, only CAM5/CARMA has a significant improvement in cloud frequency and relative humidity. An investigation of cloud extinction in the ATTREX 3 region found that each model variant struggles to reproduce observed extinctions. As a first-order approximation, we introduce randomly generated temperature perturbations to simulate the effect of gravity waves into the CAM5/CARMA simulation. These gravity waves significantly increase the incidence of low extinction ( cirrus; CARMA; ice clouds; CESM; tropical tropopause layer; ATTREX
Mauritsen, Thorsten; Bader, Jürgen; Becker, Tobias; Behrens, Jörg; Bittner, Matthias; Brokopf, Renate; Brovkin, Victor; Claussen, Martin; Crueger, Traute; Esch, Monika; Fast, Irina; Fiedler, Stephanie; Fläschner, Dagmar; Gayler, Veronika; Giorgetta, Marco; Goll, Daniel S.; Haak, Helmuth; Hagemann, Stefan; Hedemann, Christopher; Hohenegger, Cathy; Ilyina, Tatiana; Jahns, Thomas; Jimenéz‐de‐la‐Cuesta, Diego; Jungclaus, Johann; Kleinen, Thomas; Kloster, Silvia; Kracher, Daniela; Kinne, Stefan; Kleberg, Deike; Lasslop, Gitta; Kornblueh, Luis; Marotzke, Jochem; Matei, Daniela; Meraner, Katharina; Mikolajewicz, Uwe; Modali, Kameswarrao; Möbis, Benjamin; Müller, Wolfgang A.; Nabel, Julia E. M. S.; Nam, Christine C. W.; Notz, Dirk; Nyawira, Sarah-Sylvia; Paulsen, Hanna; Peters, Karsten; Pincus, Robert; Pohlmann, Holger; Pongratz, Julia; Popp, Max; Raddatz, Thomas Jürgen; Rast, Sebastian; Redler, Rene; Reick, Christian H.; Rohrschneider, Tim; Schemann, Vera; Schmidt, Hauke; Schnur, Reiner; Schulzweida, Uwe; Six, Katharina D.; Stein, Lukas; Stemmler, Irene; Stevens, Bjorn; Storch, Jin-Song von; Tian, Fangxing; Voigt, Aiko; Vrese, Philipp; Wieners, Karl-Hermann; Wilkenskjeld, Stiig; Winkler, Alexander; Roeckner, ErichMauritsen, T., J. Bader, T. Becker, J. Behrens, M. Bittner, R. Brokopf, V. Brovkin, M. Claussen, T. Crueger, M. Esch, I. Fast, S. Fiedler, D. Fläschner, V. Gayler, M. Giorgetta, D. S. Goll, H. Haak, S. Hagemann, C. Hedemann, C. Hohenegger, T. Ilyina, T. Jahns, D. Jimenéz‐de‐la‐Cuesta, J. Jungclaus, T. Kleinen, S. Kloster, D. Kracher, S. Kinne, D. Kleberg, G. Lasslop, L. Kornblueh, J. Marotzke, D. Matei, K. Meraner, U. Mikolajewicz, K. Modali, B. Möbis, W. A. Müller, J. E. M. S. Nabel, C. C. W. Nam, D. Notz, S. Nyawira, H. Paulsen, K. Peters, R. Pincus, H. Pohlmann, J. Pongratz, M. Popp, T. J. Raddatz, S. Rast, R. Redler, C. H. Reick, T. Rohrschneider, V. Schemann, H. Schmidt, R. Schnur, U. Schulzweida, K. D. Six, L. Stein, I. Stemmler, B. Stevens, J. v. Storch, F. Tian, A. Voigt, P. Vrese, K. Wieners, S. Wilkenskjeld, A. Winkler, E. Roeckner, 2019: Developments in the MPI-M Earth System Model version 1.2 (MPI-ESM1.2) and Its Response to Increasing CO2. Journal of Advances in Modeling Earth Systems, 11(4), 998-1038. doi: 10.1029/2018MS001400. A new release of the Max Planck Institute for Meteorology Earth System Model version 1.2 (MPI-ESM1.2) is presented. The development focused on correcting errors in and improving the physical processes representation, as well as improving the computational performance, versatility, and overall user friendliness. In addition to new radiation and aerosol parameterizations of the atmosphere, several relatively large, but partly compensating, coding errors in the model's cloud, convection, and turbulence parameterizations were corrected. The representation of land processes was refined by introducing a multilayer soil hydrology scheme, extending the land biogeochemistry to include the nitrogen cycle, replacing the soil and litter decomposition model and improving the representation of wildfires. The ocean biogeochemistry now represents cyanobacteria prognostically in order to capture the response of nitrogen fixation to changing climate conditions and further includes improved detritus settling and numerous other refinements. As something new, in addition to limiting drift and minimizing certain biases, the instrumental record warming was explicitly taken into account during the tuning process. To this end, a very high climate sensitivity of around 7 K caused by low-level clouds in the tropics as found in an intermediate model version was addressed, as it was not deemed possible to match observed warming otherwise. As a result, the model has a climate sensitivity to a doubling of CO2 over preindustrial conditions of 2.77 K, maintaining the previously identified highly nonlinear global mean response to increasing CO2 forcing, which nonetheless can be represented by a simple two-layer model. model development; climate sensitivity; coupled climate model
Mayer, Michael; Tietsche, Steffen; Haimberger, Leopold; Tsubouchi, Takamasa; Mayer, Johannes; Zuo, HaoMayer, M., S. Tietsche, L. Haimberger, T. Tsubouchi, J. Mayer, H. Zuo, 2019: An Improved Estimate of the Coupled Arctic Energy Budget. J. Climate, 32(22), 7915-7934. doi: 10.1175/JCLI-D-19-0233.1. This study combines state-of-the-art reanalyses such as the fifth-generation European Re-Analysis (ERA5) and the Ocean Reanalysis System 5 (ORAS5) with novel observational products to present an updated estimate of the coupled atmosphere–ocean–sea ice Arctic energy budget, including flux and storage terms covering 2001–17. Observational products provide independent estimates of crucial budget terms, including oceanic heat transport from unique mooring-derived data, radiative fluxes from satellites, and sea ice volume from merged satellite data. Results show that the time averages of independent estimates of radiative, atmospheric, and oceanic energy fluxes into the Arctic Ocean domain are remarkably consistent in the sense that their sum closely matches the observed rate of regional long-term oceanic heat accumulation of ~1 W m−2. Atmospheric and oceanic heat transports are found to be stronger compared to earlier assessments (~100 and ~16 W m−2, respectively). Data inconsistencies are larger when considering the mean annual cycle of the coupled energy budget, with RMS values of the monthly budget residual between 7 and 15 W m−2, depending on the employed datasets. This nevertheless represents an average reduction of ~72% of the residual compared to earlier work and demonstrates the progress made in data quality and diagnostic techniques. Finally, the budget residual is eliminated using a variational approach to provide a best estimate of the mean annual cycle. The largest remaining sources of uncertainty are ocean heat content and latent heat associated with sea ice melt and freeze, which both suffer from the lack of observational constraints. More ocean in situ observations and reliable sea ice thickness observations and their routinely assimilation into reanalyses are needed to further reduce uncertainty.
McTaggart‐Cowan, R.; Vaillancourt, P. A.; Zadra, A.; Chamberland, S.; Charron, M.; Corvec, S.; Milbrandt, J. A.; Paquin‐Ricard, D.; Patoine, A.; Roch, M.; Separovic, L.; Yang, J.McTaggart‐Cowan, R., P. A. Vaillancourt, A. Zadra, S. Chamberland, M. Charron, S. Corvec, J. A. Milbrandt, D. Paquin‐Ricard, A. Patoine, M. Roch, L. Separovic, J. Yang, 2019: Modernization of Atmospheric Physics Parameterization in Canadian NWP. Journal of Advances in Modeling Earth Systems, 11(11), 3593-3635. doi: 10.1029/2019MS001781. Atmospheric physics is represented in numerical models by parameterizations that use resolved-scale information to estimate the effects of physical processes on the atmospheric state. Over time, our understanding of these processes improves, new techniques are introduced to represent physics in a numerical model, and increased resolution changes the relative importance of different parameterizations within the system. As a result, the physical parameterization packages of numerical weather prediction (NWP) models undergo regular updates as older schemes are replaced with newer ones that offer an improved, and often more complex, depiction of relevant physical processes. Such changes are typically combined with a rebalancing of the physics suite because of strong interactions between parameterization schemes and the presence of compensating errors in the system. In this study, a major update to the package of physical parameterizations used in Canadian operational NWP is introduced. The primary goals of this effort were to improve the global energy budget and to facilitate an increase in the vertical resolution of operational configurations. Both of these objectives were achieved, along with a significant improvement in guidance quality for global and regional prediction systems. atmospheric physics; forecast evaluation; numerical weather prediction; physical parameterization; physical processes
Meyssignac, Benoit; Boyer, Tim; Zhao, Zhongxiang; Hakuba, Maria Z.; Landerer, Felix W.; Stammer, Detlef; Köhl, Armin; Kato, Seiji; L’Ecuyer, Tristan; Ablain, Michael; Abraham, John Patrick; Blazquez, Alejandro; Cazenave, Anny; Church, John A.; Cowley, Rebecca; Cheng, Lijing; Domingues, Catia M.; Giglio, Donata; Gouretski, Viktor; Ishii, Masayoshi; Johnson, Gregory C.; Killick, Rachel E.; Legler, David; Llovel, William; Lyman, John; Palmer, Matthew Dudley; Piotrowicz, Steve; Purkey, Sarah G.; Roemmich, Dean; Roca, Rémy; Savita, Abhishek; Schuckmann, Karina von; Speich, Sabrina; Stephens, Graeme; Wang, Gongjie; Wijffels, Susan Elisabeth; Zilberman, NathalieMeyssignac, B., T. Boyer, Z. Zhao, M. Z. Hakuba, F. W. Landerer, D. Stammer, A. Köhl, S. Kato, T. L’Ecuyer, M. Ablain, J. P. Abraham, A. Blazquez, A. Cazenave, J. A. Church, R. Cowley, L. Cheng, C. M. Domingues, D. Giglio, V. Gouretski, M. Ishii, G. C. Johnson, R. E. Killick, D. Legler, W. Llovel, J. Lyman, M. D. Palmer, S. Piotrowicz, S. G. Purkey, D. Roemmich, R. Roca, A. Savita, K. v. Schuckmann, S. Speich, G. Stephens, G. Wang, S. E. Wijffels, N. Zilberman, 2019: Measuring Global Ocean Heat Content to Estimate the Earth Energy Imbalance. Frontiers in Marine Science, 6, 432. doi: 10.3389/fmars.2019.00432. The energy radiated by the Earth towards space does not compensate the incoming radiation from the Sun leading to a small positive energy imbalance at the top of the atmosphere (0.4-1.Wm-2). This imbalance is coined Earth’s Energy Imbalance (EEI). It is mostly caused by anthropogenic greenhouse gases emissions and is driving the current warming of the planet. Precise monitoring of EEI is critical to assess the current status of climate change and the future evolution of climate. But the monitoring of EEI is challenging as EEI is two order of magnitude smaller than the radiation fluxes in and out of the Earth. Over 93% of the excess energy that is gained by the Earth in response to the positive EEI accumulates into the ocean in the form of heat. This accumulation of heat can be tracked with the ocean observing system such that today, the monitoring of Ocean Heat Content (OHC) and its long-term change provide the most efficient approach to estimate EEI. In this community paper we review the current four state-of-the-art methods to estimate global OHC changes and evaluate their relevance to derive EEI estimate on different time scales. These four methods make use of : 1) direct observations of in situ temperature; 2) satellite-based measurements of the ocean surface net heat fluxes; 3) satellite-based estimates of the thermal expansion of the ocean and 4) ocean reanalyses that assimilate observations from both satellite and in situ instruments. For each method we review the potential and the uncertainty of the method to estimate global OHC changes. We also analyze gaps in the current capability of each method and identify ways of progress for the future to fulfill the requirements of EEI monitoring. Achieving the observation of EEI with sufficient accuracy will depend on merging the remote sensing techniques with in situ measurements of key variables as an integral part of the Ocean Observing System. CERES; altimetry; Earth Energy Imbalance; ARGO; GRACE (Gravity recovery and climate experiment); internal tide tomography; ocean heat content (OHC); Ocean mass; Ocean surface fluxes; Sea level
Michibata, Takuro; Suzuki, Kentaroh; Sekiguchi, Miho; Takemura, ToshihikoMichibata, T., K. Suzuki, M. Sekiguchi, T. Takemura, 2019: Prognostic Precipitation in the MIROC6-SPRINTARS GCM: Description and Evaluation Against Satellite Observations. Journal of Advances in Modeling Earth Systems, 11(3), 839-860. doi: 10.1029/2018MS001596. A comprehensive two-moment microphysics scheme is incorporated into the MIROC6-SPRINTARS general circulation model (GCM). The new scheme includes prognostic precipitation for both rain and snow and considers their radiative effects. To evaluate the impacts of applying different treatments of precipitation and the associated radiative effect, we perform climate simulations employing both the traditional diagnostic and new prognostic precipitation schemes, the latter also being tested with and without incorporating the radiative effect of snow. The prognostic precipitation, which maintains precipitation in the atmosphere across multiple time steps, models the ratio of accretion to autoconversion as being approximately an order of magnitude higher than that for the diagnostic scheme. Such changes in microphysical process rates tend to reduce the cloud water susceptibility as the autoconversion process is the only pathway through which aerosols can influence rain formation. The resultant anthropogenic aerosol effect is reduced by approximately 21% in the prognostic precipitation scheme. Modifications to the microphysical process rates also change the vertical distribution of hydrometeors in the manner that increases the fractional occurrence of single-layered warm clouds by 38%. The new scheme mitigates the excess of supercooled liquid water produced by the previous scheme and increases the total mass of ice hydrometeors. Both characteristics are consistent with CloudSat/CALIPSO retrievals. The radiative effect of snow is significant at both longwave and shortwave (6.4 and 5.1 W/m2 in absolute values, respectively) and can alter the precipitation fields via energetic controls on precipitation. These results suggest that the prognostic precipitation scheme, with its radiative effects incorporated, makes an indispensable contribution to improving the reliability of climate modeling. climate; GCM; microphysics; aerosol-cloud-precipitation interactions; prognostic precipitation
Middlemas, Eleanor A.; Clement, Amy C.; Medeiros, Brian; Kirtman, BenMiddlemas, E. A., A. C. Clement, B. Medeiros, B. Kirtman, 2019: Cloud radiative feedbacks and El Niño Southern Oscillation. J. Climate, 32(15), 4661-4680. doi: 10.1175/JCLI-D-18-0842.1. Cloud radiative feedbacks are disabled via “cloud-locking” in the Community Earth System Model, version 1.2, (CESM1.2) to result in a shift in El Niño Southern Oscillation (ENSO) periodicity from 2-7 years to decadal timescales. We hypothesize that cloud radiative feedbacks may impact the periodicity in three ways: by (1) modulating heat flux locally into the equatorial Pacific subsurface through negative shortwave cloud feedback on sea surface temperature anomalies (SSTA), (2) damping the persistence of subtropical Southeast Pacific SSTA such that the South Pacific Meridional Mode impacts the duration of ENSO events, or (3) controlling the meridional width of off-equatorial westerly winds, which impact the periodicity of ENSO by initiating longer Rossby waves. The result of cloud-locking in CESM1.2 contrasts that of another study which found that cloud-locking in a different global climate model led to decreased ENSO magnitude across all timescales due to a lack of positive longwave feedback on the anomalous Walker circulation. CESM1.2 contains this positive longwave feedback on the anomalous Walker circulation, but either its influence on the surface is decoupled from ocean dynamics or the feedback is only active on interannual timescales. The role of cloud radiative feedbacks in ENSO in other global climate models are additionally considered. In particular, it is shown that one cannot predict the role of cloud radiative feedbacks in ENSO through a multimodel diagnostic analysis. Instead, they must be directly altered.
Mohino, Elsa; Rodríguez-Fonseca, Belén; Mechoso, C. Roberto; Losada, Teresa; Polo, IreneMohino, E., B. Rodríguez-Fonseca, C. R. Mechoso, T. Losada, I. Polo, 2019: Relationships Among Inter-model Spread and Biases in Tropical Atlantic Sea Surface Temperatures. J. Climate, 32(12), 3615–3635. doi: 10.1175/JCLI-D-18-0846.1. State-of-the-art general circulation models show important systematic errors in their simulation of sea surface temperatures (SST), especially in the Tropical Atlantic. In this work the spread in the simulation of climatological SST in the Tropical Atlantic by 24 CMIP5 models is examined, and its relationship with the mean systematic biases in the region is explored. The modes of inter-model variability are estimated by applying Principal Component (PC) analysis to the SSTs in the region 70°W-20°E, 20°S-20°N. The inter-model variability is approximately explained by the first three modes. The first mode is related to warmer SSTs in the basin, shows worldwide connections with same-signed loads over most of the tropics and is connected with lower low cloud cover over the eastern parts of the subtropical oceans. The second mode is restricted to the Atlantic, where it shows negative and positive loads to the north and south of the equator, respectively, and is connected to a too weak Atlantic Meridional Overturning Circulation (AMOC). The third mode is related to the double Intertropical Convergence Zone bias in the Pacific and to an interhemispheric asymmetry in the net radiation at the top of the atmosphere. The structure of second mode is closer to the mean bias than that of the others in the Tropical Atlantic, suggesting that model difficulties with the AMOC contribute to the regional biases.
Mohrmann, Johannes; Bretherton, Christopher S.; McCoy, Isabel L.; McGibbon, Jeremy; Wood, Robert; Ghate, Virendra; Albrecht, Bruce; Sarkar, Mampi; Zuidema, Paquita; Palikonda, RabindraMohrmann, J., C. S. Bretherton, I. L. McCoy, J. McGibbon, R. Wood, V. Ghate, B. Albrecht, M. Sarkar, P. Zuidema, R. Palikonda, 2019: Lagrangian Evolution of the Northeast Pacific Marine Boundary Layer Structure and Cloud during CSET. Mon. Wea. Rev., 147(12), 4681-4700. doi: 10.1175/MWR-D-19-0053.1. Flight data from the Cloud System Evolution over the Trades (CSET) campaign over the Pacific stratocumulus-to-cumulus transition are organized into 18 Lagrangian cases suitable for study and future modeling, made possible by the use of a track-and-resample flight strategy. Analysis of these cases shows that 2-day Lagrangian coherence of long-lived species (CO and O3) is high (r = 0.93 and 0.73, respectively), but that of subcloud aerosol, MBL depth, and cloud properties is limited. Although they span a wide range in meteorological conditions, most sampled air masses show a clear transition when considering 2-day changes in cloudiness (−31% averaged over all cases), MBL depth (+560 m), estimated inversion strength (EIS; −2.2 K), and decoupling, agreeing with previous satellite studies and theory. Changes in precipitation and droplet number were less consistent. The aircraft-based analysis is augmented by geostationary satellite retrievals and reanalysis data along Lagrangian trajectories between aircraft sampling times, documenting the evolution of cloud fraction, cloud droplet number concentration, EIS, and MBL depth. An expanded trajectory set spanning the summer of 2015 is used to show that the CSET-sampled air masses were representative of the season, with respect to EIS and cloud fraction. Two Lagrangian case studies attractive for future modeling are presented with aircraft and satellite data. The first features a clear Sc–Cu transition involving MBL deepening and decoupling with decreasing cloud fraction, and the second undergoes a much slower cloud evolution despite a greater initial depth and decoupling state. Potential causes for the differences in evolution are explored, including free-tropospheric humidity, subsidence, surface fluxes, and microphysics.
Naegele, A. C.; Randall, D. A.Naegele, A. C., D. A. Randall, 2019: Geographical and Seasonal Variability of Cloud-Radiative Feedbacks on Precipitation. Journal of Geophysical Research: Atmospheres, 124(2), 684-699. doi: 10.1029/2018JD029186. We have used observations to study the temporal covariability of precipitation and atmospheric radiative cooling (ARC, defined as positive when the atmosphere is radiatively cooled) on seasonal and longer time scales. Clouds act to decrease the globally averaged ARC, but their radiative effect on the ARC varies with latitude. Clouds decrease the ARC in the tropics, mainly by reducing the outgoing longwave radiation, but they increase the ARC in higher latitudes, primarily by increasing the downwelling longwave radiation at the surface. The temporal correlation of the zonally averaged precipitation rate and the zonally averaged ARC is about -0.7 in the tropics and +0.5 in higher latitudes, and it changes sign almost discontinuously toward the poles at approximately 30° N and 30° S. This suggests that changes in the ARC feed back negatively on precipitating tropical systems, and positively on precipitating systems at higher latitudes. cloud feedback; convective aggregation; cloud radiative effects; hydrologic cycle; precipitation
Nascimento, Gláucia dos Santos; Ruhoff, Anderson; Cavalcanti, J. Rafael; Marques, David da Motta; Roberti, Débora Regina; da Rocha, Humberto Ribeiro; Munar, Andrés Maurício; Fragoso, Carlos Ruberto; de Oliveira, Maria Betânia LealNascimento, G. d. S., A. Ruhoff, J. R. Cavalcanti, D. d. M. Marques, D. R. Roberti, H. R. da Rocha, A. M. Munar, C. R. Fragoso, M. B. L. de Oliveira, 2019: Assessing CERES Surface Radiation Components for Tropical and Subtropical Biomes. IEEE Journal of Selected Topics in Applied Earth Observations and Remote Sensing, 12(10), 3826-3840. doi: 10.1109/JSTARS.2019.2939382. An adequate estimate of the radiation components on the earth's surface may help reveal many important interactions between the earth's surface and the atmosphere. In-situ measurements of radiation components are sparse, and remote sensing is one way to overcome this limitation. The clouds and the earth's radiant energy system (CERES) provides a long-term estimate of shortwave and longwave radiation over the entire globe. This article compared and evaluated all components of the surface radiation, estimated using CERES SYN1deg Ed3A and SYN1deg Ed4A data (shortwave up and down, longwave up and down, and photosynthetically active radiation) against measurements for 15 sites located in Brazil. Our results indicated that CERES SYN1deg estimates are accurate for all variables evaluated, with the SYN1deg Ed4A version increasing the 2$ and decreasing the RMSE from the SYN1deg Ed3A version. We also evaluated the main driving factors controlling the variability of the surface radiation components, using cluster analysis and multiple linear regression. The results showed that surface temperature and total precipitable water vapor are the main driving factors affecting the variability of the different radiation components. The results also highlighted the influence of climate conditions and biome features on the estimates of surface radiation components by CERES. The radiation data provided by CERES SYN1deg Ed4A proved to be a promising alternative for large regions where meteorological information is unavailable or sparse. Remote sensing; longwave radiation; Earth; Meteorology; Atmospheric measurements; Monitoring; Atmospheric modeling; Clouds; shortwave radiation; Amazon rain forest; clouds and the earth's radiant energy system (CERES) validation
Naud, Catherine M.; Booth, James F.; Jeyaratnam, Jeyavinoth; Donner, Leo J.; Seman, Charles J.; Zhao, Ming; Guo, Huan; Ming, YiNaud, C. M., J. F. Booth, J. Jeyaratnam, L. J. Donner, C. J. Seman, M. Zhao, H. Guo, Y. Ming, 2019: Extratropical Cyclone Clouds in the GFDL Climate Model: Diagnosing Biases and the Associated Causes. J. Climate, 32(20), 6685-6701. doi: 10.1175/JCLI-D-19-0421.1. The clouds in Southern Hemisphere extratropical cyclones generated by the GFDL climate model are analyzed against MODIS, CloudSat, and CALIPSO cloud and precipitation observations. Two model versions are used: one is a developmental version of “AM4,” a model GFDL that will utilize for CMIP6, and the other is the same model with a different parameterization of moist convection. Both model versions predict a realistic top-of-atmosphere cloud cover in the southern oceans, within 5% of the observations. However, an examination of cloud cover transects in extratropical cyclones reveals a tendency in the models to overestimate high-level clouds (by differing amounts) and underestimate cloud cover at low levels (again by differing amounts), especially in the post–cold frontal (PCF) region, when compared with observations. In focusing only on the models, it is seen that their differences in high and midlevel clouds are consistent with their differences in convective activity and relative humidity (RH), but the same is not true for the PCF region. In this region, RH is higher in the model with less cloud fraction. These seemingly contradictory cloud and RH differences can be explained by differences in the cloud-parameterization tuning parameters that ensure radiative balance. In the PCF region, the model cloud differences are smaller than either of the model biases with respect to observations, suggesting that other physics changes are needed to address the bias. The process-oriented analysis used to assess these model differences will soon be automated and shared.
Or, D.; Lehmann, P.Or, D., P. Lehmann, 2019: Surface Evaporative Capacitance: How Soil Type and Rainfall Characteristics Affect Global-Scale Surface Evaporation. Water Resources Research, 55(1), 519-539. doi: 10.1029/2018WR024050. The separation of evapotranspiration (ET) into its surface evaporation (E) and transpiration (T) components remains a challenge despite its importance for linking water and carbon cycles, for water management, and for attribution of hydrologic isotope fractionation. Regional and global estimates of surface evaporation often rely on estimates of ET (e.g., Penman-Monteith) where E is deduced as a residual or as a fraction of potential evaporation. We propose a novel and direct method for estimating E from soil properties considering regional rainfall characteristics and accounting for internal drainage dynamics. A soil-dependent evaporative characteristic length defines an active surface evaporative capacitor depth below which soil water is sheltered from capillary pull to the evaporating surface. A site-specific evaporative capacitor is periodically recharged by rainfall and discharges at rates determined by interplay between internal drainage and surface evaporation. The surface evaporative capacitor concept was tested using field measurements and subsequently applied to generate a global map of climatic surface evaporation. Latitudinal comparisons with estimates from other global models (e.g., Penman-Monteith method modified by Leuning et al., 2008, https://doi.org/10.1029/2007WR006562 [PML]; Moderate Resolution Imaging Spectroradiometer [MODIS]; and Global Land-surface Evaporation: the Amsterdam Methodology [GLEAM]) show good agreement but also point to potential shortcomings of present estimates of surface evaporation. Interestingly, the ratio of surface evaporation (E) to potential evapotranspiration (ET0) is relatively constant across climates, biomes, and soil types with E/ET0 < 0.15 for 60% of all terrestrial surfaces, in agreement with recent studies. evapotranspiration; evaporation; global data; soil physics
Pagán, Brianna R.; Maes, Wouter H.; Gentine, Pierre; Martens, Brecht; Miralles, Diego G.Pagán, B. R., W. H. Maes, P. Gentine, B. Martens, D. G. Miralles, 2019: Exploring the Potential of Satellite Solar-Induced Fluorescence to Constrain Global Transpiration Estimates. Remote Sensing, 11(4), 413. doi: 10.3390/rs11040413. The opening and closing of plant stomata regulates the global water, carbon and energy cycles. Biophysical feedbacks on climate are highly dependent on transpiration, which is mediated by vegetation phenology and plant responses to stress conditions. Here, we explore the potential of satellite observations of solar-induced chlorophyll fluorescence (SIF)—normalized by photosynthetically-active radiation (PAR)—to diagnose the ratio of transpiration to potential evaporation (‘transpiration efficiency’, τ). This potential is validated at 25 eddy-covariance sites from seven biomes worldwide. The skill of the state-of-the-art land surface models (LSMs) from the eartH2Observe project to estimate τ is also contrasted against eddy-covariance data. Despite its relatively coarse (0.5°) resolution, SIF/PAR estimates, based on data from the Global Ozone Monitoring Experiment 2 (GOME-2) and the Clouds and Earth’s Radiant Energy System (CERES), correlate to the in situ τ significantly (average inter-site correlation of 0.59), with higher correlations during growing seasons (0.64) compared to decaying periods (0.53). In addition, the skill to diagnose the variability of in situ τ demonstrated by all LSMs is on average lower, indicating the potential of SIF data to constrain the formulations of transpiration in global models via, e.g., data assimilation. Overall, SIF/PAR estimates successfully capture the effect of phenological changes and environmental stress on natural ecosystem transpiration, adequately reflecting the timing of this variability without complex parameterizations. eddy-covariance; GOME-2; solar-induced chlorophyll fluorescence; transpiration; transpiration efficiency
Park, Sungsu; Oh, Eunsil; Kim, Siyun; Shin, JihoonPark, S., E. Oh, S. Kim, J. Shin, 2019: Impact of Interactive Vertical Overlap of Cumulus and Stratus on Global Aerosol, Precipitation, and Radiation Processes in the Seoul National University Atmosphere Model Version 0 With a Unified Convection Scheme (SAM0-UNICON). Journal of Advances in Modeling Earth Systems, 11(12), 4016-4043. doi: 10.1029/2019MS001643. The previously proposed parameterization for the integrated vertical overlap of cumulus and stratus is generalized to handle both conventional exponential-random stratus overlap and nonconventional (i.e., other than exponential-random) cumulus overlap in a simultaneous way. With the parameterization of the decorrelation length scale of stratus as a function of vertical wind shear, our parameterization simulates various interactive feedback between vertical cloud overlap and other physical processes. This interactive vertical overlap parameterization of cumulus and stratus was implemented into all relevant physics parameterizations (i.e., convection, stratus microphysics, radiation, aerosol wet deposition, and aerosol activation at the base of stratus) of the Seoul National University Atmosphere Model version 0 with a Unified Convection Scheme (SAM0-UNICON) in a fully consistent way. It is shown that the overall performance of the interactive cloud overlap parameterization to simulate the observed mean climate is similar to that of the original overlap parameterization. Given that an intensive tuning has not yet been performed with the new overlap parameterization, this result is quite encouraging. cloud; parameterization; overlap
Park, Sungsu; Shin, Jihoon; Kim, Siyun; Oh, Eunsil; Kim, YoonjaePark, S., J. Shin, S. Kim, E. Oh, Y. Kim, 2019: Global Climate Simulated by the Seoul National University Atmosphere Model Version 0 with a Unified Convection Scheme (SAM0-UNICON). J. Climate, 32(10), 2917-2949. doi: 10.1175/JCLI-D-18-0796.1. As a contribution to phase 6 of the Coupled Model Intercomparison Project (CMIP6), the global climate simulated by an atmospheric general circulation model (GCM), the Seoul National University Atmosphere Model version 0 with a Unified Convection Scheme (SAM0-UNICON), is compared with observation and climates simulated by the Community Atmosphere Model version 5 (CAM5) and Community Earth System Model version 1 (CESM1), on which SAM0-UNICON is based. Both SAM0-UNICON and CESM1 successfully reproduce observed global warming after 1970. The global mean climate simulated by SAM0-UNICON is roughly similar to that of CAM5/CESM1. However, SAM0-UNICON improves the simulations of the double intertropical convergence zone, shortwave cloud forcing, near-surface air temperature, aerosol optical depth, sea ice fraction, and sea surface temperature (SST), but is slightly poorer for the simulation of tropical relative humidity, Pacific surface wind stress, and ocean rainfall. Two important biases in the simulated mean climate in both models are a set of horseshoe-shaped biases of SST, sea level pressure, precipitation, and cloud radiative forcings in the central equatorial Pacific and a higher sea ice fraction in the Arctic periphery and Southern Hemispheric circumpolar regions. Both SAM0-UNICON and CESM1 simulate the observed El Niño–Southern Oscillation (ENSO) reasonably well. However, compared with CAM5/CESM1, SAM0-UNICON performs better in simulating the Madden–Julian oscillation (MJO), diurnal cycle of precipitation, and tropical cyclones. The aerosol indirect effect (AIE) simulated by SAM0-UNICON is similar to that from CAM5 but the magnitudes of the individual shortwave and longwave AIEs are substantially reduced.
Patel, Piyushkumar N.; Gautam, Ritesh; Michibata, Takuro; Gadhavi, HarishPatel, P. N., R. Gautam, T. Michibata, H. Gadhavi, 2019: Strengthened Indian Summer Monsoon Precipitation Susceptibility Linked to Dust-Induced Ice Cloud Modification. Geophysical Research Letters, 46(14), 8431-8441. doi: 10.1029/2018GL081634. A growing body of research has underscored the radiative impact of mineral dust in influencing Indian summer monsoon rainfall variability. However, the various aerosol-cloud-precipitation interaction mechanisms remain poorly understood. Here we analyze multisatellite observations to examine dust-induced modification in ice clouds and precipitation susceptibility. We show contrasting dust-induced changes in ice cloud regimes wherein despite a 25% reduction in ice particle radius in thin ice clouds, we find 40% increase in ice particle radius and ice water path in thick ice clouds resulting in the cloud deepening and subsequently strengthened precipitation susceptibility, under strong updraft regimes. The observed dust-ice cloud-precipitation interactions are supported by a strong correlation between the interannual monsoon rainfall variability and dust frequency. This microphysical-dynamical coupling appears to provide negative feedback to aerosol-cloud interactions, which acts to buffer enhanced aerosol wet scavenging. Our results underscore the importance of incorporating meteorological regime-dependent dust-ice cloud-precipitation interactions in climate simulations. satellite remote sensing; aerosol-cloud-precipitation interactions; cloud invigoration; dust-ice cloud interactions; dynamical feedback; Indian Monsoon
Peterson, Colten A.; Chen, Xiuhong; Yue, Qing; Huang, XiangleiPeterson, C. A., X. Chen, Q. Yue, X. Huang, 2019: The Spectral Dimension of Arctic Outgoing Longwave Radiation and Greenhouse Efficiency Trends From 2003 to 2016. Journal of Geophysical Research: Atmospheres, 124(15), 8467-8480. doi: 10.1029/2019JD030428. Fourteen years of spectral fluxes derived from collocated Atmospheric Infrared Sounder (AIRS) and Clouds and the Earth's Radiant Energy System (CERES) observations are used in conjunction with AIRS retrievals to examine the trends of zonal mean spectral outgoing longwave radiation (OLR) and greenhouse efficiency (GHE) in the Arctic. AIRS retrieved profiles are fed into a radiative transfer model to generate synthetic clear-sky spectral OLR. Trends are derived from the simulated clear-sky spectral OLR and GHE and then compared with their counterparts derived from collocated observations. Spectral trends in different seasons are distinctively different. March and September exhibit positive trends in spectral OLR over the far-IR dirty window and mid-IR window region for most of the Arctic. In contrast, spectral OLR trends in July are negative over the far-IR dirty window and can be positive or negative in the mid-IR window depending on the latitude. Sensitivity studies reveal that surface temperature contributes much more than atmospheric temperature and humidity to the spectral OLR and GHE trends, while the contributions from the latter two are also discernible over many spectral regions (e.g., trends in the far-IR dirty window in March). The largest increase of spectral GHE is seen north of 80°N in March across the water vapor v2 band and far-IR. When the secular fractional change of spectral OLR is less than that of surface spectral emission, an increase of spectral GHE can be expected. Spectral trend analyses reveal more information than broadband trend analyses alone. outgoing longwave radiation; Arctic climate; greenhouse efficiency; spectral flux
Pistone, Kristina; Eisenman, Ian; Ramanathan, VeerabhadranPistone, K., I. Eisenman, V. Ramanathan, 2019: Radiative Heating of an Ice-Free Arctic Ocean. Geophysical Research Letters, 46, 7474-7480. doi: 10.1029/2019GL082914. During recent decades, there has been dramatic Arctic sea ice retreat. This has reduced the top-of-atmosphere albedo, adding more solar energy to the climate system. There is substantial uncertainty regarding how much ice retreat and associated solar heating will occur in the future. This is relevant to future climate projections, including the timescale for reaching global warming stabilization targets. Here we use satellite observations to estimate the amount of solar energy that would be added in the worst-case scenario of a complete disappearance of Arctic sea ice throughout the sunlit part of the year. Assuming constant cloudiness, we calculate a global radiative heating of 0.71 W/m2 relative to the 1979 baseline state. This is equivalent to the effect of one trillion tons of CO2 emissions. These results suggest that the additional heating due to complete Arctic sea ice loss would hasten global warming by an estimated 25 years.
Popp, Max; Bony, SandrinePopp, M., S. Bony, 2019: Stronger zonal convective clustering associated with a wider tropical rain belt. Nature Communications, 10(1), 1-12. doi: 10.1038/s41467-019-12167-9. How the spatial patterns of deep convection affect the large-scale dynamics of the atmosphere remains an open question. Here, it is shown that if convection along the equator is clustered, the tropical rain belt widens and exhibits a double peak structure.
Posselt, Derek J.; Wu, Longtao; Mueller, Kevin; Huang, Lei; Irion, Fredrick W.; Brown, Shannon; Su, Hui; Santek, David; Velden, Christopher S.Posselt, D. J., L. Wu, K. Mueller, L. Huang, F. W. Irion, S. Brown, H. Su, D. Santek, C. S. Velden, 2019: Quantitative Assessment of State-Dependent Atmospheric Motion Vector Uncertainties. J. Appl. Meteor. Climatol., 58(11), 2479-2495. doi: 10.1175/JAMC-D-19-0166.1. This study examines the error characteristics of atmospheric motion vectors (AMVs) obtained by tracking the movement of water vapor features. A high-resolution numerical simulation of a dynamic weather event is used as a baseline, and AMVs tracked from retrieved water vapor fields are compared with the “true” winds produced by the model. The sensitivity of AMV uncertainty to time interval, AMV tracking window size, water vapor content, horizontal gradient, and wind structure is examined. AMVs are derived from the model water vapor field at a specific height and also from water vapor fields vertically blurred using smoothing functions consistent with high-spectral-resolution infrared (IR) and high-frequency microwave (MW) water vapor sounders. Uncertainties in water vapor AMVs are state dependent and are largest for regions with small water vapor content and small water vapor spatial gradient and in places where the flow runs parallel to contours of constant water vapor content. Smoothing of water vapor consistent with IR and MW retrievals does not increase AMV uncertainty; however, the yield of AMVs from IR sounders is much lower than from MW sounders because of the inability of IR sounders to retrieve water vapor below clouds. The yield and error are similar for AMVs in the lower and upper troposphere, even though the water vapor content in the upper troposphere is much smaller. The results have implications for the design of new observing systems, as well as the specification of errors when AMVs are ingested in data assimilation systems.
Qiu, Yun; Han, Weiqing; Lin, Xinyu; West, B. Jason; Li, Yuanlong; Xing, Wen; Zhang, Xiaolin; Arulananthan, K.; Guo, XiaogangQiu, Y., W. Han, X. Lin, B. J. West, Y. Li, W. Xing, X. Zhang, K. Arulananthan, X. Guo, 2019: Upper-Ocean Response to the Super Tropical Cyclone Phailin (2013) over the Freshwater Region of the Bay of Bengal. J. Phys. Oceanogr., 49(5), 1201-1228. doi: 10.1175/JPO-D-18-0228.1. This study investigates the impact of salinity stratification on the upper-ocean response to a category 5 tropical cyclone, Phailin, that crossed the northern Bay of Bengal (BOB) from 8 to 13 October 2013. A drastic increase of up to 5.0 psu in sea surface salinity (SSS) was observed after Phailin’s passage, whereas a weak drop of below 0.5°C was observed in sea surface temperature (SST). Rightward biases were apparent in surface current and SSS but not evident in SST. Phailin-induced SST variations can be divided into the warming and cooling stages, corresponding to the existence of the thick barrier layer (BL) and temperature inversion before and erosion after Phailin’s passage, respectively. During the warming stage, SST increased due to strong entrainment of warmer water from the BL, which overcame the cooling induced by surface heat fluxes and horizontal advection. During the cooling stage, the entrainment and upwelling dominated the SST decrease. The preexistence of the BL, which reduced entrainment cooling by ~1.09°C day−1, significantly weakened the overall Phailin-induced SST cooling. The Hybrid Coordinate Ocean Model (HYCOM) experiments confirm the crucial roles of entrainment and upwelling in the Phailin-induced dramatic SSS increase and weak SST decrease. Analyses of upper-ocean stratification associated with 16 super TCs that occurred in the BOB during 1980–2015 show that intensifications of 13 TCs were associated with a thick isothermal layer, and 5 out of the 13 were associated with a thick BL. The calculation of TC intensity with and without considering subsurface temperature demonstrates the importance of large upper-ocean heat storage in TC growth.
Quast, Ralf; Giering, Ralf; Govaerts, Yves; Rüthrich, Frank; Roebeling, RobQuast, R., R. Giering, Y. Govaerts, F. Rüthrich, R. Roebeling, 2019: Climate Data Records from Meteosat First Generation Part II: Retrieval of the In-Flight Visible Spectral Response. Remote Sensing, 11(5), 480. doi: 10.3390/rs11050480. How can the in-flight spectral response functions of a series of decades-old broad band radiometers in Space be retrieved post-flight? This question is the key to developing Climate Data Records from the Meteosat Visible and Infrared Imager on board the Meteosat First Generation (MFG) of geostationary satellites, which acquired Earth radiance images in the Visible (VIS) broad band from 1977 to 2017. This article presents a new metrologically sound method for retrieving the VIS spectral response from matchups of pseudo-invariant calibration site (PICS) pixels with datasets of simulated top-of-atmosphere spectral radiance used as reference. Calibration sites include bright desert, open ocean and deep convective cloud targets. The absolute instrument spectral response function is decomposed into generalised Bernstein basis polynomials and a degradation function that is based on plain physical considerations and able to represent typical chromatic ageing characteristics. Retrieval uncertainties are specified in terms of an error covariance matrix, which is projected from model parameter space into the spectral response function domain and range. The retrieval method considers target type-specific biases due to errors in, e.g., the selection of PICS target pixels and the spectral radiance simulation explicitly. It has been tested with artificial and well-comprehended observational data from the Spinning Enhanced Visible and Infrared Imager on-board Meteosat Second Generation and has retrieved meaningful results for all MFG satellites apart from Meteosat-1, which was not available for analysis. remote sensing; algorithmic differentiation; Climate Data Record; Earth Observation; Fundamental Climate Data Record; instrument degradation; instrument spectral response function; Meteosat Visible and Infrared Imager (MVIRI); metrology; uncertainty propagation
Raghuraman, Shiv Priyam; Paynter, David; Ramaswamy, V.Raghuraman, S. P., D. Paynter, V. Ramaswamy, 2019: Quantifying the Drivers of the Clear Sky Greenhouse Effect, 2000–2016. Journal of Geophysical Research: Atmospheres, 124(21), 11354-11371. doi: 10.1029/2019JD031017. The clear sky greenhouse effect (G) is defined as the trapping of infrared radiation by the atmosphere in the absence of clouds. The magnitude and variability of G is an important element in the understanding of Earth's energy balance; yet the quantification of the governing factors of G is poor. The global mean G averaged over 2000 to 2016 is 130–133 W m−2 across data sets. We use satellite observations from Clouds and the Earth's Radiant Energy System Energy Balance and Filled (CERES EBAF) to calculate the monthly anomalies in the clear sky greenhouse effect (ΔG). We quantify the contributions to ΔG due to changes in surface temperature, atmospheric temperature, and water vapor by performing partial radiation perturbation experiments using ERA-Interim and Geophysical Fluid Dynamics Laboratory's Atmospheric Model 4.0 climatological data. Water vapor in the middle troposphere and upper troposphere is found to contribute equally to the global mean and tropical mean ΔG. Holding relative humidity (RH) fixed in the radiative transfer calculations captures the temporal variability of global mean ΔG while variations in RH control the regional ΔG signal. The variations in RH are found to help generate the clear sky super greenhouse effect (SGE). Thirty-six percent of Earth's area exhibits SGE, and this disproportionately contributes to 70% of the globally averaged magnitude of ΔG. In the global mean, G's sensitivity to surface temperature is 3.1–4.0 W m−2 K−1, and the clear sky longwave feedback parameter is 1.5–2.0 W m−2 K−1. Observations from CERES EBAF lie at the more sensitive ends of these ranges and the spread arises from its cloud removal treatment, suggesting that it is difficult to constrain clear sky feedbacks. relative humidity; water vapor; greenhouse effect; climate feedback; middle troposphere; super greenhouse effect
Rasch, P. J.; Xie, S.; Ma, P.-L.; Lin, W.; Wang, H.; Tang, Q.; Burrows, S. M.; Caldwell, P.; Zhang, K.; Easter, R. C.; Cameron‐Smith, P.; Singh, B.; Wan, H.; Golaz, J.-C.; Harrop, B. E.; Roesler, E.; Bacmeister, J.; Larson, V. E.; Evans, K. J.; Qian, Y.; Taylor, M.; Leung, L. R.; Zhang, Y.; Brent, L.; Branstetter, M.; Hannay, C.; Mahajan, S.; Mametjanov, A.; Neale, R.; Richter, J. H.; Yoon, J.-H.; Zender, C. S.; Bader, D.; Flanner, M.; Foucar, J. G.; Jacob, R.; Keen, N.; Klein, S. A.; Liu, X.; Salinger, A. G.; Shrivastava, M.; Yang, Y.Rasch, P. J., S. Xie, P. Ma, W. Lin, H. Wang, Q. Tang, S. M. Burrows, P. Caldwell, K. Zhang, R. C. Easter, P. Cameron‐Smith, B. Singh, H. Wan, J. Golaz, B. E. Harrop, E. Roesler, J. Bacmeister, V. E. Larson, K. J. Evans, Y. Qian, M. Taylor, L. R. Leung, Y. Zhang, L. Brent, M. Branstetter, C. Hannay, S. Mahajan, A. Mametjanov, R. Neale, J. H. Richter, J. Yoon, C. S. Zender, D. Bader, M. Flanner, J. G. Foucar, R. Jacob, N. Keen, S. A. Klein, X. Liu, A. G. Salinger, M. Shrivastava, Y. Yang, 2019: An Overview of the Atmospheric Component of the Energy Exascale Earth System Model. Journal of Advances in Modeling Earth Systems, 11(8), 2377-2411. doi: 10.1029/2019MS001629. The Energy Exascale Earth System Model Atmosphere Model version 1, the atmospheric component of the Department of Energy's Energy Exascale Earth System Model is described. The model began as a fork of the well-known Community Atmosphere Model, but it has evolved in new ways, and coding, performance, resolution, physical processes (primarily cloud and aerosols formulations), testing and development procedures now differ significantly. Vertical resolution was increased (from 30 to 72 layers), and the model top extended to 60 km ( 0.1 hPa). A simple ozone photochemistry predicts stratospheric ozone, and the model now supports increased and more realistic variability in the upper troposphere and stratosphere. An optional improved treatment of light-absorbing particle deposition to snowpack and ice is available, and stronger connections with Earth system biogeochemistry can be used for some science problems. Satellite and ground-based cloud and aerosol simulators were implemented to facilitate evaluation of clouds, aerosols, and aerosol-cloud interactions. Higher horizontal and vertical resolution, increased complexity, and more predicted and transported variables have increased the model computational cost and changed the simulations considerably. These changes required development of alternate strategies for tuning and evaluation as it was not feasible to “brute force” tune the high-resolution configurations, so short-term hindcasts, perturbed parameter ensemble simulations, and regionally refined simulations provided guidance on tuning and parameterization sensitivity to higher resolution. A brief overview of the model and model climate is provided. Model fidelity has generally improved compared to its predecessors and the CMIP5 generation of climate models. climate; climate change; climate modeling; atmospheric model; Earth system; general circulation modeling
Renner, M.; Wild, M.; Schwarz, M.; Kleidon, A.Renner, M., M. Wild, M. Schwarz, A. Kleidon, 2019: Estimating Shortwave Clear-Sky Fluxes From Hourly Global Radiation Records by Quantile Regression. Earth and Space Science, 6(8), 1532-1546. doi: 10.1029/2019EA000686. Estimates of radiative fluxes under cloud-free conditions (“clear-sky”) are required in many fields, from climatic analyses of solar transmission to estimates of solar energy potential for electricity generation. Ideally, these fluxes can be obtained directly from measurements of solar fluxes at the surface. However, common standard methods to identify clear-sky conditions require observations of both the total and the diffuse radiative fluxes at very high temporal resolution of minutes, which restricts these methods to a few, well-equipped sites. Here we propose a simple method to estimate clear-sky fluxes only from typically available global radiation measurements (Rsd) at (half-)hourly resolution. Plotting a monthly sample of observed Rsd against the corresponding incoming solar radiation at the top of atmosphere (potential solar radiation) reveals a typical triangle shape with clear-sky conditions forming a distinct, linear slope in the upper range of observations. This upper slope can be understood as the fractional transmission of solar radiation representative for cloud-free conditions of the sample period. We estimate this upper slope through quantile regression. We employ data of 42 stations of the worldwide Baseline Surface Radiation Network to compare our monthly estimates with the standard clear-sky identification method developed by Long and Ackerman (2000, https://doi.org/10.1029/2000JD900077). We find very good agreement of the derived fractional solar transmission (R2 = 0.73) across sites. These results thus provide confidence in applying the proposed method to the larger set of global radiation measurements to obtain further observational constraints on clear-sky fluxes and cloud radiative effects. global radiation; clear-sky; cloud-free; quantile regression; transmission
Rizvi, Shahnilla Haider; Alam, Khan; Iqbal, Muhammad JawedRizvi, S. H., K. Alam, M. J. Iqbal, 2019: Spatio -temporal variations in urban heat island and its interaction with heat wave. Journal of Atmospheric and Solar-Terrestrial Physics, 185, 50-57. doi: 10.1016/j.jastp.2019.02.001. Most of the urban localities are facing the effects of Urban Heat Island (UHI) and extreme heat wave (HW) events. It is expected that these HW events are likely to be intensified by the effect of UHI in the future. As these events project to increase in both severity and frequency therefore, it is crucial to assess the intensity of UHI and examine the relationship between HW and UHI. In this study, observations for different coastal areas are used to quantify the impacts of UHI during the HW events. The spatial and temporal variability patterns of UHI in the metropolitan city of Karachi were also investigated using hourly temperature observations for a period of 10 years in two phases (a) from 1998 to 2002 (b) from 2012 to 2016. During the first phase (1998–2001), the maximum Urban Heat Island Intensity (UHII) for night time in summer was 1.9 °C, while during the second phase (2012–2016), it increased by 0.6 °C. Despite the fact that both phases have shown similar pattern for seasonal UHII, urban-rural temperature difference was found to be significant in summer especially in the night time. Temporal distribution of UHII for winter shows that average intensity of UHI during daytime varies between 0.1 °C and 3.2 °C, considering the overall time duration. The results indicate that UHII increased significantly during the HW period which caused more than 800 deaths in Karachi between 17th June and 24th June 2015. Heat index; Heat stroke; Heat wave; Urban heat island intensity
Rodríguez, José Antonio SobrinoRodríguez, J., . Antonio Sobrino, 2019: Fifth recent advances in quantitative remote sensing. The Fifth International Symposium on Recent Advances in Quantitative Remote Sensing was held in Torrent, Spain from 18 to 22 September 2018. It was sponsored and organized by the Global Change Unit (GCU) from the Image Processing Laboratory (IPL), University of Valencia (UVEG), Spain. This Symposium addressed the scientific advances in quantitative remote sensing in connection with real applications. Its main goal was to assess the state of the art of both theory and applications in the analysis of remote sensing data, as well as to provide a forum for researcher in this subject area to exchange views and report their latest results. In this book 89 of the 262 contributions presented in both plenary and poster sessions are arranged according to the scientific topics selected. The papers are ranked in the same order as the final programme. Science / Mechanics / Thermodynamics
Rowell, David P.Rowell, D. P., 2019: An Observational Constraint on CMIP5 Projections of the East African Long Rains and Southern Indian Ocean Warming. Geophysical Research Letters, 46(11), 6050-6058. doi: 10.1029/2019GL082847. Two outlying projections of the East African Long Rains suggest the seasonal rainfall may double by the late 21st century. Previous work has linked these extremes—found in the IPSL-CM5A model—to an exceptional March to May warming of the southern Indian Ocean. The current study shows a strong feedback between sea surface temperature (SST) increases and reduced low-level cloud cover (with similar behavior in other southern subtropical oceans). An observational constraint is developed by demonstrating a correlation across 28 models between the strength of present-day interannual SST-cloud sensitivity and future SST response. Verification of the present-day sensitivity finds that IPSL-CM5A's feedbacks are very likely overestimated. It is therefore suggested its projections should be discounted for the March to May southern Indian Ocean and East African Long Rains. This narrows the CMIP5 plausible range of Long Rains totals by a third. CMIP5; climate change; Indian Ocean; cloud feedbacks; East Africa; emergent constraint
Ruan, Ruomei; Chen, Xianyao; Zhao, Jinping; Perrie, William; Mottram, Ruth; Zhang, Minghong; Diao, Yina; Du, Ling; Wu, LixinRuan, R., X. Chen, J. Zhao, W. Perrie, R. Mottram, M. Zhang, Y. Diao, L. Du, L. Wu, 2019: Decelerated Greenland Ice Sheet Melt Driven by Positive Summer North Atlantic Oscillation. Journal of Geophysical Research: Atmospheres, 124(14), 7633-7646. doi: 10.1029/2019JD030689. The abrupt deceleration of accelerated Greenland Ice Sheet (GrIS) melting since 2013, after a period of acceleration previously noted, is studied here. It is shown that the deceleration of GrIS melting since 2013 is due to the reduction in short-wave solar radiation in the presence of increasing total cloud cover, which is driven by a more persistent positive summer North Atlantic Oscillation on the decadal time scale. By presenting the coherence with the temperature variability at the weather stations in Greenland, which have century-long records, we deduce that the acceleration of GrIS melting during the early 2000s and the subsequent deceleration since 2013 will reoccur frequently on decadal time scales, with the amplitude nearly half of the multidecadal warming trend of the GrIS melt. It can reduce the mass loss from the GrIS on short to medium time scales but is unlikely to halt mass loss related to climate change in the future. This finding highlights the importance of internal climate variability on the mass budget of the GrIS and therefore on predictions of future global sea level change and may help to assist planning for associated social and economic consequences. Greenland Ice Sheet; mass balance; summer North Atlantic Oscillation; time scale
Ruosteenoja, Kimmo; Räisänen, Petri; Devraj, Sarvesh; Garud, Shirish S; Lindfors, Anders V.Ruosteenoja, K., P. Räisänen, S. Devraj, S. S. Garud, A. V. Lindfors, 2019: Future changes in incident surface solar radiation and contributing factors in India in CMIP5 climate model simulations. J. Appl. Meteor. Climatol., 58(1), 19-35. doi: 10.1175/JAMC-D-18-0013.1. To support the planning of future solar energy production in India, forthcoming changes in incoming surface solar radiation and the main physical factors contributing to the change were inferred from simulations performed with 27 global CMIP5 climate models. According to the multi-model mean response, radiation diminishes by a few percent during the early decades of the 21st century, in tandem with strengthening aerosol and water vapour dimming. The largest reduction is anticipated for Northern India. The evolution of incident radiation in mid- and late 21st century depends substantially on the emission scenario. According to the Representative Concentration Pathways RCP2.6 and RCP4.5, solar radiation would gradually recover close to the level that prevailed in late 20th century. This results from the peaking of aerosol loading before mid-century, while the water vapour content continuously increases somewhat. Conversely, under RCP8.5, incident radiation would still decline, even though more slowly than during the early century. This coincides with a substantial increase in atmospheric water vapour content and a modest decrease in aerosol forcing. In cloud forcing, multi-model mean changes are minor but divergence among the model simulations is substantial. Moreover, cloud forcing proved to be the factor that correlates most strongly with intermodel differences in the solar radiation response. Multi-model mean changes in solar radiation are rather small and would not crucially affect the conditions of solar energy production. Nevertheless, some individual models simulate far more substantial reductions, up to ~ 10%.
Saito, Masanori; Yang, Ping; Hu, Yongxiang; Liu, Xu; Loeb, Norman; Smith, William L.; Minnis, PatrickSaito, M., P. Yang, Y. Hu, X. Liu, N. Loeb, W. L. Smith, P. Minnis, 2019: An Efficient Method for Microphysical Property Retrievals in Vertically Inhomogeneous Marine Water Clouds Using MODIS-CloudSat Measurements. Journal of Geophysical Research: Atmospheres, 124(4), 2174-2193. doi: 10.1029/2018JD029659. An efficient method is developed to infer cloud optical thickness (COT) and cloud droplet effective radius (CDER) of marine water clouds from Moderate Resolution Imaging Spectroradiometer (MODIS) and CloudSat measurements, incorporating droplet size vertical inhomogeneity. Empirical orthogonal function (EOF) analysis is employed to reduce the degrees of freedom of the droplet size profile. The first two EOFs can explain 94% of the variability in the droplet size profile. Compared to the existing bispectral CDER retrieval from MODIS assuming plane parallel vertically homogeneous clouds, the new retrieval produces smaller CDER values in clouds in which the adiabatic growth process is dominant and larger CDER values in clouds in which the collision-coalescence process is dominant. To evaluate the performance of the retrieval algorithm, we compare retrieved COT and CDER in this study with their MODIS and CloudSat counterparts on a pixel-by-pixel basis. CDER retrieval based on the vertically homogeneous assumption may be underestimated by 30% due to droplet size vertical inhomogeneity when COT is large and the collision-coalescence process is dominant in the cloud. Retrieved CDER in conjunction with the two scores for EOFs can reconstruct the vertical profile of CDER, which is useful for cloud microphysical process studies. Furthermore, potential expansion of this algorithm to MODIS pixels without CloudSat collocations is discussed. remote sensing; droplet size; EOF; marine water clouds
Saito, Masanori; Yang, Ping; Loeb, Norman G.; Kato, SeijiSaito, M., P. Yang, N. G. Loeb, S. Kato, 2019: A Novel Parameterization of Snow Albedo Based on a Two-Layer Snow Model with a Mixture of Grain Habits. J. Atmos. Sci., 76(5), 1419-1436. doi: 10.1175/JAS-D-18-0308.1. Snow albedo plays a critical role in the surface energy budget in snow-covered regions and is subject to large uncertainty due to variable physical and optical characteristics of snow. We develop an optically and microphysically consistent snow grain habit mixture (SGHM) model, aiming at an improved representation of bulk snow properties in conjunction with considering the particle size distribution, particle shape, and internally mixed black carbon (BC). Spectral snow albedos computed with two snow layers with the SGHM model implemented in an adding–doubling radiative transfer model agree with observations. Top-snow-layer optical properties essentially determine spectral snow albedo when the top-layer snow water equivalent (SWE) is large. When the top-layer SWE is less than 1 mm, the second-snow-layer optical properties have nonnegligible impacts on the albedo of the snow surface. Snow albedo enhancement with increasing solar zenith angle (SZA) largely depends on snow particle effective radius and also internally mixed BC. Based on the SGHM model and various sensitivity studies, single- and two-layer snow albedos are parameterized for six spectral bands used in NASA Langley Research Center’s modified Fu–Liou broadband radiative transfer model. Parameterized albedo is expressed as a function of snow particle effective radii of the two layers, SWE in the top layer, internally mixed BC mass fraction in both layers, and SZA. Both single-layer and two-layer parameterizations provide band-mean snow albedo consistent with rigorous calculations, achieving correlation coefficients close to 0.99 for all bands.
Schmeisser, Lauren; Bond, Nicholas A.; Siedlecki, Samantha A.; Ackerman, Thomas P.Schmeisser, L., N. A. Bond, S. A. Siedlecki, T. P. Ackerman, 2019: The Role of Clouds and Surface Heat Fluxes in the Maintenance of the 2013–2016 Northeast Pacific Marine Heatwave. Journal of Geophysical Research: Atmospheres, 124(20), 10772-10783. doi: 10.1029/2019JD030780. Starting in late 2013, the Northeast (NE) Pacific Ocean experienced anomalously warm sea surface temperatures (SSTs) that persisted for over 2 years. This marine heatwave, known as “the Blob,” produced many devastating ecological impacts with socioeconomic implications for coastal communities. The warm waters observed during the NE Pacific 2013/2016 marine heatwave altered the surface energy balance and disrupted ocean–atmosphere interactions in the region. In principle, ocean–atmosphere interactions following the formation of the marine heatwave could have perpetuated warm SSTs through a positive SST-cloud feedback. The actual situation was more complicated. While reanalysis data show a decrease in boundary layer cloud fraction and an increase in downward shortwave radiative flux at the surface coincident with warm SSTs, this was accompanied by an increase in longwave radiative fluxes at the surface, as well as an increase in sensible and latent heat fluxes out of the ocean mixed layer. The result is a small negative net heat flux anomaly (compared to the anomalies of the individual terms contributing to the net heat flux). This provides new information about the midlatitude ocean–atmosphere system while it was in a perturbed state. More specifically, a mixed layer heat budget reveals that anomalies in both the atmospheric and oceanic processes offset each other such that the anomalously warm SSTs persisted for multiple years. The results show how the atmosphere–ocean system in the NE Pacific is able to maintain itself in an anomalous state for an extended period of time. cloud feedback; marine heatwave; atmosphere–ocean interactions; extreme event; midlatitude; surface heat fluxes
Schuddeboom, Alex; Varma, Vidya; McDonald, Adrian J.; Morgenstern, Olaf; Harvey, Mike; Parsons, Simon; Field, Paul; Furtado, KalliSchuddeboom, A., V. Varma, A. J. McDonald, O. Morgenstern, M. Harvey, S. Parsons, P. Field, K. Furtado, 2019: Cluster-based Evaluation of Model Compensating Errors: A Case Study of Cloud Radiative Effect in the Southern Ocean. Geophysical Research Letters, 46(6), 3446-3453. doi: 10.1029/2018GL081686. Model evaluation is difficult and generally relies on analysis which can mask compensating errors. This paper defines new metrics, using clusters generated from a machine learning algorithm, to estimate mean and compensating errors in different model runs. As a test case, we investigate the Southern Ocean shortwave radiative bias using clusters derived by applying self-organizing maps to satellite data. In particular, the effects of changing cloud phase parameterizations in the MetOffice Unified Model are examined. Differences in cluster properties show that the regional radiative biases are substantially different than the global bias, with two distinct regions identified within the Southern Ocean, each with a different signed bias. Changing cloud phase parameterizations can reduce errors at higher latitudes, but increase errors at lower latitudes of the Southern Ocean. Ranking the parameterizations often shows a contrast in mean and compensating errors, notably in all cases large compensating errors remain. Southern Ocean; Cloud simulation; Compensating errors; Model Evaluation
Schwarz, M.; Folini, D.; Yang, S.; Wild, M.Schwarz, M., D. Folini, S. Yang, M. Wild, 2019: The Annual Cycle of Fractional Atmospheric Shortwave Absorption in Observations and Models: Spatial Structure, Magnitude, and Timing. J. Climate, 32(20), 6729-6748. doi: 10.1175/JCLI-D-19-0212.1. We use the best currently available in situ and satellite-derived surface and top-of-the-atmosphere (TOA) shortwave radiation observations to explore climatological annual cycles of fractional (i.e., normalized by incoming radiation at the TOA) atmospheric shortwave absorption a˜a˜a˜ on a global scale. The analysis reveals that a˜a˜a˜ is a rather regional feature where the reported nonexisting a˜a˜a˜ in Europe is an exception rather than the rule. In several regions, large and distinctively different a˜a˜a˜ are apparent. The magnitudes of a˜a˜a˜ reach values up to 10% in some regions, which is substantial given that the long-term global mean atmospheric shortwave absorption is roughly 23%. Water vapor and aerosols are identified as major drivers for a˜a˜a˜ while clouds seem to play only a minor role for a˜a˜a˜. Regions with large annual cycles in aerosol emissions from biomass burning also show the largest a˜a˜a˜. As biomass burning is generally related to human activities, a˜a˜a˜ is likely also anthropogenically intensified or forced in the respective regions. We also test if climate models are able to simulate the observed pattern of a˜a˜a˜. In regions where a˜a˜a˜ is driven by the annual cycle of natural aerosols or water vapor, the models perform well. In regions with large a˜a˜a˜ induced by biomass-burning aerosols, the models’ performance is very limited.
Sellar, Alistair A.; Jones, Colin G.; Mulcahy, Jane P.; Tang, Yongming; Yool, Andrew; Wiltshire, Andy; O'Connor, Fiona M.; Stringer, Marc; Hill, Richard; Palmieri, Julien; Woodward, Stephanie; Mora, Lee de; Kuhlbrodt, Till; Rumbold, Steven T.; Kelley, Douglas I.; Ellis, Rich; Johnson, Colin E.; Walton, Jeremy; Abraham, Nathan Luke; Andrews, Martin B.; Andrews, Timothy; Archibald, Alex T.; Berthou, Ségolène; Burke, Eleanor; Blockley, Ed; Carslaw, Ken; Dalvi, Mohit; Edwards, John; Folberth, Gerd A.; Gedney, Nicola; Griffiths, Paul T.; Harper, Anna B.; Hendry, Maggie A.; Hewitt, Alan J.; Johnson, Ben; Jones, Andy; Jones, Chris D.; Keeble, James; Liddicoat, Spencer; Morgenstern, Olaf; Parker, Robert J.; Predoi, Valeriu; Robertson, Eddy; Siahaan, Antony; Smith, Robin S.; Swaminathan, Ranjini; Woodhouse, Matthew T.; Zeng, Guang; Zerroukat, MohamedSellar, A. A., C. G. Jones, J. P. Mulcahy, Y. Tang, A. Yool, A. Wiltshire, F. M. O'Connor, M. Stringer, R. Hill, J. Palmieri, S. Woodward, L. d. Mora, T. Kuhlbrodt, S. T. Rumbold, D. I. Kelley, R. Ellis, C. E. Johnson, J. Walton, N. L. Abraham, M. B. Andrews, T. Andrews, A. T. Archibald, S. Berthou, E. Burke, E. Blockley, K. Carslaw, M. Dalvi, J. Edwards, G. A. Folberth, N. Gedney, P. T. Griffiths, A. B. Harper, M. A. Hendry, A. J. Hewitt, B. Johnson, A. Jones, C. D. Jones, J. Keeble, S. Liddicoat, O. Morgenstern, R. J. Parker, V. Predoi, E. Robertson, A. Siahaan, R. S. Smith, R. Swaminathan, M. T. Woodhouse, G. Zeng, M. Zerroukat, 2019: UKESM1: Description and Evaluation of the U.K. Earth System Model. Journal of Advances in Modeling Earth Systems, 11(12), 4513-4558. doi: 10.1029/2019MS001739. We document the development of the first version of the U.K. Earth System Model UKESM1. The model represents a major advance on its predecessor HadGEM2-ES, with enhancements to all component models and new feedback mechanisms. These include a new core physical model with a well-resolved stratosphere; terrestrial biogeochemistry with coupled carbon and nitrogen cycles and enhanced land management; tropospheric-stratospheric chemistry allowing the holistic simulation of radiative forcing from ozone, methane, and nitrous oxide; two-moment, five-species, modal aerosol; and ocean biogeochemistry with two-way coupling to the carbon cycle and atmospheric aerosols. The complexity of coupling between the ocean, land, and atmosphere physical climate and biogeochemical cycles in UKESM1 is unprecedented for an Earth system model. We describe in detail the process by which the coupled model was developed and tuned to achieve acceptable performance in key physical and Earth system quantities and discuss the challenges involved in mitigating biases in a model with complex connections between its components. Overall, the model performs well, with a stable pre-industrial state and good agreement with observations in the latter period of its historical simulations. However, global mean surface temperature exhibits stronger-than-observed cooling from 1950 to 1970, followed by rapid warming from 1980 to 2014. Metrics from idealized simulations show a high climate sensitivity relative to previous generations of models: Equilibrium climate sensitivity is 5.4 K, transient climate response ranges from 2.68 to 2.85 K, and transient climate response to cumulative emissions is 2.49 to 2.66 K TtC−1.
Seviour, W. J. M.; Codron, F.; Doddridge, E. W.; Ferreira, D.; Gnanadesikan, A.; Kelley, M.; Kostov, Y.; Marshall, J.; Polvani, L. M.; Thomas, J. L.; Waugh, D. W.Seviour, W. J. M., F. Codron, E. W. Doddridge, D. Ferreira, A. Gnanadesikan, M. Kelley, Y. Kostov, J. Marshall, L. M. Polvani, J. L. Thomas, D. W. Waugh, 2019: The Southern Ocean sea surface temperature response to ozone depletion: A multi-model comparison. J. Climate, 32(16), 5107–5121. doi: 10.1175/JCLI-D-19-0109.1. The effect of the Antarctic ozone hole extends downwards from the stratosphere, with clear signatures in surface weather patterns including a positive trend in the Southern Annular Mode (SAM). Several recent studies have used coupled climate models to investigate the impact of these changes on Southern Ocean sea surface temperature (SST), notably motivated by the observed cooling from the late 1970s. Here we examine the robustness of these model results through comparison of both previously published and new simulations. We focus on the calculation of ‘climate response functions’ (CRFs), transient responses to an instantaneous step-change in ozone concentrations. The CRF for most models consists of a rapid cooling of SST, followed by a slower warming trend. However, inter-model comparison reveals large uncertainties, such that even the sign of the impact of ozone depletion on historical SST, when reconstructed from the CRF, remains unconstrained. Comparison of these CRFs with SST responses to a hypothetical step-change in the SAM, inferred through lagged linear regression, shows broadly similar results. Causes of uncertainty are explored by examining relationships between model climatologies and their CRFs. The inter-model spread in CRFs can be reproduced by varying a single subgrid-scale mixing parameter within a single model. Antarctic sea-ice CRFs are also calculated: these do not generally exhibit the two-time-scale behavior of SST, suggesting a complex relationship between the two. Finally, by constraining model climatology-response relationships with observational values, we conclude that ozone depletion in unlikely to have been the primary driver of the observed SST cooling trend.
Shrestha, A. K.; Kato, S.; Wong, T.; Stackhouse, P.; Loughman, R. P.Shrestha, A. K., S. Kato, T. Wong, P. Stackhouse, R. P. Loughman, 2019: New Temporal and Spectral Unfiltering Technique for ERBE/ERBS WFOV Nonscanner Instrument Observations. IEEE Transactions on Geoscience and Remote Sensing, 1-12. doi: 10.1109/TGRS.2019.2891748. Earth Radiation Budget Experiment (ERBE) Wide-Field-of-View (WFOV) nonscanner instrument onboard Earth Radiation Budget Satellite (ERBS) provided critical 15-year outgoing broadband irradiances at the top of atmosphere (TOA) from 1985 to 1999 for studying Earth's climate. However, earlier studies show that the uncertainty in this radiation data set (Ed3) is significantly higher after the Mt. Pinatubo eruption in 1991 and satellite battery issue in 1993. Furthermore, Lee et al. showed that the transmission of ERBS WFOV shortwave dome degraded due to exposure to direct sunlight. To account for this degradation, a simple time-dependent but spectral-independent correction model was implemented in the past. This simple spectral-independent model did not completely remove the shortwave sensor artifact as seen in the temporal growth of the tropical mean day-minus-night longwave irradiance. A new temporal-spectral-dependent correction model of shortwave dome transmissivity loss similar to that used in the Clouds and the Earth's Radiant Energy System (CERES) project is developed and applied to the 15-year ERBS WFOV data. This model is constrained by the solar transmission obtained from ERBS WFOV shortwave nonscanner instrument observations of the Sun during biweekly in-flight solar calibration events. This new model is able to reduce the reported tropical day-minus-night longwave irradiance trend by ≈34%. In addition, the slope of this new trend is observed to be consistent over different regions. The remaining trend is accounted using a postprocess Ed3Rev1 correction. Furthermore, the time series analysis of these data over the Libya-4 desert site showed that the shortwave data are stable to within 0.7%. Radiometry; Earth; Instruments; Meteorology; Satellite broadcasting; Data models; Calibration; Data conversion; earth; energy measurements.
Shukla, Ravi P.; Huang, Bohua; Dirmeyer, Paul A.; Kinter, James L.Shukla, R. P., B. Huang, P. A. Dirmeyer, J. L. Kinter, 2019: The Influence of Summer Deep Soil Temperature on Early Winter Snow Conditions in Eurasia in the NCEP CFSv2 Simulation. Journal of Geophysical Research: Atmospheres, 124(16), 9062-9077. doi: 10.1029/2019JD030279. The National Centers for Environmental Prediction (NCEP) Climate Forecast System version 2 (CFSv2) has a large cold bias in the model's deep soil temperature during summer. This study explores the potential triggering effect of that bias on excessive Eurasian snow cover in early winter. Snow cover appears erroneously early in the fall, especially in western Eurasia, in long simulations with CFSv2. The seasonal transition may be too early because the model land surface temperature (LST) reaches its freezing point earlier than observed, so that new snow cannot melt. This process initiates snow-albedo feedback too early. The early cooling of LST is partially influenced by a seasonal resurfacing of the cold bias in the deep soil layer. From winter to early spring, a cold bias prevails in LST and upper soil temperature as snow cover remains. During this season, the temperature in the deep soil is generally warmer than in the upper soil and has relatively little bias. From spring to summer, the cold bias in the upper soil becomes smaller as it warms up in response to solar heating. On the other hand, the deep soil temperature has a noticeably smaller seasonal change than observed, resulting in a severe cold bias during summer. As the solar radiation declines quickly in early fall, the cold deep soil temperature causes additional cooling in the upper soil layer and helps to bring LST to the freezing point early in the western Eurasia, which leads to enhanced bias in the snow properties. deep soil temperature; Eurasia; NCEP CFSv2; seasonal transition; snow-albedo feedback; subsurface soil temperature
Sicard, MichaëlSicard, M., 2019: Validation of AERONET-Estimated Upward Broadband Solar Fluxes at the Top-Of-The-Atmosphere with CERES Measurements. Remote Sensing, 11(18), 2168. doi: 10.3390/rs11182168. The AERONET (Aerosol Robotic Network) global network provides estimations of broadband solar radiative fluxes at the surface and at the TOA (Top-Of-the-Atmosphere). This paper reports on the validation of AERONET flux estimations at the TOA with the CERES (Clouds and the Earth’s Radiant Energy System) instrument. The validation was made at eight AERONET sites worldwide with at least seven years of Level 2.0 and Version 3 data and representatives of mineral dust, biomass burning, background continental, and urban-industrial aerosol regimes. To co-locate in time and space the AERONET and CERES fluxes, several criteria based on time and distance differences and cloud coverage were defined. When the strictest criterion was applied to all sites, the linear relationship between the observed and estimated fluxes (y = 1.04x – 3.67 Wm−2) was very close to the 1:1 ideal line. The correlation coefficient was 0.96 and nearly all points were contained in the ±15% region around the 1:1 line. The average flux difference was –2.52 Wm−2 (–0.84% in relative terms). AERONET overestimations were observed at two sites and were correlated with large aerosol optical depth (AOD) (>0.2) Underestimations were observed at one desert site and were correlated with large surface albedos (>0.2). CERES; AERONET; flux comparison; Top-Of-the-Atmosphere (TOA) upward solar fluxes
Silber, Israel; Fridlind, Ann M.; Verlinde, Johannes; Ackerman, Andrew S.; Chen, Yao-Sheng; Bromwich, David H.; Wang, Sheng-Hung; Cadeddu, Maria; Eloranta, Edwin W.Silber, I., A. M. Fridlind, J. Verlinde, A. S. Ackerman, Y. Chen, D. H. Bromwich, S. Wang, M. Cadeddu, E. W. Eloranta, 2019: Persistent Supercooled Drizzle at Temperatures Below −25 °C Observed at McMurdo Station, Antarctica. Journal of Geophysical Research: Atmospheres, 124(20), 10878-10895. doi: 10.1029/2019JD030882. The rarity of reports in the literature of brief and spatially limited observations of drizzle at temperatures below −20 °C suggest that riming and other temperature-dependent cloud microphysical processes such as heterogeneous ice nucleation and ice crystal depositional growth prevent drizzle persistence in cold environments. In this study, we report on a persistent drizzle event observed by ground-based remote sensing measurements at McMurdo Station, Antarctica. The temperatures in the drizzle-producing cloud were below −25 °C and the drizzle persisted for a period exceeding 7.5 hr. Using ground-based, satellite, and reanalysis data, we conclude that drizzle was likely present in parts of a widespread cloud field, which stretched more than 1,000 km along the Ross Ice Shelf coast. Parameter space sensitivity tests using two-moment bulk microphysics in large eddy simulations constrained by the observations suggest that activated ice freezing nuclei and accumulation-mode aerosol number concentrations aloft during this persistent drizzle period were likely on the order of 0.2 L−1 and 20 cm−3, respectively. In such constrained simulations, the drizzle moisture flux through cloud base exceeds that of ice. The simulations also indicate that drizzle can lead to the formation of multiple peaks in cloud water content profiles. This study suggests that persistent drizzle at these low temperatures may be common at the low aerosol concentrations typical of the Antarctic and Southern Ocean atmospheres. Antarctica; mixed-phase clouds; LES; McMurdo Station; Persistent drizzle; Supercooled drizzle
Sindhu, Kapil Dev; Sahany, SandeepSindhu, K. D., S. Sahany, 2019: Long-term cloud fraction biases in CMIP5 GCMs over India during monsoon season. Theoretical and Applied Climatology, 137(3-4), 2559–2571. doi: 10.1007/s00704-018-02760-1. Using 24 years of cloud fraction (CF) data from the International Satellite Cloud Climatology Project (ISCCP) observations and their corresponding simulators in general circulation models (GCMs) from the Coupled Model Intercomparison Project phase 5 (CMIP5), we have analyzed cloud biases and their role on radiation over the Indian region (65–100° E and 5–40° N) for the monsoon season of June to September. The present study reports the spatial patterns of CFs and their biases in GCMs compared to observations. It is found that the simulated CFs are highly underestimated up to ~ 40%. Mean of total CF from ISCCP observations is 75% with at least 10% difference with simulated CFs. For high-topped clouds, this difference is about 3–4%. Except for high-topped clouds, other cloud types are not simulated realistically by CMIP5 models used in this study. Further, we investigated the individual cloud types classified based on cloud optical depth and cloud top pressure. We found that, in general, individual cloud types are poorly simulated by models, although some (Max Planck Institute Earth System Model, Low Resolution and Hadley Centre Global Environmental Model, version 2, Earth System) models convincingly simulate high-topped thin clouds. To assess the impact of cloud biases on the simulated radiative forcings, we studied shortwave and longwave cloud radiative forcings from CERES (Clouds and the Earth’s Radiant Energy System) observations and CMIP5 GCMs. It is noticed that the spatial patterns of biases in radiative forcings are similar to the patterns of biases in CFs for high-topped clouds, specifically over the oceanic regions. We find that the biases in cloud radiative forcings could potentially be caused due to the inefficacy of CMIP5 models in simulating high-topped anvil clouds (high-topped cirrus/stratocirrus clouds). The present study confirms that the uncertainty in simulating cloud fractions over the Indian region is still a prominent issue to be addressed in general circulation models.
Sivan, C.; Manoj, M. G.Sivan, C., M. G. Manoj, 2019: Aerosol and cloud radiative forcing over various hot spot regions in India. Advances in Space Research, 64(8), 1577-1591. doi: 10.1016/j.asr.2019.07.028. Twelve years of NASA CERES (Clouds and Earth’s Radiant Energy System) data have been used to examine the spatio-temporal variability of aerosol– and cloud– induced shortwave radiative forcing over selected hot spot regions in India. Four regions (northern semiarid – R1; monsoon trough – R2; densely populated urban – R3; and southern peninsula – R4) are selected with different surface characteristics and notable difference in meteorological and geographical features. The analysis shows that three out of the four regions (viz. R1, R2, and R3) experience high aerosol loading and forcing in the monsoon season followed by moderate forcing in pre-monsoon season. While all the seasons except the post-monsoon period show a positive linear relation between cloud optical depth and aerosol optical depth for all the regions, the post-monsoon season shows a negative relation. However, the relation between aerosol forcing and cloud forcing shows adequate non-linearity owing to the numerous factors that control cloud radiative effect. The estimated aerosol induced heating rate shows exponential decrease with height, but with high variability during each season. Irrespective of any region, the maximum heating rate is observed in the pre-monsoon season (2.86 ± 0.78, 2.49 ± 0.78, 1.89 ± 0.57, and 0.88 ± 0.28 K/day for R1, R2, R3, and R4, respectively). Plausible reasons for the variation in the above parameters are discussed. The results suggest that increased anthropogenic activities affect the thermodynamics and hence the dynamics through retention and exchange of heat, and it could affect the precipitation pattern adversely. Aerosol optical depth; CERES data; Heating rate; Cloud; Radiative forcing
Sledd, Anne; L’Ecuyer, TristanSledd, A., T. L’Ecuyer, 2019: How Much Do Clouds Mask the Impacts of Arctic Sea Ice and Snow Cover Variations? Different Perspectives from Observations and Reanalyses. Atmosphere, 10(1), 12. doi: 10.3390/atmos10010012. Decreasing sea ice and snow cover are reducing the surface albedo and changing the Arctic surface energy balance. How these surface albedo changes influence the planetary albedo is a more complex question, though, that depends critically on the modulating effects of the intervening atmosphere. To answer this question, we partition the observed top of atmosphere (TOA) albedo into contributions from the surface and atmosphere, the latter being heavily dependent on clouds. While the surface albedo predictably declines with lower sea ice and snow cover, the TOA albedo decreases approximately half as much. This weaker response can be directly attributed to the fact that the atmosphere contributes more than 70% of the TOA albedo in the annual mean and is less dependent on surface cover. The surface accounts for a maximum of 30% of the TOA albedo in spring and less than 10% by the end of summer. Reanalyses (ASR versions 1 and 2, ERA-Interim, MERRA-2, and NCEP R2) represent the annual means of surface albedo fairly well, but biases are found in magnitudes of the TOA albedo and its contributions, likely due to their representations of clouds. Reanalyses show a wide range of TOA albedo sensitivity to changing sea ice concentration, 0.04–0.18 in September, compared to 0.11 in observations. sea ice; reanalyses; arctic clouds; ice-albedo feedback
Smalley, Mark; Suselj, Kay; Lebsock, Matthew; Teixeira, JoaoSmalley, M., K. Suselj, M. Lebsock, J. Teixeira, 2019: A novel framework for evaluating and improving parameterized subtropical marine boundary layer cloudiness. Mon. Wea. Rev., 147(9), 3241–3260. doi: 10.1175/MWR-D-18-0394.1. A Single Column Model (SCM) is used to simulate a variety of environmental conditions between Los Angeles and Hawaii in order to identify physical elements of parameterizations that are required to reproduce the observed behavior of marine boundary layer (MBL) cloudiness. The SCM is composed of the JPL Eddy-Diffusivity/Mass-Flux mixing formulation and the RRTM-G radiation model. Model forcings are provided by the Modern-Era Retrospective analysis for Research and Applications, Version 2 (MERRA2). Simulated low cloud cover (LCC), rain rate, albedo, and liquid water path are compared to co-located pixel-level observations from A-Train satellites. This framework ensures that the JPL EDMF is able to simulate a continuum of real-world conditions.First, the JPL EDMF is shown to reproduce the observed mean LCC as a function of lower tropospheric stability. Joint probability distributions of lower-tropospheric cloud fraction, height, and LTS show that the JPL EDMF improves upon its MERRA2 input but struggles to match the frequency of observed intermediate-range LCC.We then illustrate the physical roles of plume lateral entrainment and eddy-diffusivity mixing length in producing a realistic behavior of LCC as a function of LTS. In low-LTS conditions, LCC is mostly sensitive to the ability of convection to mix moist air out of the MBL. In high-LTS conditions, LCC is also sensitive to the turbulent mixing of free-tropospheric air into the MBL. In the intermediate LTS regime typical of stratocumulus-cumulus transition there is proportional sensitivity to both mixing mechanisms, emphasizing the utility of a combined Eddy-Diffusivity/Mass-Flux approach for representing mixing processes.
Smith, Samantha A.; Field, Paul R.; Vosper, Simon B.; Derbyshire, Steve H.Smith, S. A., P. R. Field, S. B. Vosper, S. H. Derbyshire, 2019: Verification of a seeder–feeder orographic precipitation enhancement scheme accounting for low-level blocking. Quarterly Journal of the Royal Meteorological Society, 145(724), 2909-2932. doi: 10.1002/qj.3584. A subgrid parametrization scheme representing the enhancement of precipitation due to subgrid orography via the seeder–feeder (SF) effect has been modified to account for flow blocking in small Froude number situations. The scheme was validated in a set of limited-area model simulations with a 1.5 km grid spacing, in which the orography was degraded by varying amounts. For simulations in which the largest orographic scales are still fairly well represented, the SF scheme was able to reduce the precipitation deficit by 30 to 70%. For simulations where the hills were completely subgrid, the SF scheme was still able to reduce the precipitation deficit by 10 to 30%. As well as increasing the integrated precipitation in global simulations with various grid spacings, some of the precipitation production was shifted from the convection scheme, with its very simple microphysical representation, to the microphysics scheme. In a long-duration climate simulation, the SF scheme enhancements of orographic precipitation perturb the large-scale hydrological cycle, as evidenced by the far-field changes in both microphysical and convective precipitation. Changes over major mountain ranges were similar to those described for the case-studies, so long as the upstream precipitation impinging on the mountains was not reduced by these changes in the global hydrological cycle. Increased atmospheric drying reduces column-integrated resolved cloud water mixing ratios over mountains, reducing a positive bias in the amount of optically thick cloud with low- to mid-level tops compared to ISCCP satellite observations. The associated reductions in cloud albedo slightly reduced the RMS error in the top-of-atmosphere outgoing short-wave radiative fluxes over mountains compared to CERES satellite observations. parametrization; climate simulation; low-level flow blocking; orographic precipitation enhancement; precipitation forecasting; seeder–feeder mechanism
Soldatenko, Sergei; Colman, RobertSoldatenko, S., R. Colman, 2019: Climate variability from annual to multi-decadal timescales in a two-layer stochastic energy balance model: analytic solutions and implications for general circulation models. Tellus A: Dynamic Meteorology and Oceanography, 71(1), 1-15. doi: 10.1080/16000870.2018.1554421. A low-order stochastically forced two-layer global energy balance model (EBM) admitting an analytical solution is developed for studying natural inter-annual, decadal and multi-decadal climate variability, and ultimately to better understand forced climate change. The EBM comprises upper and lower oceanic layers with a diffusive coupling, a radiative damping term including feedbacks and stochastic atmospheric forcing. The EBM is used to analyse the influence of radiative forcing, feedbacks and climate system inertia on the global mean surface temperature variance (climate variability) and to understand why Coupled Model Intercomparison Project, Phase 5 (CMIP5) models exhibit such a wide range in the level of variability in globally averaged surface air temperature. We examine the influence of the model parameters on the climate variability on different timescales. To this end, we derive the Fokker–Planck equation for the EBM and then obtain the analytical expression that quantifies the sensitivity coefficients for all model parameters. For all timescales, the most influential factors are as follows: (1) the magnitude of the stochastic forcing, (2) the feedback mechanisms, (3) the upper layer depth, (4) the diffusion parameter and (5) the lower ocean depth. Results from the EBM imply that the range of stochastic forcing in the CMIP5 climate models is around twice as important as the strength of radiative feedback or upper layer depth in causing the model-to-model spread in the magnitude of globally averaged climate model variability. climate variability; sensitivity analysis; climate sensitivity; radiative feedbacks
Sorooshian, Armin; Anderson, Bruce; Bauer, Susanne E.; Braun, Rachel A.; Cairns, Brian; Crosbie, Ewan; Dadashazar, Hossein; Diskin, Glenn; Ferrare, Richard; Flagan, Richard C.; Hair, Johnathan; Hostetler, Chris; Jonsson, Haflidi H.; Kleb, Mary M.; Liu, Hongyu; MacDonald, Alexander B.; McComiskey, Allison; Moore, Richard; Painemal, David; Russell, Lynn M.; Seinfeld, John H.; Shook, Michael; Smith, William L.; Thornhill, Kenneth; Tselioudis, George; Wang, Hailong; Zeng, Xubin; Zhang, Bo; Ziemba, Luke; Zuidema, PaquitaSorooshian, A., B. Anderson, S. E. Bauer, R. A. Braun, B. Cairns, E. Crosbie, H. Dadashazar, G. Diskin, R. Ferrare, R. C. Flagan, J. Hair, C. Hostetler, H. H. Jonsson, M. M. Kleb, H. Liu, A. B. MacDonald, A. McComiskey, R. Moore, D. Painemal, L. M. Russell, J. H. Seinfeld, M. Shook, W. L. Smith, K. Thornhill, G. Tselioudis, H. Wang, X. Zeng, B. Zhang, L. Ziemba, P. Zuidema, 2019: Aerosol–Cloud–Meteorology Interaction Airborne Field Investigations: Using Lessons Learned from the U.S. West Coast in the Design of ACTIVATE off the U.S. East Coast. Bull. Amer. Meteor. Soc., 100(8), 1511-1528. doi: 10.1175/BAMS-D-18-0100.1. We report on a multiyear set of airborne field campaigns (2005–16) off the California coast to examine aerosols, clouds, and meteorology, and how lessons learned tie into the upcoming NASA Earth Venture Suborbital (EVS-3) campaign: Aerosol Cloud meTeorology Interactions oVer the western ATlantic Experiment (ACTIVATE; 2019–23). The largest uncertainty in estimating global anthropogenic radiative forcing is associated with the interactions of aerosol particles with clouds, which stems from the variability of cloud systems and the multiple feedbacks that affect and hamper efforts to ascribe changes in cloud properties to aerosol perturbations. While past campaigns have been limited in flight hours and the ability to fly in and around clouds, efforts sponsored by the Office of Naval Research have resulted in 113 single aircraft flights (>500 flight hours) in a fixed region with warm marine boundary layer clouds. All flights used nearly the same payload of instruments on a Twin Otter to fly below, in, and above clouds, producing an unprecedented dataset. We provide here i) an overview of statistics of aerosol, cloud, and meteorological conditions encountered in those campaigns and ii) quantification of model-relevant metrics associated with aerosol–cloud interactions leveraging the high data volume and statistics. Based on lessons learned from those flights, we describe the pragmatic innovation in sampling strategy (dual-aircraft approach with combined in situ and remote sensing) that will be used in ACTIVATE to generate a dataset that can advance scientific understanding and improve physical parameterizations for Earth system and weather forecasting models, and for assessing next-generation remote sensing retrieval algorithms.
Stackhouse, P. W.; Wong, T.; Kratz, D. P.; Sawaengphokhai, Parnchai; Wilber, A. C.; Gupta, S. K.; Loeb, N. GStackhouse, P. W., T. Wong, D. P. Kratz, P. Sawaengphokhai, A. C. Wilber, S. K. Gupta, N. G. Loeb, 2019: Earth Radiation Budget at Top-Of-Atmosphere [in “State of the Climate in 2018”].. Bull. Amer. Meteor. Soc, 100(9), S46-48. doi: 10.1175/2019BAMSStateoftheClimate.1.
Stengel, Martin; Stapelberg, Stefan; Sus, Oliver; Finkensieper, Stephan; Würzler, Benjamin; Philipp, Daniel; Hollmann, Rainer; Poulsen, Caroline; Christensen, Matthew; McGarragh, GregoryStengel, M., S. Stapelberg, O. Sus, S. Finkensieper, B. Würzler, D. Philipp, R. Hollmann, C. Poulsen, M. Christensen, G. McGarragh, 2019: Cloud_cci AVHRR-PM dataset version 3: 35 year climatology of global cloud and radiation properties. Earth System Science Data Discussions, 1-29. doi: 10.5194/essd-2019-104. Abstract. We present version 3 of the Cloud_cci AVHRR-PM dataset which contains a comprehensive set of cloud and radiative flux properties on a global scale covering the period of 1982 to 2016. The properties were retrieved from Advanced Very High Resolution Radiometer (AVHRR) measurements recorded by the afternoon (post meridiem, PM) satellites of the National Oceanic and Atmospheric Administration (NOAA) Polar Operational Environmental Satellites (POES) missions. The cloud properties in version 3 are of improved quality compared with the precursor dataset version 2, providing better global quality scores for cloud detection, cloud phase and ice water path based on validation results against A-Train sensors. Furthermore, the parameter set was extended by a suite of broadband radiative flux properties. They were calculated by combining the retrieved cloud properties with thermodynamic profiles from reanalysis and surface properties. The flux properties comprise upwelling and downwelling, shortwave and longwave broadband fluxes at the surface (bottom-of-atmosphere - BOA) and top-of-atmosphere (TOA). All fluxes were determined at AVHRR pixel level for all-sky and clear-sky conditions, which will particularly facilitate the assessment of the cloud radiative effect at BOA and TOA in future studies. Validation of the BOA downwelling fluxes against the Baseline Surface Radiation Network (BSRN) show a very good agreement. This is supported by comparisons of multi-annual mean maps with NASA's Clouds and the Earth's Radiant Energy System (CERES) products for all fluxes at BOA and TOA. The Cloud_cci AVHRR-PM version 3 dataset allows for a large variety of climate applications that build on cloud properties, radiative flux properties and/or the link between them. For the presented Cloud_cci AVHRR-PMv3 dataset a Digital Object Identifier has been issued: https://doi.org/10.5676/DWD/ESA_Cloud_cci/AVHRR-PM/V003 (Stengel et al., 2019).
Stephens, Benjamin A.; Jackson, Charles S.; Wagman, Benjamin M.Stephens, B. A., C. S. Jackson, B. M. Wagman, 2019: Effect of Tropical Nonconvective Condensation on Uncertainty in Modeled Projections of Rainfall. J. Climate, 32(19), 6571-6588. doi: 10.1175/JCLI-D-18-0833.1. We find that part of the uncertainty in the amplitude and pattern of the modeled precipitation response to CO2 forcing traces to tropical condensation not directly involved with parameterized convection. The fraction of tropical rainfall associated with large-scale condensation can vary from a few percent to well over half depending on model details and parameter settings. In turn, because of the coupling between condensation and tropical circulation, the different ways model assumptions affect the large-scale rainfall fraction also affect the patterns of the response within individual models. In two single-model ensembles based on the National Center for Atmospheric Research (NCAR) Community Atmosphere Model (CAM), versions 3.1 and 5.3, we find strong correlations between the fraction of tropical large-scale rain and both climatological rainfall and circulation and the response to CO2 forcing. While the effects of an increasing tropical large-scale rain fraction are opposite in some ways in the two ensembles—for example, the Hadley circulation weakens with the large-scale rainfall fraction in the CAM3.1 ensemble while strengthening in the CAM5.3 ensemble—we can nonetheless understand these different effects in terms of the relationship between latent heating and circulation, and we propose explanations for each ensemble. We compare these results with data from phase 5 of the Coupled Model Intercomparison Project (CMIP5), for which some of the same patterns hold. Given the importance of this partitioning, there is a need for constraining this source of uncertainty using observations. However, since a “large-scale rainfall fraction” is a modeling construct, it is not clear how observations may be used to test various modeling assumptions determining this fraction.
Stephens, Graeme L.; Christensen, Matthew; Andrews, Timothy; Haywood, James; Malavelle, Florent F.; Suzuki, Kentaroh; Jing, Xianwen; Lebsock, Mathew; Li, Jui-Lin F.; Takahashi, Hanii; Sy, OusmaneStephens, G. L., M. Christensen, T. Andrews, J. Haywood, F. F. Malavelle, K. Suzuki, X. Jing, M. Lebsock, J. F. Li, H. Takahashi, O. Sy, 2019: Cloud physics from space. Quarterly Journal of the Royal Meteorological Society, 145(724), 2854-2875. doi: 10.1002/qj.3589. A review of the progression of cloud physics from a subdiscipline of meteorology into the global science it is today is described. The discussion briefly touches on the important post-war contributions of three key individuals who were instrumental in developing cloud physics into a global science. These contributions came on the heels of the post-war weather modification efforts that influenced much of the early development of cloud physics. The review is centred on the properties of warm clouds primarily to limit the scope of the article and the connection between the early contributions to cloud physics and the current vexing problem of aerosol effects on cloud albedo is underlined. Progress toward estimating cloud properties from space and insights on warm cloud processes are described. Measurements of selected cloud properties, such as cloud liquid water path are now mature enough that multi-decadal time series of these properties exist and this climatology is used to compare to analogous low-cloud properties taken from global climate models. The too-wet (and thus too bright) and the too-dreary biases of models are called out underscoring the challenges we still face in representing warm clouds in Earth system models. We also provide strategies for using observations to constrain the indirect radiative forcing of the climate system. clouds; climate; atmosphere; microphysics; observations; remote sensing
Su, Chun-Yian; Wu, Chien-Ming; Chen, Wei-Ting; Chen, Jen-HerSu, C., C. Wu, W. Chen, J. Chen, 2019: Object-based precipitation system bias in grey zone simulation: the 2016 South China Sea summer monsoon onset. Climate Dynamics, 53(1), 617-630. doi: 10.1007/s00382-018-04607-x. This study aims to evaluate the precipitation bias in the grey zone simulation (~ 15 km) using the Central Weather Bureau Global Forecast System (CWBGFS). We develop a new evaluation method using the object-based precipitation system (OPS) to examine the bias associated with the degree of convection organization. The 2016 South China Sea (SCS) Summer Monsoon onset is selected to evaluate the model’s performance due to its sharp transition of large-scale circulation, which contributes to the complexity of precipitation pattern. The results based on OPS show that the observed precipitation tends to aggregate toward the central part of SCS during the post-onset period, while the precipitation in the model distributes more sparsely over the ocean. The observed precipitation intensity increases with the size of OPS especially for the extremes; however, the model underrepresents the relationship between the precipitation spectrum and the size of OPS. Moreover, the model simulates earlier diurnal peak time of precipitation over land in the organized systems than observation. The results also suggest that the convection scheme is insensitive to column moisture during the pre-onset period which seems to be one of the key factors to the excessive precipitation in the model. Using high horizontal resolution, however, does not improve the simulation of precipitation much in the model. The current study suggests that the precipitation bias related to aggregation of the convective systems should be regarded as an essential objective of model evaluation and improvement.
Sujith, K.; Saha, Subodh Kumar; Rai, Archana; Pokhrel, Samir; Chaudhari, Hemantkumar S.; Hazra, Anupam; Murtugudde, Raghu; Goswami, B.n.Sujith, K., S. K. Saha, A. Rai, S. Pokhrel, H. S. Chaudhari, A. Hazra, R. Murtugudde, B. Goswami, 2019: Effects of a Multilayer Snow Scheme on the Global Teleconnections of the Indian Summer Monsoon. Quarterly Journal of the Royal Meteorological Society, 145(720), 1102-1117. doi: 10.1002/qj.3480. Eurasian snow is one of the slowly varying boundary forcings, that is known to have significant influences on the mean and variability of the Indian summer monsoon rainfall (ISMR). A multilayer complex snow scheme, incorporated into the state-of-the-art coupled Climate Forecast System version 2 (CFSv2) showed significant improvements in the simulation of mean ISMR, snow, northern hemisphere surface and tropospheric temperature. Here we show that a realistic simulation of high latitude snow decreases the north-south temperature gradient, which in turn decreases the meridional transport of energy from the equator to the pole, consequently affecting the tropical sea surface temperature (SST) and air-sea interactions. The global teleconnections of the ISMR with SST and 2m temperature over land are also improved considerably in association with improved simulation of the oceanic natural modes of variability. Our findings provide new insights for the relationship between the winter Eurasian snow and the following ISMR, namely that the same relationship may be understood through a framework of meridional atmospheric energy transport and its effects on the tropical air-sea interactions. The improvements in the global teleconnection in the modified version of CFSv2 may have implications in the ISMR predictability and prediction skill. air-sea interactions; Eurasian Snow; Monsoon; teleconnections
Sun, Jian; Zhang, Kai; Wan, Hui; Ma, Po-Lun; Tang, Qi; Zhang, ShixuanSun, J., K. Zhang, H. Wan, P. Ma, Q. Tang, S. Zhang, 2019: Impact of Nudging Strategy on the Climate Representativeness and Hindcast Skill of Constrained EAMv1 Simulations. Journal of Advances in Modeling Earth Systems, 11(12), 3911-3933. doi: 10.1029/2019MS001831. Nudging is a simulation technique widely used in sensitivity studies and in the evaluation of atmosphere models. Care is needed in the experimental setup in order to achieve the desired constraint on the simulated atmospheric processes without introducing undue intervention. In this study, sensitivity experiments are conducted with the Energy Exascale Earth System Model (E3SM) Atmosphere Model Version 1 (EAMv1) to identify setups that can give results representative of the model's long-term climate and meanwhile reasonably capture characteristics of the observed meteorological conditions to facilitate the comparison of model results with measurements. We show that when the prescribed meteorological conditions are temporally interpolated to the model time to constrain EAM's horizontal winds at each time step, a nudged simulation can reproduce the characteristic evolution of the observed weather events (especially in middle and high latitudes) as well as the model's long-term climatology, although nudging also leads to nonnegligible regional changes in wind-driven aerosol emissions, low-level clouds in the stratocumulus regime, and cloud and precipitation near the maritime continent. Compared to its predecessor model used in an earlier study, EAMv1 is less sensitive to temperature nudging, although significant impacts on the cloud radiative effects still exist. EAMv1 remains very sensitive to humidity nudging. Constraining humidity substantially improves the correlation between the simulated and observed tropical precipitation but also leads to large changes in the long-term statistics of the simulated precipitation, clouds, and aerosol lifecycle. E3SM; EAMv1; hindcast; nudging
Tan, J.; Frouin, R.Tan, J., R. Frouin, 2019: Seasonal and Interannual Variability of Satellite-Derived Photosynthetically Available Radiation Over the Tropical Oceans. Journal of Geophysical Research: Oceans, 124(5), 3073-3088. doi: 10.1029/2019JC014942. The seasonal and interannual variability of photosynthetically available radiation (PAR) over the tropical oceans is examined using satellite imagery acquired from 1997 to 2017. Spatial and temporal biases between monthly PAR estimates from different instruments are determined and corrected, resulting in a consistent time series over the 20-year record. Uncertainty is evaluated in comparisons with in situ measurements at various sites. Empirical orthogonal function (EOF) analysis is performed with both seasonal and nonseasonal PAR signals, and linear trends are quantified. Seasonal cycles dominate PAR variability, with the first three seasonal EOF modes explaining 84.7% of the total variance. The seasonal patterns are related to solar position and monsoon. Canonical El Niño–Southern Oscillation (ENSO) and Modoki ENSO are related to the two leading nonseasonal EOF modes, with a correlation coefficient of 0.84 between the first mode and the multivariate ENSO index and of 0.48 between the second mode and the El Niño Modoki index. Trend analysis reveals that PAR tends to decrease by 0.2%/year in the central Pacific north of the equator and to increase by 0.2%/year in the central Pacific around 5°S. The tendency is also for PAR to increase west of Central and South America. These changes are consistent with patterns of cloud change evidenced in the satellite cloud record and predicted by global climate models. The long-term satellite PAR data set, together with information of nutrient availability and temperature, enables further studies to elucidate the causes of phytoplankton variability in the tropical oceans.
Tang, Wenjun; Yang, Kun; Qin, Jun; Li, Xin; Niu, XiaoleiTang, W., K. Yang, J. Qin, X. Li, X. Niu, 2019: A 16-year dataset (2000–2015) of high-resolution (3 h, 10 km) global surface solar radiation. Earth System Science Data, 11(4), 1905-1915. doi: https://doi.org/10.5194/essd-11-1905-2019. Abstract. The recent release of the International Satellite Cloud Climatology Project (ISCCP) HXG cloud products and new ERA5 reanalysis data enabled us to produce a global surface solar radiation (SSR) dataset: a 16-year (2000–2015) high-resolution (3 h, 10 km) global SSR dataset using an improved physical parameterization scheme. The main inputs were cloud optical depth from ISCCP-HXG cloud products; the water vapor, surface pressure and ozone from ERA5 reanalysis data; and albedo and aerosol from Moderate Resolution Imaging Spectroradiometer (MODIS) products. The estimated SSR data were evaluated against surface observations measured at 42 stations of the Baseline Surface Radiation Network (BSRN) and 90 radiation stations of the China Meteorological Administration (CMA). Validation against the BSRN data indicated that the mean bias error (MBE), root mean square error (RMSE) and correlation coefficient (R) for the instantaneous SSR estimates at 10 km scale were −11.5 W m−2, 113.5 W m−2 and 0.92, respectively. When the estimated instantaneous SSR data were upscaled to 90 km, its error was clearly reduced, with RMSE decreasing to 93.4 W m−2 and R increasing to 0.95. For daily SSR estimates at 90 km scale, the MBE, RMSE and R at the BSRN were −5.8 W m−2, 33.1 W m−2 and 0.95, respectively. These error metrics at the CMA radiation stations were 2.1 W m−2, 26.9 W m−2 and 0.95, respectively. Comparisons with other global satellite radiation products indicated that our SSR estimates were generally better than those of the ISCCP flux dataset (ISCCP-FD), the global energy and water cycle experiment surface radiation budget (GEWEX-SRB), and the Earth's Radiant Energy System (CERES). Our SSR dataset will contribute to the land-surface process simulations and the photovoltaic applications in the future. The dataset is available at https://doi.org/10.11888/Meteoro.tpdc.270112 (Tang, 2019).
Taylor, Patrick C.; Boeke, Robyn C.; Li, Ying; Thompson, David W. J.Taylor, P. C., R. C. Boeke, Y. Li, D. W. J. Thompson, 2019: Arctic cloud annual cycle biases in climate models. Atmospheric Chemistry and Physics, 19(13), 8759-8782. doi: 10.5194/acp-19-8759-2019. Abstract. Arctic clouds exhibit a robust annual cycle with maximum cloudiness in fall and minimum cloudiness in winter. These variations affect energy flows in the Arctic with a large influence on the surface radiative fluxes. Contemporary climate models struggle to reproduce the observed Arctic cloud amount annual cycle and significantly disagree with each other. The goal of this analysis is to quantify the cloud-influencing factors that contribute to winter–summer cloud amount differences, as these seasons are primarily responsible for the model discrepancies with observations. We find that differences in the total cloud amount annual cycle are primarily caused by differences in low, rather than high, clouds; the largest differences occur between the surface and 950 hPa. Grouping models based on their seasonal cycles of cloud amount and stratifying cloud amount by cloud-influencing factors, we find that model groups disagree most under strong lower tropospheric stability, weak to moderate mid-tropospheric subsidence, and cold lower tropospheric air temperatures. Intergroup differences in low cloud amount are found to be a function of lower tropospheric thermodynamic characteristics. Further, we find that models with a larger low cloud amount in winter have a larger ice condensate fraction, whereas models with a larger low cloud amount in summer have a smaller ice condensate fraction. Stratifying model output by the specifics of the cloud microphysical scheme reveals that models treating cloud ice and liquid condensate as separate prognostic variables simulate a larger ice condensate fraction than those that treat total cloud condensate as a prognostic variable and use a temperature-dependent phase partitioning. Thus, the cloud microphysical parameterization is the primary cause of inter-model differences in the Arctic cloud annual cycle, providing further evidence of the important role that cloud ice microphysical processes play in the evolution and modeling of the Arctic climate system.
Thandlam, Venugopal; Rahaman, HasiburThandlam, V., H. Rahaman, 2019: Evaluation of surface shortwave and longwave downwelling radiations over the global tropical oceans. SN Applied Sciences, 1(10), 1171. doi: 10.1007/s42452-019-1172-2. In the present study, daily downwelling shortwave (QS) and longwave radiation (QL) data from one satellite and two hybrid products have been evaluated using Global Tropical Moored Buoy Array during 2001–2009 in the tropical oceans. Daily satellite data are used from the Clouds and Earth’s Radiant Energy System (CERES) program. Data are obtained using Moderate Resolution Imaging Spectroradiometer (MODIS) (CM) aboard the Terra and Aqua satellites. Coordinated Ocean Research Experiments (CORE-II) and Tropical Flux data (TropFlux) are the other two hybrid products used in this study. The analysis shows that majority of QS observations as well as derived products lie in 200–300 Wm−2 range in all the three tropical oceans. Both QS and QL in all products overestimated the majority of the observations. Yet, they underestimated the lower (0–100 Wm−2) values in QS and higher (300–440 Wm−2) values in QL. Majority of the QL observations lie within 390–420 Wm−2 range, and CM slightly overestimated this observed distribution in the Pacific and the Atlantic Oceans. But, majority of the observations in the Indian Ocean lie within 420–450 Wm−2 range. This implies that the tropical Indian Ocean receives 30 Wm−2 more energy as compared to the tropical Pacific and the Atlantic in the form of downwelling longwave radiation. Daily observed QS shows dominant seasonal cycle over the central, the eastern Pacific and the eastern Atlantic. On the other hand, the western Pacific, the central Atlantic and the Indian Oceans show intraseasonal variations. All products show this variation with high root-mean-square error (RMSE) values (QS and QL) over the Indian Ocean than in the Pacific and the Atlantic Oceans. Downwelling radiation from CORE-II shows highest RMSE (for both QS and QL) with least correlation coefficient (CC), and TropFlux has lowest RMSE and highest CC among all products in all three tropical oceans. CM has intermediate values of standard deviation, CC and RMSE. These results are not seasonally dependent, since the seasonal statistics are consistent with seasonal changes. Assuming that the SST is only driven by the downwelling shortwave and longwave fluxes, the errors associated with monthly SST can be as large as 0.2–0.3 (0.1–0.2) °C associated with errors in QS (QL). Both QS and QL in CORE-II have lower spatial variability as compared to other datasets. QL in the tropical oceans shows seasonal spatial variability determined by intertropical convergence zone positions. This variability does not change significantly over the Pacific and the Atlantic Oceans. The summer and winter monsoon patterns in the Indian Ocean guide the QL variability. Opposite to QS, higher QL values have lower variability. Thus, this study aims at finding better radiation dataset to use in the numerical models and deduce that satellite data could be an alternative to existing reanalysis products.
Thomas, Manu Anna; Devasthale, Abhay; Koenigk, Torben; Wyser, Klaus; Roberts, Malcolm; Roberts, Christopher; Lohmann, KatjaThomas, M. A., A. Devasthale, T. Koenigk, K. Wyser, M. Roberts, C. Roberts, K. Lohmann, 2019: A statistical and process-oriented evaluation of cloud radiative effects in high-resolution global models. Geoscientific Model Development, 12(4), 1679-1702. doi: 10.5194/gmd-12-1679-2019. Abstract. This study evaluates the impact of atmospheric horizontal resolution on the representation of cloud radiative effects (CREs) in an ensemble of global climate model simulations following the protocols of the High Resolution Model Intercomparison Project (HighResMIP). We compare results from four European modelling centres, each of which provides data from “standard”- and “high”-resolution model configurations. Simulated radiative fluxes are compared with observation-based estimates derived from the Clouds and Earth's Radiant Energy System (CERES) dataset. Model CRE biases are evaluated using both conventional statistics (e.g. time and spatial averages) and after conditioning on the phase of two modes of internal climate variability, namely the El Niño–Southern Oscillation (ENSO) and the North Atlantic Oscillation (NAO). Simulated top-of-atmosphere (TOA) and surface CREs show large biases over the polar regions, particularly over regions where seasonal sea-ice variability is strongest. Increasing atmospheric resolution does not significantly improve these biases. The spatial structure of the cloud radiative response to ENSO and NAO variability is simulated reasonably well by all model configurations considered in this study. However, it is difficult to identify a systematic impact of atmospheric resolution on the associated CRE errors. Mean absolute CRE errors conditioned on the ENSO phase are relatively large (5–10 W m−2) and show differences between models. We suggest this is a consequence of differences in the parameterization of SW radiative transfer and the treatment of cloud optical properties rather than a result of differences in resolution. In contrast, mean absolute CRE errors conditioned on the NAO phase are generally smaller (0–2 W m−2) and more similar across models. Although the regional details of CRE biases show some sensitivity to atmospheric resolution within a particular model, it is difficult to identify patterns that hold across all models. This apparent insensitivity to increased atmospheric horizontal resolution indicates that physical parameterizations play a dominant role in determining the behaviour of cloud–radiation feedbacks. However, we note that these results are obtained from atmosphere-only simulations and the impact of changes in atmospheric resolution may be different in the presence of coupled climate feedbacks.
Tian, Jingjing; Dong, Xiquan; Xi, Baike; Williams, Christopher R.; Wu, PengTian, J., X. Dong, B. Xi, C. R. Williams, P. Wu, 2019: Estimation of liquid water path below the melting layer in stratiform precipitation systems using radar measurements during MC3E. Atmospheric Measurement Techniques, 12(7), 3743-3759. doi: 10.5194/amt-12-3743-2019. Abstract. In this study, the liquid water path (LWP) below the melting layer in stratiform precipitation systems is retrieved, which is a combination of rain liquid water path (RLWP) and cloud liquid water path (CLWP). The retrieval algorithm uses measurements from the vertically pointing radars (VPRs) at 35 and 3 GHz operated by the US Department of Energy Atmospheric Radiation Measurement (ARM) and National Oceanic and Atmospheric Administration (NOAA) during the field campaign Midlatitude Continental Convective Clouds Experiment (MC3E). The measured radar reflectivity and mean Doppler velocity from both VPRs and spectrum width from the 35 GHz radar are utilized. With the aid of the cloud base detected by a ceilometer, the LWP in the liquid layer is retrieved under two different situations: (I) no cloud exists below the melting base, and (II) cloud exists below the melting base. In (I), LWP is primarily contributed from raindrops only, i.e., RLWP, which is estimated by analyzing the Doppler velocity differences between two VPRs. In (II), cloud particles and raindrops coexist below the melting base. The CLWP is estimated using a modified attenuation-based algorithm. Two stratiform precipitation cases (20 and 11 May 2011) during MC3E are illustrated for two situations, respectively. With a total of 13 h of samples during MC3E, statistical results show that the occurrence of cloud particles below the melting base is low (9 %); however, the mean CLWP value can be up to 0.56 kg m−2, which is much larger than the RLWP (0.10 kg m−2). When only raindrops exist below the melting base, the average RLWP value is larger (0.32 kg m−2) than the with-cloud situation. The overall mean LWP below the melting base is 0.34 kg m−2 for stratiform systems during MC3E.
Tian, Lin; Zhang, Peng; Chen, LinTian, L., P. Zhang, L. Chen, 2019: Estimation of the Dust Aerosol Shortwave Direct Forcing Over Land Based on an Equi-albedo Method From Satellite Measurements. Journal of Geophysical Research: Atmospheres, 124(15), 8793-8807. doi: 10.1029/2019JD030974. It is important but difficult to measure the shortwave radiative forcing of the dust aerosols over land from satellite-observed radiance because the inhomogeneous surface albedo varies in a large dynamic range. In this study, we proposed a satellite-based equi-albedo method to derive the dust aerosol shortwave direct forcing over land. In the method, an equal radiance at the top of atmosphere was assumed for the region with the similar surface albedo and the similar solar zenith angle. The aerosol optical depth (AOD) from Moderate Resolution Imaging Spectroradiometer and the shortwave radiance product from Clouds and Earth's Radiant Energy System were used to derive the dust aerosol radiative forcing. The dust storm events outbroken on 9 and 24 April 2010 in Taklimakan desert were selected as study cases. The mean dust shortwave direct forcing efficiency is −35.08 W/m2 per unit of dust AOD during the dust storm events. The results were validated with the calculated radiative forcing from Moderate Resolution Imaging Spectroradiometer AOD product by the radiative transfer model. It shows that the derived radiative forcing is well correlated with the simulated one. The mean difference is 10.57 and the standard deviation is 1.35. Moreover, uncertainty has been estimated. The regional mean-directed radiative forcing due to dust are −28.98 ± 7.99 and −35.76 ± 10.61 W/m2 of these two cases directly from satellite observations. This research indicates that the proposed method is reliable and effective, which can be used to estimate the shortwave direct radiative forcing of the dust storm event.
Tornow, F.; Domenech, C.; Fischer, J.Tornow, F., C. Domenech, J. Fischer, 2019: On the Use of Geophysical Parameters for the Top-of-Atmosphere Shortwave Clear-Sky Radiance-to-Flux Conversion in EarthCARE. J. Atmos. Oceanic Technol., 36(4), 717-732. doi: 10.1175/JTECH-D-18-0087.1. We have investigated whether differences across Clouds and the Earth’s Radiant Energy System (CERES) top-of-atmosphere (TOA) clear-sky angular distribution models, estimated separately over regional (1° × 1° longitude–latitude) and temporal (monthly) bins above land, can be explained by geophysical parameters from Max Planck Institute Aerosol Climatology, version 1 (MAC-v1), ECMWF twentieth-century reanalysis (ERA-20C), and a MODIS bidirectional reflectance distribution function (BRDF)/albedo/nadir BRDF-adjusted reflectance (NBAR) Climate Modeling Grid (CMG) gap-filled products (MCD43GF) climatology. Our research aimed to dissolve binning and to isolate inherent properties or indicators of such properties, which govern the TOA radiance-to-flux conversion in the absence of clouds. We collocated over seven million clear-sky footprints from CERES Single Scanner Footprint (SSF), edition 4, data with above geophysical auxiliary data. Looking at data per surface type and per scattering direction—as perceived by the broadband radiometer (BBR) on board Earth Clouds, Aerosol and Radiation Explorer (EarthCARE)—we identified optimal subsets of geophysical parameters using two different methods: random forest regression followed by a permutation test and multiple linear regression combined with the genetic algorithm. Using optimal subsets, we then trained artificial neural networks (ANNs). Flux error standard deviations on unseen test data were on average 2.7–4.0 W m−2, well below the 10 W m−2 flux accuracy threshold defined for the mission, with the exception of footprints containing fresh snow. Dynamic surface types (i.e., fresh snow and sea ice) required simpler ANN input sets to guarantee mission-worthy flux estimates, especially over footprints consisting of several surface types.
Trenberth, Kevin E.; Zhang, YongxinTrenberth, K. E., Y. Zhang, 2019: Observed inter-hemispheric meridional heat transports and the role of the Indonesian Throughflow in the Pacific Ocean. J. Climate, 32(24), 8523–8536. doi: 10.1175/JCLI-D-19-0465.1. The net surface energy flux is computed as a residual of the energy budget using top-of-atmosphere radiation combined with the divergence of the column-integrated atmospheric energy transports, and then used with the vertically-integrated ocean heat content tendencies to compute the ocean meridional heat transports (MHTs). The mean annual cycles, and 12-month running mean MHTs as a function of latitude are presented for 2000-2016. Effects of the Indonesian Throughflow (ITF), associated with a net volume flow around Australia accompanied by a heat transport are fully included. Because the ITF-related flow necessitates a return current northward in the Tasman Sea that relaxes during El Niño, the reduced ITF during El Niño may contribute to warming in the south Tasman Sea by allowing the East Australian current to push farther south even as it gains volume from the tropical waters not flowing through the ITF. Although evident in 2015-16, when a major marine heat wave occurred, these effects can be overwhelmed by changes in the atmospheric circulation. Large interannual MHT variability in the Pacific is four times that of the Atlantic. Strong relationships reveal influences from the southern subtropics on ENSO for this period. At the equator, northward ocean MHT arises mainly in the Atlantic (0.75 PW), offset by the Pacific (-0.33 PW) and Indian Oceans (-0.20 PW) while the atmosphere transports energy southward (-0.35 PW). The net equatorial MHT southward (-0.18 PW) is enhanced by -0.1 PW that contributes to the greater warming of the southern (vs northern) oceans.
Trenberth, Kevin E.; Zhang, Yongxin; Fasullo, John T.; Cheng, LijingTrenberth, K. E., Y. Zhang, J. T. Fasullo, L. Cheng, 2019: Observation-based estimate of global and basin ocean meridional heat transport time series. J. Climate, 32(14), 4567–4583. doi: 10.1175/JCLI-D-18-0872.1. Ocean meridional heat transports (MHTs) are deduced as a residual using energy budgets to produce latitude vs time series for the globe, Indo-Pacific and Atlantic. The top-of-atmosphere (TOA) radiation is combined with the vertically-integrated atmospheric energy divergence from atmospheric reanalyses to produce the net surface energy fluxes everywhere. The latter is then combined with estimates of the vertically-integrated ocean heat content (OHC) tendency to produce estimates of the ocean heat divergence. Because seasonal sea-ice and land runoff effects are not fully considered, the mean annual cycle is incomplete, but those effects are small for interannual variability. However, there is a mismatch between 12-month inferred surface flux and the corresponding OHC changes globally, requiring adjustments to account for the Earth’s global energy imbalance. Estimates are greatly improved by building in the constraint that MHT must go to zero at the northern and southern extents of the ocean basin at all times, enabling biases between the TOA and OHC data to be reconciled. Zonal mean global, Indo-Pacific and Atlantic basin ocean MHTs are computed and presented as 12-month running means and for the mean annual cycle for 2000 to 2016. For the Indo-Pacific, the tropical and subtropical MHTs feature a strong relationship with El Niño-Southern Oscillation (ENSO), and in the Atlantic, MHT interannual variability is significantly affected by and likely influences the North Atlantic Oscillation (NAO). However, Atlantic and Pacific changes are linked, suggesting that the Northern Annular Mode (versus NAO) is predominant. There is also evidence of decadal variability or trends.
Trepte, Q. Z.; Minnis, P.; Sun-Mack, S.; Yost, C. R.; Chen, Y.; Jin, Z.; Hong, G.; Chang, F.; Smith, W. L.; Bedka, K. M.; Chee, T. L.Trepte, Q. Z., P. Minnis, S. Sun-Mack, C. R. Yost, Y. Chen, Z. Jin, G. Hong, F. Chang, W. L. Smith, K. M. Bedka, T. L. Chee, 2019: Global Cloud Detection for CERES Edition 4 Using Terra and Aqua MODIS Data. IEEE Transactions on Geoscience and Remote Sensing, 1-40. doi: 10.1109/TGRS.2019.2926620. The Clouds and Earth's Radiant Energy System (CERES) has been monitoring clouds and radiation since 2000 using algorithms developed before 2002 for CERES Edition 2 (Ed2) products. To improve cloud amount accuracy, CERES Edition 4 (Ed4) applies revised algorithms and input data to Terra and Aqua MODerate-resolution Imaging Spectroradiometer (MODIS) radiances. The Ed4 cloud mask uses 5-7 additional channels, new models for clear-sky ocean and snow/ice-surface radiances, and revised Terra MODIS calibrations. Mean Ed4 daytime and nighttime cloud amounts exceed their Ed2 counterparts by 0.035 and 0.068. Excellent consistency between average Aqua and Terra cloud fraction is found over nonpolar regions. Differences over polar regions are likely due to unresolved calibration discrepancies. Relative to Ed2, Ed4 cloud amounts agree better with those from the Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observations (CALIPSO). CALIPSO comparisons indicate that Ed4 cloud amounts are more than or as accurate as other available cloud mask systems. The Ed4 mask correctly identifies cloudy or clear areas 90%-96% of the time during daytime over nonpolar areas depending on the CALIPSO-MODIS averaging criteria. At night, the range is 88%-95%. Accuracy decreases over land. The polar day and night accuracy ranges are 90%-91% and 80%-81%, respectively. The mean Ed4 cloud fractions slightly exceed the average for seven other imager cloud masks. Remaining biases and uncertainties are mainly attributed to errors in Ed4 predicted clear-sky radiances. The resulting cloud fractions should help CERES produce a more accurate radiation budget and serve as part of a cloud property climate data record. cloud; MODIS; Clouds and the Earth's Radiant Energy System (CERES); Satellites; Meteorology; cloud remote sensing; Broadband communication; Clouds; Climate; Calibration; Cloud computing; cloud mask; MODerate-resolution Imaging Spectroradiometer (MODIS).
Vargas Zeppetello, Lucas R.; Battisti, David S.; Baker, Marcia B.Vargas Zeppetello, L. R., D. S. Battisti, M. B. Baker, 2019: The Origin of Soil Moisture Evaporation “Regimes”. J. Climate, 32(20), 6939-6960. doi: 10.1175/JCLI-D-19-0209.1. Evaporation plays an extremely important role in determining summertime surface temperature variability over land. Observations show the relationship between evaporation and soil moisture generally conforms to the Budyko “two regime” framework; namely, that evaporation is limited by available soil moisture in dry climates and by radiation in wet climates. This framework has led climate models to different parameterizations of the relationship between evaporation and soil moisture in wet and dry regions. We have developed the Simple Land–Atmosphere Model (SLAM) as a tool for studying land–atmosphere interaction in general, and summertime temperature variability in particular. We use the SLAM to show that a negative feedback between evaporation and surface temperature gives rise to the two apparent evaporation “regimes” and provide analytic solutions for evaporative cooling anomalies that demonstrate the nonlinear impact of soil moisture perturbations. Stemming from the temperature dependence of vapor pressure deficit, the feedback we identify has important implications for how transitions between wet and dry land surfaces may impact temperature variability as the climate warms. We also elucidate the impacts of surface moisture and insolation perturbations on latent and sensible heat fluxes and on surface temperature variability.
Várnai, Tamás; Gatebe, Charles; Gautam, Ritesh; Poudyal, Rajesh; Su, WenyingVárnai, T., C. Gatebe, R. Gautam, R. Poudyal, W. Su, 2019: Developing an Aircraft-Based Angular Distribution Model of Solar Reflection from Wildfire Smoke to Aid Satellite-Based Radiative Flux Estimation. Remote Sensing, 11(13), 1509. doi: 10.3390/rs11131509. This study examines the angular distribution of scattered solar radiation associated with wildfire smoke aerosols observed over boreal forests in Canada during the ARCTAS (Arctic Research of the Composition of the Troposphere from Aircraft and Satellites) campaign. First, it estimates smoke radiative parameters (550 nm optical depth of 3.9 and single scattering albedo of 0.90) using quasi-simultaneous multiangular and multispectral airborne measurements by the Cloud Absorption Radiometer (CAR). Next, the paper estimates the broadband top-of-atmosphere radiances that a satellite instrument such as the Clouds and the Earth’s Radiant Energy System (CERES) could have observed, given the narrowband CAR measurements made from an aircraft circling about a kilometer above the smoke layer. This estimation includes both an atmospheric correction that accounts for the atmosphere above the aircraft and a narrowband-to-broadband conversion. The angular distribution of estimated radiances is found to be substantially different than the angular model used in the operational data processing of CERES observations over the same area. This is because the CERES model is a monthly average model that was constructed using observations taken under smoke-free conditions. Finally, a sensitivity analysis shows that the estimated angular distribution remains accurate for a fairly wide range of smoke and underlying surface parameters. Overall, results from this work suggest that airborne CAR measurements can bring some substantial improvements in the accuracy of satellite-based radiative flux estimates. aerosol; angular distribution model; smoke; wildfire; Cloud Absorption Radiometer
Voldoire, A.; Saint‐Martin, D.; Sénési, S.; Decharme, B.; Alias, A.; Chevallier, M.; Colin, J.; Guérémy, J.-F.; Michou, M.; Moine, M.-P.; Nabat, P.; Roehrig, R.; Mélia, D. Salas y; Séférian, R.; Valcke, S.; Beau, I.; Belamari, S.; Berthet, S.; Cassou, C.; Cattiaux, J.; Deshayes, J.; Douville, H.; Ethé, C.; Franchistéguy, L.; Geoffroy, O.; Lévy, C.; Madec, G.; Meurdesoif, Y.; Msadek, R.; Ribes, A.; Sanchez‐Gomez, E.; Terray, L.; Waldman, R.Voldoire, A., D. Saint‐Martin, S. Sénési, B. Decharme, A. Alias, M. Chevallier, J. Colin, J. Guérémy, M. Michou, M. Moine, P. Nabat, R. Roehrig, D. S. y. Mélia, R. Séférian, S. Valcke, I. Beau, S. Belamari, S. Berthet, C. Cassou, J. Cattiaux, J. Deshayes, H. Douville, C. Ethé, L. Franchistéguy, O. Geoffroy, C. Lévy, G. Madec, Y. Meurdesoif, R. Msadek, A. Ribes, E. Sanchez‐Gomez, L. Terray, R. Waldman, 2019: Evaluation of CMIP6 DECK Experiments With CNRM-CM6-1. Journal of Advances in Modeling Earth Systems, 11(7), 2177-2213. doi: 10.1029/2019MS001683. This paper describes the main characteristics of CNRM-CM6-1, the fully coupled atmosphere-ocean general circulation model of sixth generation jointly developed by Centre National de Recherches Météorologiques (CNRM) and Cerfacs for the sixth phase of the Coupled Model Intercomparison Project 6 (CMIP6). The paper provides a description of each component of CNRM-CM6-1, including the coupling method and the new online output software. We emphasize where model's components have been updated with respect to the former model version, CNRM-CM5.1. In particular, we highlight major improvements in the representation of atmospheric and land processes. A particular attention has also been devoted to mass and energy conservation in the simulated climate system to limit long-term drifts. The climate simulated by CNRM-CM6-1 is then evaluated using CMIP6 historical and Diagnostic, Evaluation and Characterization of Klima (DECK) experiments in comparison with CMIP5 CNRM-CM5.1 equivalent experiments. Overall, the mean surface biases are of similar magnitude but with different spatial patterns. Deep ocean biases are generally reduced, whereas sea ice is too thin in the Arctic. Although the simulated climate variability remains roughly consistent with CNRM-CM5.1, its sensitivity to rising CO2 has increased: the equilibrium climate sensitivity is 4.9 K, which is now close to the upper bound of the range estimated from CMIP5 models. climate model; CMIP6 DECK; CNRM-CM6-1
Wall, Casey J.; Hartmann, Dennis L.; Norris, Joel R.Wall, C. J., D. L. Hartmann, J. R. Norris, 2019: Is the Net Cloud Radiative Effect Constrained to be Uniform Over the Tropical Warm Pools?. Geophysical Research Letters, 46(21), 12495-12503. doi: 10.1029/2019GL083642. Global radiative-convective equilibrium simulations are used to investigate the hypothesis that mutual interactions among cloud albedo, sea surface temperature gradients, and atmospheric circulation constrain the net cloud radiative effect (CRE) to be similar in convective and nonconvective regions over the tropical warm pools. We perform an experiment in which convective clouds interact naturally with the ocean and atmosphere by forming over the warmest water and shading it and an experiment in which this interaction is removed by randomizing cloud shading of the ocean. Removing the cloud shading interaction enhances sea surface temperature gradients, lateral atmospheric heat transport, and large-scale convective aggregation and produces convective clouds with much more negative net CRE. These findings support the hypothesis that feedbacks between sea surface temperature and convection are critical to obtaining similar net CRE in convective and nonconvective regions over the tropical warm pools. Tropical Convection; Cloud Radiative Effects; Ocean-Atmosphere Interactions
Walther, Sophia; Duveiller, Gregory; Jung, Martin; Guanter, Luis; Cescatti, Alessandro; Camps‐Valls, GustauWalther, S., G. Duveiller, M. Jung, L. Guanter, A. Cescatti, G. Camps‐Valls, 2019: Satellite Observations of the Contrasting Response of Trees and Grasses to Variations in Water Availability. Geophysical Research Letters, 46(3), 1429-1440. doi: 10.1029/2018GL080535. Interannual variations in ecosystem primary productivity are dominated by water availability. Until recently, characterizing the photosynthetic response of different ecosystems to soil moisture anomalies was hampered by observational limitations. Here, we use a number of satellite-based proxies for productivity, including spectral indices, sun-induced chlorophyll fluorescence, and data-driven estimates of gross primary production, to reevaluate the relationship between terrestrial photosynthesis and water. In contrast to nonwoody vegetation, we find a resilience of forested ecosystems to reduced soil moisture. Sun-induced chlorophyll fluorescence and data-driven gross primary production indicate an increase in photosynthesis as a result of the accompanying higher amounts of light and temperature despite lowered light-use-efficiency. Conversely, remote sensing indicators of greenness reach their detection limit and largely remain stable. Our study thus highlights the differential responses of ecosystems along a tree cover gradient and illustrates the importance of differentiating photosynthesis indicators from those of greenness for the monitoring and understanding of ecosystems. SIF; GPP; satellite; forest; photosynthesis; water effects
Wang, Jianjie; Liu, Chao; Yao, Bin; Min, Min; Letu, Husi; Yin, Yan; Yung, Yuk L.Wang, J., C. Liu, B. Yao, M. Min, H. Letu, Y. Yin, Y. L. Yung, 2019: A multilayer cloud detection algorithm for the Suomi-NPP Visible Infrared Imager Radiometer Suite (VIIRS). Remote Sensing of Environment, 227, 1-11. doi: 10.1016/j.rse.2019.02.024. A new multilayer (ML) cloud detection algorithm based on three shortwave infrared (SWIR) and two longwave infrared (LWIR) channels is developed and applied to the Visible Infrared Imager Radiometer Suite (VIIRS) onboard the Suomi-NPP satellite. The algorithm identifies ML clouds, i.e., ice clouds overlying water clouds, based on satellite multispectral observations in the 1.38, 1.6, 2.25, 8.5, and 11 μm channels. We perform synthetic radiative transfer simulations to understand the sensitivities of the aforementioned channels on ML and single-layer (SL) clouds. Active CALIOP observations are used to evaluate the algorithm. Compared with the collocated CALIOP results, the algorithm can determine SL and ML clouds correctly with success rates of approximately 80% and 60%, respectively, and has similar performance to that of the current MODIS operational ML cloud detection algorithm. The misclassification of ML clouds as SL clouds is primarily caused by thin ice clouds that are practically undetectable using LWIR tests. Furthermore, the algorithm is extended to analyze data from radiometers onboard the geostationary Himawari-8 and FengYun-4A satellites, and results similar to those of VIIRS are obtained. VIIRS; Radiometer; Longwave infrared; Multilayer clouds; Shortwave infrared
Wang, Qian; Zhang, Su-Ping; Xie, Shang-Ping; Norris, Joel R.; Sun, Jian-Xiang; Jiang, Yu-XiWang, Q., S. Zhang, S. Xie, J. R. Norris, J. Sun, Y. Jiang, 2019: Observed Variations of the Atmospheric Boundary Layer and Stratocumulus over a Warm Eddy in the Kuroshio Extension. Mon. Wea. Rev., 147(5), 1581-1591. doi: 10.1175/MWR-D-18-0381.1. A research vessel sailing across a warm eddy in the Kuroshio Extension on 13 April 2016 captured an abrupt development of stratocumulus under synoptic high pressure. Shipboard observations and results from regional atmospheric model simulations indicate that increased surface heat flux over the ocean eddy lowered surface pressure and thereby accelerated southeasterly winds. The southeasterly winds transported moisture toward the low pressure and enhanced the air–sea interface heat flux, which in turn deepened the low pressure and promoted low-level convergence and rising motion over the warm eddy. The lifting condensation level lowered and the top of the marine atmospheric boundary layer (MABL) rose, thereby aiding the development of the stratocumulus. Further experiments showed that 6°C sea surface temperature anomalies associated with the 400-km-diameter warm eddy accounted for 80% of the total ascending motion and 95% of total cloud water mixing ratio in the marine atmospheric boundary layer during the development of stratocumulus. The synthesis of in situ soundings and modeling contributes to understanding of the mechanism by which the MABL and marine stratocumulus respond to ocean eddies.
Wang, Tao; Wu, Dong L.; Gong, Jie; Tsai, VictoriaWang, T., D. L. Wu, J. Gong, V. Tsai, 2019: Tropopause Laminar Cirrus and Its Role in the Lower Stratosphere Total Water Budget. Journal of Geophysical Research: Atmospheres, 124(13), 7034-7052. doi: 10.1029/2018JD029845. Laminar cirrus are thin, extensive, isolated layers of ice clouds frequently observed in the tropical tropopause layer. Widespread laminar cirrus significantly affects tropical tropopause layer total water and thermal budget. In this study, we extract laminar cirrus from the Cloud-Aerosol Lidar with Orthogonal Polarization Level 1 attenuated total backscatter images for January 2009, in order to characterize statistical properties of laminar cirrus cloud length, base, thickness, optical depth, and layer partial ice water path. These characteristics are used to develop an algorithm identifying laminar cirrus automatically from the Cloud-Aerosol Lidar with Orthogonal Polarization Level 2 layer product for 2008–2017. The nearly 10-year records reveal that tropopause laminar cirrus occurrence (30–40% of total cirrus) is strongly anticorrelated with the tropopause temperatures in that colder tropopause in frequent (super)saturation during boreal winter favors in situ formation of clouds. Interannually, anomalously warmer troposphere temperature (ΔT), easterly shear of the quasi-biennial oscillation, and stronger upwelling branch of the Brewer-Dobson circulation enhance laminar cirrus formation via cooling of the tropopause. The tropopause laminar cirrus carries 0.05 mg/m3 ( 0.5 ppmv) of ice water content during boreal winter and tropopause; TTL; ice water content (IWC); laminar cirrus; total water budget; water vapor (H2O)
Wang, Wenshan; Zender, Charles S.; van As, Dirk; Miller, Nathaniel B.Wang, W., C. S. Zender, D. van As, N. B. Miller, 2019: Spatial distribution of melt-season cloud radiative effects over Greenland: Evaluating satellite observations, reanalyses, and model simulations against in situ measurements. Journal of Geophysical Research: Atmospheres, 124(1), 57-71. doi: 10.1029/2018JD028919. Arctic clouds can profoundly influence surface radiation and thus surface melt. Over Greenland, these cloud radiative effects (CRE) vary greatly with the diverse topography. To investigate the ability of assorted platforms to reproduce heterogeneous CRE, we evaluate CRE spatial distributions from a satellite product, reanalyses, and a global climate model against estimates from 21 automatic weather stations (AWS). Net CRE estimated from AWS generally decreases with elevation, forming a “warm center” distribution. CRE areal averages from the five large-scale data sets we analyze are all around 10 W m−2. MERRA-2, ERA-Interim, and CERES CRE estimates agree with AWS and reproduce the “warm center” distribution. However, the NCAR Arctic System Reanalysis (ASR) and the CESM Large ENSemble community project (LENS) show strong warming in the south and northwest, forming a “warm L-shape” distribution. Discrepancies are mainly caused by longwave CRE in the accumulation zone. MERRA-2, ERA-Interim, and CERES successfully reproduce cloud fraction and its dominant positive influence on longwave CRE in this region. On the other hand, longwave CRE from ASR and LENS correlates strongly with ice water path instead of with cloud fraction or liquid water path. Moreover, ASR overestimates cloud fraction and LENS underestimates liquid water path substantially, both with limited spatial variability. MERRA-2 best captures the observed inter-station changes, captures most of the observed cloud-radiation physics, and largely reproduces both albedo and cloud properties. The “warm center” CRE spatial distribution indicates that clouds enhance surface melt in the higher accumulation zone and reduce surface melt in the lower ablation zone. Greenland; Cloud; Radiation; Automatic weather stations
Wang, Yipu; Li, Rui; Min, Qilong; Zhang, Leiming; Yu, Guirui; Bergeron, YvesWang, Y., R. Li, Q. Min, L. Zhang, G. Yu, Y. Bergeron, 2019: Estimation of Vegetation Latent Heat Flux over Three Forest Sites in ChinaFLUX using Satellite Microwave Vegetation Water Content Index. Remote Sensing, 11(11), 1359. doi: 10.3390/rs11111359. Latent heat flux (LE) and the corresponding water vapor lost from the Earth’s surface to the atmosphere, which is called Evapotranspiration (ET), is one of the key processes in the water cycle and energy balance of the global climate system. Satellite remote sensing is the only feasible technique to estimate LE over a large-scale region. While most of the previous satellite LE methods are based on the optical vegetation index (VI), here we propose a microwave-VI (EDVI) based LE algorithm which can work for both day and night time, and under clear or non-raining conditions. This algorithm is totally driven by multiple-sensor satellite products of vegetation water content index, solar radiation, and cloud properties, with some aid from a reanalysis dataset. The satellite inputs and the performance of this algorithm are validated with in situ measurements at three ChinaFLUX forest sites. Our results show that the selected satellite observations can indeed serve as the inputs for the purpose of estimating ET. The instantaneous estimations of LE (LEcal) from this algorithm show strong positive temporal correlations with the in situ measured LE (LEobs) with the correlation coefficients (R) of 0.56–0.88 in the study years. The mean bias is kept within 16.0% (23.0 W/m2) across the three sites. At the monthly scale, the correlations between the retrieval and the in situ measurements are further improved to an R of 0.84–0.95 and the bias is less than 14.3%. The validation results also indicate that EDVI-based LE method can produce stable LEcal under different cloudy skies with good accuracy. Being independent of any in situ measurements as inputs, this algorithm shows great potential for estimating ET under both clear and cloudy skies on a global scale for climate study. satellite remote sensing; cloudy sky; ChinaFLUX; clouds and earth’s radiation energy system (CERES); evapotranspiration (ET); Microwave emissivity difference vegetation index (EDVI)
Wehrli, Kathrin; Guillod, Benoit P.; Hauser, Mathias; Leclair, Matthieu; Seneviratne, Sonia I.Wehrli, K., B. P. Guillod, M. Hauser, M. Leclair, S. I. Seneviratne, 2019: Identifying Key Driving Processes of Major Recent Heat Waves. Journal of Geophysical Research: Atmospheres, 124(22), 11746-11765. doi: 10.1029/2019JD030635. Heat waves lead to major impacts on human health, food production, and ecosystems. To assess their predictability and how they are projected to change under global warming, it is crucial to improve our understanding of the underlying processes affecting their occurrence and intensity under present-day climate conditions. Beside greenhouse gas forcing, processes in the different components of the climate system—in particular the land surface, atmospheric circulation, and the oceans—may play a key role in changing the odds for a particular event. This study aims to identify the role of the individual drivers for five heat waves (and, in some cases, of concurrent droughts) in the recent decade. Simulations are performed with the Community Earth System Model using nudging of horizontal atmospheric circulation and prescription of soil moisture. The fully constrained model accurately reproduces how anomalous an event was. Factorial experiments, which force the model toward observations for one or several key components at a time, allow us to identify how much of the observed temperature anomaly of each event can be attributed to each driver. Considering all analyzed events, atmospheric circulation and soil moisture play similarly important roles, each contributing between 20% and 70% to the events' anomalies. This highlights that the role of thermodynamics can be just as important as that of the dynamics for temperature extremes, a possibly underestimated feature. In addition, recent climate change amplified the events and contributed between 10% and 40% of the events' anomalies. extreme events; atmospheric nudging; global climate models; heat waves; soil moisture prescription
Wei, Yu; Zhang, Xiaotong; Hou, Ning; Zhang, Weiyu; Jia, Kun; Yao, YunjunWei, Y., X. Zhang, N. Hou, W. Zhang, K. Jia, Y. Yao, 2019: Estimation of surface downward shortwave radiation over China from AVHRR data based on four machine learning methods. Solar Energy, 177, 32-46. doi: 10.1016/j.solener.2018.11.008. Downward shortwave radiation (DSR) is one of the major driving forces of climate system. Knowledge of the Earth’s radiation budget is essential for improving our understanding of the Earth’s climate. Therefore, accurate estimation of DSR has great significance. Satellite remote sensing is a practical way to derive DSR with high spatial resolution and coverage. In this study, four machine learning methods, including gradient boosting regression tree (GBRT), random forest (RF), multivariate adaptive regression spline (MARS), and artificial neural network (ANN), were applied to estimate DSR at a spatial resolution of 5 km and a temporal resolution of 1 day using Advanced Very High Resolution Radiometer (AVHRR) data. The DSR estimates based on four machine learning methods were evaluated using ground measurements at 96 sites over China. The measurements were collected from the Climate Data Center of the Chinese Meteorological Administration (CDC/CMA) from 2001 to 2003. The evaluation results showed that the GBRT method performed best at both daily and monthly time scales under both clear and cloudy sky conditions. The validation results at the daily time scale showed an overall root mean square error (RMSE) of 30.34 W m−2 and an R value of 0.90 under clear sky conditions, whereas these values were 42.03 W m−2 and 0.86, respectively, under cloudy sky conditions. The DSR estimates had an overall RMSE value of 16.93 W m−2 and an R value of 0.97 at the monthly time scale. The Clouds and Earth's Radiant Energy System (CERES) Energy Balanced and Filled (EBAF) data sets were also used for comparison with the DSR estimates based on the GBRT method. The DSR estimates based on the GBRT method exhibited similar spatial distributions with those of the CERES-EBAF DSR product. Moreover, the DSR estimates based on the GBRT method did not show a clear overestimation tendency, as the CERES-EBAF DSR product did, at the CDC/CMA sites. AVHRR; Downward shortwave radiation; GBRT; Machine learning methods
Wild, Martin; Hakuba, Maria Z.; Folini, Doris; Dorig-Ott, Patricia; Schar, Christoph; Kato, Seiji; Long, Charles N.Wild, M., M. Z. Hakuba, D. Folini, P. Dorig-Ott, C. Schar, S. Kato, C. N. Long, 2019: The cloud-free global energy balance and inferred cloud radiative effects: an assessment based on direct observations and climate models.. Climate dynamics, 52(7), 4787-4812. doi: 10.1007/s00382-018-4413-y. In recent studies we quantified the global mean Earth energy balance based on direct observations from surface and space. Here we infer complementary referenceestimates for its components specifically under cloud-free conditions. While the clear-sky fluxes at the top of atmosphere (TOA) are accurately known from satellite measurements, the corresponding fluxes at the Earth's surface are not equally well established, as they cannot be directly measured from space. This is also evident in 38 global climate models from CMIP5, which are shown to greatly vary in their clear-sky surface radiation budgets. To better constrain the latter, we established new clear-sky reference climatologies of surface downward shortwave and longwave radiative fluxes from worldwide distributed Baseline Surface Radiation Network sites. 33 out of the 38 CMIP5 models overestimate the clear-sky downward shortwave reference climatologies, whereas both substantial overestimations and underestimations are found in the longwave counterparts in some of the models. From the bias structure of the CMIP5 models we infer best estimates for the global mean surface downward clear-sky shortwave and longwave radiation, at 247 and 314 Wm-2, respectively. With a global mean surface albedo of 13.5% and net shortwave clear-sky flux of 287 Wm-2 at the TOA this results in a global mean clear-sky surface and atmospheric shortwave absorption of 214 and 73 Wm-2, respectively. From the newly-established diagrams of the global energy balance under clear-sky and all-sky conditions, we quantify the cloud radiative effects not only at the TOA, but also within the atmosphere and at the surface.
Woelfle, M. D.; Bretherton, C. S.; Hannay, C.; Neale, R.Woelfle, M. D., C. S. Bretherton, C. Hannay, R. Neale, 2019: Evolution of the Double-ITCZ Bias Through CESM2 Development. Journal of Advances in Modeling Earth Systems, 11(7), 1873-1893. doi: 10.1029/2019MS001647. The structure of the east Pacific Intertropical Convergence Zone (ITCZ) as simulated in the Community Earth System Model version 2 (CESM2) is greatly improved as compared to its previous version, CESM version 1. Examination of intermediate model versions created as part of the development process for CESM2 shows the improvement in the ITCZ is well correlated with a reduction in the relative warmth of southeast Pacific sea surface temperatures (SSTs) as compared to the broader tropical mean. Cooling SST in this region enhances the zonal SST and surface pressure gradients and reduces the anomalously southward SST gradient present in boreal spring in early version of CESM2. The improvements in southeast Pacific SST are attributed to increases in low cloud cover and the associated shortwave cloud forcing over the southeast. Sensitivity tests using fixed SST simulations demonstrate the increase in cloud cover between two intermediate model versions, 119 and 125, to be driven by removal of the dependence of autoconversion and accretion rates on cloud water variance as well as the removal of a secondary condensation scheme. Both of these changes reduce drizzle rates in warm clouds increasing cloud lifetime and cloud fraction in the stratocumulus to trade cumulus transition region. The improvements in southeast Pacific shortwave cloud forcing and ITCZ climatology persist through subsequent changes to the cloud microphysics parameterizations. Despite improvements in the east Pacific ITCZ, the global mean ITCZ position and Pacific cold tongue bias strength do not exhibit a systematic improvement across the development simulations. climate model; ITCZ; CESM; model bias; double ITCZ; Pacific rainfall
Wu, M.; Lee, J.-E.Wu, M., J. Lee, 2019: Thresholds for Atmospheric Convection in Amazonian Rainforests. Geophysical Research Letters, 46(16), 10024-10033. doi: 10.1029/2019GL082909. The Amazon rainforest is known as the “Green Ocean” for its maritime-like convection and cloud microphysics during the wet season. Although previous studies suggest the dominant thermodynamic processes involved in deep convection may differ between land and ocean, a comprehensive understanding of the thermodynamics of Amazonian convection is lacking. Using 404,971 daytime precipitating cloud profiles from the CloudSat satellite, we observe a regime transition from congestus dominance to cumulonimbus dominance when convective available potential energy exceeds a threshold in Amazonia and also in shrublands, but not in oceanic regions. In addition, the cloud regime transition is linked to boundary layer moisture in the two continental regions, while it is linked to lower-free-tropospheric moisture in the oceanic region. As the dry season progresses in Amazonia and modifies the free-tropospheric stability, a moderate plant water stress and increased incoming solar energy facilitate the initiation of deep convection and the onset of the wet season. CloudSat; atmospheric convection; tropical rainforest
Xia, Youlong; Hao, ZengchaoXia, Y., Z. Hao, 2019: Regional and Global Land Data Assimilation Systems: Innovations, Challenges, and Prospects. Journal of Meteorological Research, 33(2), 159-189. doi: 10.1007/s13351-019-8172-4.
Xie, Yuanyu; Wang, Yuxuan; Dong, Wenhao; Wright, Jonathon S.; Shen, Lu; Zhao, ZijianXie, Y., Y. Wang, W. Dong, J. S. Wright, L. Shen, Z. Zhao, 2019: Evaluating the Response of Summertime Surface Sulfate to Hydroclimate Variations in the Continental United States: Role of Meteorological Inputs in the GEOS-Chem Model. Journal of Geophysical Research: Atmospheres, 124(3), 1662-1679. doi: 10.1029/2018JD029693. Understanding the response of sulfate to climate change is crucial given tight couplings between sulfate and the hydrological cycle. As the sources and sinks of sulfate are sensitive to cloud and precipitation processes, the accuracy of model simulations depends on the accuracy of these meteorological inputs. In this study, we evaluate the GEOS-Chem model in simulating summertime surface sulfate concentrations in the continental United States across different levels of dryness and compare the model performance based on two sets of meteorological fields: Modern Era Retrospective Analysis for Research and Applications (MERRA) and MERRA-2. Both simulations fail to reproduce observed increases in sulfate during drought, as indicated by negative correlation slopes between surface sulfate concentrations and the standardized precipitation evapotranspiration index (SPEI). This deficiency can be largely attributed to too large a decrease in clouds and hence aqueous phase sulfate production as conditions shift from wet to dry. MERRA-2-driven GEOS-Chem (M2GC) shows improvements in cloud and precipitation fields relative to the MERRA-driven GEOS-Chem, hence eliminating approximately half of the bias in the simulated sulfate-SPEI slope. However, M2GC still underestimates boundary layer cloud fraction, overestimates liquid water content, and overestimates the rates of the decrease in both quantities as conditions become drier. Explicitly correcting these cloud biases in M2GC results in a 60–80% reduction of the bias in the simulated sulfate-SPEI slope. The strong sensitivity of simulated sulfate to prescribed cloud fields suggests the need for more comprehensive assessment of cloud inputs for sulfate simulations under current and future climate change scenarios. clouds; sulfate; precipitation; aqueous phase production; hydrological cycles
Xie, Zhiling; Wang, BinXie, Z., B. Wang, 2019: Summer atmospheric heat sources over the western-central Tibetan Plateau: An integrated analysis of multiple reanalysis and satellite datasets. J. Climate, 32(4), 1181–1202. doi: 10.1175/JCLI-D-18-0176.1. Multiple bias-corrected top-quality reanalysis datasets, gauge-based observations, and selected satellite products are synthetically employed to revisit the climatology and variability of the summer atmospheric heat sources over the Tibetan Plateau (TP). Verification-based selection and ensemble-mean methods are utilized to combine various datasets. Different from previous works, this study pays special attention to estimating the total heat source (TH) and its components over the data-void western plateau (70° - 85°E), including the surface sensible heat (SH), latent heat released by precipitation (LH), and net radiation flux (RD).Consistent with previous studies, the climatology of summer SH (LH) typically increases (decreases) from southeast to northwest. Generally, LH dominates TH over most of the TP. A notable new finding is a minimum TH area over the high-altitude region of the northwestern TP, where the Karakoram Mountain Range is located. We find that during the period of 1984-2006, TH shows insignificant trends over the eastern and central TP, whereas exhibits an evident increasing trend over the western TP that is attributed to the rising tendency of LH before 1996 and that of RD after 1996. The year-to-year variation of TH over the central-eastern TP is highly correlated with that of LH, but that’s not the case over the western TP. It is also worth noting that the variations of TH in each summer month are not significantly correlated with each other, hence study of the interannual variation of the TP heat sources should consider the remarkable subseasonal variations.
Xu, Donghui; Agee, Elizabeth; Wang, Jingfeng; Ivanov, Valeriy Y.Xu, D., E. Agee, J. Wang, V. Y. Ivanov, 2019: Estimation of Evapotranspiration of Amazon Rainforest Using the Maximum Entropy Production Method. Geophysical Research Letters, 46(3), 1402-1412. doi: 10.1029/2018GL080907. Energy budget of Amazonian forests has a large influence on regional and global climate, but relevant data are scarce. A novel energy partition method based on the maximum entropy production (MEP) theory is applied to simulate evapotranspiration in Amazonia. Using site-level eddy flux data, the MEP method shows high skill at the hourly, daily, and monthly scales. Consistent performance under different levels of land surface dryness is revealed, hinting that drought signal is appropriately resolved. The site-level MEP-based estimates outperform the estimates of the Moderate Resolution Imaging Spectroradiometer evapotranspiration product, which is commonly used for large-scale assessments. At the Amazon basin scale, the two series yield similar averages but exhibit spatial differences. The parameter parsimony and demonstrated skill of the MEP method make it an attractive approach for environments with diverse strategies of water flux control. remote sensing; Amazon rainforest; evapotranspiration; maximum entropy production; water stress
Xu, Kuan-Man; Hu, Yongxiang; Wong, TakmengXu, K., Y. Hu, T. Wong, 2019: Convective Aggregation and Indices Examined from CERES Cloud Object Data. Journal of Geophysical Research: Atmospheres, 124(24), 13604-13624. doi: 10.1029/2019JD030816. Convective aggregation is a self-aggregation phenomenon appearing in idealized radiative-convective equilibrium simulations under constant, uniform sea surface temperature (SST). To gain an understanding of observed convective aggregation or organization, three metrics, i.e., simple convective aggregation index (SCAI), modified SCAI (MCAI), and convective organization potential (COP), are evaluated with cloud object data from CERES. MCAI is related to object sizes through a modified inter-object distance (IOD). It is found that large-size object groups are less aggregated according to SCAI but more organized according to COP, compared to small-size object groups. The opposite sensitivities to object-group size can be explained by the dominant roles of the IOD in SCAI and the sum of object radii in COP as object-group sizes increase. However, large-size object groups are slightly more aggregated than small-size ones according to MCAI. Both SCAI and MCAI increase with the number of cloud objects (N) in an object group but COP has a weak dependency on N. Further sorting by object-group total area shows that sensitivity of MCAI to object-group area agrees with that of SCAI for small-area ranges but with that of COP for large-area ranges, which is related to the weak sensitivity of the modified IOD to object-group area, as compared to that of the original IOD. Finally, the three metrics show the similar contrasts between continental and oceanic convection and the same weak sensitivity to SST. The latter suggests that self-aggregation is weaker at higher SSTs than at lower SSTs, in contrast to the findings of many simulations. Cloud object; Convective aggregation; Convective aggregation index
Yang, Quan; Zhang, Feng; Zhang, Hua; Wang, Zhili; Li, Jiangnan; Wu, Kun; Shi, Yining; Peng, YiranYang, Q., F. Zhang, H. Zhang, Z. Wang, J. Li, K. Wu, Y. Shi, Y. Peng, 2019: Assessment of two-stream approximations in a climate model. Journal of Quantitative Spectroscopy and Radiative Transfer, 225, 25-34. doi: 10.1016/j.jqsrt.2018.12.016. The accuracies of the two-stream discrete-ordinate-method (DOM) and Eddington approximation schemes are systematically compared using the BCC_RAD radiative transfer scheme used in a general circulation model (GCM). It is found that the two-stream DOM produces more accurate results for the upward radiative flux, downward radiative flux and heating rate under clear-sky conditions in an offline radiation model, whereas the Eddington approximation is more accurate under all-sky conditions. An experiment using satellite data as the approximation of cloud properties confirms the superiority of the Eddington approximation under cloudy-sky conditions. Experiments using the GCM of the Beijing Climate Center (BCC_AGCM2.0.1) show that, compared to the two-stream DOM, the Eddington approximation can enhance the fraction of low cloud, and this increased cloud fraction can affect the differences in radiative fluxes between these schemes. This study suggests that the more suitable approach in GCMs is to use the Eddington approximation. General circulation model; Radiative transfer; Two-stream approximation
Yang, Yuting; Roderick, Michael L.Yang, Y., M. L. Roderick, 2019: Radiation, surface temperature and evaporation over wet surfaces. Quarterly Journal of the Royal Meteorological Society, 145(720), 1118-1129. doi: 10.1002/qj.3481. Predicting evaporation from wet surfaces (water, wet soil and canopy surfaces) has long been of major interest in hydrological, meteorological and agricultural communities. In practical applications of the existing models/theories of wet surface evaporation (e.g., the Priestley-Taylor model), net radiation (Rn) and/or surface temperature (Ts; or near-surface air temperature) are considered to be independent external forcings that determine the evaporation rate. However, neither Rn nor Ts are independent of evaporation, since Rn directly depends on Ts via the outgoing longwave radiation. In this study, we use monthly data for the global ocean to investigate the relation between radiation, evaporation and surface temperature. We use a new theoretical formulation to show that as Ts increases, a greater fraction of Rn is partitioned to evaporation (i.e., higher evaporative fraction) but Rn declines because of an increase in outgoing longwave radiation. The consequence is that a maximum evaporation rate emerges naturally from that trade-off. We find that this maximum corresponds to the actual evaporation over global ocean surfaces at both local and global scales. In addition, the maximum in evaporation defines a Ts that corresponds to independent estimates of sea surface temperature. These results suggest that the concept of maximum evaporation reported here is a natural attribute of a wet evaporating surface. Evaporation; Surface temperature; Radiation; Bowen ratio; Ocean surfaces
Yang, Zesu; Zhang, Qiang; Hao, Xiaocui; Yue, PingYang, Z., Q. Zhang, X. Hao, P. Yue, 2019: Changes in Evapotranspiration Over Global Semiarid Regions 1984–2013. Journal of Geophysical Research: Atmospheres, 124(6), 2946-2963. doi: 10.1029/2018JD029533. Global mean evapotranspiration (ET) has been increasing in recent decades under climate warming. Yet the magnitude and spatial distribution of ET variation remain highly uncertain. ET changes in different regions are still poorly understood due to limitations in observation records, especially in semiarid regions with undeveloped economic systems and sparse observations. Based on the Priestley-Taylor Jet Propulsion Laboratory model, ET was estimated over global typical semiarid regions for 1984–2013. All of these regions show a decreasing ET trend, which is opposite to the trend in global mean ET. In particular, North Africa has the fastest decreasing trend, 8.6 mm/year, while South Africa has the slowest decreasing trend, 0.7 mm/year. North America, South America, northern Africa, and Australia have declining trends in ET during both warm and cold seasons, while the Loess Plateau, East Asia, central Asia, and South Africa have declining trends in ET only during warm seasons. Accounting for basic factors controlling ET, three important results are identified: First, atmospheric demand is increasing over all semiarid regions due to climate warming; second, the effect of atmospheric composition and cloud weakening radiation is strengthening over all semiarid regions; and finally, annual precipitation is decreasing over all semiarid regions except for South Africa. Factorial experiments indicate that the remarkable declining trend in relative air humidity forces the decreasing trend in ET over all semiarid regions. These results imply a slowing water cycle in global semiarid regions. climate change; evapotranspiration trend; global semiarid areas; PT-JPL model
Yin, Jun; Calabrese, Salvatore; Daly, Edoardo; Porporato, AmilcareYin, J., S. Calabrese, E. Daly, A. Porporato, 2019: The Energy Side of Budyko: Surface-Energy Partitioning From Hydrological Observations. Geophysical Research Letters, 46(13), 7456-7463. doi: 10.1029/2019GL083373. Land-surface partitioning of net radiation into sensible and latent heat fluxes is critical for hydroclimatic processes but remains highly uncertain due to limited observations. We show that a suitable extension of the Budyko's curve, a well-known framework in hydrology for water balance estimation, can be utilized effectively to partition the surface energy fluxes by expressing the long-term evaporative fraction (EF) as a function of the dryness index only. The combination of this energy partitioning method with hydrological observations allows us to estimate the surface energy components at watershed and continental scales. Using this new framework, we show that North American Regional Reanalysis data overestimate surface evaporation, likely influencing the modeling of atmospheric convection. The obtained hydrologic constrains on energy partitioning can be used to provide more accurate estimations of surface energy fluxes for hydroclimatic predictions. Budyko's curve; Budyko's energy curve; hydrological observations; MOPEX; NARR; surface energy partitioning
Yu, LisanYu, L., 2019: Global Air–Sea Fluxes of Heat, Fresh Water, and Momentum: Energy Budget Closure and Unanswered Questions. Annual Review of Marine Science, 11(1), 227-248. doi: 10.1146/annurev-marine-010816-060704. The ocean interacts with the atmosphere via interfacial exchanges of momentum, heat (via radiation and convection), and fresh water (via evaporation and precipitation). These fluxes, or exchanges, constitute the oceansurface energy and water budgets and define the ocean’s role in Earth’s climate and its variability on both short and long timescales. However, direct flux measurements are available only at limited locations. Air–sea fluxes are commonly estimated from bulk flux parameterization using flux-related near-surface meteorological variables (winds, sea and air temperatures, and humidity) that are available from buoys, ships, satellite remote sensing, numerical weather prediction models, and/or a combination of any of these sources. Uncertainties in parameterization-based flux estimates are large, and when they are integrated over the ocean basins, they cause a large imbalance in the global-ocean budgets. Despite the significant progress that has been made in quantifying surface fluxes in the past 30 years, achieving a global closure of ocean-surface energy and water budgets remains a challenge for flux products constructed from all data sources. This review provides a personal perspective on three questions: First, to what extent can time-series measurements from air–sea buoys be used as benchmarks for accuracy and reliability in the context of the budget closures? Second, what is the dominant source of uncertainties for surface flux products, the flux-related variables or the bulk flux algorithms? And third, given the coupling between the energy and water cycles, precipitation and surface radiation can act as twin budget constraints—are the community-standard precipitation and surface radiation products pairwise compatible? Expected final online publication date for the Annual Review of Marine Science Volume 11 is January 3, 2019. Please see http://www.annualreviews.org/page/journal/pubdates for revised estimates.
Yu, Lisan; Jin, X.; Stackhouse, P. W.; Wilber, A. C.; Kato, S.; Loeb, N. G; Weller, R.Yu, L., X. Jin, P. W. Stackhouse, A. C. Wilber, S. Kato, N. G. Loeb, R. Weller, 2019: Global ocean heat, freshwater, and momentum fluxes.[in "State of the Climate in 2018"]. Bull. Amer. Meteor. Soc, 100(9), S81-84. doi: 10.1175/2019BAMSStateoftheClimate.1.
Yu, Shanshan; Xin, Xiaozhou; Liu, Qinhuo; Zhang, Hailong; Li, LiYu, S., X. Xin, Q. Liu, H. Zhang, L. Li, 2019: An Improved Parameterization for Retrieving Clear-Sky Downward Longwave Radiation from Satellite Thermal Infrared Data. Remote Sensing, 11(4), 425. doi: 10.3390/rs11040425. Surface downward longwave radiation (DLR) is a crucial component in Earth’s surface energy balance. Yu et al. (2013) developed a parameterization for retrieving clear-sky DLR at high spatial resolution by combined use of satellite thermal infrared (TIR) data and column integrated water vapor (IWV). We extended the Yu2013 parameterization to Moderate Resolution Imaging Spectroradiometer (MODIS) data based on atmospheric radiative simulation, and we modified the parameterization to decrease the systematic negative biases at large IWVs. The new parameterization improved DLR accuracy by 1.9 to 3.1 W/m2 for IWV ≥3 cm compared to the Yu2013 algorithm. We also compared the new parameterization with four algorithms, including two based on Top-of-Atmosphere (TOA) radiance and two using near-surface meteorological parameters and water vapor. The algorithms were first evaluated using simulated data and then applied to MODIS data and validated using surface measurements at 14 stations around the globe. The results suggest that the new parameterization outperforms the TOA-radiance based algorithms in the regions where ground temperature is substantially different (enough that the difference between them is as large as 20 K) from skin air temperature. The parameterization also works well at high elevations where atmospheric parameter-based algorithms often have large biases. Furthermore, comparing different sources of atmospheric input data, we found that using the parameters interpolated from atmospheric reanalysis data improved the DLR estimation by 7.8 W/m2 for the new parameterization and 19.1 W/m2 for other algorithms at high-altitude sites, as compared to MODIS atmospheric products. downward longwave radiation; MODIS; parameterization; brightness temperature; ground-air temperature difference; water vapor content
Yu, Y.; Shi, J.; Wang, T.; Letu, H.; Yuan, P.; Zhou, W.; Hu, L.Yu, Y., J. Shi, T. Wang, H. Letu, P. Yuan, W. Zhou, L. Hu, 2019: Evaluation of the Himawari-8 Shortwave Downward Radiation (SWDR) Product and its Comparison With the CERES-SYN, MERRA-2, and ERA-Interim Datasets. IEEE Journal of Selected Topics in Applied Earth Observations and Remote Sensing, 12(2), 519-532. doi: 10.1109/JSTARS.2018.2851965. The land surface shortwave downward radiation (SWDR), also known as surface incident solar radiation, is usually defined as the total solar spectral energy between 300 nm and 3000 nm that arrives at the earth's surface. The SWDR is an essential variable for numerous land models and thus need to be accurately mapped using various approaches. Although numerous efforts have been made to assess the applicability and accuracy of the SWDR datasets produced by satellite and numeric models, few studies have evaluated the performance of the SWDR products from Himawari-8. In this paper, the Himawari-8 SWDR products with both 1 km and 5 km spatial scales were evaluated using ground measurements. The validation results indicate that both of the Himawari-8 SWDR products are in close agreement with ground measurements, even though obvious biases are found. Also, an in-depth intercomparison between the Himawari-8 SWDR product at a 5 km resolution and three other SWDR radiation datasets (CERES-SYN, MERRA-2, and ERA-Interim) was conducted. Here, the Himawari-8 showed the highest levels of accuracy among the four SWDR datasets. Considering its higher temporal and spatial resolutions, the Himawari-8 SWDR products are more detailed and provide the unprecedented potential to improve land surface modeling and reveal the cloud-radiation interactions, even at a 10-min temporal scale. Remote sensing; clouds; evaluation; ERA-Interim; atmospheric techniques; atmospheric radiation; Earth; Land surface; Atmospheric modeling; Sea surface; Earth surface; Himawari-8; Clouds; solar radiation; surface incident solar radiation; Clouds and the Earth's Radiant Energy System Synoptic (CERES-SYN); land surface shortwave downward radiation (SWDR); Modern-Era Retrospective Analysis for Research and Applications; Spatial resolution; Version 2 (MERRA-2); CERES-SYN dataset; cloud-radiation interactions; ERA-Interim dataset; ground measurements; Himawari-8 shortwave downward radiation product; Himawari-8 SWDR product; land models; land surface shortwave downward radiation; MERRA-2 dataset; numeric model; satellite model; size 1.0 km; size 5.0 km; SWDR datasets; SWDR products; SWDR radiation datasets; total solar spectral energy; wavelength 300.0 nm to 3000.0 nm
Yu, Yueyue; Taylor, Patrick C.; Cai, MingYu, Y., P. C. Taylor, M. Cai, 2019: Seasonal variations of Arctic low-level clouds and its linkage to sea ice seasonal variations. Journal of Geophysical Research: Atmospheres, 124(22), 12206-12226. doi: 10.1029/2019JD031014. Using CALIPSO-CloudSat-Clouds and the Earth's Radiant Energy System (CERES)-Moderate Resolution Imaging Spectrometer (MODIS) (C3M) dataset, this study documents the seasonal variation of sea ice, cloud, and atmospheric properties in the Arctic (70°N–82°N) for 2007–2010. A surface type stratification—consisting Permanent Ocean, Land, Permanent Ice, and Transient Sea Ice—is used to investigate the influence of surface type on low-level Arctic cloud liquid water path (LWP) seasonality. The results show significant variations in the Arctic low-level cloud LWP by surface type linked to differences in thermodynamic state. Subdividing the Transient Ice region (seasonal sea ice zone) by melt/freeze season onset dates reveals a complex influence of sea ice variations on low cloud LWP seasonality. We find that lower tropospheric stability (LTS) is the primary factor affecting the seasonality of cloud LWP. Our results suggest that variations in sea ice melt/freeze onset have a significant influence on the seasonality of low-level cloud LWP by modulating the lower tropospheric thermal structure and not by modifying the surface evaporation rate in late spring and mid-summer. We find no significant dependence of the May low-level cloud LWP peak on the melt/freeze onset dates, whereas and September/October low-level cloud LWP maximum shifts later in the season for earlier melt/later freeze onset regions. The Arctic low cloud LWP seasonality is controlled by several surface-atmosphere interaction processes; the importance of each varies seasonally due to the thermodynamic properties of sea ice. Our results demonstrate that when analyzing Arctic cloud-sea ice interactions, a seasonal perspective is critical. Arctic cloud; atmosphere-surface interactions; cloud-sea ice interactions; seasonal cycle
Yue, Qing; Kahn, Brian H.; Fetzer, Eric J.; Wong, Sun; Huang, Xianglei; Schreier, MathiasYue, Q., B. H. Kahn, E. J. Fetzer, S. Wong, X. Huang, M. Schreier, 2019: Temporal and Spatial Characteristics of Short-term Cloud Feedback on Global and Local Interannual Climate Fluctuations from A-Train Observations. J. Climate, 32(6), 1875–1893. doi: 10.1175/JCLI-D-18-0335.1. Observations from multiple sensors on the NASA Aqua satellite are used to estimate the temporal and spatial variability of short-term cloud responses (CR) and cloud feedbacks (λ) for different cloud types, with respect to the interannual variability within the A-Train era (July 2002-June 2017). Short-term cloud feedbacks by cloud type are investigated both globally and locally by three different definitions in the literature: (1) the global mean cloud feedback parameter λGG from regressing the global mean cloud-induced TOA radiation anomaly ΔRG with the global mean surface temperature change ΔTGS; (2) the local feedback parameter λLL from regressing the local ΔR with the local surface temperature change ΔTS; and (3) the local feedback parameter λGL from regressing global ΔRG with local ΔTS. Observations show significant temporal variability in the magnitudes and spatial patterns in λGG and λGL, whereas λLL remains essentially time invariant for different cloud types. The global mean net λGG exhibits a gradual transition from negative to positive in the A-Train era due to a less negative λGG from low clouds and an increased positive λGG from high clouds over the Warm Pool Region associated with the 2015-2016 strong El Niño event. Strong temporal variability in λGL is intrinsically linked to its dependence on global ΔRG, and the scaling of λGL with surface temperature change patterns to obtain global feedback λGG does not hold. Despite the shortness of the A-Train record, statistically robust signals can be obtained for different cloud types and regions of interest.
Zeng, Linglin; Hu, Shun; Xiang, Daxiang; Zhang, Xiang; Li, Deren; Li, Lin; Zhang, TingqiangZeng, L., S. Hu, D. Xiang, X. Zhang, D. Li, L. Li, T. Zhang, 2019: Multilayer Soil Moisture Mapping at a Regional Scale from Multisource Data via a Machine Learning Method. Remote Sensing, 11(3), 284. doi: 10.3390/rs11030284. Soil moisture mapping at a regional scale is commonplace since these data are required in many applications, such as hydrological and agricultural analyses. The use of remotely sensed data for the estimation of deep soil moisture at a regional scale has received far less emphasis. The objective of this study was to map the 500-m, 8-day average and daily soil moisture at different soil depths in Oklahoma from remotely sensed and ground-measured data using the random forest (RF) method, which is one of the machine-learning approaches. In order to investigate the estimation accuracy of the RF method at both a spatial and a temporal scale, two independent soil moisture estimation experiments were conducted using data from 2010 to 2014: a year-to-year experiment (with a root mean square error (RMSE) ranging from 0.038 to 0.050 m3/m3) and a station-to-station experiment (with an RMSE ranging from 0.044 to 0.057 m3/m3). Then, the data requirements, importance factors, and spatial and temporal variations in estimation accuracy were discussed based on the results using the training data selected by iterated random sampling. The highly accurate estimations of both the surface and the deep soil moisture for the study area reveal the potential of RF methods when mapping soil moisture at a regional scale, especially when considering the high heterogeneity of land-cover types and topography in the study area. remote sensing; ground monitoring; multilayer soil moisture mapping; RF method
Zhan, Chuan; Allan, Richard P.; Liang, Shunlin; Wang, Dongdong; Song, ZhenZhan, C., R. P. Allan, S. Liang, D. Wang, Z. Song, 2019: Evaluation of Five Satellite Top-of-Atmosphere Albedo Products over Land. Remote Sensing, 11(24), 2919. doi: 10.3390/rs11242919. Five satellite top-of-atmosphere (TOA) albedo products over land were evaluated in this study including global products from the Advanced Very High Resolution Radiometer (AVHRR) (TAL-AVHRR), Moderate Resolution Imaging Spectroradiometer (MODIS) (TAL-MODIS), and Clouds and the Earth’s Radiant Energy System (CERES); one regional product from the Climate Monitoring Satellite Application Facility (CM SAF); and one harmonized product termed Diagnosing Earth’s Energy Pathways in the Climate system (DEEP-C). Results showed that overall, there is good consistency among these five products, particularly after the year 2000. The differences among these products in the high-latitude regions were relatively larger. The percentage differences among TAL-AVHRR, TAL-MODIS, and CERES were generally less than 20%, while the differences between TAL-AVHRR and DEEP-C before 2000 were much larger. Except for the obvious decrease in the differences after 2000, the differences did not show significant changes over time, but varied among different regions. The differences between TAL-AVHRR and the other products were relatively large in the high-latitude regions of North America, Asia, and the Maritime Continent, while the differences between DEEP-C and CM SAF in Europe and Africa were smaller. Interannual variability was consistent between products after 2000, before which the differences among the three products were much larger. CERES; evaluation; TOA albedo; CM SAF; DEEP-C; TAL-AVHRR; TAL-MODIS
Zhang, Bosong; Kramer, Ryan J.; Soden, Brian J.Zhang, B., R. J. Kramer, B. J. Soden, 2019: Radiative Feedbacks Associated with the Madden–Julian Oscillation. J. Climate, 32(20), 7055-7065. doi: 10.1175/JCLI-D-19-0144.1. Radiative kernels derived from CloudSat/CALIPSO measurements are used to diagnose radiative feedbacks induced by the Madden–Julian oscillation (MJO). Over the Indo-Pacific warm pool, positive cloud and water vapor feedbacks are coincident with the convective envelope of the MJO during its active phases, whereas the lapse rate feedback shows faster eastward propagation than the convective envelope. During phase 2/3, when the convective envelope is over the Indian Ocean, water vapor exhibits a vertically coherent response, with the largest anomalies and strongest feedback in the midtroposphere. Though spatial structures of the feedbacks vary, the most prominent difference lies in the magnitude. Cloud changes induce the largest radiative perturbations associated with the MJO. It is also found that the strength of the cloud feedback per unit of precipitation is greater for strong MJO events, suggesting that the strength of individual MJO events is largely dictated by the magnitude of cloud radiative heating of the atmosphere. In addition, stronger radiative heating due to water vapor and clouds helps the MJO survive the barrier effect of the Maritime Continent, leading to farther eastward propagation. These results offer process-oriented metrics that could help to improve model simulations and predictions of the MJO in the future.
Zhang, Guang J.; Song, Xiaoliang; Wang, YongZhang, G. J., X. Song, Y. Wang, 2019: The double ITCZ syndrome in GCMs: A coupled feedback problem among convection, clouds, atmospheric and ocean circulations. Atmospheric Research, 229, 255-268. doi: 10.1016/j.atmosres.2019.06.023. The appearance of a spurious double ITCZ south of the equator in coupled general circulation models has been a stubborn problem ever since the beginning of coupled model development. This article reviews the past research in this area, with a focus on three possible major contributors to the double ITCZ biases: 1) the southeastern Pacific marine stratus clouds and associated warm sea surface temperature (SST) biases; 2) the extratropical shortwave absorption biases over Southern Ocean; and 3) convective parameterization. The negative biases in marine boundary layer clouds in the southeastern Pacific lead to warm SST biases. Through coupled atmosphere-ocean interactions, it contributes to the double ITCZ bias. Positive shortwave absorption biases over Southern Ocean is believed to be an extratropical contributor to the double ITCZ biases in models. Since the heat from excess shortwave absorption must be transported to the northern hemisphere by the Hadley circulation, the position of the ITCZ must shift southward. However, later research finds that reducing the extratropical shortwave absorption has little effect on the ITCZ position. One possibility is that some feedback mechanism involving subtropical low-level clouds as intermediary is missing. For convective parameterization, changes in various elements in convection schemes can have large impacts on the ITCZ simulation. It involves a complex chain of interactions among convection, large-scale atmospheric circulation, SST, and upper ocean circulation. In one scheme, changes in the scheme lead to the elimination of double ITCZ in all seasons, giving hope that we can finally take on the double ITCZ problem.
Zhang, Shuhua; Li, Xingong; She, Jiangfeng; Peng, XiaominZhang, S., X. Li, J. She, X. Peng, 2019: Assimilating remote sensing data into GIS-based all sky solar radiation modeling for mountain terrain. Remote Sensing of Environment, 231, 111239. doi: 10.1016/j.rse.2019.111239. Solar radiation is the ultimate energy resource of earth surface energy balance and the main driving force of atmospheric, ecological and hydrological processes. Solar radiation over complex terrain has large spatial and temporal variation because of terrain shading and high cloud heterogeneity. While most existing GIS-based solar radiation models only work under clear sky condition, this research presents a solar radiation model which considers both terrain shading and anisotropic cloud attenuation and diffuse radiation using MODIS atmospheric products. Specifically, we use skyshed map, sky cloud maps, and sky weight map to represent angular distribution of sky obstruction, anisotropic cloud properties, and diffuse radiance over hemispherical sky, respectively. Combining skyshed map, sky weight map and sky cloud maps, we develop a solar radiation model where 3D geometrical relationships among sun, cloud, and terrain are considered and anisotropic diffuse radiance and cloud attenuation are modeled. Model results are evaluated using field observations in the Kunlun Mountains of western China. At Terra and Aqua overpass time, our model performs well with a mean relative bias (MRB) of −0.2%. It underestimates in clear and partly cloudy sky with a MRB of −5.86% and −4.79% and has a mean absolute relative bias (MARB) of 8.11% and 21.59% respectively. It overestimates under overcast sky with a MRB of 1.68% and has a MARB of 31.71%. Our model performs better when compared with existing instantaneous solar radiation products. For daily solar radiation, our model shows good performance with a MRB of 1.43% and MARB of 17.02%. Our model shows significant spatial variation of solar radiation within the study area with the influences from terrain and cloud. Our research provides a novel and improved approach to assimilating remote sensing data into GIS-based solar radiation modeling in mountainous terrain where observations are sparse and difficult to obtain. Solar radiation; Cloud attenuation; Sky cloud map; Terrain shadow
Zhang, Taiping; Stackhouse, Paul W.; Cox, Stephen J.; Mikovitz, J. Colleen; Long, Charles N.Zhang, T., P. W. Stackhouse, S. J. Cox, J. C. Mikovitz, C. N. Long, 2019: Clear-sky shortwave downward flux at the Earth's surface: Ground-based data vs. satellite-based data. Journal of Quantitative Spectroscopy and Radiative Transfer, 224, 247-260. doi: 10.1016/j.jqsrt.2018.11.015. The radiative flux data and other meteorological data in the BSRN archive start in 1992, but the RadFlux data, the clear-sky radiative fluxes at the BSRN sites empirically inferred through regression analyses of actually observed clear-sky fluxes, did not come into existence until the early 2000s, and at first, they were limited to the 7 NOAA SURFRAD and 4 DOE ARM sites, a subset of the BSRN sites. Recently, the RadFlux algorithm was applied more extensively to the BSRN sites for the production of clear-sky ground-based fluxes. At the time of this writing, there are 7119 site-months of clear-sky fluxes at 42 BSRN sites spanning from 1992 to late 2017. These data provide an unprecedented opportunity to validate the satellite-based clear-sky fluxes. In this paper, the GEWEX SRB GSW(V3.0) clear-sky shortwave downward fluxes spanning 24.5 years from July 1983 to December 2007, the CERES SYN1deg(Ed4A) and EBAF(Ed4.0) clear-sky shortwave fluxes spanning March 2000 to mid-2017 are compared with their RadFlux counterparts on the hourly, 3-hourly, daily and monthly time scales. All the three datasets show reasonable agreement with their ground-based counterparts. Comparison of the satellite-based surface shortwave clear-sky radiative fluxes to the BSRN RadFlux analysis shows negative biases (satellite-based minus RadFlux). Further analysis shows that the satellite-based atmosphere contains greater aerosol loading as well as more precipitable water than RadFlux analysis estimates. CERES; Solar radiation; Satellite; GEWEX SRB; RadFlux
Zhang, Weiyu; Zhang, Xiaotong; Li, Wenhong; Hou, Ning; Wei, Yu; Jia, Kun; Yao, Yunjun; Cheng, JieZhang, W., X. Zhang, W. Li, N. Hou, Y. Wei, K. Jia, Y. Yao, J. Cheng, 2019: Evaluation of Bayesian Multimodel Estimation in Surface Incident Shortwave Radiation Simulation over High Latitude Areas. Remote Sensing, 11(15), 1776. doi: 10.3390/rs11151776. Surface incident shortwave radiation (SSR) is crucial for understanding the Earth’s climate change issues. Simulations from general circulation models (GCMs) are one of the most practical ways to produce long-term global SSR products. Although previous studies have comprehensively assessed the performance of the GCMs in simulating SSR globally or regionally, studies assessing the performance of these models over high-latitude areas are sparse. This study evaluated and intercompared the SSR simulations of 48 GCMs participating in the fifth phase of the Coupled Model Intercomparison Project (CMIP5) using quality-controlled SSR surface measurements at 44 radiation sites from three observation networks (GC-NET, BSRN, and GEBA) and the SSR retrievals from the Clouds and the Earth’s Radiant Energy System, Energy Balanced and Filled (CERES EBAF) data set over high-latitude areas from 2000 to 2005. Furthermore, this study evaluated the performance of the SSR estimations of two multimodel ensemble methods, i.e., the simple model averaging (SMA) and the Bayesian model averaging (BMA) methods. The seasonal performance of the SSR estimations of individual GCMs, the SMA method, and the BMA method were also intercompared. The evaluation results indicated that there were large deficiencies in the performance of the individual GCMs in simulating SSR, and these GCM SSR simulations did not show a tendency to overestimate the SSR over high-latitude areas. Moreover, the ensemble SSR estimations generated by the SMA and BMA methods were superior to all individual GCM SSR simulations over high-latitude areas, and the estimations of the BMA method were the best compared to individual GCM simulations and the SMA method-based estimations. Compared to the CERES EBAF SSR retrievals, the uncertainties of the SSR estimations of the GCMs, the SMA method, and the BMA method are relatively large during summer. CMIP5; Bayesian model averaging; general circulation models; high-latitude areas; multimodel ensembles; surface incident shortwave radiation
Zhang, Xiaotong; Wang, Dongdong; Liu, Qiang; Yao, Yunjun; Jia, Kun; He, Tao; Jiang, Bo; Wei, Yu; Ma, Han; Zhao, Xiang; Li, Wenhong; Liang, ShunlinZhang, X., D. Wang, Q. Liu, Y. Yao, K. Jia, T. He, B. Jiang, Y. Wei, H. Ma, X. Zhao, W. Li, S. Liang, 2019: An Operational Approach for Generating the Global Land Surface Downward Shortwave Radiation Product From MODIS Data. IEEE Transactions on Geoscience and Remote Sensing, 57(7), 4636-4650. doi: 10.1109/TGRS.2019.2891945. Surface shortwave net radiation (SSNR) and surface downward shortwave radiation (DSR) are the two surface shortwave radiation components in earth's radiation budget and the fundamental quantities of energy available at the earth's surface. Although several global radiation products from global circulation models, global reanalyses, and satellite observations have been released, their coarse spatial resolutions and low accuracies limit their application. In this paper, the Global LAnd Surface Satellite (GLASS) DSR product was generated from the Moderate Resolution Imaging Spectroradiometer top-of-atmosphere (TOA) spectral reflectance based on a direct-estimation method. First, the TOA reflectances were derived based on the atmospheric radiative transfer simulations under different solar/view geometries; second, a linear regression relationship between the TOA reflectance and SSNR was developed under various atmospheric conditions and surface properties for different solar/view geometries; third, the coefficients derived from the linear regression were used to compute the SSNR; and finally, the DSR was estimated using the SSNR estimates and broadband albedo at the surface. A 13-year (2003-2015) GLASS DSR product was generated at a 5-km spatial resolution and 1-day temporal resolution. Compared with the ground measurements collected from 525 stations from 2003 to 2005 around the world, the model-computed SSNR (DSR) had an overall bias of 8.82 (3.72) W/m2 and a root mean square error of 28.83 (32.84) W/m2 at the daily time scale. Moreover, the global land annual mean of the DSR was determined to be 184.8 W/m2 with a standard deviation of 0.8 W/m2 over a 13-year (2003-2015) period. Remote sensing; radiative transfer; MODIS; atmospheric techniques; atmospheric radiation; Earth; radiometry; Satellites; Land surface; Atmospheric modeling; Ocean temperature; Earth surface; remote sensing; atmospheric radiative transfer simulations; coarse spatial resolutions; Earth radiation budget; GLASS DSR product; global circulation models; global land annual mean; global land surface downward shortwave radiation product; Global LAnd Surface Satellite; global radiation products; global reanalyses; Globalirradiance; incident shortwave radiation; model-computed SSNR; solar-view geometries; SSNR estimates; surface shortwave net radiation; surface shortwave radiation components; TOA reflectance; top-of-atmosphere spectral reflectance
Zhang, Xiaoyan; Zhang, BaoqingZhang, X., B. Zhang, 2019: The responses of natural vegetation dynamics to drought during the growing season across China. Journal of Hydrology, 574, 706-714. doi: 10.1016/j.jhydrol.2019.04.084. Knowledge of vegetative responses to drought across hydroclimatic zones is crucial for understanding ecohydrologic cycles. Based on monthly self-calibrated Palmer drought severity index (PDSI), standardized precipitation evapotranspiration index (SPEI) at different time scales (1–48 month scales), and normalized difference vegetation index (NDVI), this study examined the relationship between natural vegetation dynamics and drought in the growing season during 1982–2012 at 293 sites over China. Pearson correlations between NDVI and drought indices (PDSI and SPEI) were employed to quantify the association between vegetation and drought. The results show that the Pearson correlations between PDSI and NDVI in growing season (CNP) ranged from −0.47 to 0.84, and the maximum correlation between SPEI and NDVI in growing season (MaxSPEI) ranged from −0.31 to 0.86, within which the negative correlations were mainly observed in the areas dominated by forest in south China. Moreover, the CNP was highly and nonlinearly related to the aridity index (∅) (MaxSPEI showed a similar trend). The relationship between CNP and ∅ indicated that, water stress was not the limiting factor for natural vegetation in humid regions (∅4.68; in extreme arid regions, the natural vegetation exhibited less sensitivity to drought. These tendencies could be seen worldwide. The varied physiological properties of plants and the response of photosynthesis to energy processes probably explain some discernible variation. Drought assessment; Drought impacts; Hydroclimatic zones; Vegetation variations; Water availability
Zhang, Yang; Jena, Chinmay; Wang, Kai; Paton-Walsh, Clare; Guérette, Élise-Andrée; Utembe, Steven; Silver, Jeremy David; Keywood, MelitaZhang, Y., C. Jena, K. Wang, C. Paton-Walsh, É. Guérette, S. Utembe, J. D. Silver, M. Keywood, 2019: Multiscale Applications of Two Online-Coupled Meteorology-Chemistry Models during Recent Field Campaigns in Australia, Part I: Model Description and WRF/Chem-ROMS Evaluation Using Surface and Satellite Data and Sensitivity to Spatial Grid Resolutions. Atmosphere, 10(4), 189. doi: 10.3390/atmos10040189. Air pollution and associated human exposure are important research areas in Greater Sydney, Australia. Several field campaigns were conducted to characterize the pollution sources and their impacts on ambient air quality including the Sydney Particle Study Stages 1 and 2 (SPS1 and SPS2), and the Measurements of Urban, Marine, and Biogenic Air (MUMBA). In this work, the Weather Research and Forecasting model with chemistry (WRF/Chem) and the coupled WRF/Chem with the Regional Ocean Model System (ROMS) (WRF/Chem-ROMS) are applied during these field campaigns to assess the models’ capability in reproducing atmospheric observations. The model simulations are performed over quadruple-nested domains at grid resolutions of 81-, 27-, 9-, and 3-km over Australia, an area in southeastern Australia, an area in New South Wales, and the Greater Sydney area, respectively. A comprehensive model evaluation is conducted using surface observations from these field campaigns, satellite retrievals, and other data. This paper evaluates the performance of WRF/Chem-ROMS and its sensitivity to spatial grid resolutions. The model generally performs well at 3-, 9-, and 27-km resolutions for sea-surface temperature and boundary layer meteorology in terms of performance statistics, seasonality, and daily variation. Moderate biases occur for temperature at 2-m and wind speed at 10-m in the mornings and evenings due to the inaccurate representation of the nocturnal boundary layer and surface heat fluxes. Larger underpredictions occur for total precipitation due to the limitations of the cloud microphysics scheme or cumulus parameterization. The model performs well at 3-, 9-, and 27-km resolutions for surface O3 in terms of statistics, spatial distributions, and diurnal and daily variations. The model underpredicts PM2.5 and PM10 during SPS1 and MUMBA but overpredicts PM2.5 and underpredicts PM10 during SPS2. These biases are attributed to inaccurate meteorology, precursor emissions, insufficient SO2 conversion to sulfate, inadequate dispersion at finer grid resolutions, and underprediction in secondary organic aerosol. The model gives moderate biases for net shortwave radiation and cloud condensation nuclei but large biases for other radiative and cloud variables. The performance of aerosol optical depth and latent/sensible heat flux varies for different simulation periods. Among all variables evaluated, wind speed at 10-m, precipitation, surface concentrations of CO, NO, NO2, SO2, O3, PM2.5, and PM10, aerosol optical depth, cloud optical thickness, cloud condensation nuclei, and column NO2 show moderate-to-strong sensitivity to spatial grid resolutions. The use of finer grid resolutions (3- or 9-km) can generally improve the performance for those variables. While the performance for most of these variables is consistent with that over the U.S. and East Asia, several differences along with future work are identified to pinpoint reasons for such differences. model evaluation; air quality; WRF/Chem; satellite retrievals; MUMBA; SPS1; SPS2; Sydney; WRF/Chem-ROMS
Zhang, Yuxiang; Li, Rui; Min, Qilong; Bo, Haixu; Fu, Yuyun; Wang, Yipu; Gao, ZongtingZhang, Y., R. Li, Q. Min, H. Bo, Y. Fu, Y. Wang, Z. Gao, 2019: The Controlling Factors of Atmospheric Formaldehyde (HCHO) in Amazon as Seen From Satellite. Earth and Space Science, 6(6), 959-971. doi: 10.1029/2019EA000627. To understand the relative importance of biogenic emission, biomass burning emission on volatile organic compounds in Amazon, the spatial and temporal correlations between atmospheric column-integrated formaldehyde (HCHO) and fire count, vegetation hydrological states index, surface solar radiation flux, near-surface air temperature are studied using synergized satellite products and reanalysis data. A recently developed microwave-based vegetation index (emissivity difference vegetation index, EDVI) with high temporal resolution is used for the linkages between vegetation and HCHO at daily scale with and without fire contaminations. At large regional scale, EDVI shows highest spatial correlation with HCHO indicating the important controlling effect of biogenic emission. In given subregions with frequent fires, the temporal variations of monthly HCHO show much stronger correlations with fire count. The temporal correlations between monthly HCHO and EDVI are vague and even negative in some subregions. Radiation and temperature show stable positive temporal correlations with HCHO, particularly in areas with few fires. After excluding the samples contaminated by fires, the daily temporal correlation between vegetation (EDVI) and HCHO becomes significant and positive in most areas except the northern rainforest with weak temporal variations of EDVI. We proposed a bilinear model of biogenic-emission-induced HCHO (B-HCHO) using radiation and EDVI as inputs. The bias between modeled long-term mean B-HCHO and satellite observation is less than 20%. And the daily time series of modeled B-HCHO matches observations as well. It is the first time to provide satellite observational evidences of the relative importance of biogenic emission and biomass burning emission on HCHO, the proxy of atmospheric volatile organic compounds concentration.
Zhang, Yuying; Xie, Shaocheng; Lin, Wuyin; Klein, Stephen A.; Zelinka, Mark; Ma, Po-Lun; Rasch, Philip J.; Qian, Yun; Tang, Qi; Ma, Hsi-YenZhang, Y., S. Xie, W. Lin, S. A. Klein, M. Zelinka, P. Ma, P. J. Rasch, Y. Qian, Q. Tang, H. Ma, 2019: Evaluation of Clouds in Version 1 of the E3SM Atmosphere Model with Satellite Simulators. Journal of Advances in Modeling Earth Systems, 11, 1253-1268. doi: 10.1029/2018MS001562. This study systematically evaluates clouds simulated by the Energy Exascale Earth System Model (E3SM) Atmosphere Model version one (EAMv1) against satellite cloud observations. Both low (1°) and high (0.25°) resolution EAMv1 configurations generally underestimate clouds in low and midlatitudes and overestimate clouds in the Arctic although the error is smaller in the high-resolution model. The underestimate of clouds is due to the underestimate of optically thin to intermediate clouds, as EAMv1 generally overestimates optically intermediate to thick clouds. Other model errors include the largely under-predicted marine stratocumulus along the coasts and high clouds over the tropical deep convection regions. The underestimate of thin clouds results in too much LW radiation being emitted to space and too little SW radiation being reflected back to space while the overestimate of optically intermediate and thick clouds leads to too little LW radiation being emitted to space and too much SW radiation being reflected back to space. EAMv1 shows better skill in reproducing the observed distribution of clouds and their properties and has smaller radiatively relevant errors in the distribution of clouds than most of the CFMIP1 and CFMIP2 models. It produces more supercooled liquid cloud fraction than CAM5 and most CMIP5 models primarily due to a new ice nucleation scheme and secondarily due to a reduction of the ice deposition growth rate.
Zheng, Lei; Zhao, Guosong; Dong, Jinwei; Ge, Quansheng; Tao, Jian; Zhang, Xuezhen; Qi, Youcun; Doughty, Russell B.; Xiao, XiangmingZheng, L., G. Zhao, J. Dong, Q. Ge, J. Tao, X. Zhang, Y. Qi, R. B. Doughty, X. Xiao, 2019: Spatial, temporal, and spectral variations in albedo due to vegetation changes in China’s grasslands. ISPRS Journal of Photogrammetry and Remote Sensing, 152, 1-12. doi: 10.1016/j.isprsjprs.2019.03.020. Changes in Earth’s albedo due to vegetation dynamics, snow cover, and land cover change have attracted much attention. However, the effects of vegetation dynamics on albedo have not been comprehensively documented according to its spatial (regional), temporal (within growing season), and spectral (visible, near-infrared, and shortwave) characteristics. This study examined the effects of vegetation greenness on albedo from 2000 to 2014 in China’s grasslands, which have considerable intra- and inter-annual variations, using remote sensing-based albedo and two-band Enhanced Vegetation Index (EVI2) data. Generally, we found an insignificant negative correlation between the shortwave (SW) albedo and EVI2 for grasslands in China. However, the visible (VIS) albedo was more sensitive to changes in vegetation greenness than near-infrared (NIR) albedo in China’s grasslands. The relationship between the NIR albedo and EVI2 was more complicated, especially in the Tibetan Plateau (TP), where the correlation was negative in the early growing season and positive in the late growing season; while the correlation between the NIR albedo and EVI2 was always negative in main part of Inner Mongolia (IM). The different albedo-EVI2 relationships in IM and TP may be related to differences in soil albedos. The higher sensitivity of the SW albedo to vegetation greenness change in IM, the stronger effect on land surface radiation budget. Our finding about vegetation-induced changes in albedo differ in space, time and spectral bands is expected to contribute to the improvement of land surface models. China; Climate change; Albedo; Grassland; Greenness
Zhong, Lei; Zou, Mijun; Ma, Yaoming; Huang, Ziyu; Xu, Kepiao; Wang, Xian; Ge, Nan; Cheng, MeilinZhong, L., M. Zou, Y. Ma, Z. Huang, K. Xu, X. Wang, N. Ge, M. Cheng, 2019: Estimation of Downwelling Shortwave and Longwave Radiation in the Tibetan Plateau Under All-Sky Conditions. Journal of Geophysical Research: Atmospheres, 124(21), 11086-11102. doi: 10.1029/2019JD030763. Downwelling shortwave radiation (DSWR) and downwelling longwave radiation (DLWR) are two important components of the Earth's surface radiation balance. In this study, the Heliosat method and the parameterization of Crawford and Duchon (1999, https://doi.org/10.1175/1520-0450(1999)0382.0.CO;2, hereafter CD99) were calibrated to make them suitable for estimation of DSWR and DLWR over the Tibetan Plateau (TP). Based on meteorological data, forcing data, and observations from polar-orbiting satellites, the cloud albedo was calculated, and the clear-sky index estimation scheme of the Heliosat method was improved. These improvements were then applied to derive 10-day DSWR under all-sky conditions over the TP by combining the clear-sky shortwave radiation scheme with a clear-sky index. The coefficient of the CD99 parameterization scheme clear-sky DLWR was also calibrated, and 10-day all-sky DLWR was then determined and validated using ground-based measurements. The spatiotemporal distributions of DSWR and DLWR were analyzed in detail. The results showed that the modified methods are efficient and applicable for downward radiation retrieval under all-sky conditions over the TP with a reasonable accuracy. The mean percentage errors for DSWR and DLWR were −4.75% and 0.11%, respectively. The variation in the monthly DSWR (DLWR) showed a convex shape, with a maximum appearing in May (July). The spatial distributions of DLWR showed a southeast-high and northwest-low pattern. As the subsolar point moves northward, DSWR increases gradually and is clearly influenced by the Asian summer monsoon.
Zou, Xun; Bromwich, David H.; Nicolas, Julien P.; Montenegro, Alvaro; Wang, Sheng-HungZou, X., D. H. Bromwich, J. P. Nicolas, A. Montenegro, S. Wang, 2019: West Antarctic Surface Melt Event of January 2016 Facilitated by Foehn Warming. Quarterly Journal of the Royal Meteorological Society, 145(719), 687-704. doi: 10.1002/qj.3460. The Ross Ice Shelf (RIS) buttresses ice streams from the Antarctic continent and restrains the grounded ice sheet from flowing into the ocean, which is important for the stability of the ice sheet. In recent decades, West Antarctic ice shelves, including the RIS, have experienced more frequent surface melting during summer. We investigated the role of warm, descending foehn winds in a major melt event that occurred on the RIS in January 2016. Only a few summer melt events of this magnitude have been observed since 1979. Backward trajectories from the area of earliest melting were constructed using the Antarctic Mesoscale Prediction System (AMPS) to investigate the dominant mechanisms at the beginning of the melt event, mainly from 10 to 13 January. Analysis was conducted over two distinct areas. The foehn effect contributed around 2-4 °C to the surface temperature increase over the coastal mountains of Marie Byrd Land (MBL) and around 1 °C over the much lower Edward VII Peninsula. Most of the foehn warming was caused by isentropic drawdown of air aloft. On 10 January, the second-most important contributor for both mountain ranges was the thermodynamic mechanism. On 11 January, the second-most important mechanism was the sensible and radiative heat flux. This study contributes to a better understanding of surface melt events over the RIS and benefits research associated with the stability of West Antarctic ice shelves. foehn warming; Ross Ice Shelf; surface melting; West Antarctic warming

2018

Abdel-Lathif, Ahmat Younous; Roehrig, Romain; Beau, Isabelle; Douville, HervéAbdel-Lathif, A. Y., R. Roehrig, I. Beau, H. Douville, 2018: Single-Column Modeling of Convection During the CINDY2011/DYNAMO Field Campaign With the CNRM Climate Model Version 6. Journal of Advances in Modeling Earth Systems, 45(5), 2404-2412. doi: 10.1002/2017MS001077. A single-column model (SCM) approach is used to assess the CNRM climate model (CNRM-CM) version 6 ability to represent the properties of the apparent heat source (Q1) and moisture sink (Q2) as observed during the 3 month CINDY2011/DYNAMO field campaign, over its Northern Sounding Array (NSA). The performance of the CNRM SCM is evaluated in a constrained configuration in which the latent and sensible heat surface fluxes are prescribed, as, when forced by observed sea surface temperature, the model is strongly limited by the underestimate of the surface fluxes, most probably related to the SCM forcing itself. The model exhibits a significant cold bias in the upper troposphere, near 200 hPa, and strong wet biases close to the surface and above 700 hPa. The analysis of the Q1 and Q2 profile distributions emphasizes the properties of the convective parameterization of the CNRM-CM physics. The distribution of the Q2 profile is particularly challenging. The model strongly underestimates the frequency of occurrence of the deep moistening profiles, which likely involve misrepresentation of the shallow and congestus convection. Finally, a statistical approach is used to objectively define atmospheric regimes and construct a typical convection life cycle. A composite analysis shows that the CNRM SCM captures the general transition from bottom-heavy to mid-heavy to top-heavy convective heating. Some model errors are shown to be related to the stratiform regimes. The moistening observed during the shallow and congestus convection regimes also requires further improvements of this CNRM-CM physics. 3371 Tropical convection; 3365 Subgrid-scale (SGS) parameterization; statistical analysis; tropical convection; CINDY2011/DYNAMO field campaign; single-column modeling; subgrid-scale (SGS) parameterization
Ahlgrimm, Maike; Forbes, Richard M.; Hogan, Robin J.; Sandu, IrinaAhlgrimm, M., R. M. Forbes, R. J. Hogan, I. Sandu, 2018: Understanding global model systematic shortwave radiation errors in subtropical marine boundary layer cloud regimes. Journal of Advances in Modeling Earth Systems, 10(8), 2042-2060. doi: 10.1029/2018MS001346. Global numerical weather prediction and climate models are subject to long-standing systematic shortwave radiation errors due to deficiencies in the representation of boundary layer clouds over the ocean. In the subtropics, clouds are typically too reflective in the cumulus regime and not reflective enough in the stratocumulus regime. Potential sources of error include cloud cover, liquid water path, effective radius and subgrid heterogeneity, but diagnosing the absolute contributions of each to the radiation bias is hampered by uncertainties and sometimes contradictory information from different observational products. This paper draws on a set of ship-based observations of boundary layer clouds obtained during the ARM MAGIC campaign along a north-east Pacific Ocean transect, crossing both stratocumulus and shallow cumulus cloud regimes. The surface-based observations of cloud properties are compared with various satellite products, taking account of the diurnal cycle, to provide an improved quantitative assessment of the deficiencies in the ECMWF global numerical weather prediction model. A series of offline radiation calculations are then performed to assess the impact on the shortwave radiation bias of “correcting” each of the model's deficiencies in cloud characteristics along the transect. A reduction in the bias is achieved by improving the agreement between modelled and observed in-cloud LWP frequency distributions. In the cumulus regime, this is accomplished primarily by reducing the all-sky water path, while for the stratocumulus regime, an underestimate of cloud cover and liquid water and an overestimate in effective radius and subgrid heterogeneity all contribute to a lack of reflected shortwave radiation. cloud properties; marine boundary layer clouds; shortwave bias
Ahn, Seo-Hee; Lee, Kyu-Tae; Rim, Se-Hun; Zo, Il-Sung; Kim, Bu-YoAhn, S., K. Lee, S. Rim, I. Zo, B. Kim, 2018: Surface Downward Longwave Radiation Retrieval Algorithm for GEO-KOMPSAT-2A/AMI. Asia-Pacific Journal of Atmospheric Sciences, 54(2), 237-251. doi: 10.1007/s13143-018-0007-1. This study contributes to the development of an algorithm to retrieve the Earth’s surface downward longwave radiation (DLR) for 2nd Geostationary Earth Orbit KOrea Multi-Purpose SATellite (GEO-KOMPSAT-2A; GK-2A)/Advanced Meteorological Imager (AMI). Regarding simulation data for algorithm development, we referred to Clouds and the Earth’s Radiant Energy System (CERES), and the European Centre for Medium-Range Weather Forecasts (ECMWF) ERA-interim reanalysis data. The clear sky DLR calculations were in good agreement with the Gangneung-Wonju National University (GWNU) Line-By-Line (LBL) model. Compared with CERES data, the Root Mean Square Error (RMSE) was 10.14Wm−2. In the case of cloudy sky DLR, we estimated the cloud base temperature empirically by utilizing cloud liquid water content (LWC) according to the cloud type. As a result, the correlation coefficients with CERES all sky DLRs were greater than 0.99. However, the RMSE between calculated DLR and CERES data was about 16.67Wm−2, due to ice clouds and problems of mismatched spatial and temporal resolutions for input data. This error may be reduced when GK-2A is launched and its products can be used as input data. Accordingly, further study is needed to improve the accuracy of DLR calculation by using high-resolution input data. In addition, when compared with BSRN surface-based observational data and retrieved DLR for all sky, the correlation coefficient was 0.86 and the RMSE was 31.55 Wm−2, which indicates relatively high accuracy. It is expected that increasing the number of experimental Cases will reduce the error.
Alamirew, N. K.; Todd, M. C.; Ryder, C. L.; Marsham, J. H.; Wang, Y.Alamirew, N. K., M. C. Todd, C. L. Ryder, J. H. Marsham, Y. Wang, 2018: The early summertime Saharan heat low: sensitivity of the radiation budget and atmospheric heating to water vapour and dust aerosol. Atmos. Chem. Phys., 18(2), 1241-1262. doi: 10.5194/acp-18-1241-2018. The Saharan heat low (SHL) is a key component of the west African climate system and an important driver of the west African monsoon across a range of timescales of variability. The physical mechanisms driving the variability in the SHL remain uncertain, although water vapour has been implicated as of primary importance. Here, we quantify the independent effects of variability in dust and water vapour on the radiation budget and atmospheric heating of the region using a radiative transfer model configured with observational input data from the Fennec field campaign at the location of Bordj Badji Mokhtar (BBM) in southern Algeria (21.4° N, 0.9° E), close to the SHL core for June 2011. Overall, we find dust aerosol and water vapour to be of similar importance in driving variability in the top-of-atmosphere (TOA) radiation budget and therefore the column-integrated heating over the SHL (∼  7 W m−2 per standard deviation of dust aerosol optical depth – AOD). As such, we infer that SHL intensity is likely to be similarly enhanced by the effects of dust and water vapour surge events. However, the details of the processes differ. Dust generates substantial radiative cooling at the surface (∼  11 W m−2 per standard deviation of dust AOD), presumably leading to reduced sensible heat flux in the boundary layer, which is more than compensated by direct radiative heating from shortwave (SW) absorption by dust in the dusty boundary layer. In contrast, water vapour invokes a radiative warming at the surface of ∼  6 W m−2 per standard deviation of column-integrated water vapour in kg m−2. Net effects involve a pronounced net atmospheric radiative convergence with heating rates on average of 0.5 K day−1 and up to 6 K day−1 during synoptic/mesoscale dust events from monsoon surges and convective cold-pool outflows (haboobs). On this basis, we make inferences on the processes driving variability in the SHL associated with radiative and advective heating/cooling. Depending on the synoptic context over the region, processes driving variability involve both independent effects of water vapour and dust and compensating events in which dust and water vapour are co-varying. Forecast models typically have biases of up to 2 kg m−2 in column-integrated water vapour (equivalent to a change in 2.6 W m−2 TOA net flux) and typically lack variability in dust and thus are expected to poorly represent these couplings. An improved representation of dust and water vapour and quantification of associated radiative impact in models is thus imperative to further understand the SHL and related climate processes.
Almeida, Cláudia M. de; Feitosa, Raul Q.; Hernandez, Jaime; Scavuzzo, Carlos M.; Aragão, Luiz E. O. C. deAlmeida, C. M. d., R. Q. Feitosa, J. Hernandez, C. M. Scavuzzo, L. E. O. C. d. Aragão, 2018: Coping with environmental challenges in Latin America. ISPRS Journal of Photogrammetry and Remote Sensing, 145, 211-212. doi: 10.1016/j.isprsjprs.2018.10.001.
Angal, A.; Xiong, X.; Mu, Q.; Doelling, D. R.; Bhatt, R.; Wu, A.Angal, A., X. Xiong, Q. Mu, D. R. Doelling, R. Bhatt, A. Wu, 2018: Results From the Deep Convective Clouds-Based Response Versus Scan-Angle Characterization for the MODIS Reflective Solar Bands. IEEE Transactions on Geoscience and Remote Sensing, 56(2), 1115-1128. doi: 10.1109/TGRS.2017.2759660. The Terra and Aqua Moderate-Resolution Imaging Spectroradiometer (MODIS) scan mirror reflectance is a function of the angle of incidence (AOI) and was characterized prior to launch by the instrument vendor. The relative change of the prelaunch response versus scan angle (RVS) is tracked and linearly scaled on-orbit using observations at two AOIs of 11.2° and 50.2° corresponding to the moon view and solar diffuser, respectively. As the missions continue to operate well beyond their design life of six years, the assumption of linear scaling between the two AOIs is known to be inadequate in accurately characterizing the RVS, particularly at short wavelengths. Consequently, an enhanced approach of supplementing the on-board measurements with response trends from desert pseudoinvariant calibration sites (PICS) was formulated in MODIS Collection 6 (C6). An underlying assumption for the continued effectiveness of this approach is the long-term (multiyear) and short-term (month to month) stability of the PICS. Previous work has shown that the deep convective clouds (DCC) can also be used to monitor the on-orbit RVS performance with less trend uncertainties compared with desert sites. In this paper, the raw sensor response to the DCC is used to characterize the on-orbit RVS on a band and mirror-side basis. These DCC-based RVS results are compared with those of C6 PICS-based RVS, showing an agreement within 2% observed in most cases. The pros and cons of using a DCC-based RVS approach are also discussed in this paper. Although this reaffirms the efficacy of the C6 PICS-based RVS, the DCC-based RVS approach presents itself as an effective alternative for future considerations. Potential applications of this approach to other instruments, such as Suomi National Polar-orbiting Partnership, Joint Polar Satellite Systems, and Visible Infrared Imaging Radiometer Suite, are also discussed.
Bair, Edward H.; Abreu Calfa, Andre; Rittger, Karl; Dozier, JeffBair, E. H., A. Abreu Calfa, K. Rittger, J. Dozier, 2018: Using machine learning for real-time estimates of snow water equivalent in the watersheds of Afghanistan. The Cryosphere Discussions, 1-21. doi: 10.5194/tc-2017-196. In the mountains, snowmelt often provides most of the runoff. Operational estimates use imagery from optical and passive microwave sensors, but each has its limitations. An accurate approach, which we validate in Afghanistan and the Sierra Nevada USA, reconstructs spatially distributed snow water equivalent (SWE) by calculating snowmelt backward from a remotely sensed date of disappearance. However, reconstructed SWE estimates are available only retrospectively; they do not provide a forecast. To estimate SWE throughout the snowmelt season, we consider physiographic and remotely sensed information as predictors and reconstructed SWE as the target. The period of analysis matches the AMSR-E radiometer’s lifetime from 2003 to 2011, for the months of April through June. The spatial resolution of the predictions is 3.125 km, to match the resolution of a microwave brightness temperature product. Two machine learning techniques – bagged regression trees and feed-forward neural networks – produced similar mean results, with 0–14 % bias and 46–48 mm RMSE on average. Nash–Sutcliffe efficiencies averaged 0.68 for all years. Daily SWE climatology and fractional snow-covered area are the most important predictors. We conclude that these methods can accurately estimate SWE during the snow season in remote mountains, and thereby provide an independent estimate to forecast runoff and validate other methods to assess the snow resource.
Balsamo, Gianpaolo; Agustì-Parareda, Anna; Albergel, Clément; Arduini, Gabriele; Beljaars, Anton; Bidlot, Jean; Bousserez, Nicolas; Boussetta, Souhail; Brown, Andy; Buizza, Roberto; Buontempo, Carlo; Chevallier, Frédéric; Choulga, Margarita; Cloke, Hannah; Cronin, Meghan F.; Dahoui, Mohamed; De Rosnay, Patricia; Dirmeyer, Paul A.; Drusch, Matthias; Dutra, Emanuel; Ek, Michael B.; Gentine, Pierre; Hewitt, Helene; Keeley, Sarah P. E.; Kerr, Yann; Kumar, Sujay; Lupu, Cristina; Mahfouf, Jean-François; McNorton, Joe; Mecklenburg, Susanne; Mogensen, Kristian; Muñoz-Sabater, Joaquín; Orth, Rene; Rabier, Florence; Reichle, Rolf; Ruston, Ben; Pappenberger, Florian; Sandu, Irina; Seneviratne, Sonia I.; Tietsche, Steffen; Trigo, Isabel F.; Uijlenhoet, Remko; Wedi, Nils; Woolway, R. Iestyn; Zeng, XubinBalsamo, G., A. Agustì-Parareda, C. Albergel, G. Arduini, A. Beljaars, J. Bidlot, N. Bousserez, S. Boussetta, A. Brown, R. Buizza, C. Buontempo, F. Chevallier, M. Choulga, H. Cloke, M. F. Cronin, M. Dahoui, P. De Rosnay, P. A. Dirmeyer, M. Drusch, E. Dutra, M. B. Ek, P. Gentine, H. Hewitt, S. P. E. Keeley, Y. Kerr, S. Kumar, C. Lupu, J. Mahfouf, J. McNorton, S. Mecklenburg, K. Mogensen, J. Muñoz-Sabater, R. Orth, F. Rabier, R. Reichle, B. Ruston, F. Pappenberger, I. Sandu, S. I. Seneviratne, S. Tietsche, I. F. Trigo, R. Uijlenhoet, N. Wedi, R. I. Woolway, X. Zeng, 2018: Satellite and In Situ Observations for Advancing Global Earth Surface Modelling: A Review. Remote Sensing, 10(12), 2038. doi: 10.3390/rs10122038. In this paper, we review the use of satellite-based remote sensing in combination with in situ data to inform Earth surface modelling. This involves verification and optimization methods that can handle both random and systematic errors and result in effective model improvement for both surface monitoring and prediction applications. The reasons for diverse remote sensing data and products include (i) their complementary areal and temporal coverage, (ii) their diverse and covariant information content, and (iii) their ability to complement in situ observations, which are often sparse and only locally representative. To improve our understanding of the complex behavior of the Earth system at the surface and sub-surface, we need large volumes of data from high-resolution modelling and remote sensing, since the Earth surface exhibits a high degree of heterogeneity and discontinuities in space and time. The spatial and temporal variability of the biosphere, hydrosphere, cryosphere and anthroposphere calls for an increased use of Earth observation (EO) data attaining volumes previously considered prohibitive. We review data availability and discuss recent examples where satellite remote sensing is used to infer observable surface quantities directly or indirectly, with particular emphasis on key parameters necessary for weather and climate prediction. Coordinated high-resolution remote-sensing and modelling/assimilation capabilities for the Earth surface are required to support an international application-focused effort. direct and inverse methods; earth system modelling; earth-observations
Beer, Tom; Li, Jianping; Alverson, KeithBeer, T., J. Li, K. Alverson, 2018: Global Change and Future Earth: The Geoscience Perspective. Global Change and Future Earth is derived from the work of several programs of the International Union of Geodesy and Geophysics (IUGG). It demonstrates how multi- and inter-disciplinary research outputs from the geoscience community can be applied to tackle the physical and societal impacts of climate change and contribute to the Future Earth programme of the International Council for Science. The volume brings together an international team of eminent researchers to provide authoritative reviews on the wide-ranging ramifications of climate change spanning eight key themes: planetary issues; geodetic issues; the Earth's fluid environment; regions of the Earth; urban environments; food security; and risk, safety and security; and climate change and global change. Covering the challenges faced by urban and rural areas, and in both developed and developing counties, this volume provides an important resource for a global audience of graduate students and researchers from a broad range of disciplines, as well as policy advisors and practitioners. Technology & Engineering / Agriculture / Agronomy / Soil Science; Science / Earth Sciences / Meteorology & Climatology; Science / Earth Sciences / Geology; Science / Earth Sciences / Hydrology; Science / Environmental Science; Science / Physics / Geophysics
Bender, F. A.-M.; Frey, L.; McCoy, D. T.; Grosvenor, D. P.; Mohrmann, J. K.Bender, F. A., L. Frey, D. T. McCoy, D. P. Grosvenor, J. K. Mohrmann, 2018: Assessment of aerosol–cloud–radiation correlations in satellite observations, climate models and reanalysis. Climate Dynamics, 1-22. doi: 10.1007/s00382-018-4384-z. Representing large-scale co-variability between variables related to aerosols, clouds and radiation is one of many aspects of agreement with observations desirable for a climate model. In this study such relations are investigated in terms of temporal correlations on monthly mean scale, to identify points of agreement and disagreement with observations. Ten regions with different meteorological characteristics and aerosol signatures are studied and correlation matrices for the selected regions offer an overview of model ability to represent present day climate variability. Global climate models with different levels of detail and sophistication in their representation of aerosols and clouds are compared with satellite observations and reanalysis assimilating meteorological fields as well as aerosol optical depth from observations. One example of how the correlation comparison can guide model evaluation and development is the often studied relation between cloud droplet number and water content. Reanalysis, with no parameterized aerosol–cloud coupling, shows weaker correlations than observations, indicating that microphysical couplings between cloud droplet number and water content are not negligible for the co-variations emerging on larger scale. These observed correlations are, however, not in agreement with those expected from dominance of the underlying microphysical aerosol–cloud couplings. For instance, negative correlations in subtropical stratocumulus regions show that suppression of precipitation and subsequent increase in water content due to aerosol is not a dominating process on this scale. Only in one of the studied models are cloud dynamics able to overcome the parameterized dependence of rain formation on droplet number concentration, and negative correlations in the stratocumulus regions are reproduced. Aerosol–cloud–radiation interaction; GCM-evaluation; Reanalysis; Satellite observations; Volcanic aerosol
Bhatt, Rajendra; Doelling, David; Haney, Conor; Scarino, Benjamin; Gopalan, Arun; Bhatt, Rajendra; Doelling, David; Haney, Conor; Scarino, Benjamin; Gopalan, ArunBhatt, R., D. Doelling, C. Haney, B. Scarino, A. Gopalan, R. Bhatt, D. Doelling, C. Haney, B. Scarino, A. Gopalan, 2018: Consideration of Radiometric Quantization Error in Satellite Sensor Cross-Calibration. Remote Sensing, 10(7), 1131. doi: 10.3390/rs10071131. The radiometric resolution of a satellite sensor refers to the smallest increment in the spectral radiance that can be detected by the imaging sensor. The fewer bits that are used for signal discretization, the larger the quantization error in the measured radiance. In satellite inter-calibration, a difference in radiometric resolution between a reference and a target sensor can induce a calibration bias, if not properly accounted for. The effect is greater for satellites with a quadratic count response, such as the Geostationary Meteorological Satellite-5 (GMS-5) visible imager, where the quantization difference can introduce non-linearity in the inter-comparison datasets, thereby affecting the cross-calibration slope and offset. This paper describes a simulation approach to highlight the importance of considering the radiometric quantization in cross-calibration and presents a correction method for mitigating its impact. The method, when applied to the cross-calibration of GMS-5 and Terra Moderate Resolution Imaging Spectroradiometer (MODIS) sensors, improved the absolute calibration accuracy of the GMS-5 imager. This was validated via radiometric inter-comparison of GMS-5 and Multifunction Transport Satellite-2 (MTSAT-2) imager top-of-atmosphere (TOA) measurements over deep convective clouds (DCC) and Badain Desert invariant targets. The radiometric bias between GMS-5 and MTSAT-2 was reduced from 1.9% to 0.5% for DCC, and from 7.7% to 2.3% for Badain using the proposed correction method. MODIS; calibration; GMS-5; quantization
Bran, Sherin Hassan; Jose, Subin; Srivastava, RohitBran, S. H., S. Jose, R. Srivastava, 2018: Investigation of optical and radiative properties of aerosols during an intense dust storm: A regional climate modeling approach. Journal of Atmospheric and Solar-Terrestrial Physics, 168, 21-31. doi: 10.1016/j.jastp.2018.01.003. The dynamical and optical properties of aerosols during an intense dust storm event over the Arabian Sea have been studied using Weather Research and Forecasting model coupled with Chemistry (WRF-Chem) and space borne instruments such as MODIS, MISR, CALIPSO and CERES during the period 17 to 24 March, 2012. The model captures the spatio-temporal and vertical variations of meteorological and optical parameters, however an overestimation in simulated aerosol optical parameters are observed when compared to satellite retrievals. The correlation coefficients (R) between simulated and observed AOD from MODIS and MISR are found to be 0.54 and 0.32 respectively. Model simulated AOD on dusty days (20 and 21 March 2012) increased by 2–3 times compared to non-dusty days (17 and 24 March 2012) and the single scattering albedo (SSA) and the asymmetry parameter increased from 0.96 to 0.99 and from 0.56 to 0.66, respectively. The R between simulated shortwave (SW) radiation at top of the atmosphere (TOA) and TOA SW radiation obtained from CERES is found to be 0.43, however the model simulated SW radiation at the TOA showed an underestimation with respect to CERES. The shortwave aerosol radiative forcing (SWARF) during the event over surface and TOA are ∼ -19.3 and ∼ -14.2 Wm-2 respectively, which is about 2–5 times higher when compared to the respective forcing values during non-dust days. Estimated net radiative forcing was in the range of −13 to −21 Wm-2 at TOA and −12 to −20 Wm-2 at the surface. The heating rate during event days within the lower atmosphere near 850 hPa is found to 0.32 − 0.4 K day−1 and 0.18 − 0.22 K day−1 on dusty and non-dusty days, respectively. Results of this study may be useful for a better modeling of atmospheric aerosols and its optical and radiative properties over oceanic region. Arabian Sea; AOD; SWARF; Dust storm; Heating rate; WRF-Chem
Bright, Ryan M.; Eisner, Stephanie; Lund, Marianne T.; Majasalmi, Titta; Myhre, Gunnar; Astrup, RasmusBright, R. M., S. Eisner, M. T. Lund, T. Majasalmi, G. Myhre, R. Astrup, 2018: Inferring Surface Albedo Prediction Error Linked to Forest Structure at High Latitudes. Journal of Geophysical Research: Atmospheres, 123(10), 4910-4925. doi: 10.1029/2018JD028293.
Bromwich, D. H.; Wilson, A. B.; Bai, L.; Liu, Z.; Barlage, M.; Shih, C.-F.; Maldonado, S.; Hines, K. M.; Wang, S.-H.; Woollen, J.; Kuo, B.; Lin, H.-C.; Wee, T.-K.; Serreze, M. C.; Walsh, J. E.Bromwich, D. H., A. B. Wilson, L. Bai, Z. Liu, M. Barlage, C. Shih, S. Maldonado, K. M. Hines, S. Wang, J. Woollen, B. Kuo, H. Lin, T. Wee, M. C. Serreze, J. E. Walsh, 2018: The Arctic System Reanalysis Version 2. Bull. Amer. Meteor. Soc., 99(4), 805–828. doi: 10.1175/BAMS-D-16-0215.1. The new regional-15 km Arctic System Reanalysis version 2 provides the accuracy and details necessary for many Arctic climate studies over the period 2000–2012.
Carmona, F.; Holzman, M.; Rivas, R.; Degano, M.F.; Kruse, E.; Bayala, M.Carmona, F., M. Holzman, R. Rivas, M. Degano, E. Kruse, M. Bayala, 2018: Evaluation of two models using CERES data for reference evapotranspiration estimation. Revista de Teledetección, 51, 87-98. doi: 10.4995/raet.2018.9259. Evapotranspiration is the most important variable in the Pampas plain. Information provided by sensors onboard satellite missions allows represent the spatial and temporal variability of evapotranspiration, which cannot be achieved using only measurements of weather stations. In this work, the Priestley and Taylor (PT) and FAO Penman Monteith (FAO PM) equations were adapted to estimate the reference evapotranspiration, ET 0 , using only CERES satellite products (SYN1 and CldTypHist). In order to evaluate the reference evapotranspiration from CERES, a comparison with in situ measurements was conducted. We used ET data provided by the Oficina de Riesgo Agropecuario, corresponding to 24 stations placed in the Pampean Region of Argentina (2001-2016). Results showed very good agreement between the estimates with CERES products and in situ values, with errors between ±0.8 and ±1.1 mm d– 1  and r 2  greater than 0.75  at daily scale, and errors between ±14  and ±19  mm month –1   and r 2   greater than 0.9, at monthly scale better results were obtained with adapted model FAO PM than PT. Finally, ET 0 monthly maps for the Pampean Region of Argentina were elaborated, which allowed knowing the temporal-spatial variation in the validation area. In conclusion, the methods presented here are a suitable alternative to estimate the reference evapotranspiration without requiring ground measurements.
Carmona, Facundo; Orte, P. Facundo; Rivas, Raúl; Wolfram, Elian; Kruse, EduardoCarmona, F., P. F. Orte, R. Rivas, E. Wolfram, E. Kruse, 2018: Development and Analysis of a New Solar Radiation Atlas for Argentina from Ground-Based Measurements and CERES_SYN1deg data. The Egyptian Journal of Remote Sensing and Space Science, 21(3), 211-217. doi: 10.1016/j.ejrs.2017.11.003. Currently, quantifying global solar radiation at surface in Argentina is crucial for the development of projects related to solar energy, calculation of evapotranspiration and eco-sustainability architecture, among other environmental issues. In recent years, several models have been developed to estimate the solar energy resources by means of various techniques, e.g. satellite imaging, kriging, or Artificial Neural Networks. The use of satellite data allows for a better spatial representation, being of great relevance in areas with lack of terrain measurements. In this paper, we use the CERES_SYN1deg to develop a new Global Solar Radiation Atlas for Argentina. In this study, we developed maps of annual and monthly mean daily global solar radiation using CERES_SYN1deg data between 2000 and 2016. In order to validate the global solar radiation data provided by CERES_SYN1deg, they were compared with ground-based measurements in the time overlap of both instruments, in four monitoring sites of the SAVER-Net project and an additional site in Tandil, which belongs to the Remote Sensing Group of IHLLA. The maps show the spatial and temporal variation of global solar radiation in Argentina. Comparisons with ground-based pyranometers reveal relative differences of around 3% at a monthly scale for all sites, while the biases can be neglected. Therefore, it is possible to conclude that the maps could be very useful for different technical and scientific purposes, and the comparison with ground-based data demonstrates CERES_SYN1deg’s reliability. Remote sensing; Global solar radiation; CERES_SYN1deg product; SAVER-Net
Chen, Dong; Loboda, Tatiana V.; He, Tao; Zhang, Yi; Liang, ShunlinChen, D., T. V. Loboda, T. He, Y. Zhang, S. Liang, 2018: Strong cooling induced by stand-replacing fires through albedo in Siberian larch forests. Scientific Reports, 8(1), 4821. doi: 10.1038/s41598-018-23253-1. The Siberian larch forests, taking up about a fifth of the global boreal biome, are different from the North American boreal forests in that they generally do not undergo a secondary succession. While wildfires in the boreal forests in North America have been shown to exert a cooling effect on the climate system through a sharp increase in surface albedo associated with canopy removal and species composition change during succession, the magnitude of the surface forcing resulting from fire-induced albedo change and its longevity in Siberia have not been previously quantified. Here we show that in contrast to previous expectations, stand-replacing fires exert a strong cooling effect similar in magnitude to that in North America. This cooling effect is attributable to the increase in surface albedo during snow-on periods. However, the observed earlier snowmelt in the region, and subsequently a longer snow-free season, has resulted in a warming effect which has the potential to offset the fire-induced cooling. The net albedo-induced forcing of the Siberian larch forests in the future would hinge on the interaction between the fire-induced cooling effect and the climate-induced warming effect, both of which will be impacted by the expected further warming in the region.
Chen, Xiuhong; Huang, Xianglei; Dong, Xiquan; Xi, Baike; Dolinar, Erica K.; Loeb, Norman G.; Kato, Seiji; Stackhouse, Paul W.; Bosilovich, Michael G.Chen, X., X. Huang, X. Dong, B. Xi, E. K. Dolinar, N. G. Loeb, S. Kato, P. W. Stackhouse, M. G. Bosilovich, 2018: Using AIRS and ARM SGP Clear-Sky Observations to Evaluate Meteorological Reanalyses: A Hyperspectral Radiance Closure Approach. Journal of Geophysical Research: Atmospheres, 123(20), 11,720-11,734. doi: 10.1029/2018JD028850. Using the ground-based measurements from the Atmospheric Radiation Measurement (ARM) Southern Great Plains (SGP) site and spectral radiance from the Atmospheric Infrared Sounder (AIRS) on National Aeronautics and Space Administration Aqua, we evaluate the temperature and humidity profiles from European Center for Medium Range Weather Forecasting ERA-Interim and Modern-Era Retrospective analysis for Research and Applications Version 2 reanalyses. Four sets of synthetic AIRS spectra are calculated using 51 clear-sky sounding profiles from the ARM SGP observations, the collocated AIRS L2 retrievals and the two reanalyses, respectively. A subset of AIRS channels sensitive to temperature, CO2, or H2O but not to other trace gases is chosen and further categorized into different groups according to the peak altitudes of their weighting functions. Synthetic radiances are then compared to the observed AIRS radiances for each group. For all groups, the observed AIRS radiances agree well with the synthetic ones based on the ARM SGP soundings or the AIRS L2 retrievals. The brightness temperature (BT) differences are within ±0.5 K. For two reanalyses, BT differences in all temperature-sensitive groups are generally within ±0.5 K; but the mean BT differences in all groups sensitive to both T and H2O are negative. Together, they suggest a wet bias in the free troposphere in both reanalyses. Moreover, such BT differences can be seen in the analysis of AIRS clear-sky radiances over the entire 30–40°N zone. A grid-search retrieval suggests that 9–30% reduction for reanalysis humidity between 200 and 800 hPa is needed to correct such wet bias. AIRS radiances; ARM soundings; reanalysis bias correction
Chen, Ying-Wen; Seiki, Tatsuya; Kodama, Chihiro; Satoh, Masaki; Noda, Akira T.Chen, Y., T. Seiki, C. Kodama, M. Satoh, A. T. Noda, 2018: Impact of Precipitating Ice Hydrometeors on Longwave Radiative Effect Estimated by a Global Cloud-System Resolving Model. Journal of Advances in Modeling Earth Systems, 10(2), 284-296. doi: 10.1002/2017MS001180. Satellite observation and general circulation model (GCM) studies suggest that precipitating ice makes nonnegligible contributions to the radiation balance of the Earth. However, in most GCMs, precipitating ice is diagnosed and its radiative effects are not taken into account. Here we examine the longwave radiative impact of precipitating ice using a global nonhydrostatic atmospheric model with a double-moment cloud microphysics scheme. An off-line radiation model is employed to determine cloud radiative effects according to the amount and altitude of each type of ice hydrometeor. Results show that the snow radiative effect reaches 2 W m−2 in the tropics, which is about half the value estimated by previous studies. This effect is strongly dependent on the vertical separation of ice categories and is partially generated by differences in terminal velocities, which are not represented in GCMs with diagnostic precipitating ice. Results from sensitivity experiments that artificially change the categories and altitudes of precipitating ice show that the simulated longwave heating profile and longwave radiation field are sensitive to the treatment of precipitating ice in models. This study emphasizes the importance of incorporating appropriate treatments for the radiative effects of precipitating ice in cloud and radiation schemes in GCMs in order to capture the cloud radiative effects of upper level clouds. 0321 Cloud/radiation interaction; 1620 Climate dynamics; global cloud-system resolving modeling; longwave radiation impact; precipitating ice hydrometeors
Chepfer, H.; Noel, V.; Chiriaco, M.; Wielicki, B.; Winker, D.; Loeb, N.; Wood, R.Chepfer, H., V. Noel, M. Chiriaco, B. Wielicki, D. Winker, N. Loeb, R. Wood, 2018: The Potential of a Multidecade Spaceborne Lidar Record to Constrain Cloud Feedback. Journal of Geophysical Research: Atmospheres, 123(10), 5433-5454. doi: 10.1002/2017JD027742. Synthetic multidecadal spaceborne lidar records are used to examine when a cloud response to anthropogenic forcing would be detectable from spaceborne lidar observations. The synthetic records are generated using long-term cloud changes predicted by two Coupled Model Intercomparison Program 5 models seen through the COSP/lidar (CFMIP, Cloud Feedback Model Intercomparison Project, Observation Simulators Package) and cloud interannual variability observed by the CALIPSO (Cloud Aerosol Lidar and Infrared Pathfinder Satellite Observations) spaceborne lidar during the past decade. CALIPSO observations do not show any significant trend yet. Our analysis of the synthetic time series suggests that the tropical cloud longwave feedback and the Southern Ocean cloud shortwave feedback might be constrained with 70% confidence with, respectively, a 20-year and 29-year uninterrupted lidar-in-space record. A 27-year record might be needed to separate the two different model predictions in the tropical subsidence clouds. Assuming that combining the CALIPSO and Earth-CARE (Earth Clouds, Aerosols and Radiation Explorer) missions will lead to a spaceborne lidar record of at least 16 years, we examine the impact of gaps and calibration offsets between successive missions. A 2-year gap between Earth-CARE and the following spaceborne lidar would have no significant impact on the capability to constrain the cloud feedback if all the space lidars were perfectly intercalibrated. Any intercalibration shift between successive lidar missions would delay the capability to constrain the cloud feedback mechanisms, larger shifts leading to longer delays. clouds; climate; space lidar
Ciesielski, Paul E.; Johnson, Richard H.; Schubert, Wayne H.; Ruppert, James H.Ciesielski, P. E., R. H. Johnson, W. H. Schubert, J. H. Ruppert, 2018: Diurnal Cycle of the ITCZ in DYNAMO. J. Climate, 31(11), 4543–4562. doi: 10.1175/JCLI-D-17-0670.1. During the 2011 special observing period of the Dynamics of the Madden-Julian Oscillation (DYNAMO; MJO) field experiment, two sounding arrays were established over the central Indian Ocean, one north and one south of the equator, referred to here as the NSA and SSA, respectively. Three-hourly soundings from these arrays augmented by observations of radiation and rainfall are used to investigate the diurnal cycle of ITCZ convection during the MJO suppressed phase. During the first half of October when convection was suppressed over the NSA but prominent over the SSA, the circulation over the sounding arrays could be characterized as a local Hadley cell. Strong rising motion was present within the ITCZ extending across the SSA with compensating subsidence over the NSA. A prominent diurnal pulsing of this cell was observed, impacting conditions on both sides of the equator, with the cell running strongest in the early morning hours (05-08 LT) and notably weakening later in the day (17-20LT). The declining daytime subsidence over the NSA may have assisted the moistening of the low to mid-troposphere there during the pre-onset stage of the MJO. Apparent heating Q1 within the ITCZ exhibited a diurnal evolution from early morning bottom-heavy profiles to weaker daytime top-heavy profiles, indicating a progression from convective to stratiform precipitation. Making use of the weak temperature gradient approximation, results suggest that both horizontal radiative heating gradients and direct cloud radiative forcing have an important influence on diurnal variations of vertical motion and convection within the ITCZ.
Collier, Nathan; Hoffman, Forrest M.; Lawrence, David M.; Keppel‐Aleks, Gretchen; Koven, Charles D.; Riley, William J.; Mu, Mingquan; Randerson, James T.Collier, N., F. M. Hoffman, D. M. Lawrence, G. Keppel‐Aleks, C. D. Koven, W. J. Riley, M. Mu, J. T. Randerson, 2018: The International Land Model Benchmarking (ILAMB) System: Design, Theory, and Implementation. Journal of Advances in Modeling Earth Systems, 10(11), 2731-2754. doi: 10.1029/2018MS001354. The increasing complexity of Earth system models (ESMs) has inspired efforts to quantitatively assess model fidelity through rigorous comparison with best-available measurements and observational data products. ESMs exhibit a high degree of spread in predictions of land biogeochemistry, biogeophysics, and hydrology, which are sensitive to forcing from other model components. Based on insights from prior land model evaluation studies and community workshops, the authors developed an open source model benchmarking software package that generates graphical diagnostics and scores model performance in support of the International Land Model Benchmarking (ILAMB) project. Employing a suite of in situ, remote sensing, and reanalysis datasets, the ILAMB package performs comprehensive model assessment across a wide range of land variables and generates a hierarchical set of webpages containing statistical analyses and figures designed to provide the user insights into strengths and weaknesses of multiple models or model versions. Described here is the benchmarking philosophy and mathematical methodology embodied in the most recent implementation of the ILAMB package. Comparison methods unique to a few specific datasets are presented, and guidelines for configuring an ILAMB analysis and interpreting resulting model performance scores are discussed. ILAMB is being adopted by modeling teams and centers during model development and for model intercomparison projects, and community engagement is sought for extending evaluation metrics and adding new observational datasets to the benchmarking framework. model evaluation; benchmarking; earth system model
Crueger, T.; Giorgetta, M. A.; Brokopf, R.; Esch, M.; Fiedler, S.; Hohenegger, C.; Kornblueh, L.; Mauritsen, T.; Nam, C.; Naumann, A. K.; Peters, K.; Rast, S.; Roeckner, E.; Sakradzija, M.; Schmidt, H.; Vial, J.; Vogel, R.; Stevens, B.Crueger, T., M. A. Giorgetta, R. Brokopf, M. Esch, S. Fiedler, C. Hohenegger, L. Kornblueh, T. Mauritsen, C. Nam, A. K. Naumann, K. Peters, S. Rast, E. Roeckner, M. Sakradzija, H. Schmidt, J. Vial, R. Vogel, B. Stevens, 2018: ICON-A, The Atmosphere Component of the ICON Earth System Model: II. Model Evaluation. Journal of Advances in Modeling Earth Systems, 10(7), 1638-1662. doi: 10.1029/2017MS001233. We evaluate the new icosahedral nonhydrostatic atmospheric (ICON-A) general circulation model of the Max Planck Institute for Meteorology that is flexible to be run at grid spacings from a few tens of meters to hundreds of kilometers. A simulation with ICON-A at a low resolution (160 km) is compared to a not-tuned fourfold higher-resolution simulation (40 km). Simulations using the last release of the ECHAM climate model (ECHAM6.3) are also presented at two different resolutions. The ICON-A simulations provide a compelling representation of the climate and its variability. The climate of the low-resolution ICON-A is even slightly better than that of ECHAM6.3. Improvements are obtained in aspects that are sensitive to the representation of orography, including the representation of cloud fields over eastern-boundary currents, the latitudinal distribution of cloud top heights, and the spatial distribution of convection over the Indian Ocean and the Maritime Continent. Precipitation over land is enhanced, in particular at high-resolution ICON-A. The response of precipitation to El Niño sea surface temperature variability is close to observations, particularly over the eastern Indian Ocean. Some parameterization changes lead to improvements, for example, with respect to rain intensities and the representation of equatorial waves, but also imply a warmer troposphere, which we suggest leads to an unrealistic poleward mass shift. Many biases familiar to ECHAM6.3 are also evident in ICON-A, namely, a too zonal SPCZ, an inadequate representation of north hemispheric blocking, and a relatively poor representation of tropical intraseasonal variability. model; circulation; general
Dai, Z.; Weisenstein, D. K.; Keith, D. W.Dai, Z., D. K. Weisenstein, D. W. Keith, 2018: Tailoring meridional and seasonal radiative forcing by sulfate aerosol solar geoengineering. Geophysical Research Letters, 45(2), 1030-1039. doi: 10.1002/2017GL076472. We study the possibility of designing solar radiation management schemes to achieve a desired meridional radiative forcing (RF) profile using a two-dimensional chemistry-transport-aerosol model. Varying SO2 or H2SO4 injection latitude, altitude, and season, we compute RF response functions for a broad range of possible injection schemes, finding that linear combinations of these injection cases can roughly achieve RF profiles that have been proposed to accomplish various climate objectives. Globally averaged RF normalized by the sulfur injection rate (the radiative efficacy) is largest for injections at high altitudes, near the equator, and using emission of H2SO4 vapor into an aircraft wake to produce accumulation-mode particles. There is a trade-off between radiative efficacy and control as temporal and spatial control is best achieved with injections at lower altitudes and higher latitudes. These results may inform studies using more realistic models that couple aerosol microphysics, chemistry, and stratospheric dynamics. 0305 Aerosols and particles; Solar geoengineering; Stratospheric H2SO4 injection; Stratospheric SO2 injection
Dessler, A. E.; Forster, P. M.Dessler, A. E., P. M. Forster, 2018: An estimate of equilibrium climate sensitivity from interannual variability. Journal of Geophysical Research: Atmospheres, 123(16), 8634-8645. doi: 10.1029/2018JD028481. Estimating the equilibrium climate sensitivity (ECS; the equilibrium warming in response to a doubling of CO2) from observations is one of the big problems in climate science. Using observations of interannual climate variations covering the period 2000 to 2017 and a model-derived relationship between interannual variations and forced climate change, we estimate ECS is likely 2.4-4.6 K (17-83% confidence interval), with a mode and median value of 2.9 and 3.3 K, respectively. This analysis provides no support for low values of ECS (below 2 K) suggested by other analyses. The main uncertainty in our estimate is not observational uncertainty, but rather uncertainty in converting observations of short-term, mainly unforced climate variability to an estimate of the response of the climate system to long-term forced warming. equilibrium climate sensitivity; interannual variability
Dessler, A. E.; Mauritsen, T.; Stevens, B.Dessler, A. E., T. Mauritsen, B. Stevens, 2018: The influence of internal variability on Earth's energy balance framework and implications for estimating climate sensitivity. Atmos. Chem. Phys., 18(7), 5147-5155. doi: 10.5194/acp-18-5147-2018.
Dewey, M.; Goldblatt, C.Dewey, M., C. Goldblatt, 2018: Evidence for Radiative-Convective Bistability in Tropical Atmospheres. Geophysical Research Letters, 45(19), 10,673-10,681. doi: 10.1029/2018GL078903. Earth's energy balance requires that energy absorbed and emitted at the top of the atmosphere be equal; to first order this balance is maintained via the Planck feedback: outgoing longwave radiation increases as surface temperature increases. Failure of the Planck feedback to stabilize the climate is described by three generally independent phenomena: the super-greenhouse effect, the runaway greenhouse, and multiple equilibria of radiative-convective atmospheres. Here we use satellite observations and models to show that the existence of the super-greenhouse gives rise to a radiative-convective instability which is relevant to Earth's tropics. The super-greenhouse is caused by the low troposphere becoming optically thick, causing a positive feedback on near surface temperature and moisture, driving deep convection, column moistening, and reduced outgoing longwave radiation. Aspects of the runaway greenhouse physics are implicated, but a local runaway greenhouse is avoided. These results have implications for understanding the response of the tropics to a warming world. clouds; convection; tropics; satellite observations; super-greenhouse effect; runaway greenhouse
Dewitte, Steven; Clerbaux, NicolasDewitte, S., N. Clerbaux, 2018: Decadal Changes of Earth’s Outgoing Longwave Radiation. Remote Sensing, 10(10), 1539. doi: 10.3390/rs10101539. The Earth Radiation Budget (ERB) at the top of the atmosphere quantifies how the earth gains energy from the sun and loses energy to space. Its monitoring is of fundamental importance for understanding ongoing climate change. In this paper, decadal changes of the Outgoing Longwave Radiation (OLR) as measured by the Clouds and Earth’s Radiant Energy System from 2000 to 2018, the Earth Radiation Budget Experiment from 1985 to 1998, and the High-resolution Infrared Radiation Sounder from 1985 to 2018 are analysed. The OLR has been rising since 1985, and correlates well with the rising global temperature. An observational estimate of the derivative of the OLR with respect to temperature of 2.93 +/− 0.3 W/m 2 K is obtained. The regional patterns of the observed OLR change from 1985–2000 to 2001–2017 show a warming pattern in the Northern Hemisphere in particular in the Arctic, as well as tropical cloudiness changes related to a strengthening of La Niña. earth radiation budget; outgoing longwave radiation
Doelling, David; Haney, Conor; Bhatt, Rajendra; Scarino, Benjamin; Gopalan, ArunDoelling, D., C. Haney, R. Bhatt, B. Scarino, A. Gopalan, 2018: Geostationary Visible Imager Calibration for the CERES SYN1deg Edition 4 Product. Remote Sensing, 10(2), 288. doi: 10.3390/rs10020288. The Clouds and the Earth’s Radiant Energy System (CERES) project relies on geostationary (GEO) imager derived TOA broadband fluxes and cloud properties to account for the regional diurnal fluctuations between the Terra and Aqua CERES and MODIS measurements. Anchoring the GEO visible calibration to the MODIS reference calibration and stability is critical for consistent fluxes and cloud retrievals across the 16 GEO imagers utilized in the CERES record. The CERES Edition 4A used GEO and MODIS ray-matched radiance pairs over all-sky tropical ocean (ATO-RM) to transfer the MODIS calibration to the GEO imagers. The primary GEO ATO-RM calibration was compared with the deep convective cloud (DCC) ray-matching and invariant desert/DCC target calibration methodologies, which are all tied to the same Aqua-MODIS calibration reference. Results indicate that most GEO record mean calibration method biases are within 1% with respect to ATO-RM. Most calibration method temporal trends were within 0.5% relative to ATO-RM. The monthly gain trend standard errors were mostly within 1% for all methods and GEOs. The close agreement amongst the independent calibration techniques validates all methodologies, and verifies that the coefficients are not artifacts of the methodology but rather adequately represent the true GEO visible imager degradation. MODIS; calibration; DCC; Earth invariant targets; geostationary; ray-matching
Donahue, Aaron S.; Caldwell, Peter M.Donahue, A. S., P. M. Caldwell, 2018: Impact of Physics Parameterization Ordering in A Global Atmosphere Model. Journal of Advances in Modeling Earth Systems, 10(2), 481–499. doi: 10.1002/2017MS001067. Because weather and climate models must capture a wide variety of spatial and temporal scales, they rely heavily on parameterizations of sub-grid scale processes. The goal of this study is to demonstrate that the assumptions used to couple these parameterizations have an important effect on the climate of version 0 of the Energy Exascale Earth System Model (E3SM) General Circulation Model (GCM), a close relative of version 1 of the Community Earth System Model (CESM1). Like most GCMs, parameterizations in E3SM are sequentially split in the sense that parameterizations are called one after another with each subsequent process feeling the effect of the preceding processes. This coupling strategy is non-commutative in the sense that the order in which processes are called impacts the solution. By examining a suite of 24 simulations with deep convection, shallow convection, macrophysics/microphysics, and radiation parameterizations reordered, process order is shown to have a big impact on predicted climate. In particular, reordering of processes induces differences in net climate feedback that are as big as the inter-model spread in phase 5 of the Coupled Model Inter-comparison Project. One reason why process ordering has such a large impact is that the effect of each process is influenced by the processes preceding it. Where output is written is therefore an important control on apparent model behavior. Application of K-means clustering demonstrates that the positioning of macro-/micro- physics and shallow convection plays a critical role on the model solution. 3305 Climate change and variability; 3365 Subgrid-scale (SGS) parameterization; 3337 Global climate models; 3336 Numerical approximations and analyses; 3367 Theoretical modeling; Global Climate Models; Net Climate Feedback; Physics Parameterizations; Sequential Time Splitting
Douglas, Alyson; L'Ecuyer, TristanDouglas, A., T. L'Ecuyer, 2018: Understanding Aerosol-Cloud-Radiation Interactions Using Local Meteorology and Cloud State Constraints. Atmospheric Chemistry and Physics Discussions, 1-25. doi: 10.1029/2018GL078903. Abstract. While many studies have tried to quantify the sign and the magnitude of the warm cloud response to aerosol loading, both remain uncertain owing to the multitude of factors that modulate microphysical and thermodynamic processes within the cloud. Constraining aerosol-cloud interactions using the local meteorology and cloud liquid water may offer a way to account for covarying influences, potentially increasing our confidence in observational estimates of warm cloud indirect effects. Four years of collocated satellite observations from the NASA A-Train constellation, combined with reanalaysis from MERRA-2, are used to partition warm clouds into regimes based on stability, the free atmospheric relative humidity, and liquid water path. Organizing the sizable number of satellite observations into regimes is shown to minimize the covariance between the environment or liquid water path and the indirect effect. Controlling for local meteorology and cloud state mitigates artificial signals and reveals substantial variance in both the sign and magnitude of the cloud radiative response, including regions where clouds become systematically darker with increased aerosol concentration in dry, unstable environments. The reverse Twomey effect, as it has been called, is evident even under the most stringent of constraints, confirming it is not an artificial signal or an isolated phenomenon. These results suggest it is not meaningful to report a single global sensitivity of cloud radiative effect to aerosol. To the contrary, we find the sensitivity can range from −.46 to .11 Wm−2ln(AI) regionally.
Draper, Clara S.; Reichle, Rolf H.; Koster, Randal D.Draper, C. S., R. H. Reichle, R. D. Koster, 2018: Assessment of MERRA-2 Land Surface Energy Flux Estimates. J. Climate, 31(2), 671–691. doi: 10.1175/JCLI-D-17-0121.1. In the Modern-Era Retrospective analysis for Research and Applications, version 2 (MERRA-2) system the land is forced by replacing the model-generated precipitation with observed precipitation before it reaches the surface. This approach is motivated by the expectation that the resultant improvements in soil moisture will lead to improved land surface latent heating (LH). Here we assess aspects of the MERRA-2 land surface energy budget and 2 m air temperatures (T2m). For global land annual averages, MERRA-2 appears to overestimate the LH (by 5 Wm−2 ), the sensible heating (by 6 Wm−2), and the downwelling shortwave radiation (by 14 Wm−2), while underestimating the downwelling and upwelling (absolute) longwave radiation (by 10-15 Wm−2 each). These results differ only slightly from those for NASA’s previous reanalysis, MERRA. Comparison to various gridded reference data sets over Boreal summer (June-July-August) suggests that MERRA-2 has particularly large positive biases (>20 Wm−2) where LH is energy-limited, and that these biases are associated with evaporative fraction biases rather than radiation biases. For time series of monthly means during Boreal summer, the globally averaged anomaly correlations (Ranom) with reference data were improved from MERRA to MERRA-2, for LH (from 0.39 to 0.48 vs. GLEAM data) and the daily maximum T2m (from 0.69 to 0.75 vs. CRU data). In regions where T2m is particularly sensitive to the precipitation corrections (including the central US, the Sahel, and parts of south Asia), the changes in the T2m Ranom are relatively large, suggesting that the observed precipitation influenced the T2m performance.
Duda, David P.; Bedka, Sarah T.; Minnis, Patrick; Spangenberg, Douglas; Khlopenkov, Konstantin; Chee, Thad; Smith Jr., William L.Duda, D. P., S. T. Bedka, P. Minnis, D. Spangenberg, K. Khlopenkov, T. Chee, W. L. Smith Jr., 2018: Northern Hemisphere Contrail Properties Derived from Terra and Aqua MODIS Data for 2006 and 2012. Atmospheric Chemistry and Physics Discussions, 1-30. doi: 10.5194/acp-2018-993. Abstract. Linear contrail coverage, optical property, and radiative forcing data over the Northern Hemisphere (NH) are derived from a year (2012) of Terra and Aqua Moderate-resolution Imaging Spectroradiometer (MODIS) imagery, and are compared with previously published 2006 results (Duda et al., 2013; Bedka et al., 2013; Spangenberg et al., 2013) using a consistent retrieval methodology. Differences in the observed Terra-minus-Aqua screened contrail coverage and patterns in the 2012 annual-mean air traffic estimated with respect to satellite overpass time suggest that most contrails detected by the contrail detection algorithm (CDA) form approximately 2h before overpass time. The 2012 screened NH contrail coverage (Mask B) shows a relative 3% increase (from 0.136% to 0.140%) compared to 2006 data for Terra and increased by almost 7% (0.134% to 0.143%) for Aqua. A new post-processing algorithm added to the contrail mask processing estimated that the total contrail cirrus coverage visible in the MODIS imagery may be three to four times larger than the linear contrail coverage detected by the CDA. This estimate is similar in magnitude to the spreading factor estimated by Minnis et al. (2013). Contrail property retrievals of the 2012 data indicate that both contrail optical depth and contrail effective diameter decreased approximately 10% between 2006 and 2012. The decreases may be attributed to better background cloudiness characterization, changes in the waypoint screening, or changes in contrail temperature. The total mean contrail radiative forcing (TCRF) for all 2012 Terra observations were −6.3, 14.3, and 8.0mWm−2 for the shortwave (SWCRF), longwave (LWCRF), and net forcings, respectively. These values are approximately 20% less than the corresponding 2006 Terra estimates. The decline in TCRF results from the decrease in normalized CRF, partially offset by the 3% increase in overall contrail coverage in 2012. The TCRFs for 2012 Aqua are similar, −6.4, 15.5, and 9.0mWm−2 for shortwave, longwave, and net radiative forcing. The strong correlation between the relative changes in both total SWCRF and LWCRF between 2006 and 2012 and the corresponding relative changes in screened contrail coverage over each air traffic region suggests that regional changes in TCRF from year to year are dominated by interannual changes in contrail coverage over each area.
Duveiller, Gregory; Hooker, Josh; Cescatti, AlessandroDuveiller, G., J. Hooker, A. Cescatti, 2018: A dataset mapping the potential biophysical effects of vegetation cover change. Scientific Data, 5, 180014. doi: 10.1038/sdata.2018.14. Changing the vegetation cover of the Earth has impacts on the biophysical properties of the surface and ultimately on the local climate. Depending on the specific type of vegetation change and on the background climate, the resulting competing biophysical processes can have a net warming or cooling effect, which can further vary both spatially and seasonally. Due to uncertain climate impacts and the lack of robust observations, biophysical effects are not yet considered in land-based climate policies. Here we present a dataset based on satellite remote sensing observations that provides the potential changes i) of the full surface energy balance, ii) at global scale, and iii) for multiple vegetation transitions, as would now be required for the comprehensive evaluation of land based mitigation plans. We anticipate that this dataset will provide valuable information to benchmark Earth system models, to assess future scenarios of land cover change and to develop the monitoring, reporting and verification guidelines required for the implementation of mitigation plans that account for biophysical land processes.
Duveiller, Gregory; Hooker, Josh; Cescatti, AlessandroDuveiller, G., J. Hooker, A. Cescatti, 2018: The mark of vegetation change on Earth’s surface energy balance. Nature Communications, 9(1), 679. doi: 10.1038/s41467-017-02810-8. Depending on where and when it occurs, vegetation cover change can affect local climate by altering the surface energy balance. Based on satellite data, this study provides the first data-driven assessment of such effects for multiple vegetation transitions at global scale.
Feng, Fei; Wang, KaicunFeng, F., K. Wang, 2018: Merging Satellite Retrievals and Reanalyses to Produce Global Long-Term and Consistent Surface Incident Solar Radiation Datasets. Remote Sensing, 10(1), 115. doi: 10.3390/rs10010115. Surface incident solar radiation (Rs) is a key parameter in many climatic and ecological processes. The data from satellites and reanalysis have been widely used. However, for reanalysis, Rs data has been shown to have substantial spatial bias, and the time span of reliable satellite Rs is too short for climatic and ecological studies. Combining reanalysis and satellite data would be an effective method for generating long-term and consistent Rs datasets. Here, we apply a cumulative probability density function-based (CPDF) method to merge eight reanalyses with the latest available satellite Rs data from Clouds and Earth’s Radiant Energy System Energy Balanced and Filled (CERES EBAF) surface retrievals. The CPDF method not only reduces the spatial bias of the reanalysis Rs data, but also makes the Rs datasets in a global, long-term and consistent way. The observed Rs data collected at 54 Baseline Surface Radiation Network (BSRN) stations from 1992 to 2016 are used to evaluate the method. Results show that the CPDF method could reduce the mean absolute biases (MAB) of the reanalysis Rs effectively by 21.24–64.36%. The European Centre for Medium-Range Weather Forecasts Re-Analysis interim (ERA-interim) reanalysis Rs data, which are available for 1979 onward, perform the best before MAB = 13.20 W·m−2 and after MAB = 10.40 W·m−2 merging. This small post-merging MAB of the ERA-interim reanalysis is caused by the MAB of 9.90 W·m−2 in the satellite Rs retrievals. The Japanese 55-year reanalysis provides Rs values back to 1958, and CPDF can reduce its MAB by 32.87%, to 11.17 W·m−2. The National Oceanic and Atmospheric Administration (NOAA)-CIRES twentieth-century reanalysis (CIRES) and the ECMWF twentieth-century reanalysis (ERA20CM) provide century-long Rs estimates. CIRES performs better after merging. The MAB of CIRES can be reduced by 32.10%, to 12.99 W·m−2, while ERA20CM’s can be reduced by 12.51%, to 16.40 W·m−2. data fusion; bias correction; CERES EBAF; reanalyses; surface incident solar radiation
Feng, Jiaojiao; Wang, Weizhen; Li, JingFeng, J., W. Wang, J. Li, 2018: An LM-BP Neural Network Approach to Estimate Monthly-Mean Daily Global Solar Radiation Using MODIS Atmospheric Products. Energies, 11(12), 3510. doi: 10.3390/en11123510. Solar energy is one of the most widely used renewable energy sources in the world and its development and utilization are being integrated into people’s lives. Therefore, accurate solar radiation data are of great significance for site-selection of photovoltaic (PV) power generation, design of solar furnaces and energy-efficient buildings. Practically, it is challenging to get accurate solar radiation data because of scarce and uneven distribution of ground-based observation sites throughout the country. Many artificial neural network (ANN) estimation models are therefore developed to estimate solar radiation, but the existing ANN models are mostly based on conventional meteorological data; clouds, aerosols, and water vapor are rarely considered because of a lack of instrumental observations at the conventional meteorological stations. Based on clouds, aerosols, and precipitable water-vapor data from Moderate Resolution Imaging Spectroradiometer (MODIS), along with conventional meteorological data, back-propagation (BP) neural network method was developed in this work with Levenberg-Marquardt (LM) algorithm (referred to as LM-BP) to simulate monthly-mean daily global solar radiation (M-GSR). Comparisons were carried out among three M-GSR estimates, including the one presented in this study, the multiple linear regression (MLR) model, and remotely-sensed radiation products by Cloud and the Earth’s radiation energy system (CERES). The validation results indicate that the accuracy of the ANN model is better than that of the MLR model and CERES radiation products, with a root mean squared error (RMSE) of 1.34 MJ·m−2 (ANN), 2.46 MJ·m−2 (MLR), 2.11 MJ·m−2 (CERES), respectively. Finally, according to the established ANN-based method, the M-GSR of 36 conventional meteorological stations for 12 months was estimated in 2012 in the study area. Solar radiation data based on the LM-BP method of this study can provide some reference for the utilization of solar and heat energy. clouds; aerosols; precipitable water vapor; solar radiation; LM-BP neural network
Forzieri, Giovanni; Duveiller, Gregory; Georgievski, Goran; Li, Wei; Robertson, Eddy; Kautz, Markus; Lawrence, Peter; Martin, Lorea Garcia San; Anthoni, Peter; Ciais, Philippe; Pongratz, Julia; Sitch, Stephen; Wiltshire, Andy; Arneth, Almut; Cescatti, AlessandroForzieri, G., G. Duveiller, G. Georgievski, W. Li, E. Robertson, M. Kautz, P. Lawrence, L. G. S. Martin, P. Anthoni, P. Ciais, J. Pongratz, S. Sitch, A. Wiltshire, A. Arneth, A. Cescatti, 2018: Evaluating the Interplay Between Biophysical Processes and Leaf Area Changes in Land Surface Models. Journal of Advances in Modeling Earth Systems, 10(5), 1102-1126. doi: 10.1002/2018MS001284.
Foster, M. J.; Ackerman, S. A.; Bedka, Kristopher; Di Girolamo, L.; Frey, R. A.; Heidinger, A. K.; Sun-Mack, S.; Phillips, C.; Menzel, W. P.; Stengal, M; Zhao, GFoster, M. J., S. A. Ackerman, K. Bedka, L. Di Girolamo, R. A. Frey, A. K. Heidinger, S. Sun-Mack, C. Phillips, W. P. Menzel, M. Stengal, G. Zhao, 2018: Cloudiness [in “State of the Climate in 2017”].. Bull. Amer. Meteor. Soc, 99(8), S31-32. doi: 10.1175/2018BAMSStateoftheClimate.1.
Frey, W. R.; Morrison, A. L.; Kay, J. E.; Guzman, R.; Chepfer, H.Frey, W. R., A. L. Morrison, J. E. Kay, R. Guzman, H. Chepfer, 2018: The combined influence of observed Southern Ocean clouds and sea ice on top‐of‐atmosphere albedo. Journal of Geophysical Research: Atmospheres, 123(9), 4461-4475. doi: 10.1029/2018JD028505.
Fu, Yuyun; Li, Rui; Huang, Jianguo; Bergeron, Yves; Fu, Yunfei; Wang, Yu; Gao, ZongtingFu, Y., R. Li, J. Huang, Y. Bergeron, Y. Fu, Y. Wang, Z. Gao, 2018: Satellite-Observed Impacts of Wildfires on Regional Atmosphere Composition and the Shortwave Radiative Forcing: A Multiple Case Study. Journal of Geophysical Research: Atmospheres, 123(15), 8326-8343. doi: 10.1029/2017JD027927. Emissions of aerosols and trace gases from wildfires and their direct shortwave radiative forcing (DSRF) at the top of atmosphere were studied using satellite observations from Moderate-Resolution Imaging Spectroradiometer, Atmospheric Infrared Sounder, Clouds and Earth Radiant Energy System on Aqua, and Ozone Monitoring Instrument on Aura. The dominant fuel types of the selected fire cases in the northeast of China (NEC), Siberia (Russia), and California (USA) are cropland, mixed forest, and needle-leaf forest, respectively. For the cropland fire case in NEC, the fire radiative power-based emission coefficients (Ce) of aerosol is 20.51 ± 2.55 g/MJ, half that of the forest fire cases in Siberia (40.01 ± 9.21 g/MJ) and California (45.23 ± 8.81 g/MJ), and the carbon monoxide (CO) Ce (23.94 ± 11.83 g/MJ) was about one third and half that of the forest fire cases in Siberia and California, respectively. However, the NOx (NO2 + NO) Ce (2.76 ± 0.25g MJ−1) of the cropland fire in NEC was nearly 3 times that of those forest fire cases. Ratios of NOx to aerosol, HCHO, and CO in the cropland case in NEC show much higher values than those in the forest fire cases. Despite the differences of the Ce and the composition ratios, the DSRF efficiency of smoke aerosol at the top of atmosphere showed similar values among those fire cases. Our results highlight the large variability of emission rate and relative chemical composition but similar DSRF efficiencies among wildfires, which would provide valuable information for understanding the impact of fire on air quality and climate. satellite remote sensing; direct shortwave radiative forcing; emission rate; fire radiative power; wildfire
Furtado, KalliFurtado, K., 2018: Chapter 8 - Subgrid Representation of Mixed-Phase Clouds in a General Circulation Model A2 - Andronache, Constantin. Mixed-Phase Clouds, 185-214. Abstract The ubiquity and longevity of supercooled liquid-water and mixed-phase clouds in nature is at odds with the relative lack of these cloud types in numerical models of cloudy atmospheres when compared to observations. Amongst the mechanisms proposed for the longevity of mixed-phase conditions in nature is that small-scale turbulent motions compete with ice microphysical processes to maintain a statistical steady state in which a constant amount of liquid water exists for a long of period time. In this chapter we review previous work on understanding this mechanism and show how it can be developed into a parametrization of mixed-phase clouds. The parametrization is based on exact, steady-state solutions for the statistics of supersaturation fluctuations in a turbulent cloud layer from which expressions for the liquid-cloud properties can be derived. We review the implementation of the parametrization in a general circulation model and discuss implications of the parametrization for long-standing biases in the radiative properties of simulated mid- and high-latitude cloud-systems.
Furtado, Kalli; Field, Paul R.; Luo, Yali; Liu, Xi; Guo, Zhun; Zhou, Tianjun; Shipway, Benjamin J.; Hill, Adrian A.; Wilkinson, Jonathan M.Furtado, K., P. R. Field, Y. Luo, X. Liu, Z. Guo, T. Zhou, B. J. Shipway, A. A. Hill, J. M. Wilkinson, 2018: Cloud-microphysical factors affecting simulations of deep convection during the presummer rainy-season in southern China. Journal of Geophysical Research: Atmospheres, 123(18), 10,477-10,505. doi: 10.1029/2017JD028192. The sensitivity of subtropical deep-convection to the parametrization of cloud microphysics is elucidated through high-resolution modelling of extreme presummer-rainfall over southern China. An ensemble of physics-configuration experiments is used to identify several drivers of model errors in comparison to radar observations from the South China Monsoon Rainfall Experiment (SCMREX), and remotely-sensed estimates of cloud, precipitation and radiation from satellites in the A-train constellation. The benefits of increasing the number of prognostic variables in the microphysics scheme is assessed, relative to the effects of the parametrization of cloud microphysical-properties and cloud-fraction diagnosis. By matching individual parametrizations between the microphysical configurations, it is shown that a small subset of the parametrization changes can reproduce most of the dependence of model performance on physics configuration. In particular, biases that are due to the low-level clouds and rain are strongly influenced by cloud-fraction diagnosis and rain-drop size distribution, whereas variations in the effects of high clouds are strongly influenced by differences in the parametrization of ice-crystal sedimentation. Hence, for the case studied here, these parametrizations give more insight into the causes of variability in model performance than does the number of model prognostics per se. clouds; microphysics; observations; China; modelling; monsoons
Garimella, S.; Rothenberg, D. A.; Wolf, M. J.; Wang, C.; Cziczo, D. J.Garimella, S., D. A. Rothenberg, M. J. Wolf, C. Wang, D. J. Cziczo, 2018: How Uncertainty in Field Measurements of Ice Nucleating Particles Influences Modeled Cloud Forcing. J. Atmos. Sci., 75(1), 179-187. doi: 10.1175/JAS-D-17-0089.1. Field and laboratory measurements using continuous flow diffusion chambers (CFDCs) have been used to construct parameterizations of the number of ice nucleating particles (INPs) in mixed-phase and completely glaciated clouds in weather and climate models. Because of flow nonidealities, CFDC measurements are subject to systematic low biases. Here, the authors investigate the effects of this undercounting bias on simulated cloud forcing in a global climate model. The authors assess the influence of measurement variability by constructing a stochastic parameterization framework to endogenize measurement uncertainty. The authors find that simulated anthropogenic longwave ice-bearing cloud forcing in a global climate model can vary up to 0.8 W m−2 and can change sign from positive to negative within the experimentally constrained bias range. Considering the variability in the undercounting bias, in a range consistent with recent experiments, leads to a larger negative cloud forcing than that when the variability is ignored and only a constant bias is assumed.
Geiss, Andrew; Marchand, RogerGeiss, A., R. Marchand, 2018: Cloud responses to climate variability over the extratropical oceans as observed by MISR and MODIS. Atmospheric Chemistry and Physics Discussions, 1-30. doi: 10.5194/acp-2018-520. Abstract. Linear temporal trends in cloud fraction over the extratropical oceans, observed by NASA's Multiangle Imaging Spectro-Radiometer (MISR) during the period 2000–2013, are examined in the context of coincident ECMWF reanalysis data using a maximum covariance analysis. Changes in specific cloud types defined with respect to cloud top height and cloud optical depth are related to trends in reanalysis variables. A pattern of reduced high altitude optically thick cloud and increased low altitude cloud of moderate optical depth is found to be associated with increased temperatures, geopotential heights, and anticyclonicity over the extratropical oceans. These and other trends in cloud occurrence are shown to be correlated with changes in the El Niño Southern Oscillation, the Pacific Decadal Oscillation, the North Pacific Index, and the Southern Annular Mode.
George, Geet; Sarangi, Chandan; Tripathi, Sachchida Nand; Chakraborty, Tirthankar; Turner, AndrewGeorge, G., C. Sarangi, S. N. Tripathi, T. Chakraborty, A. Turner, 2018: Vertical Structure and Radiative Forcing of Monsoon Clouds over Kanpur during the 2016 INCOMPASS field campaign. Journal of Geophysical Research: Atmospheres, 123(4), 2152–2174. doi: 10.1002/2017JD027759. An overview of cloud vertical structure (CVS) and cloud radiative forcing (CRF) during Indian summer monsoon is obtained over Kanpur, through observations made during the Interaction of Convective Organisation and Monsoon Precipitation, Atmosphere, Surface and Sea (INCOMPASS) field campaign of 2016. Associations of CVS parameters with CRF at surface and top of atmosphere (TOA) are also investigated. 137 radiosondes were launched at Indian Institute of Technology Kanpur (IITK), between 5th and 28th July, 2016. CVS is determined using an algorithm that identifies cloud layers from vertical profiles of relative humidity (RH), with altitude-dependent RH thresholds. CVS is analysed by separating the campaign period on the basis of presence and absence of depressions/low-pressure systems. Compared to non-depression periods, low-pressure events showed significant difference in all CVS and CRF parameters except cloud-top height. CVS was multi-layered in ∼75% launches, with deep, mixed-phase clouds being present in ∼70% launches. CRF was calculated from clear-sky measurements and TOA observations from Clouds and the Earth's Radiant Energy System (CERES) satellite retrievals, and surface measurements. A net cooling effect was found overall, with instantaneous shortwave forcing (SWCRF) (mean values of -95.92 and -101.89 W/m2 at surface and TOA, respectively) dominating longwave forcing (LWCRF) (mean values of 15.33 and 66.55 W/m2 at surface and TOA, respectively). Results suggest that SWCRF depends on total depth of cloud layers, and is independent of cloud altitude, whereas LWCRF depends on both depth and vertical location of cloud layers, with base and top heights regulating LWCRF at surface and TOA, respectively. 3310 Clouds and cloud feedbacks; 0321 Cloud/radiation interaction; 3329 Mesoscale meteorology; 3374 Tropical meteorology; cloud base top height depth; cloud forcing surface TOA; cloud multi layers; india monsoon indo gangetic plain; monsoon depression low pressure; radiosondes weather balloons
Giardina, Francesco; Konings, Alexandra G.; Kennedy, Daniel; Alemohammad, Seyed Hamed; Oliveira, Rafael S.; Uriarte, Maria; Gentine, PierreGiardina, F., A. G. Konings, D. Kennedy, S. H. Alemohammad, R. S. Oliveira, M. Uriarte, P. Gentine, 2018: Tall Amazonian forests are less sensitive to precipitation variability. Nature Geoscience, 11(6), 405-409. doi: 10.1038/s41561-018-0133-5. Tall trees are less sensitive to variation in precipitation than short trees, according to analyses of photosynthetic sensitivity to drought in tall and short Amazon forests. The results demonstrate higher resilience of tall trees to drought.
Giorgetta, M. A.; Brokopf, R.; Crueger, T.; Esch, M.; Fiedler, S.; Helmert, J.; Hohenegger, C.; Kornblueh, L.; Köhler, M.; Manzini, E.; Mauritsen, T.; Nam, C.; Raddatz, T.; Rast, S.; Reinert, D.; Sakradzija, M.; Schmidt, H.; Schneck, R.; Schnur, R.; Silvers, L.; Wan, H.; Zängl, G.; Stevens, B.Giorgetta, M. A., R. Brokopf, T. Crueger, M. Esch, S. Fiedler, J. Helmert, C. Hohenegger, L. Kornblueh, M. Köhler, E. Manzini, T. Mauritsen, C. Nam, T. Raddatz, S. Rast, D. Reinert, M. Sakradzija, H. Schmidt, R. Schneck, R. Schnur, L. Silvers, H. Wan, G. Zängl, B. Stevens, 2018: ICON-A, the Atmosphere Component of the ICON Earth System Model: I. Model Description. Journal of Advances in Modeling Earth Systems, 10(7), 1613-1637. doi: 10.1029/2017MS001242. ICON-A is the new icosahedral nonhydrostatic (ICON) atmospheric general circulation model in a configuration using the Max Planck Institute physics package, which originates from the ECHAM6 general circulation model, and has been adapted to account for the changed dynamical core framework. The coupling scheme between dynamics and physics employs a sequential updating by dynamics and physics, and a fixed sequence of the physical processes similar to ECHAM6. To allow a meaningful initial comparison between ICON-A and the established ECHAM6-LR model, a setup with similar, low resolution in terms of number of grid points and levels is chosen. The ICON-A model is tuned on the base of the Atmospheric Model Intercomparison Project (AMIP) experiment aiming primarily at a well balanced top-of atmosphere energy budget to make the model suitable for coupled climate and Earth system modeling. The tuning addresses first the moisture and cloud distribution to achieve the top-of-atmosphere energy balance, followed by the tuning of the parameterized dynamic drag aiming at reduced wind errors in the troposphere. The resulting version of ICON-A has overall biases, which are comparable to those of ECHAM6. Problematic specific biases remain in the vertical distribution of clouds and in the stratospheric circulation, where the winter vortices are too weak. Biases in precipitable water and tropospheric temperature are, however, reduced compared to the ECHAM6. ICON-A will serve as the basis of further development and as the atmosphere component to the coupled model, ICON-Earth system model (ESM). model tuning; atmospheric GCM; ICON-A; model description
Girihagama, Lakshika; Nof, DoronGirihagama, L., D. Nof, 2018: Why is the ocean surface slightly warmer than the atmosphere?. Journal of Marine Research, 76(1), 23-46. doi: 10.1357/002224018824082007. How much warmer is the ocean surface than the atmosphere directly above it? The present study offers a means to quantify this temperature difference using a conceptual nonlinear one-dimensional global energy balance coupled ocean–atmosphere model ("Aqua Planet"). The significance of our idealized model, which is of intermediate complexity, is its ability to obtain an analytical solution for the global average temperatures. Our analytical model results show that, for the present climate, predicted global mean ocean temperature is 291.1 K whereas surface atmospheric temperature above the ocean surface is 287.4 K. Thus, the modeled surface ocean is 3.7 K warmer than the atmosphere above it. Temporal perturbation of the global mean solution obtained for "Aqua Planet" showed a stable system. Oscillation amplitude of the atmospheric temperature anomaly is greater in magnitude than those found in the ocean. There is a phase shift (a lag in the ocean), which is caused by oceanic thermal inertia. Climate feedbacks due to selected climate parameters such as incoming radiation, cloud cover, and CO2 are discussed. Warming obtained with our model compares well with Intergovernmental Panel on Climate Change's (IPCC) estimations. Application of our model to local regions illuminates the importance of evaporative cooling in determining derived air–sea temperature offsets, where an increase in the latter increases the systems overall sensitivity to evaporative cooling. ATMOSPHERE INTERACTION; CONCEPTUAL CLIMATE MODELS; OCEAN–; TEMPERATURE DIFFERENCE
Grosvenor, Daniel P.; Sourdeval, Odran; Zuidema, Paquita; Ackerman, Andrew; Alexandrov, Mikhail D.; Bennartz, Ralf; Boers, Reinout; Cairns, Brian; Chiu, J. Christine; Christensen, Matthew; Deneke, Hartwig M.; Diamond, Michael S.; Feingold, Graham; Fridlind, Ann; Hünerbein, Anja; Knist, Christine L.; Kollias, Pavlos; Marshak, Alexander; McCoy, Daniel; Merk, Daniel; Painemal, David; Rausch, John; Rosenfeld, Daniel; Russchenberg, Herman; Seifert, Patric; Sinclair, Kenneth; Stier, Philip; van Diedenhoven, Bastiaan; Wendisch, Manfred; Werner, Frank; Wood, Robert; Zhang, Zhibo; Quaas, JohannesGrosvenor, D. P., O. Sourdeval, P. Zuidema, A. Ackerman, M. D. Alexandrov, R. Bennartz, R. Boers, B. Cairns, J. C. Chiu, M. Christensen, H. M. Deneke, M. S. Diamond, G. Feingold, A. Fridlind, A. Hünerbein, C. L. Knist, P. Kollias, A. Marshak, D. McCoy, D. Merk, D. Painemal, J. Rausch, D. Rosenfeld, H. Russchenberg, P. Seifert, K. Sinclair, P. Stier, B. van Diedenhoven, M. Wendisch, F. Werner, R. Wood, Z. Zhang, J. Quaas, 2018: Remote sensing of droplet number concentration in warm clouds: A review of the current state of knowledge and perspectives. Reviews of Geophysics, 56(2), 409-453. doi: 10.1029/2017RG000593.
Gryspeerdt, Edward; Quaas, Johannes; Goren, Tom; Klocke, Daniel; Brueck, MatthiasGryspeerdt, E., J. Quaas, T. Goren, D. Klocke, M. Brueck, 2018: An automated cirrus classification. Atmospheric Chemistry and Physics, 18(9), 6157-6169. doi: 10.5194/acp-18-6157-2018. Cirrus clouds play an important role in determining the radiation budget of the earth, but many of their properties remain uncertain, particularly their response to aerosol variations and to warming. Part of the reason for this uncertainty is the dependence of cirrus cloud properties on the cloud formation mechanism, which itself is strongly dependent on the local meteorological conditions.
Hanea, A. M.; Nane, G. F.; Wielicki, B. A.; Cooke, R. M.Hanea, A. M., G. F. Nane, B. A. Wielicki, R. M. Cooke, 2018: Bayesian networks for identifying incorrect probabilistic intuitions in a climate trend uncertainty quantification context. Journal of Risk Research, 1-16. doi: 10.1080/13669877.2018.1437059. Probabilistic thinking can often be unintuitive. This is the case even for simple problems, let alone the more complex ones arising in climate modelling, where disparate information sources need to be combined. The physical models, the natural variability of systems, the measurement errors and their dependence upon the observational period length should be modelled together in order to understand the intricacies of the underlying processes. We use Bayesian networks (BNs) to connect all the above-mentioned pieces in a climate trend uncertainty quantification framework. Inference in such models allows us to observe some seemingly nonsensical outcomes. We argue that they must be pondered rather than discarded until we understand how they arise. We would like to stress that the main focus of this paper is the use of BNs in complex probabilistic settings rather than the application itself.
Hartmann, Dennis L.; Gasparini, Blaž; Berry, Sara E.; Blossey, Peter N.Hartmann, D. L., B. Gasparini, S. E. Berry, P. N. Blossey, 2018: The Life Cycle and Net Radiative Effect of Tropical Anvil Clouds. Journal of Advances in Modeling Earth Systems, 10(12), 3012-3029. doi: 10.1029/2018MS001484. We explore the importance of the life cycle of detrained tropical anvil clouds in producing a weak net cloud radiative effect (NCRE) by tropical convective systems. We simulate a horizontally homogeneous elevated ice cloud in a 2-D framework using the System for Atmospheric Modeling cloud-resolving model. The initially thick cloud produces a negative NCRE, which is later canceled by a positive NCRE as the cloud thins and rises. Turning off interactive cloud radiation reveals that cloud radiative heating and in-cloud convection are fundamental in driving net radiative neutrality. In-cloud convection acts to thin initially thick anvil clouds and loft and maintain thin cirrus. The maintenance of anvil clouds is tied to the recycling of water vapor and cloud ice through sublimation, nucleation, and deposition as air parcels circulate vertically within the cloud layer. Without interactive radiation, the cloud sediments and sublimates away, producing a large negative NCRE. The specification of cloud microphysics substantially influences the cloud's behavior and life cycle , but the tendency of the life cycle to produce compensating cloud radiative effects is robust to substantial changes in the microphysics. Our study shows that small-scale processes within upper level ice clouds likely have a strong influence on the NCRE associated with tropical convective cloud systems. cirrus clouds; tropical convection; anvil clouds; climate sensitivity
He, Jian; He, Ruoying; Zhang, YangHe, J., R. He, Y. Zhang, 2018: Impacts of Air-sea Interactions on Regional Air Quality Predictions Using a Coupled Atmosphere-ocean Model in Southeastern U.S.. Aerosol and Air Quality Research, 18(4), 1044-1067. doi: 10.4209/aaqr.2016.12.0570. Air-sea interactions have significant impacts on coastal convection and surface fluxes exchange. They are important for the spatial and vertical distributions of air pollutants that affect public health, particularly in densely populated coastal areas. To understand the impacts of air-sea interactions on coastal air quality predictions, sensitivity simulations with different atmosphere-ocean coupling are conducted in this work over southeastern U.S. in July 2010 using the Weather Research and Forecasting Model with Chemistry (WRF/Chem). The results show that comparing to WRF/Chem without air-sea interactions, WRF/Chem with a 1-D ocean mixed layer model (WRF/Chem-OML) and WRF/Chem coupled with a 3-D Regional Ocean Modeling System (WRF/Chem-ROMS) predict the domain averaged changes in the sea surface temperature of 0.06°C and 0.94°C, respectively for July average. The simulated differences in the surface concentrations of O3 and PM2.5 between WRF/Chem-ROMS and WRF/Chem can be as large as 17.3 ppb and 7.9 µg m–3, respectively, with the largest changes occurring not only along coast and remote ocean, but also over some inland areas. Extensive validations against observations show that WRF/Chem-ROMS improves the predictions of most cloud and radiative variables, and surface concentrations of some chemical species such as SO2, NO2, maximum 1-h and 8-h O3, SO42–, NH4+, NO3–, and PM10. This illustrates the benefits and needs of using coupled atmosphere-ocean model with advanced model representations of air-sea interactions for regional air quality modeling.
He, Lijie; Wang, Lunche; Lin, Aiwen; Zhang, Ming; Xia, Xiangao; Tao, Minghui; Zhou, HaoHe, L., L. Wang, A. Lin, M. Zhang, X. Xia, M. Tao, H. Zhou, 2018: What drives changes in aerosol properties over the Yangtze River Basin in past four decades?. Atmospheric Environment, 190, 269-283. doi: 10.1016/j.atmosenv.2018.07.034. Since the Reform and Opening up in China, aerosols increasingly affect the country's climate change and human health. However, remote sensing studies have been inconclusive as to long-term trends in Chinese aerosol emissions. The newly-released MERRA-2 product provides a long-term (1980 onward) aerosol reanalysis dataset, and thus is used in this study for identifying trends in aerosol optical depth (AOD) and aerosol direct radiative effect (ADRE) in clear sky over the Yangtze River Basin (YRB) based on the MK nonparametric method. Results reveal that there is a notable turning point in AOD trends around 2008, i.e., significantly increasing by 0.0201 year−1 before 2008 and then deceasing by −0.0185 year−1. The reason may be the decreases of S02, NOx and soot (dust) emissions from major cities in the YRB since 2006. Likewise, the cooling (warming) effects at the top of atmosphere (TOA), surface (SFC) and atmosphere (ATM) strongly increase by −0.3744 and −0.5652 (0.2935) wm−2 year−1 before 2008, and then significantly decrease by 0.2731 and 0.5868 (−0.3145) wm−2 year−1. Trend analyses confirm that changes in AOD dominate ADRE trends. Furthermore, AOD is significantly negatively (positively) associated with NDVI and precipitation (GDP and Population density) over most areas of the YRB. Besides, similar spatial trends with AOD are also identified in GDP and NDVI. This indicates that increases in GDP and decreases in NDVI caused by rapid urbanization partly lead to the growth of AOD over the middle and lower reaches of the YRB. However, changes in precipitation and Population density alone may not be the main factors for the increasing AOD. Aerosol optical depth; Aerosol direct radiative effect; Impact factor analysis; Trend analysis; Yangtze river basin
Hegyi, Bradley M.; Taylor, Patrick C.Hegyi, B. M., P. C. Taylor, 2018: The unprecedented 2016-17 Arctic sea ice growth season: the crucial role of atmospheric rivers and longwave fluxes. Geophysical Research Letters, 45(10), 5204-5212. doi: 10.1029/2017GL076717. The 2016-17 Arctic sea ice growth season (October-March) exhibited one of the lowest end-of-season sea ice volume and extent of any year since 1979. An analysis of MERRA2 atmospheric reanalysis data and CERES radiative flux data reveals that a record warm and moist Arctic atmosphere supported the reduced sea ice growth. Numerous regional episodes of increased atmospheric temperature and moisture, transported from lower latitudes, increased the cumulative energy input from downwelling longwave surface fluxes. In those same episodes, the efficiency of the atmosphere cooling radiatively to space was reduced, increasing the amount of energy retained in the Arctic atmosphere and reradiated back toward the surface. Overall, the Arctic radiative cooling efficiency shows a decreasing trend since 2000. The results presented highlight the increasing importance of atmospheric forcing on sea ice variability demonstrating that episodic Arctic atmospheric rivers, regions of elevated poleward water vapor transport, and the subsequent surface energy budget response is a critical mechanism actively contributing to the evolution of Arctic sea ice. Arctic sea ice growth; Atmospheric water vapor; Longwave fluxes
Hill, Peter G.; Allan, Richard P.; Chiu, J. Christine; Bodas-Salcedo, Alejandro; Knippertz, PeterHill, P. G., R. P. Allan, J. C. Chiu, A. Bodas-Salcedo, P. Knippertz, 2018: Quantifying the contribution of different cloud types to the radiation budget in southern West Africa. J. Climate, 31(13), 5273–5291. doi: 10.1175/JCLI-D-17-0586.1. The contribution of cloud to the radiation budget of southern West Africa (SWA) is poorly understood yet is important for understanding regional monsoon evolution and for evaluating and improving climate models, which have large biases in this region. Radiative transfer calculations applied to atmospheric profiles obtained from the CERES-CloudSat-CALIPSO-MODIS (CCCM) dataset are used to investigate the effects of 12 different cloud types (defined by their vertical structure) on the regional energy budget of SWA (5–10 °N, 8 °W-8 °E) during June-September. We show that the large regional mean cloud radiative effect in SWA is due to non-negligible contributions from many different cloud types; 8 cloud types have a cloud fraction larger than 5 % and contribute at least 5 % of the regional mean shortwave cloud radiative effect at the top of atmosphere. Low-clouds, which are poorly observed by passive satellite measurements, were found to cause net radiative cooling of the atmosphere, which reduces the heating from other cloud types by approximately 10 %. The sensitivity of the radiation budget to underestimating low-cloud cover is also investigated. The radiative effect of missing low-cloud is found to be up to approximately –25 W m-2 for upwelling shortwave irradiance at the top of atmosphere and 35 W m-2 for downwelling shortwave irradiance at the surface.
Hill, Spencer A.; Ming, Yi; Zhao, MingHill, S. A., Y. Ming, M. Zhao, 2018: Robust Responses of the Sahelian Hydrological Cycle to Global Warming. J. Climate, 31(24), 9793-9814. doi: 10.1175/JCLI-D-18-0238.1. How the globally uniform component of sea surface temperature (SST) warming influences rainfall in the African Sahel remains insufficiently studied, despite mean SST warming being among the most robustly simulated and theoretically grounded features of anthropogenic climate change. A prior study using the NOAA Geophysical Fluid Dynamics Laboratory (GFDL) AM2.1 atmospheric general circulation model (AGCM) demonstrated that uniform SST warming strengthens the prevailing northerly advection of dry Saharan air into the Sahel. The present study uses uniform SST warming simulations performed with 7 GFDL and 10 CMIP5 AGCMs to assess the robustness of this drying mechanism across models and uses observations to assess the physical credibility of the severe drying response in AM2.1. In all 17 AGCMs, mean SST warming enhances the free-tropospheric meridional moisture gradient spanning the Sahel and with it the Saharan dry-air advection. Energetically, this is partially balanced by anomalous subsidence, yielding decreased precipitation in 14 of the 17 models. Anomalous subsidence and precipitation are tightly linked across the GFDL models but not the CMIP5 models, precluding the use of this relationship as the start of a causal chain ending in an emergent observational constraint. For AM2.1, cloud–rainfall covariances generate radiative feedbacks on drying through the subsidence mechanism and through surface hydrology that are excessive compared to observations at the interannual time scale. These feedbacks also act in the equilibrium response to uniform warming, calling into question the Sahel’s severe drying response to warming in all coupled models using AM2.1.
Holzman, Mauro E.; Carmona, Facundo; Rivas, Raúl; Niclòs, RaquelHolzman, M. E., F. Carmona, R. Rivas, R. Niclòs, 2018: Early assessment of crop yield from remotely sensed water stress and solar radiation data. ISPRS Journal of Photogrammetry and Remote Sensing, 145, 297-308. doi: 10.1016/j.isprsjprs.2018.03.014. Soil moisture (SM) available for evapotranspiration is crucial for food security, given the significant interannual yield variability of rainfed crops in large agricultural regions. Also, incoming solar radiation (Rs) influences the photosynthetic rate of vegetated surfaces and can affect productivity. The aim of this work is to evaluate the ability of crop water stress and Rs remotely sensed data to forecast yield at regional scale. Temperature Vegetation Dryness Index (TVDI) was computed as an indicator of crop water stress and soil moisture availability. TVDI during critical growth stage of crops was calculated from MODIS products: MODIS/AQUA 8-day composite LST at 1 km and 16-day composite vegetation index at 1 km. Rs data were obtained from Clouds and the Earth’s Radiant Energy System (CERES). The relationship between TVDI, Rs and yield of wheat, corn and soybean was analyzed. High R2 values (0.55–0.82, depending on crop and region) were found in different agro-climatic regions of Argentine Pampas. Validation results showed the suitability of the model RMSE = 330–1300 kg ha−1, Relative Error = 13–34%. However, results were significantly improved considering the most important factor affecting yield. Rs proved to be important for winter crops in humid areas, where incoming radiation can be a limiting factor. In semi-arid regions, soils with low water retention capacity and summer crops, crop water stress showed the best results. Overall, results reflected that the proposed approach is suitable for crop yield forecasting at regional scale several weeks previous to harvest. Evapotranspiration; Crop water stress; Food security; Yield estimation
Hu, Zeyuan; Cronin, Timothy W.; Tziperman, EliHu, Z., T. W. Cronin, E. Tziperman, 2018: Suppression of Cold Weather Events over High-Latitude Continents in Warm Climates. J. Climate, 31(23), 9625-9640. doi: 10.1175/JCLI-D-18-0129.1. Recent studies, using Lagrangian single-column atmospheric models, have proposed that in warmer climates more low clouds would form as maritime air masses advect into Northern Hemisphere high-latitude continental interiors during winter (DJF). This increase in low cloud amount and optical thickness could reduce surface radiative cooling and suppress Arctic air formation events, partly explaining both the warm winter high-latitude continental interior climate and frost-intolerant species found there during the Eocene and the positive lapse-rate feedback in future Arctic climate change scenarios. Here the authors examine the robustness of this low-cloud mechanism in a three-dimensional atmospheric model that includes large-scale dynamics. Different warming scenarios are simulated under prescribed CO2 and sea surface temperature, and the sensitivity of winter temperatures and clouds over high-latitude continental interior to mid- and high-latitude sea surface temperatures is examined. Model results show that winter 2-m temperatures on extreme cold days increase about 50% faster than the winter mean temperatures and the prescribed SST. Low cloud fraction and surface longwave cloud radiative forcing also increase in both the winter mean state and on extreme cold days, consistent with previous Lagrangian air-mass studies, but with cloud fraction increasing for different reasons than proposed by previous work. At high latitudes, the cloud longwave warming effect dominates the shortwave cooling effect, and the net cloud radiative forcing at the surface tends to warm high-latitude land but cool midlatitude land. This could contribute to the reduced meridional temperature gradient in warmer climates and help explain the greater warming of winter cold extremes relative to winter mean temperatures.
Hua, Shan; Liu, Yuzhi; Jia, Rui; Chang, Shuting; Wu, Chuqiao; Zhu, Qingzhe; Shao, Tianbin; Wang, BingHua, S., Y. Liu, R. Jia, S. Chang, C. Wu, Q. Zhu, T. Shao, B. Wang, 2018: Role of clouds in accelerating cold-season warming during 2000–2015 over the Tibetan Plateau. International Journal of Climatology, 38(13), 4950-4966. doi: 10.1002/joc.5709. With the global warming slowdown in the twenty-first century, a huge discrepancy in regional climate warming has been identified over the main region of the Tibetan Plateau (TP). Compared with the +0.04 °C/decade warming from 1961 to 1999, the warming greatly accelerated for the period 2000–2015 at a rate of +0.30 °C/decade. During the same period, warming in the cold season (November to March) was more pronounced than in the warm season (May to September) over the TP. The results also indicated that the middle-level cloud (middle cloud) decreased (−0.359%/year), while the high-level cloud (high cloud) increased (+0.241%/year) over almost all the TP during the cold season. Further analysis showed positive net cloud radiative forcing over the western TP from 2000–2015, that is, a heating effect of clouds, especially in the cold season. Combining the trends of the increase in high cloud and the decrease in middle cloud over most parts of the TP, the decreased albedo effect of middle cloud and the increased longwave greenhouse effect of high cloud may have partially contributed to the sustained warming, especially in the cold season from 2000 to 2015. Meanwhile, the results showed that the warming rate and cloud area fraction changes were significantly amplified with elevation. The analysis based on a model of Coupled Model Intercomparison Project Phase 5 shows that the decreased middle cloud plays more important role than the increased high cloud in modulating the enhanced warming over the TP, especially in the cold season. cloud; cloud radiative forcing; warming; Tibetan plateau
Hwang, Jiwon; Choi, Yong-Sang; Kim, WonMoo; Su, Hui; Jiang, Jonathan H.Hwang, J., Y. Choi, W. Kim, H. Su, J. H. Jiang, 2018: Observational estimation of radiative feedback to surface air temperature over Northern High Latitudes. Climate Dynamics, 50(1-2), 615-628. doi: 10.1007/s00382-017-3629-6. The high-latitude climate system contains complicated, but largely veiled physical feedback processes. Climate predictions remain uncertain, especially for the Northern High Latitudes (NHL; north of 60°N), and observational constraint on climate modeling is vital. This study estimates local radiative feedbacks for NHL based on the CERES/Terra satellite observations during March 2000–November 2014. The local shortwave (SW) and longwave (LW) radiative feedback parameters are calculated from linear regression of radiative fluxes at the top of the atmosphere on surface air temperatures. These parameters are estimated by the de-seasonalization and 12-month moving average of the radiative fluxes over NHL. The estimated magnitudes of the SW and the LW radiative feedbacks in NHL are 1.88 ± 0.73 and 2.38 ± 0.59 W m−2 K−1, respectively. The parameters are further decomposed into individual feedback components associated with surface albedo, water vapor, lapse rate, and clouds, as a product of the change in climate variables from ERA-Interim reanalysis estimates and their pre-calculated radiative kernels. The results reveal the significant role of clouds in reducing the surface albedo feedback (1.13 ± 0.44 W m−2 K−1 in the cloud-free condition, and 0.49 ± 0.30 W m−2 K−1 in the all-sky condition), while the lapse rate feedback is predominant in LW radiation (1.33 ± 0.18 W m−2 K−1). However, a large portion of the local SW and LW radiative feedbacks were not simply explained by the sum of these individual feedbacks.
Hyder, Patrick; Edwards, John M.; Allan, Richard P.; Hewitt, Helene T.; Bracegirdle, Thomas J.; Gregory, Jonathan M.; Wood, Richard A.; Meijers, Andrew J. S.; Mulcahy, Jane; Field, Paul; Furtado, Kalli; Bodas-Salcedo, Alejandro; Williams, Keith D.; Copsey, Dan; Josey, Simon A.; Liu, Chunlei; Roberts, Chris D.; Sanchez, Claudio; Ridley, Jeff; Thorpe, Livia; Hardiman, Steven C.; Mayer, Michael; Berry, David I.; Belcher, Stephen E.Hyder, P., J. M. Edwards, R. P. Allan, H. T. Hewitt, T. J. Bracegirdle, J. M. Gregory, R. A. Wood, A. J. S. Meijers, J. Mulcahy, P. Field, K. Furtado, A. Bodas-Salcedo, K. D. Williams, D. Copsey, S. A. Josey, C. Liu, C. D. Roberts, C. Sanchez, J. Ridley, L. Thorpe, S. C. Hardiman, M. Mayer, D. I. Berry, S. E. Belcher, 2018: Critical Southern Ocean climate model biases traced to atmospheric model cloud errors. Nature Communications, 9(1), 3625. doi: 10.1038/s41467-018-05634-2. The Southern Ocean is critically important for global climate yet poorly represented by climate models. Here the authors trace sea surface temperature biases in this region to cloud-related errors in atmospheric-model simulated surface heat fluxes and provide a pathway to improve the models.
Itterly, Kyle F.; Taylor, Patrick C.; Dodson, Jason BrantItterly, K. F., P. C. Taylor, J. B. Dodson, 2018: Sensitivity of the Amazonian convective diurnal cycle to its environment in observations and reanalysis. Journal of Geophysical Research: Atmospheres, 123(22), 12,621-12,646. doi: 10.1029/2018JD029251. Atmospheric model parameterizations of tropical deep convection struggle to reproduce the observed diurnal variability of convection in the Amazon leading to climatological biases in the energy budget and water cycle. To identify the physical process contributions to these biases, we analyze the relationships between the convective diurnal cycle and atmosphere state variables relevant to convection in the Amazon using satellite observations and reanalysis data sets for wet and dry seasons between 2002-2016 and two GOAmazon periods. The analysis first stratifies the diurnal cycle into convective and non-convective days using a daily maximum rain rate threshold of 0.5 mm hour-1. Secondly, the population of days is constrained by requiring reanalysis and observations to agree on the occurrence of convective rain rates, controlling for frequency-dependent biases in convection. The model-generated precipitation phase in MERRA-2 is closer to observations than ERA during 2002-2016, which exhibits a systematic noontime bias and exaggerated diurnal amplitude. Despite the systematic noontime precipitation bias, ERA produces better agreement with GOAmazon observations due to the frequent midmorning arrival of the coastal front acting to shift the observed diurnal cycle closer to noon. Model disagreement between middle-tropospheric vertical velocity is largest overnight during the dissipation stage of convection; acting to sustain biases through radiative effects. Specifically, the slower dissipation of convection in MERRA-2 acts to reduce morning surface fluxes and increase convective inhibition whereas enhanced nocturnal mid-tropospheric subsidence and higher boundary layer humidity in ERA reduces morning convective inhibition leading to an earlier initiation of afternoon deep convection. Amazonian Convection; Convective Diurnal Cycle; GoAmazon Diurnal Cycle; Humidity and Convection; Reanalysis Model Evaluation; Sensitivity to Environment
Jia, Aolin; Liang, Shunlin; Jiang, Bo; Zhang, Xiaotong; Wang, GuoxinJia, A., S. Liang, B. Jiang, X. Zhang, G. Wang, 2018: Comprehensive Assessment of Global Surface Net Radiation Products and Uncertainty Analysis. Journal of Geophysical Research: Atmospheres, 123(4), 1970-1989. doi: 10.1002/2017JD027903. Earth surface net radiation (Rn) characterizes the surface radiation budget and plays a critical role in ecological, biogeochemical, and hydrological processes. The Rn products from remote sensing and reanalysis have not been validated comprehensively. In this study, four Rn products (CERES, ERA-Interim, MERRA2, and JRA-55) were validated using global ground measurements on monthly (255 sites) and annual (172 sites) timescales. These products have similar accuracies, with average root-mean-square error ranges of 5.35 Wm-2 (monthly) and 2.30 Wm-2 (annually). However, varying accuracies and systemic biases exist across different climatic zones. The annual land Rn intercomparison illustrates that large uncertainty exists over polar regions and deserts. A significantly negative annual anomaly in the CERES product for the 2001–2008 period is identified when examining annual Rn anomalies over the global land surface. Detailed uncertainty analysis indicates that the global CERES Rn anomaly is mainly due to different versions of input data such as aerosol optical thickness and atmospheric profiles (in 2006 and 2008) and cloud properties (in 2002). This work demonstrates that temporal analysis provides powerful quality control for global time series satellite products when the validation using ground measurements fails to capture potential issues. CERES; 1640 Remote sensing; 0321 Cloud/radiation interaction; 1814 Energy budgets; 1873 Uncertainty assessment; 1988 Temporal analysis and representation; net radiation; Assessment; global products; uncertainty analysis
Jia, Rui; Liu, Yuzhi; Hua, Shan; Zhu, Qingzhe; Shao, TianbinJia, R., Y. Liu, S. Hua, Q. Zhu, T. Shao, 2018: Estimation of the Aerosol Radiative Effect over the Tibetan Plateau Based on the Latest CALIPSO Product. Journal of Meteorological Research, 32(5), 707-722. doi: 10.1007/s13351-018-8060-3. Based on the CALIPSO (Cloud–Aerosol Lidar and Infrared Pathfinder Satellite Observation) Version 4.10 products released on 8 November 2016, the Level 2 (L2) aerosol product over the Tibetan Plateau (TP) is evaluated and the aerosol radiative effect is also estimated in this study. As there are still some missing aerosol data points in the daytime CALIPSO Version 4.10 L2 product, this study re-calculated the aerosol extinction coefficient to explore the aerosol radiative effect over the TP based on the CALIPSO Level 1 (L1) and CloudSat 2B-CLDCLASS-LIDAR products. The energy budget estimation obtained by using the AODs (aerosol optical depths) from calculated aerosol extinction coefficient as an input to a radiative transfer model shows better agreement with the Earth’s Radiant Energy System (CERES) and CloudSat 2B-FLXHR-LIDAR observations than that with the input of AODs from aerosol extinction coefficient from CALIPSO Version 4.10 L2 product. The radiative effect and heating rate of aerosols over the TP are further simulated by using the calculated aerosol extinction coefficient. The dust aerosols may heat the atmosphere by retaining the energy in the layer. The instantaneous heating rate can be as high as 5.5 K day–1 depending on the density of the dust layers. Overall, the dust aerosols significantly affect the radiative energy budget and thermodynamic structure of the air over the TP, mainly by altering the shortwave radiation budget. The significant influence of dust aerosols over the TP on the radiation budget may have important implications for investigating the atmospheric circulation and future regional and global climate. Tibetan Plateau; aerosol radiative effect; Cloud–Aerosol Lidar and Infrared Pathfinder Satellite Observation (CALIPSO) Version 4.10 product
Jian, Bida; Li, Jiming; Wang, Guoyin; He, Yongli; Han, Ying; Zhang, Min; Huang, JianpingJian, B., J. Li, G. Wang, Y. He, Y. Han, M. Zhang, J. Huang, 2018: The impacts of atmospheric and surface parameters on long-term variations in the planetary albedo. J. Climate, 31(21), 8705–8718. doi: 10.1175/JCLI-D-17-0848.1. Planetary albedo (PA, shortwave broadband albedo) and its long-term variations, which are controlled in a complex way by various atmospheric and surface properties, play a key role in controlling the global and regional energy budget. This study investigates the contributions of different atmospheric and surface properties on the long-term variations of PA based on 13 years (2003–2015) of albedo, cloud and ice coverage datasets from the Clouds and the Earth’s Radiant Energy System (CERES) Single Scanner Footprint (SSF) Edition4A product, vegetation product from Moderate Resolution Imaging Spectroradiometer (MODIS) and surface albedo product from the CLARA-A2 (Cloud, Albedo, and Radiation dataset, version 2). According to the temporal correlation analysis, statistical results indicate that variations in PA are closely related to the variations of cloud properties (e.g., cloud fraction, ice water path and liquid water path) and surface parameters (e.g., ice/snow percent coverage and normalized difference vegetation index), but their temporal relationships vary among the different regions. Generally, the stepwise multiple linear regression models can capture the observed PA anomalies for most regions. Based on the contribution calculation, cloud fraction dominates the variability of PA in the mid and low latitudes while ice/snow percent coverage (or surface albedo) dominate the variability in the mid high and latitudes. Changes in cloud liquid water path and ice water path are the secondary dominant factor over most regions whereas change in vegetation cover is the least important factor over land. These results verify the effects of atmospheric and surface factors on planetary albedo changes, thus may be of benefit for improving the parameterization of the PA and determining the climate feedbacks.
Joiner, Joanna; Yoshida, Yasuko; Anderson, Martha; Holmes, Thomas; Hain, Christopher; Reichle, Rolf; Koster, Randal; Middleton, Elizabeth; Zeng, Fan-WeiJoiner, J., Y. Yoshida, M. Anderson, T. Holmes, C. Hain, R. Reichle, R. Koster, E. Middleton, F. Zeng, 2018: Global relationships among traditional reflectance vegetation indices (NDVI and NDII), evapotranspiration (ET), and soil moisture variability on weekly timescales. Remote Sensing of Environment, 219, 339-352. doi: 10.1016/j.rse.2018.10.020. Monitoring the effects of water availability on vegetation globally using satellites is important for applications such as drought early warning, precision agriculture, and food security as well as for more broadly understanding relationships between water and carbon cycles. In this global study, we examine how quickly several satellite-based indicators, assumed to have relationships with water availability, respond, on timescales of days to weeks, in comparison with variations in root-zone soil moisture (RZM) that extends to about 1 m depth. The satellite indicators considered are the normalized difference vegetation and infrared indices (NDVI and NDII, respectively) derived from reflectances obtained with moderately wide (20–40 nm) spectral bands in the visible and near-infrared (NIR) and evapotranspiration (ET) estimated from thermal infrared observations and normalized by a reference ET. NDVI is primarily sensitive to chlorophyll contributions and vegetation structure while NDII may contain additional information on water content in leaves and canopy. ET includes both the loss of root zone soil water through transpiration (modulated by stomatal conductance) as well as evaporation from bare soil. We find that variations of these satellite-based drought indicators on time scales of days to weeks have significant correlations with those of RZM in the same water-limited geographical locations that are dominated by grasslands, shrublands, and savannas whose root systems are generally contained within the 1 m RZM layer. Normalized ET interannual variations show generally a faster response to water deficits and enhancements as compared with those of NDVI and NDII, particularly in sparsely vegetated regions. Evapotranspiration; Drought; Root zone soil moisture; Vegetation; Vegetation index
Kacenelenbogen, Meloë S.; Vaughan, Mark A.; Redemann, Jens; Young, Stuart A.; Liu, Zhaoyan; Hu, Yongxiang; Omar, Ali H.; LeBlanc, Samuel; Shinozuka, Yohei; Livingston, John; Zhang, Qin; Powell, Kathleen A.Kacenelenbogen, M., . S., M. A. Vaughan, J. Redemann, S. A. Young, Z. Liu, Y. Hu, A. H. Omar, S. LeBlanc, Y. Shinozuka, J. Livingston, Q. Zhang, K. A. Powell, 2018: Estimations of Global Shortwave Direct Aerosol Radiative Effects Above Opaque Water Clouds Using a Combination of A-Train Satellite Sensors. Atmospheric Chemistry and Physics Discussions, 1-96. doi: 10.5194/acp-2018-1090. Abstract. All-sky Direct Aerosol Radiative Effects (DARE) play a significant yet still uncertain role in climate. This is partly due to poorly quantified radiative properties of Aerosol Above Clouds (AAC). We compute global estimates of short-wave top-of-atmosphere DARE over Opaque Water Clouds (OWC), DAREOWC, using observation-based aerosol and cloud radiative properties from a combination of A-Train satellite sensors and a radiative transfer model. There are three major differences between our DAREOWC calculations and previous studies: (1) we use the Depolarization Ratio method (DR) on CALIOP (Cloud Aerosol LIdar with Orthogonal Polarization) Level 1 measurements to compute the AAC frequencies of occurrence and the AAC Aerosol Optical Depths (AOD), thus introducing fewer uncertainties compared to using the CALIOP standard product; (2) we apply our calculations globally, instead of focusing exclusively on regional AAC hotspots such as the southeast Atlantic; and (3) instead of the traditional look-up table approach, we use a combination of satellite-based sensors to obtain AAC intensive radiative properties. Our results agree with previous findings on the dominant locations of AAC (South and North East Pacific, Tropical and South East Atlantic, northern Indian Ocean and North West Pacific), the season of maximum occurrence, aerosol optical depths (a majority in the 0.01–0.02 range and that can exceed 0.2 at 532nm) and aerosol extinction-to-backscatter ratios (a majority in the 40–50sr range at 532nm which is typical of dust aerosols) over the globe. We find positive averages of global seasonal DAREOWC between 0.13 and 0.26W·m−2 (i.e., a warming effect on climate). Regional seasonal DAREOWC values range from −0.06W·m−2 in the Indian Ocean, offshore from western Australia (in March–April–May) to 2.87W·m−2 in the South East Atlantic (in September–October–November). High positive values are usually paired with high aerosol optical depths (>0.1) and low single scattering albedos (
Kato, Seiji; Rose, Fred G.; Rutan, David A.; Thorsen, Tyler J.; Loeb, Norman G.; Doelling, David R.; Huang, Xianglei; Smith, William L.; Su, Wenying; Ham, Seung HeeKato, S., F. G. Rose, D. A. Rutan, T. J. Thorsen, N. G. Loeb, D. R. Doelling, X. Huang, W. L. Smith, W. Su, S. H. Ham, 2018: Surface Irradiances of Edition 4.0 Clouds and the Earth’s Radiant Energy System (CERES) Energy Balanced and Filled (EBAF) Data Product. J. Climate, 31(11), 4501–4527. doi: 10.1175/JCLI-D-17-0523.1. The algorithm to produce the Clouds and the Earth’s Energy System (CERES) Ed4.0 Energy Balanced and Filled (EBAF)-surface data product is explained. The algorithm forces computed top-of-atmosphere (TOA) irradiances to match with Ed4.0 EBAF-TOA irradiances by adjusting surface, cloud and atmospheric properties. Surface irradiances are subsequently adjusted using radiative kernels. The adjustment process is composed of two parts, bias correction and Lagrange multiplier. The bias in temperature and specific humidity between 200 hPa and 500 hPa used for the irradiance computation is corrected based on observations by Atmospheric Infrared Sounder (AIRS). Similarly, the bias in the cloud fraction is corrected based on observations by Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observation (CALIPSO), and CloudSat. Remaining errors in surface, cloud and atmospheric properties are corrected in the Lagrange multiplier process. Ed4.0 global annual mean (January 2005 thorough December 2014) surface net shortwave (SW) and longwave (LW) irradiances, respectively, increases by 1.3 Wm-2 and decreases by 0.2 Wm-2 compared to EBAF Ed2.8 counterparts (the previous version), resulting increasing in net SW+LW surface irradiance by 1.1 Wm-2. The uncertainty in surface irradiances over ocean, land and polar regions at various spatial scales are estimated. The uncertainties in all-sky global annual mean upward and downward shortwave irradiance are, respectively, 3 Wm-2 and 4 Wm-2, and the uncertainties in upward and downward longwave irradiance are respectively, 3 Wm-2 and 6 Wm-2. With an assumption of all errors being independent the uncertainty in the global annual mean surface LW+SW net irradiance is 8 Wm-2.
Katsumata, Masaki; Mori, Shuichi; Hamada, Jun-Ichi; Hattori, Miki; Syamsudin, Fadli; Yamanaka, Manabu D.Katsumata, M., S. Mori, J. Hamada, M. Hattori, F. Syamsudin, M. D. Yamanaka, 2018: Diurnal cycle over a coastal area of the Maritime Continent as derived by special networked soundings over Jakarta during HARIMAU2010. Progress in Earth and Planetary Science, 5(1), 64. doi: 10.1186/s40645-018-0216-3. This study investigates the nature and mechanisms of the diurnal precipitation system over a coastal area of the Maritime Continent (MC) by utilizing the data from a field campaign, HARIMAU2010. During the 1-month campaign, diurnal cycles over Jakarta were well identified by special networked soundings and a C-band radar. Radar and satellites captured the convective-type heavy rains that appeared in the afternoon over the array, which were followed by stratiform-type precipitation during the night. Thermodynamic budget analyses were also performed using sounding data. The period-averaged vertical profiles of Q1 and Q2 indicate that diurnal precipitation acted as deep convection in the diabatic heating and drying. The diurnal composite of the obtained parameters revealed key processes such as (1) just before the onset of the afternoon convective rain, the lower troposphere was moistened by subarray-scale processes; (2) moistening of the troposphere continued during the convective heavy precipitation; (3) the stratiform rains during the night were partly maintained by consuming the pre-existing hydrometeor aloft; and (4) in the early morning, the clouds redeveloped over the ocean to produce precipitation as well as hydrometeor aloft. The possible physical processes promoting lower-tropospheric moistening before onset of the convective rain are also discussed.
Kim, Bu-Yo; Lee, Kyu-Tae; Jee, Joon-Bum; Zo, Il-SungKim, B., K. Lee, J. Jee, I. Zo, 2018: Retrieval of outgoing longwave radiation at top-of-atmosphere using Himawari-8 AHI data. Remote Sensing of Environment, 204(Supplement C), 498-508. doi: 10.1016/j.rse.2017.10.006. This study proposes an algorithm to retrieve the outgoing longwave radiation at the top of the atmosphere (TOA OLR) using the advanced Himawari imager (AHI) unit that is a narrowband sensor installed in Himawari-8, a geostationary satellite providing window and water vapor imagery. The outgoing longwave radiation at the top of the atmosphere (TOA OLR) was retrieved by an empirical method where a radiative transfer model (RTM) was used to simulate various atmospheric conditions, such as the surface temperature, water vapor, and cloud characteristics (e.g., cloud optical thickness and cloud height). The results of an algorithm using a single channel (OLR12.4) and two channels (OLR6.2+12.4) were converted into Terra Cloud and Earth's Radiant Energy System (CERES) TOA OLR for the daytime (0105–0135 UTC) and nighttime (1325–1355 UTC) cases of a scene analysis (typhoon Goni on August 18, 2015). Long-term analysis (August 2015–July 2016) and statistical analysis (i.e., mean, bias, root mean square error (RMSE), and correlation coefficient) were conducted. The analysis results showed that the largest error was produced in the cloudy areas (overcast areas), and the minimum RMSE and a high correlation coefficient were observed over an ocean area. In the scene analysis, however, the daytime and nighttime average RMSE of the CERES TOA OLR and OLR6.2+12.4 was 12.21Wm−2 and showed the correlation coefficient of 0.971. It was an improved result over the RMSE (12.33Wm−2) and correlation coefficient (0.967) shown in the analysis of OLR12.4. In the long-term analysis, the average RMSE was 11.83Wm−2 and showed a correlation coefficient of 0.972 (OLR12.4 showed 12.17Wm−2 and 0.969). Furthermore, to minimize the difference in the cloud area that had the largest error, the study analyzed TOA OLR at the significance level of 95% (±2 RMSE). As a result, the scene analysis showed an RMSE of 10.54Wm−2 and correlation coefficient of 0.977, and the long-term data showed an RMSE of 10.23Wm−2 and correlation coefficient of 0.979. Radiative transfer model; Clouds and the Earth's Radiant Energy System; Himawari-8; Advanced Himawari imager; Narrowband; Outgoing longwave radiation
Kim, Bu-Yo; Lee, Kyu-Tae; Kim, Bu-Yo; Lee, Kyu-TaeKim, B., K. Lee, B. Kim, K. Lee, 2018: Radiation Component Calculation and Energy Budget Analysis for the Korean Peninsula Region. Remote Sensing, 10(7), 1147. doi: 10.3390/rs10071147. In this study, a radiation component calculation algorithm was developed using channel data from the Himawari-8 Advanced Himawari Imager (AHI) and meteorological data from the Unified Model (UM) Local Data Assimilation and Prediction System (LDAPS). In addition, the energy budget of the Korean Peninsula region in 2016 was calculated and its regional differences were analyzed. Radiation components derived using the algorithm were calibrated using the broadband radiation component data from the Clouds and the Earth’s Radiant Energy System (CERES) to improve their accuracy. The calculated radiation components and the CERES data showed an annual mean percent bias of less than 3.5% and a high correlation coefficient of over 0.98. The energy budget of the Korean Peninsula region was −2.4 Wm−2 at the top of the atmosphere (RT), −14.5 Wm−2 at the surface (RS), and 12.1 Wm−2 in the atmosphere (RA), with regional energy budget differences. The Seoul region had a high surface temperature (289.5 K) and a RS of −33.4 Wm−2 (surface emission), whereas the Sokcho region had a low surface temperature (284.7 K) and a RS of 5.0 Wm−2 (surface absorption), for a difference of 38.5 Wm−2. In short, regions with relatively high surface temperatures tended to show energy emission, and regions with relatively low surface temperatures tended to show energy absorption. Such regional energy imbalances can cause weather and climate changes and bring about meteorological disasters, and thus research on detecting energy budget changes must be continued. energy budget; energy imbalance; Himawari-8 AHI; Korean Peninsula region; UM LDAPS
Kim, Ji-Eun; Zhang, Chidong; Kiladis, George N.; Bechtold, PeterKim, J., C. Zhang, G. N. Kiladis, P. Bechtold, 2018: Heating and Moistening of the MJO during DYNAMO in ECMWF Reforecasts. J. Atmos. Sci., 75(5), 1429–1452. doi: 10.1175/JAS-D-17-0170.1. Reforecasts produced by the ECMWF Integrated Forecasting System (IFS) were used to study heating and moistening processes associated with three MJO events over the equatorial Indian Ocean during the Dynamics of the Madden-Julian Oscillation (DYNAMO) field campaign. Variables produced by and derived from the IFS reforecast (IFS-RF) agree reasonably well with observations over the DYNAMO sounding arrays, and they vary smoothly from western to eastern equatorial Indian Ocean. This lends confidence towards using IFS-RF as a surrogate of observations over the equatorial Indian Ocean outside the DYNAMO arrays. The apparent heat source Q1 and apparent moisture sink Q2 produced by IFS are primarily generated by parameterized cumulus convection, followed by microphysics and radiation. The vertical growth of positive Q1 and Q2 associated with the progression of MJO convection can be gradual, stepwise, or rapid depending on the event and its location over the broader equatorial Indian Ocean. The time for convective heating and drying to progress from shallow (800 hPa) to deep (400 hPa) can be
Kolly, A.; Huang, Y.Kolly, A., Y. Huang, 2018: The radiative feedback during the ENSO cycle: Observations vs. Models. Journal of Geophysical Research: Atmospheres, 123(17), 9097-9108. doi: 10.1029/2018JD028401. Observational and model data are used to study the radiative feedbacks during the El Niño Southern Oscillation (ENSO) cycle. We extend the previous works by analyzing the feedbacks with respect to not only top-of-atmosphere (TOA) but also the surface and atmospheric radiation budgets, using a newly developed set of radiation kernels. We find that the tropical radiative budgets undergo distinctive variations during ENSO. The radiative perturbation is especially significant for the atmospheric energy budget. We find that the cloud feedback during the developing phase of ENSO heats the atmosphere over the west and central Pacific differentially, which acts to strengthen the development. We also find that a prominent cloud feedback bias persists in the newer version global climate models. This bias results from wrong extent of compensation between longwave and shortwave effects, which points to the importance of validating the radiative sensitivity of clouds in the GCMs. ENSO; radiative forcing; cloud radiative feedback; energetics of ENSO
Lacour, A.; Chepfer, H.; Miller, N. B.; Shupe, M. D.; Noel, V.; Fettweis, X.; Gallee, H.; Kay, J. E.; Guzman, R.; Cole, J.Lacour, A., H. Chepfer, N. B. Miller, M. D. Shupe, V. Noel, X. Fettweis, H. Gallee, J. E. Kay, R. Guzman, J. Cole, 2018: How Well Are Clouds Simulated over Greenland in Climate Models? Consequences for the Surface Cloud Radiative Effect over the Ice Sheet. J. Climate, 31(22), 9293-9312. doi: 10.1175/JCLI-D-18-0023.1. Using lidar and radiative flux observations from space and ground, and a lidar simulator, we evaluate clouds simulated by climate models over the Greenland ice sheet, including predicted cloud cover, cloud fraction profile, cloud opacity, and surface cloud radiative effects. The representation of clouds over Greenland is a central concern for the models because clouds impact ice sheet surface melt. We find that over Greenland, most of the models have insufficient cloud cover during summer. In addition, all models create too few nonopaque, liquid-containing clouds optically thin enough to let direct solar radiation reach the surface (−1% to −3.5% at the ground level). Some models create too few opaque clouds. In most climate models, the cloud properties biases identified over all Greenland also apply at Summit, Greenland, proving the value of the ground observatory in model evaluation. At Summit, climate models underestimate cloud radiative effect (CRE) at the surface, especially in summer. The primary driver of the summer CRE biases compared to observations is the underestimation of the cloud cover in summer (−46% to −21%), which leads to an underestimated longwave radiative warming effect (CRELW = −35.7 to −13.6 W m−2 compared to the ground observations) and an underestimated shortwave cooling effect (CRESW = +1.5 to +10.5 W m−2 compared to the ground observations). Overall, the simulated clouds do not radiatively warm the surface as much as observed.
Lee, Sang-Ho; Kim, Bu-Yo; Lee, Kyu-Tae; Zo, Il-Sung; Jung, Hyun-Seok; Rim, Se-HunLee, S., B. Kim, K. Lee, I. Zo, H. Jung, S. Rim, 2018: Retrieval of Reflected Shortwave Radiation at the Top of the Atmosphere Using Himawari-8/AHI Data. Remote Sensing, 10(2), 213. doi: 10.3390/rs10020213. This study developed a retrieval algorithm for reflected shortwave radiation at the top of the atmosphere (RSR). This algorithm is based on Himawari-8/AHI (Advanced Himawari Imager) whose sensor characteristics and observation area are similar to the next-generation Geostationary Korea Multi-Purpose Satellite/Advanced Meteorological Imager (GK-2A/AMI). This algorithm converts the radiance into reflectance for six shortwave channels and retrieves the RSR with a regression coefficient look-up-table according to geometry of the solar-viewing (solar zenith angle, viewing zenith angle, and relative azimuth angle) and atmospheric conditions (surface type and absence/presence of clouds), and removed sun glint with high uncertainty. The regression coefficients were calculated using numerical experiments from the radiative transfer model (SBDART), and ridge regression for broadband albedo at the top of the atmosphere (TOA albedo) and narrowband reflectance considering anisotropy. The retrieved RSR were validated using Terra, Aqua, and S-NPP/CERES data on the 15th day of every month from July 2015 to February 2017. The coefficient of determination (R2) between AHI and CERES for scene analysis was higher than 0.867 and the Bias and root mean square error (RMSE) were −21.34–5.52 and 51.74–59.28 Wm−2. The R2, Bias, and RMSE for the all cases were 0.903, −2.34, and 52.12 Wm−2, respectively. broadband albedo at the top of the atmosphere (TOA albedo); Clouds and the Earth Radiant Energy System (CERES); Geostationary Korea Multi-Purse Satellite/Advanced Meteorological Imager (GK-2A/AMI); Himawari-8/Advanced Meteorological Imager (Himawari-8/AHI); reflected shortwave radiation at the top of the atmosphere (RSR)
Lee, Sang-Ho; Lee, Kyu-Tae; Kim, Bu-Yo; Zo, ll-Sung; Jung, Hyun-Seok; Rim, Se-HunLee, S., K. Lee, B. Kim, l. Zo, H. Jung, S. Rim, 2018: Retrieval Algorithm for Broadband Albedo at the Top of the Atmosphere. Asia-Pacific Journal of Atmospheric Sciences, 54(2), 165-178. doi: 10.1007/s13143-018-0001-7. The objective of this study is to develop an algorithm that retrieves the broadband albedo at the top of the atmosphere (TOA albedo) for radiation budget and climate analysis of Earth’s atmosphere using Geostationary Korea Multi-Purse Satellite/Advanced Meteorological Imager (GK-2A/AMI) data. Because the GK-2A satellite will launch in 2018, we used data from the Japanese weather satellite Himawari-8 and onboard sensor Advanced Himawari Imager (AHI), which has similar sensor properties and observation area to those of GK-2A. TOA albedo was retrieved based on reflectance and regression coefficients of shortwave channels 1 to 6 of AHI. The regression coefficient was calculated using the results of the radiative transfer model (SBDART) and ridge regression. The SBDART used simulations of the correlation between TOA albedo and reflectance of each channel according to each atmospheric conditions (solar zenith angle, viewing zenith angle, relative azimuth angle, surface type, and absence/presence of clouds). The TOA albedo from Himawari-8/AHI were compared to that from the National Aeronautics and Space Administration (NASA) satellite Terra with onboard sensor Clouds and the Earth’s Radiant Energy System (CERES). The correlation coefficients between the two datasets from the week containing the first day of every month between 1st August 2015 and 1st July 2016 were high, ranging between 0.934 and 0.955, with the root mean square error in the 0.053-0.068 range.
Li, J.-L. F.; Suhas, E.; Richardson, Mark; Lee, Wei-Liang; Wang, Yi-Hui; Yu, Jia-Yuh; Lee, Tong; Fetzer, Eric; Stephens, Graeme; Shen, Min-HuaLi, J. F., E. Suhas, M. Richardson, W. Lee, Y. Wang, J. Yu, T. Lee, E. Fetzer, G. Stephens, M. Shen, 2018: The Impacts of Bias in Cloud-Radiation-Dynamics Interactions on Central-Pacific Seasonal and El Nino Simulations in Contemporary GCMs. Earth and Space Science, 5(2), 50-60. doi: 10.1002/2017EA000304. Most of the global climate models (GCMs) in the Coupled Model Intercomparison Project, phase 5 (CMIP5) do not include precipitating ice (a.k.a. falling snow) in their radiation calculations. We examine the importance of the radiative effects of precipitating ice on simulated surface wind stress and sea surface temperatures (SSTs) in terms of seasonal variation and in the evolution of Central Pacific El Nino (CP-El Nino) events. Using controlled simulations with the CESM1 model, we show that the exclusion of precipitating ice radiative effects generates a persistent excessive upper-level radiative cooling and an increasingly unstable atmosphere over convective regions such as the western Pacific and tropical convergence zones. The invigorated convection leads to persistent anomalous low-level outflows which weaken the easterly trade winds, reducing upper-ocean mixing and leading to a positive SST bias in the model mean state. In CP-El Nino events, this means that outflow from the modeled convection in the central Pacific reduces winds to the east, allowing unrealistic eastward propagation of warm SST anomalies following the peak in CP-El Nino activity. Including the radiative effects of precipitating ice reduces these model biases and improves the simulated life cycle of the CP-El Nino. Improved simulations of present day tropical seasonal variations and CP-El Nino events would increase the confidence in simulating their future behaviour. radiation; ENSO; GCM; cloud; 0321 Cloud/radiation interaction; 3373 Tropical dynamics; 3371 Tropical convection; 1627 Coupled models of the climate system; 4522 ENSO
Liu, Chunlei; Allan, Richard P.Liu, C., R. P. Allan, 2018: Unrealistic increases in wind speed explain reduced eastern Pacific heat flux in reanalyses. J. Climate, 31(8), 2981–2993. doi: 10.1175/JCLI-D-17-0642.1. Tropical eastern Pacific sea surface temperature plays a pivotal role in mechanisms that determine global mean surface temperature variability. In this study, the surface flux contribution to recent cooling of the tropical eastern Pacific is investigated using data from three atmospheric reanalyses with full assimilation of observations, an observations-based net surface energy flux reconstruction and fifteen atmospheric-only climate model simulations. For the ERA-Interim reanalysis, 78% of the decrease in net surface flux (-0.65 Wm-2yr-1 over 1988-2008) is explained by the latent heat flux variability. Latent heat flux variability differs between datasets and this is investigated using a bulk formula. We find that discrepancies in wind speed change explain contrasting latent heat flux trends across datasets. The significant increase of 0.26 ms-1decade-1 in wind speed over the tropical eastern Pacific in the ERA-Interim reanalysis is not reproduced by satellite or buoy observations and atmospheric-only climate model simulations, casting questions on the reliability of reanalysis-based surface fluxes over the tropical eastern Pacific.
Liu, Dongqing; Yang, Ben; Zhang, Yaocun; Qian, Yun; Huang, Anning; Zhou, Yang; Zhang, LujunLiu, D., B. Yang, Y. Zhang, Y. Qian, A. Huang, Y. Zhou, L. Zhang, 2018: Combined impacts of convection and microphysics parameterizations on the simulations of precipitation and cloud properties over Asia. Atmospheric Research, 212, 172-185. doi: 10.1016/j.atmosres.2018.05.017. Convection and microphysics parameterization schemes (i.e. CPS and MPS) are two important components related to the precipitation and cloud simulations in climate models, and one parameterization's impacts on the results can be dependent on the treatments in the other one. This study investigates the individual and combined impacts of CPS and MPS on the precipitation and cloud simulations over Asia based on nine regional model experiments using combinations of three CPSs of the Kain–Fritsch (KF), Zhang–McFarlane (ZM), and Grell 3D ensemble (G3), and three MPSs of the WRF double-moment 5-class (WDM5), WRF double-moment 6-class (WDM6), and Morrison double-moment (MORR). We first evaluate the simulated precipitation and find the experiment configured with the ZM CPS and MORR MPS performs the best when considering both the precipitation mean magnitude and spatial pattern. The sensitivity analysis results show that enhanced convection due to changing the CPS can cause strengthened or weakened stratiform processes, depending on the height of convective detrainments relative to that of convective drying, which is different among CPSs. In general, the CPS impacts on precipitation and clouds are larger when associating with the MORR MPS than with the other two MPSs as the former simulates more clouds and exhibits larger sensitivity of stratiform-type drying to convective detrainments. The MPS impacts on the precipitation and cloud simulations are also highly related to the CPS's behavior in simulating ice detrainments. Compared to the sum of the individual effects of CPS and MPS, simultaneously changing the two parameterizations causes considerably larger impacts on the precipitation and cloud simulations, suggesting the strong nonlinear interaction between the CPS and MPS. WRF model; Asia; Convection and microphysics parameterizations; Nonlinear combined impacts; Precipitation and cloud simulations
Liu, Dongyang; Liu, Qi; Liu, Guosheng; Wei, Junbo; Deng, Shumei; Fu, YunfeiLiu, D., Q. Liu, G. Liu, J. Wei, S. Deng, Y. Fu, 2018: Multiple factors explaining the deficiency of Cloud Profiling Radar on detecting oceanic warm clouds. Journal of Geophysical Research: Atmospheres, 123(15), 8135-8158. doi: 10.1029/2017JD028053. The CPR detecting efficiency on low-level clouds is affected by many situations, including surface clutter, spatial resolution, and radar sensitivity. These factors can uniquely or jointly result in missed detections of oceanic single-layer warm clouds. 57% of missed detections are attributed to a single factor and the rest are attributed to two or more factors that are indistinguishable. For missed warm clouds above 1 km, 30% result from the non-overcast effect, while the CPR range resolution is the major cause for the overcast ones. In particular, 18.4% are attributed exclusively to specific cloud microphysics, which is characterized by droplet effective radius (DER) and cloud optical thickness (COT). Compared to COT, the CPR detection is more dependent on DER, with a critical value standing around 10 μm. It is only for larger DER that the effects from COT turn to arise. Given LWP, clouds with larger DER and smaller COT are more likely to generate sufficient reflectivity and be detected than their counterpart. For clouds with the same DER and COT, opposite detecting results are primarily determined by the different droplet size distributions that lead to a variable reflectivity across the CPR detecting limit. Over global oceans, total miss rate of cloud occurrences approaches 0.73, while the loss rate of cloud water mass is 0.42 due to the smaller LWP of CPR-missed clouds. The CPR missed detections also lead to uncertainties in cloud radiative forcing estimations. A notable overestimation of shortwave cloud forcingat160% is found at BOA and TOA. Cloud microphysics; CPR missed detection; Miss rate; Radar reflectivity; Single-layer warm clouds
Liu, Meixian; Xu, Xianli; Sun, Alexander Y.; Luo, Wei; Wang, KelinLiu, M., X. Xu, A. Y. Sun, W. Luo, K. Wang, 2018: Why do karst catchments exhibit higher sensitivity to climate change? Evidence from a modified Budyko model. Advances in Water Resources, 122, 238-250. doi: 10.1016/j.advwatres.2018.10.013. Karst landscape, covers more than 10% of the global land surface and plays an important role in supporting ecosystems and human society, may be strongly influenced by climate change. Vegetation available water (VAW) is a key variable impacting the sensitivity of ecosystems to a changing environment. However, VAW in karst region is difficult to determine and remains uncertain. This study improved a dynamic Budyko-type water balance model, by introducing a nonlinear equation linking climate, vegetation and Budyko-type water balance. This model was calibrated using evolutionary algorithm based on monthly runoff. Comparison results in the Pearl, Yangtze and 12 karst catchments in south China, suggested high effectiveness of this improved model in simulating monthly runoff and evapotranspiration. Furthermore, in the 12 karst catchments, the max VAW was negatively correlated to the portion of karst landscape of the catchment (POK, r = −0.63,  α = 0.027) and the elasticity of evapotranspiration to precipitation (r = −0.60,  α = 0.04). These implied that karst catchments with higher POK had lower VAW, making the ecosystems rely more on precipitation. Climate sensitivity; Budyko framework; Ecohydrology; Hydrological modeling; Water balance
Liu, Yi Y.; van Dijk, Albert I. J. M.; Miralles, Diego G.; McCabe, Matthew F.; Evans, Jason P.; de Jeu, Richard A. M.; Gentine, Pierre; Huete, Alfredo; Parinussa, Robert M.; Wang, Lixin; Guan, Kaiyu; Berry, Joe; Restrepo-Coupe, NataliaLiu, Y. Y., A. I. J. M. van Dijk, D. G. Miralles, M. F. McCabe, J. P. Evans, R. A. M. de Jeu, P. Gentine, A. Huete, R. M. Parinussa, L. Wang, K. Guan, J. Berry, N. Restrepo-Coupe, 2018: Enhanced canopy growth precedes senescence in 2005 and 2010 Amazonian droughts. Remote Sensing of Environment, 211, 26-37. doi: 10.1016/j.rse.2018.03.035. Unprecedented droughts hit southern Amazonia in 2005 and 2010, causing a sharp increase in tree mortality and carbon loss. To better predict the rainforest's response to future droughts, it is necessary to understand its behavior during past events. Satellite observations provide a practical source of continuous observations of Amazonian forest. Here we used a passive microwave-based vegetation water content record (i.e., vegetation optical depth, VOD), together with multiple hydrometeorological observations as well as conventional satellite vegetation measures, to investigate the rainforest canopy dynamics during the 2005 and 2010 droughts. During the onset of droughts in the wet-to-dry season (May–July) of both years, we found large-scale positive anomalies in VOD, leaf area index (LAI) and enhanced vegetation index (EVI) over the southern Amazonia. These observations are very likely caused by enhanced canopy growth. Concurrent below-average rainfall and above-average radiation during the wet-to-dry season can be interpreted as an early arrival of normal dry season conditions, leading to enhanced new leaf development and ecosystem photosynthesis, as supported by field observations. Our results suggest that further rainfall deficit into the subsequent dry season caused water and heat stress during the peak of 2005 and 2010 droughts (August–October) that exceeded the tolerance limits of the rainforest, leading to widespread negative VOD anomalies over the southern Amazonia. Significant VOD anomalies were observed mainly over the western part in 2005 and mainly over central and eastern parts in 2010. The total area with significant negative VOD anomalies was comparable between these two drought years, though the average magnitude of significant negative VOD anomalies was greater in 2005. This finding broadly agrees with the field observations indicating that the reduction in biomass carbon uptake was stronger in 2005 than 2010. The enhanced canopy growth preceding drought-induced senescence should be taken into account when interpreting the ecological impacts of Amazonian droughts. Satellite; Amazonian droughts; Canopy water content; Passive microwave; Soil water deficit; Surface temperature; Vapor pressure deficit
Liu, Zhihua; Ballantyne, Ashley P.; Cooper, L. AnnieLiu, Z., A. P. Ballantyne, L. A. Cooper, 2018: Increases in Land Surface Temperature in Response to Fire in Siberian Boreal Forests and Their Attribution to Biophysical Processes. Geophysical Research Letters, 45(13), 6485-6494. doi: 10.1029/2018GL078283. Wildfire is the most prevalent natural disturbance in boreal forests and impacts climate through biogeochemical (e.g., greenhouse gas emission from biomass burning) and biophysical (e.g., albedo [α], evapotranspiration [ET], and roughness) processes. We used satellite observations to investigate the immediate (i.e., 1 year after fire) biophysical effects of fire in Siberian boreal forests. We found that boreal forest fires have a net annual warming effect (0.0728 to 0.325 K) due to strong summer warming and weak winter cooling. Fires also increased the diurnal temperature range and seasonal amplitude. These effects are strongest in summer and significantly higher in evergreen than in deciduous coniferous forests. Decreases in ET contributed to warming effects in summer, and increases in α contributed to cooling in winter. Our results suggest that the increase in observed land surface temperature immediately following fires in boreal ecosystems is most likely due to reduced ET leading to a strong positive feedback on the surface radiative budget. climate; remote sensing; boreal fire; disturbance; forest; land surface temperature
Loeb, Norman G.; Doelling, David R.; Wang, Hailan; Su, Wenying; Nguyen, Cathy; Corbett, Joseph G.; Liang, Lusheng; Mitrescu, Cristian; Rose, Fred G.; Kato, SeijiLoeb, N. G., D. R. Doelling, H. Wang, W. Su, C. Nguyen, J. G. Corbett, L. Liang, C. Mitrescu, F. G. Rose, S. Kato, 2018: Clouds and the Earth’s Radiant Energy System (CERES) Energy Balanced and Filled (EBAF) Top-of-Atmosphere (TOA) Edition 4.0 Data Product. J. Climate, 31(2), 895–918. doi: 10.1175/JCLI-D-17-0208.1. The Clouds and the Earth’s Radiant Energy System (CERES) Energy Balanced and Filled (EBAF) top-of-atmosphere (TOA) Ed4.0 data product is described. EBAF Ed4.0 is an update to EBAF Ed2.8, incorporating all of the Ed4.0 suite of CERES data product algorithm improvements and consistent input datasets throughout the record. A one-time adjustment to SW and LW TOA fluxes is made to ensure that global mean net TOA flux for July 2005-June 2015 is consistent with the in-situ value of 0.71 W m–2. While global mean all-sky TOA flux differences between Ed4.0 and Ed2.8 are within 0.5 Wm-2, appreciable SW regional differences occur over marine stratocumulus and snow/sea-ice regions. Marked regional differences in SW clear-sky TOA flux occur in polar regions and dust areas over ocean. Clear-sky LW TOA fluxes in EBAF Ed4.0 exceed Ed2.8 in regions of persistent high cloud cover. Owing to substantial differences in global mean clear-sky TOA fluxes, the net cloud radiative effect in EBAF Ed4.0 is -18 Wm-2 compared to -21 Wm-2 in EBAF Ed2.8. We estimate the overall uncertainty in 1°x1° latitude-longitude regional monthly all-sky TOA flux to be 3 Wm-2 (1σ) for the Terra-only period and 2.5 Wm-2 for the Terra-Aqua period both for SW and LW. The SW clear-sky regional monthly uncertainty is estimated to be 6 Wm-2 for the Terra-only period and 5 Wm-2 for the Terra-Aqua period. The LW clear-sky regional monthly uncertainty is 5 Wm-2 for Terra-only and 4.5 Wm-2 for Terra-Aqua.
Loeb, Norman G.; Thorsen, Tyler J.; Norris, Joel R.; Wang, Hailan; Su, WenyingLoeb, N. G., T. J. Thorsen, J. R. Norris, H. Wang, W. Su, 2018: Changes in Earth’s Energy Budget during and after the “Pause” in Global Warming: An Observational Perspective. Climate, 6(3), 62. doi: 10.3390/cli6030062. This study examines changes in Earth’s energy budget during and after the global warming “pause” (or “hiatus”) using observations from the Clouds and the Earth’s Radiant Energy System. We find a marked 0.83 ± 0.41 Wm−2 reduction in global mean reflected shortwave (SW) top-of-atmosphere (TOA) flux during the three years following the hiatus that results in an increase in net energy into the climate system. A partial radiative perturbation analysis reveals that decreases in low cloud cover are the primary driver of the decrease in SW TOA flux. The regional distribution of the SW TOA flux changes associated with the decreases in low cloud cover closely matches that of sea-surface temperature warming, which shows a pattern typical of the positive phase of the Pacific Decadal Oscillation. Large reductions in clear-sky SW TOA flux are also found over much of the Pacific and Atlantic Oceans in the northern hemisphere. These are associated with a reduction in aerosol optical depth consistent with stricter pollution controls in China and North America. A simple energy budget framework is used to show that TOA radiation (particularly in the SW) likely played a dominant role in driving the marked increase in temperature tendency during the post-hiatus period. clouds; energy budget; global warming hiatus
Loeb, Norman G.; Yang, Ping; Rose, Fred G.; Hong, Gang; Sun-Mack, Sunny; Minnis, Patrick; Kato, Seiji; Ham, Seung-Hee; Smith, William L.; Hioki, Souichiro; Tang, GuanglinLoeb, N. G., P. Yang, F. G. Rose, G. Hong, S. Sun-Mack, P. Minnis, S. Kato, S. Ham, W. L. Smith, S. Hioki, G. Tang, 2018: Impact of Ice Cloud Microphysics on Satellite Cloud Retrievals and Broadband Flux Radiative Transfer Model Calculations. J. Climate, 31(5), 1851–1864. doi: 10.1175/JCLI-D-17-0426.1. Ice cloud particles exhibit a range of shapes and sizes affecting a cloud’s single-scattering properties. Because they cannot be inferred from passive visible/infrared imager measurements, assumptions about the bulk single-scattering properties of ice clouds are fundamental to satellite cloud retrievals and broadband radiative flux calculations. To examine the sensitivity to ice particle model assumptions, three sets of models are used in satellite imager retrievals of ice cloud fraction, thermodynamic phase, optical depth, effective height and particle size, and in top-of-atmosphere and surface broadband radiative flux calculations. The three ice particle models include smooth hexagonal ice columns (SMOOTH), roughened hexagonal ice columns, and a two-habit model (THM) comprised of an ensemble of hexagonal columns and 20-element aggregates. While the choice of ice particle model has a negligible impact on daytime cloud fraction and thermodynamic phase, the global mean ice cloud optical depth retrieved from THM is smaller than SMOOTH by 2.3 (28%), and the regional root-mean-square-difference (RMSD) is 2.8 (32%). Effective radii derived from THM are 3.9 μm (16%) smaller than SMOOTH values and the RMSD is 5.2 μm (21%). In contrast, the regional RMSD in top-of-atmosphere (TOA) and surface flux between the THM and SMOOTH is only 1% in the SW and 0.3% in the LW when a consistent ice particle model is assumed in the cloud property retrievals and forward radiative transfer model calculations. Consequently, radiative fluxes derived using a consistent ice particle model assumption throughout provide a more robust reference for climate model evaluation compared to ice cloud property retrievals.
Lohmann, Ulrike; Neubauer, DavidLohmann, U., D. Neubauer, 2018: The importance of mixed-phase and ice clouds for climate sensitivity in the global aerosol–climate model ECHAM6-HAM2. Atmospheric Chemistry and Physics, 18(12), 8807-8828. doi: 10.5194/acp-18-8807-2018. How clouds change in a warmer climate remains one of the largest uncertainties for the equilibrium climate sensitivity (ECS). While a large spread in the cloud feedback arises from low-level clouds, it was recently shown that mixed-phase clouds are also important for ECS. If mixedphase clouds in the current climate contain too few supercooled cloud droplets, too much ice will change to liquid water in a warmer climate. As shown by Tan et al. (2016), this overestimates the negative cloud-phase feedback and underestimates ECS in the CAM global climate model (GCM). Here we use the newest version of the ECHAM6-HAM2 GCM to investigate the importance of mixed-phase and ice clouds for ECS.
Lorenz, Ruth; Herger, Nadja; Sedláček, Jan; Eyring, Veronika; Fischer, Erich M.; Knutti, RetoLorenz, R., N. Herger, J. Sedláček, V. Eyring, E. M. Fischer, R. Knutti, 2018: Prospects and caveats of weighting climate models for summer maximum temperature projections over North America. Journal of Geophysical Research: Atmospheres, 23(9), 4509-4526. doi: 10.1029/2017JD027992.
Lutsko, Nicholas J.; Takahashi, KenLutsko, N. J., K. Takahashi, 2018: What Can the Internal Variability of CMIP5 Models Tell Us About Their Climate Sensitivity?. J. Climate, 31(3), 5051–5069. doi: 10.1175/JCLI-D-17-0736.1. The relationship between climate models’ internal variability and their response to external forcings is investigated. Frequency-dependent regressions are performed between the outgoing top-of-atmosphere (TOA) energy fluxes and the global-mean surface temperature in the pre-industrial control simulations of the CMIP5 archive. Two distinct regimes are found. At sub-decadal frequencies the surface temperature and the outgoing short-wave flux are in quadrature, while the outgoing long-wave flux is linearly related to temperature and acts as a negative feedback on temperature perturbations. On longer time-scales the outgoing short-wave and long-wave fluxes are both linearly related to temperature, with the long-wave continuing to act as a negative feedback and the short-wave acting as a positive feedback on temperature variability. In addition to the different phase relationships, the two regimes can also be seen in estimates of the coherence and of the frequency-dependent regression co-efficients. The frequency-dependent regression co-efficients for the total cloudy-sky flux on time-scales of 2.5 to 3 years are found to be strongly (r2 >0.6) related to the models’ equilibrium climate sensitivities (ECSs), suggesting a potential “emergent constraint” for Earth’s ECS. However, O(100) years of data are required for this relationship to become robust. A simple model for Earths surface temperature variability and its relationship to the TOA fluxes is used to provide a physical explanation of these results.
Ma, H.-Y.; Klein, S. A.; Xie, S.; Zhang, C.; Tang, S.; Tang, Q.; Morcrette, C. J.; Van Weverberg, K.; Petch, J.; Ahlgrimm, M.; Berg, L. K.; Cheruy, F.; Cole, J.; Forbes, R.; Gustafson, W. I.; Huang, M.; Liu, Y.; Merryfield, W.; Qian, Y.; Roehrig, R.; Wang, Y.-C.Ma, H., S. A. Klein, S. Xie, C. Zhang, S. Tang, Q. Tang, C. J. Morcrette, K. Van Weverberg, J. Petch, M. Ahlgrimm, L. K. Berg, F. Cheruy, J. Cole, R. Forbes, W. I. Gustafson, M. Huang, Y. Liu, W. Merryfield, Y. Qian, R. Roehrig, Y. Wang, 2018: CAUSES: On the Role of Surface Energy Budget Errors to the Warm Surface Air Temperature Error Over the Central United States. Journal of Geophysical Research: Atmospheres, 123(5), 2888-2909. doi: 10.1002/2017JD027194.
Ma, Po-Lun; Rasch, Philip J.; Chepfer, Hélène; Winker, David M.; Ghan, Steven J.Ma, P., P. J. Rasch, H. Chepfer, D. M. Winker, S. J. Ghan, 2018: Observational constraint on cloud susceptibility weakened by aerosol retrieval limitations. Nature Communications, 9(1), 2640. doi: 10.1038/s41467-018-05028-4. Cloud susceptibility to aerosols in models frequently exceeds satellite estimates. Here the authors show that the discrepancy can be explained by retrieval limitations especially in clean environments, suggesting that conventional comparison strategies may lead to misunderstanding.
Ma, Zhanshan; Liu, Qijun; Zhao, Chuanfeng; Shen, Xueshun; Wang, Yuan; Jiang, Jonathan H.; Li, Zhe; Yung, YukMa, Z., Q. Liu, C. Zhao, X. Shen, Y. Wang, J. H. Jiang, Z. Li, Y. Yung, 2018: Application and Evaluation of an Explicit Prognostic Cloud-Cover Scheme in GRAPES Global Forecast System. Journal of Advances in Modeling Earth Systems, 10(3), 652-667. doi: 10.1002/2017MS001234. An explicit prognostic cloud-cover scheme (PROGCS) is implemented into the Global/Regional Assimilation and Prediction System (GRAPES) for global middle-range numerical weather predication system (GRAPES_GFS) to improve the model performance in simulating cloud cover and radiation. Unlike the previous diagnostic cloud-cover scheme (DIAGCS), PROGCS considers the formation and dissipation of cloud cover by physically connecting it to the cumulus convection and large-scale stratiform condensation processes. Our simulation results show that clouds in mid-high latitudes arise mainly from large-scale stratiform condensation processes, while cumulus convection and large-scale condensation processes jointly determine cloud cover in low latitudes. Compared with DIAGCS, PROGCS captures more consistent vertical distributions of cloud cover with the observations from Atmospheric Radiation Measurements (ARM) program at the Southern Great Plains (SGP) site and simulates more realistic diurnal cycle of marine stratocumulus with the ERA-Interim reanalysis data. The low, high, and total cloud covers that are determined via PROGCS appear to be more realistic than those simulated via DIAGCS when both are compared with satellite retrievals though the former maintains slight negative biases. In addition, the simulations of outgoing longwave radiation (OLR) at the top of the atmosphere (TOA) from PROGCS runs have been considerably improved as well, resulting in less biases in radiative heating rates at heights below 850 hPa and above 400 hPa of GRAPES_GFS. Our results indicate that a prognostic method of cloud-cover calculation has significant advantage over the conventional diagnostic one, and it should be adopted in both weather and climate simulation and forecast. radiative flux; 0321 Cloud/radiation interaction; 1622 Earth system modeling; 0320 Cloud physics and chemistry; cloud cover; diagnostic cloud-cover scheme; GRAPES_GFS; prognostic cloud-cover scheme
Mao, Feiyue; Pan, Zengxin; Henderson, David S.; Wang, Wei; Gong, WeiMao, F., Z. Pan, D. S. Henderson, W. Wang, W. Gong, 2018: Vertically resolved physical and radiative response of ice clouds to aerosols during the Indian summer monsoon season. Remote Sensing of Environment, 216, 171-182. doi: 10.1016/j.rse.2018.06.027. Changes in aerosol loading affect cloud albedo and emission and Earth's radiative balance with a low level of scientific understanding. In this study, we investigate the vertical response of ice clouds to aerosols within the Indian subcontinent during monsoon season (2006–2010) based on multiple satellite observations. As a function of aerosol loading, we find that the cloud optical depth, cloud geometrical depth and ice water path decrease by 0.23 (from 0.39 to 0.16), 0.8 km (from 2.6 to 1.8 km), 5.1 g/m2 (from 7.9 to 2.8 g/m2), respectively, and that ice particles possibly decrease in size and become more spherical in shape as aerosol optical depth (AOD) increases from 0.1 to 1; these changes tend to plateau as AOD increases beyond 1. The absolute negative response between ice clouds and aerosols under moist and unstable atmospheric conditions is stronger than that under drier and stable atmospheric conditions, and vice versa. Moreover, the negative impact of smoke on ice clouds is stronger than dust and polluted dust, which is likely related to the strong absorption properties and poor ice nucleation efficiency of smoke. Aerosol impacts on ice clouds lead to a decrease in the net cloud radiative effect of 7.3 W/m2 (from 18.5 to 11.2 W/m2) as AOD increases from 0.1 to 1. This change in ice cloud properties mainly results in the decrease in downwelling LW radiation to the surface and consequently weakened radiative forcing of ice clouds during the Indian summer monsoon season. Indian summer monsoon; Ice clouds; Indirect effect; Semi-direct effect; Three dimension observations
Matthews, GrantMatthews, G., 2018: Real-Time Determination of Earth Radiation Budget Spectral Signatures for Nonlinear Unfiltering of Results from MERBE. J. Appl. Meteor. Climatol., 57(2), 273-294. doi: 10.1175/JAMC-D-16-0406.1. AbstractAmong the best ways to gain more certainty in climate model prediction is to compare and constrain simulations with worldwide satellite measurements of the Earth radiation budget (ERB) short- and longwave radiant fluxes (SW and LW), which drive climate processes. Recent calls to ensure orbital ERB measurements track true climate, rather than instrument changes, led to the creation of the Moon and Earth Radiation Budget Experiment (MERBE). This independent project is recalibrating multiple existing ERB devices from different international space agencies so they adhere to common SI-traceable radiometric standards, by regularly sampling the unaltering constants of lunar reflectivity/emissivity, thus ensuring no artificial trends exist. This work details the use of MODTRAN to give an instantaneous SW and LW Earth spectrum for all scenes viewed by devices in the project, to then be used with instrument spectral responses for unfiltering radiances. In the majority of cases when data from a collocated imager are available, a dual-layer unfiltering is also performed separately on cloudy and cloud-free areas, yielding clear and overcast ERB spectral results. Additionally, use is made of improved in-flight methods to derive spectral responses from a previous American Meteorological Society study, and comparisons between Earth MERBE radiances from two identical devices operating on Terra/Aqua are shown along with results from the CERES project. These demonstrate an order of magnitude improvement in relative accuracy for edition 1 MERBE results over CERES and show that the latest CERES data are less accurate and stable than claimed.
Matthews, GrantMatthews, G., 2018: First decadal lunar results from the Moon and Earth Radiation Budget Experiment. Applied Optics, 57(7), 1594. doi: 10.1364/AO.57.001594.
Matthews, GrantMatthews, G., 2018: Signal Processing Enhancements to Improve Instantaneous Accuracy of a Scanning Bolometer: Application to MERBE. IEEE Transactions on Geoscience and Remote Sensing, 56(6), 3421-3431. doi: 10.1109/TGRS.2018.2799823.
Mayer, Michael; Balmaseda, Magdalena Alonso; Haimberger, LeopoldMayer, M., M. A. Balmaseda, L. Haimberger, 2018: Unprecedented 2015/16 Indo-Pacific heat transfer speeds up Tropical Pacific heat recharge. Geophysical Research Letters, 45(7), 3274-3284. doi: 10.1002/2018GL077106. El Nino events are characterized by anomalously warm tropical Pacific surface waters and concurrent ocean heat discharge, a precursor of subsequent cold La Nina conditions. Here we show that El Nino 2015/16 departed from this norm: despite extreme peak surface temperatures, Tropical Pacific (30N-30S) upper ocean heat content (OHC) increased by 9.6±1.7 ZJ (1ZJ=1021J), in stark contrast to the previous strong El Nino in 1997/98 (-11.5±2.9 ZJ). Unprecedented reduction of Indonesian Throughflow volume and heat transport played a key role in the anomalous 2015/16 event. We argue that this anomaly is linked with the previously documented intensified warming and associated rising sea levels in the Indian Ocean during the last decade. Additionally, increased absorption of solar radiation acted to dampen Pacific OHC discharge. These results explain the weak and short-lived La Nina conditions in 2016/17 and indicate the need for realistic representation of Indo-Pacific energy transfers for skilful seasonal-to-decadal predictions. 3359 Radiative processes; 3339 Ocean/atmosphere interactions; 4522 ENSO; 4215 Climate and interannual variability; 4260 Ocean data assimilation and reanalysis; 3339; 3359; 4215; 4260; 4522
McCoy, Daniel T.; Field, Paul R.; Schmidt, Anja; Grosvenor, Daniel P.; Bender, Frida A.-M.; Shipway, Ben J.; Hill, Adrian A.; Wilkinson, Jonathan M.; Elsaesser, Gregory S.McCoy, D. T., P. R. Field, A. Schmidt, D. P. Grosvenor, F. A. Bender, B. J. Shipway, A. A. Hill, J. M. Wilkinson, G. S. Elsaesser, 2018: Aerosol midlatitude cyclone indirect effects in observations and high-resolution simulations. Atmospheric Chemistry and Physics, 18(8), 5821-5846. doi: 10.5194/acp-18-5821-2018.
McHardy, Theodore M.; Dong, Xiquan; Xi, Baike; Thieman, Mandana M.; Minnis, Patrick; Palikonda, RabindraMcHardy, T. M., X. Dong, B. Xi, M. M. Thieman, P. Minnis, R. Palikonda, 2018: Comparison of Daytime Low-Level Cloud Properties Derived from GOES and ARM SGP Measurements. Journal of Geophysical Research: Atmospheres, 123(15), 8221-8237. doi: 10.1029/2018JD028911. Large-scale satellite data are critical for both verifying and improving general circulation model (GCM) parameterizations of clouds and radiation for climate prediction. For reliable application of satellite datasets in cloud processes and climate models, it is important to have a reasonable estimate of the errors in the derived cloud properties. The daytime single-layered low-level cloud properties retrieved by the Geostationary Operational Environmental Satellite system (GOES) are compared with ground-based observations and retrievals over the Department of Energy (DOE) Atmospheric Radiation Measurement (ARM) Southern Great Plains (SGP) Central Facility (SCF) from June 1998 through December 2006. The GOES retrievals are made via the Visible-Infrared Solar-infrared Split-window technique (VISST). They are spatially averaged within a 0.15° x 0.15° box centered on the ARM SGP site and the ARM surface observations are temporally averaged ± 15 minutes around the GOES scans to produce collocated pairs. Comparisons are made for monthly means, diurnal means, and one-to-one GOES and ARM collocated pairs. GOES Teff is highly correlated with ARM Ttop cloud temperature, having an R2 value of 0.75, though GOES exhibits a cold bias. GOES retrieved τ and LWP have very good agreement with ARM retrievals with R2s of 0.45 and 0.47, while re (GOES), on average, is about 2 μm greater than ARM re. An examination of solar and viewing geometry has shown that GOES retrieved mean re and τ values are impacted by solar zenith angle (SZA) and especially scattering angle (SCA), which is not unexpected and needs to be accounted for by users. GOES; ARM SGP; Microphysics; Stratocumulus
Miyakawa, Tomoki; Noda, Akira T.; Kodama, ChihiroMiyakawa, T., A. T. Noda, C. Kodama, 2018: The Impact of Hybrid Usage of a Cumulus Parameterization Scheme on Tropical Convection and Large-Scale Circulations in a Global Cloud-System Resolving Model. Journal of Advances in Modeling Earth Systems, 10(11), 2952-2970. doi: 10.1029/2018MS001302. The impact of activating a cumulus parameterization scheme in the global nonhydrostatic icosahedral atmospheric model (NICAM) coupled with a one-dimensional (1-D) mixed-layer ocean model is assessed using a cloud-system-resolving, 14-km mesh. The Chikira-Sugiyama (CS) scheme, which employs an entrainment rate sensitive to the humidity of the environment, can consider congestus clouds in the tropics when used in conventional global climate models. Congestus clouds are underresolved in the default 14-km mesh NICAM. In the present study, boreal summer NICAM simulations are performed with and without the CS scheme, and several different scheme parameters are evaluated. The results show that the horizontal scale of convection and precipitable water increased in the tropics when using the CS scheme. Model adjustments were apparent at two different timescales: a rapid adjustment within the first week and a slower adjustment at 1 to 2 months. Both effects were magnified in the simulations that employed smaller values for the parameter that defines the fractional of loss of buoyancy-generated energy in parameterized convection. The upward branch of the Hadley circulation shifted northward, and the Walker circulation was enhanced when the CS scheme was activated. These large-scale adjustments suggested that increased midtropospheric moisture in the tropics tends to favor larger organized convective activities, which require an abundant supply of moisture, which, in this case, is available to the north of the equatorial West Pacific Ocean. cumulus parameterization; convective aggregation; general circulation; global cloud-system-resolving model
Moch, Jonathan M.; Dovrou, Eleni; Mickley, Loretta J.; Keutsch, Frank N.; Cheng, Yuan; Jacob, Daniel J.; Jiang, Jingkun; Li, Meng; Munger, J. William; Qiao, Xiaohui; Zhang, QiangMoch, J. M., E. Dovrou, L. J. Mickley, F. N. Keutsch, Y. Cheng, D. J. Jacob, J. Jiang, M. Li, J. W. Munger, X. Qiao, Q. Zhang, 2018: Contribution of hydroxymethane sulfonate to ambient particulate matter: A potential explanation for high particulate sulfur during severe winter haze in Beijing. Geophysical Research Letters, 45(21), 11,969-11,979. doi: 10.1029/2018GL079309. PM2.5 during severe winter haze in Beijing, China, has reached levels as high as 880 μg m-3, with sulfur compounds contributing significantly to PM2.5 composition. This sulfur has been traditionally assumed to be sulfate, although atmospheric chemistry models are unable to account for such large sulfate enhancements under dim winter conditions. Using a 1-D model, we show that well characterized but previously overlooked chemistry of aqueous-phase HCHO and S (IV) in cloud droplets to form a S (IV)-HCHO adduct, hydroxymethane sulfonate (HMS), may explain high particulate sulfur in wintertime Beijing. We also demonstrate in the laboratory that methods of ion chromatography typically used to measure ambient particulates easily misinterpret HMS as sulfate. Our findings suggest that HCHO and not SO2 has been the limiting factor in many haze events in Beijing and that to reduce severe winter pollution in this region, policymakers may need to address HCHO sources such as transportation. China; Air pollution; formaldehyde; hydroxymethane sulfonate; PM2.5; sulfate
Mulcahy, J. P.; Jones, C.; Sellar, A.; Johnson, B.; Boutle, I. A.; Jones, A.; Andrews, T.; Rumbold, S. T.; Mollard, J.; Bellouin, N.; Johnson, C. E.; Williams, K. D.; Grosvenor, D. P.; McCoy, D. T.Mulcahy, J. P., C. Jones, A. Sellar, B. Johnson, I. A. Boutle, A. Jones, T. Andrews, S. T. Rumbold, J. Mollard, N. Bellouin, C. E. Johnson, K. D. Williams, D. P. Grosvenor, D. T. McCoy, 2018: Improved aerosol processes and effective radiative forcing in HadGEM3 and UKESM1. Journal of Advances in Modeling Earth Systems, 10(11), 2786-2805. doi: 10.1029/2018MS001464. Abstract Aerosol processes and, in particular, aerosol-cloud interactions cut across the traditional physical-Earth system boundary of coupled Earth system models and remain one of the key uncertainties in estimating anthropogenic radiative forcing of climate. Here, we calculate the historical aerosol effective radiative forcing (ERF) in the HadGEM3-GA7 climate model in order to assess the suitability of this model for inclusion in the UK Earth system model, UKESM1. The aerosol ERF, calculated for the year 2000 relative to 1850, is large and negative in the standard GA7 model leading to an unrealistic negative total anthropogenic forcing over the 20th century. We show how underlying assumptions and missing processes in both the physical model and aerosol parameterizations lead to this large aerosol ERF. A number of model improvements are investigated to assess their impact on the aerosol ERF. These include; an improved representation of cloud droplet spectral dispersion, updates to the aerosol activation scheme and black carbon optical properties. One of the largest contributors to the aerosol forcing uncertainty is insufficient knowledge of the pre-industrial aerosol climate. We evaluate the contribution of uncertainties in the natural marine emissions of dimethyl sulphide (DMS) and organic aerosol to the ERF. The combination of model improvements derived from these studies weaken the aerosol ERF by up to 50% of the original value and lead to a total anthropogenic historical forcing more in-line with assessed values. climate models; aerosol forcing; effective radiative forcing; model development
Müller, W. A.; Jungclaus, J. H.; Mauritsen, T.; Baehr, J.; Bittner, M.; Budich, R.; Bunzel, F.; Esch, M.; Ghosh, R.; Haak, H.; Ilyina, T.; Kleine, T.; Kornblueh, L.; Li, H.; Modali, K.; Notz, D.; Pohlmann, H.; Roeckner, E.; Stemmler, I.; Tian, F.; Marotzke, J.Müller, W. A., J. H. Jungclaus, T. Mauritsen, J. Baehr, M. Bittner, R. Budich, F. Bunzel, M. Esch, R. Ghosh, H. Haak, T. Ilyina, T. Kleine, L. Kornblueh, H. Li, K. Modali, D. Notz, H. Pohlmann, E. Roeckner, I. Stemmler, F. Tian, J. Marotzke, 2018: A Higher-resolution Version of the Max Planck Institute Earth System Model (MPI-ESM1.2-HR). Journal of Advances in Modeling Earth Systems, 10(7), 1383-1413. doi: 10.1029/2017MS001217. The MPI-ESM1.2 is the latest version of the Max Planck Institute Earth System Model and is the baseline for the Coupled Model Intercomparison Project Phase 6 and current seasonal and decadal climate predictions. This paper evaluates a coupled higher-resolution version (MPI-ESM1.2-HR) in comparison with its lower-resolved version (MPI-ESM1.2-LR). We focus on basic oceanic and atmospheric mean states and selected modes of variability, the El Niño/Southern Oscillation and the North Atlantic Oscillation. The increase in atmospheric resolution in MPI-ESM1.2-HR reduces the biases of upper-level zonal wind and atmospheric jet stream position in the northern extratropics. This results in a decrease of the storm track bias over the northern North Atlantic, for both winter and summer season. The blocking frequency over the European region is improved in summer, and North Atlantic Oscillation and related storm track variations improve in winter. Stable Atlantic meridional overturning circulations are found with magnitudes of 16 Sv for MPI-ESM1.2-HR and 20 Sv for MPI-ESM1.2-LR at 26°N. A strong sea surface temperature bias of 5°C along with a too zonal North Atlantic current is present in both versions. The sea surface temperature bias in the eastern tropical Atlantic is reduced by 1°C due to higher-resolved orography in MPI-ESM-HR, and the region of the cold-tongue bias is reduced in the tropical Pacific. MPI-ESM1.2-HR has a well-balanced radiation budget and its climate sensitivity is explicitly tuned to 3 K. Although the obtained reductions in long-standing biases are modest, the improvements in atmospheric dynamics make this model well suited for prediction and impact studies. climate variability; Earth System Modeling
Myers, Timothy A.; Mechoso, Carlos R.; Cesana, Gregory V.; DeFlorio, Michael J.; Waliser, Duane E.Myers, T. A., C. R. Mechoso, G. V. Cesana, M. J. DeFlorio, D. E. Waliser, 2018: Cloud feedback key to marine heatwave off Baja California. Geophysical Research Letters, 45(9), 4345-4352. doi: 10.1029/2018GL078242.
Myers, Timothy A.; Mechoso, Carlos R.; DeFlorio, Michael J.Myers, T. A., C. R. Mechoso, M. J. DeFlorio, 2018: Coupling between marine boundary layer clouds and summer-to-summer sea surface temperature variability over the North Atlantic and Pacific. Climate Dynamics, 50(3-4), 955-969. doi: 10.1007/s00382-017-3651-8. Climate modes of variability over the Atlantic and Pacific may be amplified by a positive feedback between sea-surface temperature (SST) and marine boundary layer clouds. However, it is well known that climate models poorly simulate this feedback. Does this deficiency contribute to model-to-model differences in the representation of climate modes of variability? Over both the North Atlantic and Pacific, typical summertime interannual to interdecadal SST variability exhibits horseshoe-like patterns of co-located anomalies of shortwave cloud radiative effect (CRE), low-level cloud fraction, SST, and estimated inversion strength over the subtropics and midlatitudes that are consistent with a positive cloud feedback. During winter over the midlatitudes, this feedback appears to be diminished. Models participating in the Coupled Model Intercomparison Project phase 5 that simulate a weak feedback between subtropical SST and shortwave CRE produce smaller and less realistic amplitudes of summertime SST and CRE variability over the northern oceans compared to models with a stronger feedback. The change in SST amplitude per unit change in CRE amplitude among the models and observations may be understood as the temperature response of the ocean mixed layer to a unit change in radiative flux over the course of a season. These results highlight the importance of boundary layer clouds in interannual to interdecadal atmosphere–ocean variability over the northern oceans during summer. The results also suggest that deficiencies in the simulation of these clouds in coupled climate models contribute to underestimation in their simulation of summer-to-summer SST variability.
Osipov, Sergey; Stenchikov, GeorgiyOsipov, S., G. Stenchikov, 2018: Simulating the Regional Impact of Dust on the Middle East Climate and the Red Sea. Journal of Geophysical Research: Oceans, 123(2), 1032-1047. doi: 10.1002/2017JC013335. The Red Sea is located between North Africa and the Arabian Peninsula, the largest sources of dust in the world. Satellite retrievals show very high aerosol optical depth in the region, which increases during the summer season, especially over the southern Red Sea. Previously estimated and validated radiative effect from dust is expected to have a profound thermal and dynamic impact on the Red Sea, but that impact has not yet been studied or evaluated. Due to the strong dust radiative effect at the sea surface, uncoupled ocean modeling approaches with prescribed atmospheric boundary conditions result in an unrealistic ocean response. Therefore, to study the impact of dust on the regional climate of the Middle East and the Red Sea, we employed the Regional Ocean Modeling System fully coupled with the Weather Research and Forecasting model. We modified the atmospheric model to account for the radiative effect of dust. The simulations show that, in the equilibrium response, dust cools the Red Sea, reduces the surface wind speed, and weakens both the exchange at the Bab-el-Mandeb strait and the overturning circulation. The salinity distribution, freshwater, and heat budgets are significantly altered. A validation of the simulations against satellite products indicates that accounting for radiative effect from dust almost completely removes the bias and reduces errors in the top of the atmosphere fluxes and sea surface temperature. Our results suggest that dust plays an important role in the energy balance, thermal, and circulation regimes in the Red Sea. radiative forcing; dust; 0305 Aerosols and particles; 1616 Climate variability; 3355 Regional modeling; 4504 Air/sea interactions; energy balance; 4845 Nutrients and nutrient cycling; biological productivity; overturning circulation; Red Sea
Ottaviani, Matteo; Foster, Robert; Gilerson, Alexander; Ibrahim, Amir; Carrizo, Carlos; El-Habashi, Ahmed; Cairns, Brian; Chowdhary, Jacek; Hostetler, Chris; Hair, Johnathan; Burton, Sharon; Hu, Yongxiang; Twardowski, Michael; Stockley, Nicole; Gray, Deric; Slade, Wayne; Cetinic, IvonaOttaviani, M., R. Foster, A. Gilerson, A. Ibrahim, C. Carrizo, A. El-Habashi, B. Cairns, J. Chowdhary, C. Hostetler, J. Hair, S. Burton, Y. Hu, M. Twardowski, N. Stockley, D. Gray, W. Slade, I. Cetinic, 2018: Airborne and shipborne polarimetric measurements over open ocean and coastal waters: Intercomparisons and implications for spaceborne observations. Remote Sensing of Environment, 206, 375-390. doi: 10.1016/j.rse.2017.12.015. Comprehensive polarimetric closure is demonstrated using observations from two in-situ polarimeters and Vector Radiative Transfer (VRT) modeling. During the Ship-Aircraft Bio-Optical Research (SABOR) campaign, the novel CCNY HyperSAS-POL polarimeter was mounted on the bow of the R/V Endeavor and acquired hyperspectral measurements from just above the surface of the ocean, while the NASA GISS Research Scanning Polarimeter was deployed onboard the NASA LaRC's King Air UC-12B aircraft. State-of-the-art, ancillary measurements were used to characterize the atmospheric and marine contributions in the VRT model, including those of the High Spectral Resolution Lidar (HSRL), the AErosol RObotic NETwork for Ocean Color (AERONET-OC), a profiling WETLabs ac-9 spectrometer and the Multi-spectral Volume Scattering Meter (MVSM). An open-ocean and a coastal scene are analyzed, both affected by complex aerosol conditions. In each of the two cases, it is found that the model is able to accurately reproduce the Stokes components measured simultaneously by each polarimeter at different geometries and viewing altitudes. These results are mostly encouraging, considering the different deployment strategies of RSP and HyperSAS-POL, which imply very different sensitivities to the atmospheric and ocean contributions, and open new opportunities in above-water polarimetric measurements. Furthermore, the signal originating from each scene was propagated to the top of the atmosphere to explore the sensitivity of polarimetric spaceborne observations to changes in the water type. As expected, adding polarization as a measurement capability benefits the detection of such changes, reinforcing the merits of the full-Stokes treatment in modeling the impact of atmospheric and oceanic constituents on remote sensing observations.
Ovando, Gustavo; Sayago, Silvina; Bocco, MónicaOvando, G., S. Sayago, M. Bocco, 2018: Evaluating accuracy of DSSAT model for soybean yield estimation using satellite weather data. ISPRS Journal of Photogrammetry and Remote Sensing, 138, 208-217. doi: 10.1016/j.isprsjprs.2018.02.015. Crop models allow simulating the development and yield of the crops, to represent and to evaluate the influence of multiple factors. The DSSAT cropping system model is one of the most widely used and contains CROPGRO module for soybean. This crop has a great importance for many southern countries of Latin America and for Argentina. Solar radiation and rainfall are necessary variables as inputs for crop models; however these data are not as readily available. The satellital products from Clouds and Earth's Radiant Energy System (CERES) and Tropic Rainfall Measurement Mission (TRMM) provide continuous spatial and temporal information of solar radiation and precipitation, respectively. This study evaluates and quantifies the uncertainty in estimating soybean yield using a DSSAT model, when recorded weather data are replaced with CERES and TRMM ones. Different percentages of data replacements, soybean maturity groups and planting dates are considered, for 2006–2016 period in Oliveros (Argentina). Results show that CERES and TRMM products can be used for soybean yield estimation with DSSAT considering that: percentage of data replacement, campaign, planting date and maturity group, determine the amounts and trends of yield errors. Replacements with CERES data up to 30% result in %RMSE lower than 10% in 87% of the cases; while the replacement with TRMM data presents the best statisticals in campaigns with high yields. Simulations based entirely on CERES solar radiation give better results than those with TRMM. In general, similar percentages of replacement show better performance in the estimation of soybean yield for solar radiation than the replacement of precipitation values. CERES; TRMM; Argentina; Crop models
Painemal, DavidPainemal, D., 2018: Global Estimates of Changes in Shortwave Low-Cloud Albedo and Fluxes Due to Variations in Cloud Droplet Number Concentration Derived From CERES-MODIS Satellite Sensors. Geophysical Research Letters, 45(17), 9288-9296. doi: 10.1029/2018GL078880. Fifteen years of Aqua Clouds and the Earth's Radiant Energy Systems (CERES) and MOderate resolution Imaging Spectroradiometer (MODIS) observations are combined to derive nearly global maps of shortwave albedo (A) and flux (F) response to changes in cloud droplet number concentration (Nd). Absolute ( ) and relative ( ) albedo susceptibilities are computed by exploiting the linear relationship between A and ln (Nd) for shallow liquid clouds. Subtropical stratiform clouds over the eastern Pacific, eastern Atlantic, and off the coast of eastern Asia yield the highest Sr, followed by the extratropical oceans during their hemispheric summer. When Sr is cast in terms of F, the eastern Pacific clouds dominate Sr. Sa is mainly governed by Nd, with offshore clouds producing high Sa. While both Sa and Sr are advantageous for understanding radiative aspects of the aerosol indirect effect, Sr is more suitable for calculating changes in A and F due to the linearity of the A-ln (Nd) relationship.
Pan, X; Yang, Y; Liu, Y; Fan, X; Shan, L; Zhang, XPan, X., Y. Yang, Y. Liu, X. Fan, L. Shan, X. Zhang, 2018: Quantifying the contributions of environmental parameters to CERES surface net radiation error in China. International Archives of the Photogrammetry, Remote Sensing & Spatial Information Sciences, 42(3), 1339-1345. doi: 10.5194/isprs-archives-XLII-3-1339-2018. Error source analyses are critical for the satellite-retrieved surface net radiation (Rn) products. In this study, we evaluate the Rn error sources in the Clouds and the Earth's Radiant Energy System (CERES) project at 43 sites from July in 2007 to December in 2007 in China. The results show that cloud fraction (CF), land surface temperature (LST), atmospheric temperature (AT) and algorithm error dominate the Rn error, with error contributions of ~-20, ~15, ~10 and ~10 W/m2 (net shortwave (NSW)/longwave (NLW) radiation), respectively. For NSW, the dominant error source is algorithm error (more than 10 W/m2), particularly in spring and summer with abundant cloud. For NLW, due to the high sensitivity of algorithm and large LST/CF error, LST and CF are the largest error sources, especially in northern China. The AT influences the NLW error large in southern China because of the large AT error in there. The total precipitable water has weak influence on Rn error even with the high sensitivity of algorithm. In order to improve Rn quality, CF and LST (AT) error in northern (southern) China should be decreased.
Pan, Zengxin; Mao, Feiyue; Wang, Wei; Logan, Timothy; Hong, JiaPan, Z., F. Mao, W. Wang, T. Logan, J. Hong, 2018: Examining Intrinsic Aerosol-Cloud Interactions in South Asia Through Multiple Satellite Observations. Journal of Geophysical Research: Atmospheres, 23(19), 11,210-11,224. doi: 10.1029/2017JD028232. Changes in anthropogenic aerosol loading affect cloud albedo and the Earth's radiative balance with a low level of scientific understanding. Aerosol-cloud interaction and its effects on climate are mainly evaluated using passive observations in a global scale. Here this study estimated the intrinsic response of clouds to aerosols by combining active and passive satellite observations from July 2006 to February 2011 in South Asia. We evaluate the average radiative forcing by the intrinsic aerosol-cloud interaction for warm liquid clouds as 0.63 ± 0.19, −0.34 ± 0.40, and 1.11 ± 0.08 W/m2 during the annual, monsoon, and nonmonsoon periods in South Asia, respectively. Relationships derived among liquid water path, cloud droplet number concentration, and consequent cloud albedo are assessed as a function of aerosol concentration. The intensity of the aerosol-cloud interaction gradually weakens with increasing cloud base height above ground level in South Asia, is associated with aerosol vertical distribution and vertical atmospheric upward motion. Moreover, distinct regional and seasonal variations in the aerosol-cloud interaction are observed for liquid water path, cloud droplet number concentration, and the resulting cloud albedo in South Asia. These variations are associated with water vapor and aerosol absorption levels. Results contribute to the understanding and modeling of aerosol-cloud interactions and determining their effects on radiative forcing and climate in South Asia. aerosol-cloud interaction; South Asia; vertical variations
Pan, Zengxin; Mao, Feiyue; Wang, Wei; Zhu, Bo; Lu, Xin; Gong, WeiPan, Z., F. Mao, W. Wang, B. Zhu, X. Lu, W. Gong, 2018: Impacts of 3D Aerosol, Cloud, and Water Vapor Variations on the Recent Brightening during the South Asian Monsoon Season. Remote Sensing, 10(4), 651. doi: 10.3390/rs10040651. South Asia is experiencing a levelling-off trend in solar radiation and even a transition from dimming to brightening. Any change in incident solar radiation, which is the only significant energy source of the global ecosystem, profoundly affects our habitats. Here, we use multiple observations of the A-Train constellation to evaluate the impacts of three-dimensional (3D) aerosol, cloud, and water vapor variations on the changes in surface solar radiation during the monsoon season (June–September) in South Asia from 2006 to 2015. Results show that surface shortwave radiation (SSR) has possibly increased by 16.2 W m−2 during this period. However, an increase in aerosol loading is inconsistent with the SSR variations. Instead, clouds are generally reduced and thinned by approximately 8.8% and 280 m, respectively, with a decrease in both cloud water path (by 34.7 g m−2) and particle number concentration under cloudy conditions. Consequently, the shortwave cloud radiative effect decreases by approximately 45.5 W m−2 at the surface. Moreover, precipitable water in clear-sky conditions decreases by 2.8 mm (mainly below 2 km), and related solar brightening increases by 2.5 W m−2. Overall, the decreases in 3D water vapor and clouds distinctly result in increased absorption of SSR and subsequent surface brightening. cloud; aerosol; water vapor; A-Train; brightening; South Asia
Parishani, Hossein; Pritchard, Michael S.; Bretherton, Christopher S.; Terai, Christopher R.; Wyant, Matthew C.; Khairoutdinov, Marat; Singh, BalwinderParishani, H., M. S. Pritchard, C. S. Bretherton, C. R. Terai, M. C. Wyant, M. Khairoutdinov, B. Singh, 2018: Insensitivity of the Cloud Response to Surface Warming Under Radical Changes to Boundary Layer Turbulence and Cloud Microphysics: Results From the Ultraparameterized CAM. Journal of Advances in Modeling Earth Systems, 10(12), 3139-3158. doi: 10.1029/2018MS001409. Abstract We study the cloud response to a +4K surface warming in a new multiscale climate model that uses enough interior resolution to begin explicitly resolving boundary layer turbulence (i.e., ultraparameterization or UP). UP's predictions are compared against those from standard superparameterization (SP). The mean cloud radiative effect feedback turns out to be remarkably neutral across all of our simulations, despite some radical changes in both cloud microphysical parameter settings and cloud-resolving model grid resolution. The overall low cloud response to warming is a positive low cloud feedback over land, a negative feedback (driven by cloud optical depth increase) at high latitudes, and weak feedback over the low-latitude oceans. The most distinct effects of UP result from tuning decisions impacting high-latitude cloud feedback. UP's microphysics is tuned to optimize the model present-day, top-of-atmosphere radiation fluxes against CERES observations, by lowering the cloud ice-liquid phase shift temperature ramp, adjusting the ice/liquid autoconversion rate, and increasing the ice fall speed. This reduces high-latitude low cloud amounts and damps the optical depth feedback at high latitudes, leading to a slightly more positive global cloud feedback compared to SP. A sensitivity test that isolates these microphysical impacts from UP's grid resolution confirms that the microphysical settings are mostly responsible for the differences between SP and UP cloud feedback. cloud feedback; low clouds; model tuning; ultraparameterization; boundary layer; surface warming
Park, R.-S.; Kwon, Y. C.Park, R., Y. C. Kwon, 2018: The Implications for radiative cloud forcing via the link between shallow convection and planetary boundary layer mixing. Journal of Geophysical Research: Atmospheres, 123(23), 13,203-13,218. doi: 10.1029/2018JD028678. In this study, the role of shallow convection and its links with planetary boundary layer (PBL) mixing is analyzed using a global atmospheric model. All of the simulations are conducted with the Korean Integrated Model (KIM), which is a next-generation operational global model for Korea Meteorological Administration (KMA). The simulation results show that the direct effect of shallow convection enhances additional vertical mixing inside the shallow convective layer whereas its indirect effect reduces vertical mixing inside the PBL by changing the PBL height, thus vertical mixing strength. It is also found that the impact of shallow convection on low-level clouds is tightly related to the overlapping between PBL and shallowing convection. When the PBL height is located in the relatively higher (lower) part of the shallow convective layer, the mixing across the top of the PBL becomes smaller (larger). Therefore, the diffusivity profile of KIM shallow convection scheme is modified according to the overlapping pattern of PBL mixing and shallow convection. The systematic bias of downward solar radiation at the surface of KIM is improved with the revised diffusivity profile of the shallow convection scheme proposed in this study. Clouds; PBL mixing; Radiation; Shallow convection; vertical transport
Park, SungsuPark, S., 2018: An Economical Analytical Equation for the Integrated Vertical Overlap of Cumulus and Stratus. Journal of Advances in Modeling Earth Systems, 10(3), 826-841. doi: 10.1002/2017MS001190. By extending the previously proposed heuristic parameterization, the author derived an analytical equation computing the overlap areas between the precipitation (or radiation) areas and the cloud areas in a cloud system consisting of cumulus and stratus. The new analytical equation is accurate and much more efficient than the previous heuristic equation, which suffers from the truncation error in association with the digitalization of the overlap areas. Global test simulations with the new analytical formula in an offline mode showed that the maximum cumulus overlap simulates more surface precipitation flux than the random cumulus overlap. On the other hand, the maximum stratus overlap simulates less surface precipitation flux than random stratus overlap, which is due to the increase in the evaporation rate of convective precipitation from the random to maximum stratus overlap. The independent precipitation approximation (IPA) marginally decreases the surface precipitation flux, implying that IPA works well with other parameterizations. In contrast to the net production rate of precipitation and surface precipitation flux that increase when the cumulus and stratus are maximally and randomly overlapped, respectively, the global mean net radiative cooling and longwave cloud radiative forcing (LWCF) increase when the cumulus and stratus are randomly overlapped. On the global average, the vertical cloud overlap exerts larger impacts on the precipitation flux than on the radiation flux. The radiation scheme taking the subgrid variability of water vapor between the cloud and clear portions into account substantially increases the global mean LWCF in tropical deep convection and midlatitude storm track regions. 3354 Precipitation; 3311 Clouds and aerosols; 3337 Global climate models; 3336 Numerical approximations and analyses; cumulus and stratus; 3367 Theoretical modeling; Economical Overlap Equation; Parameterization; Vertical cloud overlap
Paulot, Fabien; Paynter, David; Ginoux, Paul; Naik, Vaishali; Horowitz, Larry W.Paulot, F., D. Paynter, P. Ginoux, V. Naik, L. W. Horowitz, 2018: Changes in the aerosol direct radiative forcing from 2001 to 2015: observational constraints and regional mechanisms. Atmospheric Chemistry and Physics, 18(17), 13265-13281. doi: 10.5194/acp-18-13265-2018. Abstract. We present estimates of changes in the direct aerosol effects (DRE) and its anthropogenic component (DRF) from 2001 to 2015 using the GFDL chemistry–climate model AM3 driven by CMIP6 historical emissions. AM3 is evaluated against observed changes in the clear-sky shortwave direct aerosol effect (DREswclr) derived from the Clouds and the Earth's Radiant Energy System (CERES) over polluted regions. From 2001 to 2015, observations suggest that DREclrsw increases (i.e., less radiation is scattered to space by aerosols) over western Europe (0.7–1Wm−2decade−1) and the eastern US (0.9–1.4Wm−2decade−1), decreases over India (−1 to −1.6Wm−2decade−1), and does not change significantly over eastern China. AM3 captures these observed regional changes in DREclrsw well in the US and western Europe, where they are dominated by the decline of sulfate aerosols, but not in Asia, where the model overestimates the decrease of DREclrsw. Over India, the model bias can be partly attributed to a decrease of the dust optical depth, which is not captured by our model and offsets some of the increase of anthropogenic aerosols. Over China, we find that the decline of SO2 emissions after 2007 is not represented in the CMIP6 emission inventory. Accounting for this decline, using the Modular Emission Inventory for China, and for the heterogeneous oxidation of SO2 significantly reduces the model bias. For both India and China, our simulations indicate that nitrate and black carbon contribute more to changes in DREclrsw than in the US and Europe. Indeed, our model suggests that black carbon (+0.12Wm−2) dominates the relatively weak change in DRF from 2001 to 2015 (+0.03Wm−2). Over this period, the changes in the forcing from nitrate and sulfate are both small and of the same magnitude (−0.03Wm−2 each). This is in sharp contrast to the forcing from 1850 to 2001 in which forcings by sulfate and black carbon largely cancel each other out, with minor contributions from nitrate. The differences between these time periods can be well understood from changes in emissions alone for black carbon but not for nitrate and sulfate; this reflects non-linear changes in the photochemical production of nitrate and sulfate associated with changes in both the magnitude and spatial distribution of anthropogenic emissions.
Penner, Joyce E.; Zhou, Cheng; Garnier, Anne; Mitchell, David L.Penner, J. E., C. Zhou, A. Garnier, D. L. Mitchell, 2018: Anthropogenic Aerosol Indirect Effects in Cirrus Clouds. Journal of Geophysical Research: Atmospheres, 123(20), 11,652-11,677. doi: 10.1029/2018JD029204. We have implemented a parameterization for forming ice in large-scale cirrus clouds that accounts for the changes in updrafts associated with a spectrum of waves acting within each time step in the model. This allows us to account for the frequency of homogeneous and heterogenous freezing events that occur within each time step of the model and helps to determine more realistic ice number concentrations as well as changes to ice number concentrations. The model is able to fit observations of ice number at the lowest temperatures in the tropical tropopause, but is still somewhat high in tropical latitudes with temperatures between 195 °K and 215 °K. The climate forcings associated with different representations of heterogeneous ice nuclei (IN or INPs) are primarily negative unless large additions of IN are made, such as when we assumed that all aircraft soot acts as an IN. However, they can be close to zero if it is assumed that all background dust can act as an INP irrespective of how much sulfate is deposited on these particles. Our best estimate for the forcing of anthropogenic aircraft soot in this model is -0.2 ± 0.06 Wm-2 while that from anthropogenic fossil/bio-fuel soot is -0.093± 0.033 Wm-2. Natural and anthropogenic open biomass burning leads to a net forcing of -0.057 ± 0.05 Wm-2. Cirrus cloud formation; Climate forcing; Gravity waves; heterogeneous ice nuclei
Peters, Ian Marius; Liu, Haohui; Reindl, Thomas; Buonassisi, TonioPeters, I. M., H. Liu, T. Reindl, T. Buonassisi, 2018: Global Prediction of Photovoltaic Field Performance Differences Using Open-Source Satellite Data. Joule, 2(2), 307-322. doi: 10.1016/j.joule.2017.11.012. Summary Accurate field-performance prediction is essential for the calculation of return-on-investment for photovoltaic projects. Leading software predicting field performance was developed for traditional technologies and markets. Yet emerging markets are projected to install over half of all solar cells by the end of this decade, with persisting interest in new technologies. In this study, we map photovoltaic system performance over the entire planet, for standard and emerging technologies, using open-source satellite data. We validate results using time-resolved field-performance data of cadmium telluride and silicon modules in temperate (Perrysburg, OH, USA) and hot-humid (Singapore) climates. Watt for watt, we find that CdTe produces up to 6% more energy than Si in tropical regions. This result emphasizes the significance of local performance evaluation to complement standard testing condition efficiencies. We extend our model to emerging materials including lead-halide perovskites and III-V thin films, and demonstrate that larger band gaps have performance advantages in hot and humid environments. CdTe; energy yield; performance calculations; photovoltaics; silicon; solar cell performance
Pettorelli, Nathalie; Bühne, Henrike Schulte to; Tulloch, Ayesha; Dubois, Grégoire; Macinnis‐Ng, Cate; Queirós, Ana M.; Keith, David A.; Wegmann, Martin; Schrodt, Franziska; Stellmes, Marion; Sonnenschein, Ruth; Geller, Gary N.; Roy, Shovonlal; Somers, Ben; Murray, Nicholas; Bland, Lucie; Geijzendorffer, Ilse; Kerr, Jeremy T.; Broszeit, Stefanie; Leitão, Pedro J.; Duncan, Clare; Serafy, Ghada El; He, Kate S.; Blanchard, Julia L.; Lucas, Richard; Mairota, Paola; Webb, Thomas J.; Nicholson, EmilyPettorelli, N., H. S. t. Bühne, A. Tulloch, G. Dubois, C. Macinnis‐Ng, A. M. Queirós, D. A. Keith, M. Wegmann, F. Schrodt, M. Stellmes, R. Sonnenschein, G. N. Gelle