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Dr. William Smith

Dr. William SmithBill Smith leads the CERES Cloud working group and is responsible for producing, evaluating and distributing global cloud property datasets derived from satellite imagers.

The CERES Cloud WG aims to derive spatially and temporally consistent pixel-level cloud properties from the MODIS and VIIRS imagers flown with CERES instruments in low-earth orbits and from imagers on the global constellation of geostationary satellites flown during the CERES record. Understanding clouds, their geographic distribution, composition, altitudes, and radiative properties (i.e., how they reflect, absorb, and emit energy), is key to understanding Earth’s energy budget and climate. Satellite imager spectral radiances are analyzed to distinguish clouds from cloud free areas, and further interpreted with a combination of theoretical and empirical methods to derive their physical characteristics. The cloud properties are critical for applications in CERES data processing sub-systems including those responsible for (1) the inversion of the CERES instrument radiances to energy fluxes, (2) the computation of surface fluxes and atmospheric heating rates, and (3) for time interpolating the twice daily CERES observations to properly account for diurnal changes.

Contact Information

NASA Langley Research Center
Mail Stop 420, Hampton, VA 23681-2199

Phone: 757-864-8577

Fax: 757-864-7996





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.
Minnis, Patrick; Sun-Mack, Szedung; Chen, Yan; Chang, Fu-Lung; Yost, Christopher R.; Smith, William L.; Heck, Patrick W.; Arduini, Robert F.; Bedka, Sarah T.; Yi, Yuhong; Hong, Gang; Jin, Zhonghai; Painemal, David; Palikonda, Rabindra; Scarino, Benjamin R.; Spangenberg, Douglas A.; Smith, Rita A.; Trepte, Qing Z.; Yang, Ping; Xie, YuMinnis, P., S. Sun-Mack, Y. Chen, F. Chang, C. R. Yost, W. L. Smith, P. W. Heck, R. F. Arduini, S. T. Bedka, Y. Yi, G. Hong, Z. Jin, D. Painemal, R. Palikonda, B. R. Scarino, D. A. Spangenberg, R. A. Smith, Q. Z. Trepte, P. Yang, Y. Xie, 2020: CERES MODIS Cloud Product Retrievals for Edition 4–Part I: Algorithm Changes. IEEE Transactions on Geoscience and Remote Sensing, 1-37. doi: 10.1109/TGRS.2020.3008866. The Edition 2 (Ed2) cloud property retrieval algorithm system was upgraded and applied to the MODerate-resolution Imaging Spectroradiometer (MODIS) data for the Clouds and the Earth's Radiant Energy System (CERES) Edition 4 (Ed4) products. New calibrations for solar channels and the use of the 1.24-μm channel for cloud optical depth (COD) over snow improve the daytime consistency between Terra and Aqua MODIS retrievals. Use of additional spectral channels and revised logic enhanced the cloud-top phase retrieval accuracy. A new ice crystal reflectance model and a CO₂-channel algorithm retrieved higher ice clouds, while a new regional lapse rate technique produced more accurate water cloud heights than in Ed2. Ice cloud base heights are more accurate due to a new cloud thickness parameterization. Overall, CODs increased, especially over the polar (PO) regions. The mean particle sizes increased slightly for water clouds, but more so for ice clouds in the PO areas. New experimental parameters introduced in Ed4 are limited in utility, but will be revised for the next CERES edition. As part of the Ed4 retrieval evaluation, the average properties are compared with those from other algorithms and the differences between individual reference data and matched Ed4 retrievals are explored. Part II of this article provides a comprehensive, objective evaluation of selected parameters. More accurate interpretation of the CERES radiation measurements has resulted from the use of the Ed4 cloud properties. cloud; MODIS; Meteorology; Optical imaging; Integrated optics; Clouds; Climate; Cloud computing; Ice; cloud height; cloud optical depth (COD); cloud particle size; cloud phase; cloud remote sensing MODerate-resolution Imaging Spectroradiometer (MODIS); clouds and the Earth's radiant energy system (CERES); validation.
Painemal, David; Chang, Fu-Lung; Ferrare, Richard; Burton, Sharon; Li, Zhujun; Smith Jr., William L.; Minnis, Patrick; Feng, Yan; Clayton, MarianPainemal, D., F. Chang, R. Ferrare, S. Burton, Z. Li, W. L. Smith Jr., P. Minnis, Y. Feng, M. Clayton, 2020: Reducing uncertainties in satellite estimates of aerosol–cloud interactions over the subtropical ocean by integrating vertically resolved aerosol observations. Atmospheric Chemistry and Physics, 20(12), 7167-7177. doi: Abstract. Satellite quantification of aerosol effects on clouds relies on aerosol optical depth (AOD) as a proxy for aerosol concentration or cloud condensation nuclei (CCN). However, the lack of error characterization of satellite-based results hampers their use for the evaluation and improvement of global climate models. We show that the use of AOD for assessing aerosol–cloud interactions (ACIs) is inadequate over vast oceanic areas in the subtropics. Instead, we postulate that a more physical approach that consists of matching vertically resolved aerosol data from the Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observations (CALIPSO) satellite at the cloud-layer height with Moderate Resolution Imaging Spectroradiometer (MODIS) Aqua cloud retrievals reduces uncertainties in satellite-based ACI estimates. Combined aerosol extinction coefficients (σ) below cloud top (σBC) from the Cloud-Aerosol Lidar with Orthogonal Polarization (CALIOP) and cloud droplet number concentrations (Nd) from MODIS Aqua yield high correlations across a broad range of σBC values, with σBC quartile correlations ≥0.78. In contrast, CALIOP-based AOD yields correlations with MODIS Nd of 0.54–0.62 for the two lower AOD quartiles. Moreover, σBC explains 41 % of the spatial variance in MODIS Nd, whereas AOD only explains 17 %, primarily caused by the lack of spatial covariability in the eastern Pacific. Compared with σBC, near-surface σ weakly correlates in space with MODIS Nd, accounting for a 16 % variance. It is concluded that the linear regression calculated from ln(Nd)–ln(σBC) (the standard method for quantifying ACIs) is more physically meaningful than that derived from the Nd–AOD pair.
Wall, Casey J.; Norris, Joel R.; Gasparini, Blaž; Smith, William L.; Thieman, Mandana M.; Sourdeval, OdranWall, C. J., J. R. Norris, B. Gasparini, W. L. Smith, M. M. Thieman, O. Sourdeval, 2020: Observational Evidence that Radiative Heating Modifies the Life Cycle of Tropical Anvil Clouds. J. Climate, 33(20), 8621–8640. doi: 10.1175/JCLI-D-20-0204.1.
Yost, Christopher R.; Minnis, Patrick; Sun-Mack, Sunny; Chen, Yan; Smith, William L.Yost, C. R., P. Minnis, S. Sun-Mack, Y. Chen, W. L. Smith, 2020: CERES MODIS Cloud Product Retrievals for Edition 4–Part II: Comparisons to CloudSat and CALIPSO. IEEE Transactions on Geoscience and Remote Sensing, 1-30. doi: 10.1109/TGRS.2020.3015155. Assessments of the Clouds and the Earth's Radiant Energy System Edition 4 (Ed4) cloud retrievals are critical for climate studies. Ed4 cloud parameters are evaluated using instruments in the A-Train Constellation. Cloud-Aerosol LiDAR with Orthogonal Polarization (CALIOP) and Cloud Profiling Radar (CPR) retrievals are compared with Ed4 retrievals from the Aqua Moderate-Resolution Imaging Spectroradiometer (MODIS) as a function of the CALIOP horizontal averaging (HA) scale. Regardless of the HA scale, MODIS daytime (nighttime) water cloud fraction (CF) is greater (less) than that from CALIOP. MODIS ice CF is less than CALIOP overall, with the largest differences in polar regions. Ed4 and CALIOP retrieve the same cloud phase in 70%-98% of simultaneous observations depending on the time of day, surface conditions, HA scales, and type of cloud vertical structure. Mean cloud top height (CTH) differences for single-layer water clouds over snow-/ice-free surfaces are less than 100 m. Base altitude positive biases of 170-460 m may be impacted by CPR detection limitations. Average MODIS ice CTHs are underestimated by 70 m for some deep convective clouds and up to 2.2 km for thin cirrus. Ice cloud base altitudes are typically underestimated (overestimated) during daytime (nighttime). MODIS and CALIOP cirrus optical depths over oceans are within 46% and 5% for daytime and nighttime observations, respectively. Ice water path differences depend on the CALIOP retrieval version and warrant further investigation. Except for daytime cirrus optical depth, Ed4 cloud property retrievals are at least as accurate as other long-term operational cloud property retrieval systems. cloud; Clouds and the Earth's Radiant Energy System (CERES); cloud remote sensing; Climate; cloud height; cloud optical depth (COD); cloud phase; validation.; Cloud-Aerosol LiDAR and Infrared Pathfinder Satellite Observation (CALIPSO); MODerate-resolution Imaging Spectroradiometer (MODIS)


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.
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.
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
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.
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).


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.
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.
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.
Sun-Mack, S.; Minnis, P.; Chen, Y.; Doelling, D. R.; Scarino, B. R.; Haney, C. O.; Smith, W. L.Sun-Mack, S., P. Minnis, Y. Chen, D. R. Doelling, B. R. Scarino, C. O. Haney, W. L. Smith, 2018: Calibration Changes to Terra MODIS Collection-5 Radiances for CERES Edition 4 Cloud Retrievals. IEEE Transactions on Geoscience and Remote Sensing, 1-17. doi: 10.1109/TGRS.2018.2829902. Previous research has revealed inconsistencies between the Collection 5 (C5) calibrations of certain channels common to the Terra and Aqua Moderate Resolution Imaging Spectroradiometers (MODISs). To achieve consistency between the Terra and Aqua MODIS radiances used in the Clouds and the Earth's Radiant Energy System (CERES) Edition 4 (Ed4) cloud property retrieval system, adjustments were developed and applied to the Terra C5 calibrations for channels 1-5, 7, 20, and 26. These calibration corrections, developed independently of those used for the later MODIS Collection 6 (C6), ranged from -3.0% for channel 5 to +4.3% for channel 26. For channel 20, the Terra C5 brightness temperatures were decreased nonlinearly by 0.55 K at 300-10 K or more at 220 K. The corrections were applied to the Terra C5 data for CERES Ed4 and resulted in Terra-Aqua radiance consistency that is as good as or better than that of the C6 data sets. The C5 adjustments led to more consistent Aqua and Terra cloud property retrievals than seen in the previous CERES edition. After Ed4 began processing, other calibration artifacts were found in some corrected channels and in some of the uncorrected thermal channels. Because no corrections were developed or applied for those artifacts, some anomalies or false trends could have been introduced into the Ed4 cloud property record. Thus, despite the much improved consistency achieved for the Terra and Aqua data sets in Ed4, the CERES Ed4 cloud property data sets should be used cautiously for cloud trend studies due to those remaining calibration artifacts. climate; cloud; MODIS; Earth; Clouds and the Earth's Radiant Energy System (CERES); Satellites; Meteorology; Moderate Resolution Imaging Spectroradiometer (MODIS); Market research; Clouds; Calibration
Tian, Jingjing; Dong, Xiquan; Xi, Baike; Minnis, Patrick; Smith, William L.; Sun-Mack, Sunny; Thieman, Mandana; Wang, JingyuTian, J., X. Dong, B. Xi, P. Minnis, W. L. Smith, S. Sun-Mack, M. Thieman, J. Wang, 2018: Comparisons of Ice Water Path in Deep Convective Systems Among Ground-Based, GOES, and CERES-MODIS Retrievals. Journal of Geophysical Research: Atmospheres, 123(3), 1708-1723. doi: 10.1002/2017JD027498. Retrievals of convective cloud microphysical properties based on passive satellite imagery are difficult. To help quantify their uncertainties, ice water paths (IWPs) retrieved from the NASA Clouds and the Earth's Radiant Energy System project using Geostationary Operational Environmental Satellite (GOES) and Terra/Aqua MODerate-resolution Imaging Spectroradiometer observations are compared with IWPs retrieved from Next-Generation Radar (NEXRAD) observations over a large domain (32°N to 40°N and 105°W to 91°W) during the 2011 Midlatitude Continental Convective Clouds Experiment field campaign. Based on comparisons of pixel-level (4 km × 4 km) daytime IWP retrievals from NEXRAD and GOES, it is found that NEXRAD- and GOES-retrieved mean IWPs are 2.03 and 1.83 kg m−2, respectively, for ice-phase cloud in thick anvil area. Their mean difference of 0.20 kg m−2 (with 95% confidence interval: 0.14–0.26 kg m−2) is within the uncertainty of NEXRAD retrievals. However, the low correlation between pixel-to-pixel comparisons indicates a large variation in GOES-retrieved IWP. For mixed-phase clouds in thick anvil areas, in addition to IWPs, total water paths (TWPs, sum of ice and liquid water path) are estimated with aid of aircraft measurements for NEXRAD retrievals and corrected using a TWP parameterization for GOES retrievals. The mean values of estimated TWPs from NEXRAD (corrected using aircraft in situ measurements) and GOES are similar. GOES and Clouds and the Earth's Radiant Energy System-MODerate-resolution Imaging Spectroradiometer-retrieved IWPs/TWPs generally do not exceed 5 kg m−2. Large differences and low correlations exist between satellite and NEXRAD retrievals in stratiform rain areas. Possible reasons for the differences between retrievals are discussed. 0320 Cloud physics and chemistry; 3314 Convective processes; deep convection; 3360 Remote sensing; 0319 Cloud optics; satellite remote sensing; ice particles; cloud microphysics retrieval
Wall, Casey J.; Hartmann, Dennis L.; Thieman, Mandana M.; Smith, William L.; Minnis, PatrickWall, C. J., D. L. Hartmann, M. M. Thieman, W. L. Smith, P. Minnis, 2018: The Life Cycle of Anvil Clouds and the Top-of-Atmosphere Radiation Balance over the Tropical West Pacific. J. Climate, 31(24), 10059-10080. doi: 10.1175/JCLI-D-18-0154.1. Observations from a geostationary satellite are used to study the life cycle of mesoscale convective systems (MCS), their associated anvil clouds, and their effects on the radiation balance over the warm pool of the tropical western Pacific Ocean. In their developing stages, MCS primarily consist of clouds that are optically thick and have a negative net cloud radiative effect (CRE). As MCS age, ice crystals in the anvil become larger, the cloud top lowers somewhat, and cloud radiative effects decrease in magnitude. Shading from anvils causes cool anomalies in the underlying sea surface temperature (SST) of up to −0.6°C. MCS often occur in clusters that are embedded within large westward-propagating disturbances, and therefore shading from anvils can cool SSTs over regions spanning hundreds of kilometers. Triggering of convection is more likely to follow a warm SST anomaly than a cold SST anomaly on a time scale of several days. This information is used to evaluate hypotheses for why, over the warm pool, the average shortwave and longwave CRE are individually large but nearly cancel. The results are consistent with the hypothesis that the cancellation in CRE is caused by feedbacks among cloud albedo, large-scale circulation, and SST.


Smith, William L.; Hansen, Christy; Bucholtz, Anthony; Anderson, Bruce E.; Beckley, Matthew; Corbett, Joseph G.; Cullather, Richard I.; Hines, Keith M.; Hofton, Michelle; Kato, Seiji; Lubin, Dan; Moore, Richard H.; Segal Rosenhaimer, Michal; Redemann, Jens; Schmidt, Sebastian; Scott, Ryan; Song, Shi; Barrick, John D.; Blair, J. Bryan; Bromwich, David H.; Brooks, Colleen; Chen, Gao; Cornejo, Helen; Corr, Chelsea A.; Ham, Seung-Hee; Kittelman, A. Scott; Knappmiller, Scott; LeBlanc, Samuel; Loeb, Norman G.; Miller, Colin; Nguyen, Louis; Palikonda, Rabindra; Rabine, David; Reid, Elizabeth A.; Richter-Menge, Jacqueline A.; Pilewskie, Peter; Shinozuka, Yohei; Spangenberg, Douglas; Stackhouse, Paul; Taylor, Patrick; Thornhill, K. Lee; van Gilst, David; Winstead, EdwardSmith, W. L., C. Hansen, A. Bucholtz, B. E. Anderson, M. Beckley, J. G. Corbett, R. I. Cullather, K. M. Hines, M. Hofton, S. Kato, D. Lubin, R. H. Moore, M. Segal Rosenhaimer, J. Redemann, S. Schmidt, R. Scott, S. Song, J. D. Barrick, J. B. Blair, D. H. Bromwich, C. Brooks, G. Chen, H. Cornejo, C. A. Corr, S. Ham, A. S. Kittelman, S. Knappmiller, S. LeBlanc, N. G. Loeb, C. Miller, L. Nguyen, R. Palikonda, D. Rabine, E. A. Reid, J. A. Richter-Menge, P. Pilewskie, Y. Shinozuka, D. Spangenberg, P. Stackhouse, P. Taylor, K. L. Thornhill, D. van Gilst, E. Winstead, 2017: Arctic Radiation-IceBridge Sea and Ice Experiment: The Arctic Radiant Energy System during the Critical Seasonal Ice Transition. Bull. Amer. Meteor. Soc., 98(7), 1399-1426. doi: 10.1175/BAMS-D-14-00277.1. AbstractThe National Aeronautics and Space Administration (NASA)?s Arctic Radiation-IceBridge Sea and Ice Experiment (ARISE) acquired unique aircraft data on atmospheric radiation and sea ice properties during the critical late summer to autumn sea ice minimum and commencement of refreezing. The C-130 aircraft flew 15 missions over the Beaufort Sea between 4 and 24 September 2014. ARISE deployed a shortwave and longwave broadband radiometer (BBR) system from the Naval Research Laboratory; a Solar Spectral Flux Radiometer (SSFR) from the University of Colorado Boulder; the Spectrometer for Sky-Scanning, Sun-Tracking Atmospheric Research (4STAR) from the NASA Ames Research Center; cloud microprobes from the NASA Langley Research Center; and the Land, Vegetation and Ice Sensor (LVIS) laser altimeter system from the NASA Goddard Space Flight Center. These instruments sampled the radiant energy exchange between clouds and a variety of sea ice scenarios, including prior to and after refreezing began. The most critical and unique aspect of ARISE mission planning was to coordinate the flight tracks with NASA Cloud and the Earth?s Radiant Energy System (CERES) satellite sensor observations in such a way that satellite sensor angular dependence models and derived top-of-atmosphere fluxes could be validated against the aircraft data over large gridbox domains of order 100?200 km. This was accomplished over open ocean, over the marginal ice zone (MIZ), and over a region of heavy sea ice concentration, in cloudy and clear skies. ARISE data will be valuable to the community for providing better interpretation of satellite energy budget measurements in the Arctic and for process studies involving ice?cloud?atmosphere energy exchange during the sea ice transition period.


Minnis, Patrick; Hong, Gang; Sun-Mack, Szedung; Smith, William L.; Chen, Yan; Miller, Steven D.Minnis, P., G. Hong, S. Sun-Mack, W. L. Smith, Y. Chen, S. D. Miller, 2016: Estimating Nocturnal Opaque Ice Cloud Optical Depth from MODIS Multispectral Infrared Radiances Using a Neural Network Method. Journal of Geophysical Research: Atmospheres, 121(9), 4907–4932. doi: 10.1002/2015JD024456. Retrieval of ice cloud properties using IR measurements has a distinct advantage over the visible and near-IR techniques by providing consistent monitoring regardless of solar illumination conditions. Historically, the IR bands at 3.7, 6.7, 11.0, and 12.0 µm have been used to infer ice cloud parameters by various methods, but the reliable retrieval of ice cloud optical depth τ is limited to non-opaque cirrus with τ  0319 Cloud optics; 0320 Cloud physics and chemistry; 3360 Remote sensing; CloudSat; ice cloud; MODIS; neural network; night; optical depth
Zhou, D.K.; Liu, X.; Larar, A.M.; Tian, J.; Smith, W.L.; Kizer, S.H.; Wu, W.; Liu, Q.; Goldberg, M.D.Zhou, D., X. Liu, A. Larar, J. Tian, W. Smith, S. Kizer, W. Wu, Q. Liu, M. Goldberg, 2016: First Suomi NPP Cal/Val Campaign: Intercomparison of Satellite and Aircraft Sounding Retrievals. IEEE Journal of Selected Topics in Applied Earth Observations and Remote Sensing, 9(9), 4037 - 4046. doi: 10.1109/JSTARS.2016.2516765. Satellite ultraspectral infrared sensors provide key data records essential for weather forecasting and climate change science. The Suomi National Polar-orbiting Partnership (NPP) satellite environmental data records (EDRs) are retrieved from calibrated ultraspectral radiance or sensor data records (SDRs). Understanding the accuracy of retrieved EDRs is critical. The first Suomi NPP Calibration/Validation Campaign was conducted during May 2013. The NASA high-altitude ER-2 aircraft carrying ultraspectral interferometer sounders such as the National Airborne Sounder Testbed-Interferometer (NAST-I) flew under the Suomi NPP satellite that carries the cross-track infrared sounder (CrIS) and the advanced technology microwave sounder (ATMS). Here, we intercompare the EDRs produced with different retrieval algorithms from SDRs measured from satellite and aircraft. The available dropsonde and radiosonde measurements together with the European Centre for Medium-Range Weather Forecasts (ECMWF) analysis are used to assess the results of this experiment. This study indicates that the CrIS/ATMS retrieval accuracy meets the Suomi NPP EDR requirement, except in the planetary boundary layer (PBL) where we have less confidence in meeting the requirement due to retrieval null-space error. aircraft; Atmospheric measurements; Atmospheric modeling; Extraterrestrial measurements; geophysical inverse problems; infrared measurements; Remote sensing; Satellite broadcasting; Satellites; Temperature measurement


Wielicki, Bruce A.; Young, D. F.; Mlynczak, M. G.; Thome, K. J.; Leroy, S.; Corliss, J.; Anderson, J. G.; Ao, C.O.; Bantges, R.; Best, F.; Bowman, K.; Brindley, H.; Butler, J. J.; Collins, W.; Dykema, J. A.; Doelling, D. R.; Feldman, D. R.; Fox, N.; Huang, X.; Holz, R.; Huang, Y.; Jin, Z.; Jennings, D.; Johnson, D. G.; Jucks, K.; Kato, S.; Kirk-Davidoff, D. B.; Knuteson, R.; Kopp, G.; Kratz, D. P.; Liu, X.; Lukashin, C.; Mannucci, A. J.; Phojanamongkolkij, N.; Pilewskie, P.; Ramaswamy, V.; Revercomb, H.; Rice, J.; Roberts, Y.; Roithmayr, C. M.; Rose, F.; Sandford, S.; Shirley, E. L.; Smith, W.L.; Soden, B.; Speth, P. W.; Sun, W.; Taylor, P.C.; Tobin, D.; Xiong, X.Wielicki, B. A., D. F. Young, M. G. Mlynczak, K. J. Thome, S. Leroy, J. Corliss, J. G. Anderson, C. Ao, R. Bantges, F. Best, K. Bowman, H. Brindley, J. J. Butler, W. Collins, J. A. Dykema, D. R. Doelling, D. R. Feldman, N. Fox, X. Huang, R. Holz, Y. Huang, Z. Jin, D. Jennings, D. G. Johnson, K. Jucks, S. Kato, D. B. Kirk-Davidoff, R. Knuteson, G. Kopp, D. P. Kratz, X. Liu, C. Lukashin, A. J. Mannucci, N. Phojanamongkolkij, P. Pilewskie, V. Ramaswamy, H. Revercomb, J. Rice, Y. Roberts, C. M. Roithmayr, F. Rose, S. Sandford, E. L. Shirley, W. Smith, B. Soden, P. W. Speth, W. Sun, P. Taylor, D. Tobin, X. Xiong, 2013: Achieving Climate Change Absolute Accuracy in Orbit. Bull. Amer. Meteor. Soc., 130308154356007. doi: 10.1175/BAMS-D-12-00149.1.


Smith, William L.; Minnis, Patrick; Fleeger, Cecilia; Spangenberg, Douglas; Palikonda, Rabindra; Nguyen, LouisSmith, W. L., P. Minnis, C. Fleeger, D. Spangenberg, R. Palikonda, L. Nguyen, 2012: Determining the Flight Icing Threat to Aircraft with Single-Layer Cloud Parameters Derived from Operational Satellite Data. J. Appl. Meteor. Climatol., 51(10), 1794-1810. doi: 10.1175/JAMC-D-12-057.1. AbstractAn algorithm is developed to determine the flight icing threat to aircraft utilizing quantitative information on clouds derived from meteorological satellite data as input. Algorithm inputs include the satellite-derived cloud-top temperature, thermodynamic phase, water path, and effective droplet size. The icing-top and -base altitude boundaries are estimated from the satellite-derived cloud-top and -base altitudes using the freezing level obtained from numerical weather analyses or a lapse-rate approach. The product is available at the nominal resolution of the satellite pixel. Aircraft pilot reports (PIREPs) over the United States and southern Canada provide direct observations of icing and are used extensively in the algorithm development and validation on the basis of correlations with Geostationary Operational Environmental Satellite imager data. Verification studies using PIREPs, Tropospheric Airborne Meteorological Data Reporting, and NASA Icing Remote Sensing System data indicate that the satellite algorithm performs reasonably well, particularly during the daytime. The algorithm is currently being run routinely using data taken from a variety of satellites across the globe and is providing useful information on icing conditions at high spatial and temporal resolutions that are unavailable from any other source. Algorithms; Cloud retrieval; Icing; Nowcasting; satellite observations


Minnis, P.; Sun-Mack, Szedung; Chen, Yan; Khaiyer, M.M.; Yi, Yuhong; Ayers, J.K.; Brown, R.R.; Dong, Xiquan; Gibson, S.C.; Heck, P.W.; Lin, Bing; Nordeen, M.L.; Nguyen, L.; Palikonda, R.; Smith, W.L.; Spangenberg, D.A.; Trepte, Q.Z.; Xi, BaikeMinnis, P., S. Sun-Mack, Y. Chen, M. Khaiyer, Y. Yi, J. Ayers, R. Brown, X. Dong, S. Gibson, P. Heck, B. Lin, M. Nordeen, L. Nguyen, R. Palikonda, W. Smith, D. Spangenberg, Q. Trepte, B. Xi, 2011: CERES Edition-2 Cloud Property Retrievals Using TRMM VIRS and Terra and Aqua MODIS Data #x2014;Part II: Examples of Average Results and Comparisons With Other Data. IEEE Transactions on Geoscience and Remote Sensing, 49(11), 4401-4430. doi: 10.1109/TGRS.2011.2144602. Cloud properties were retrieved by applying the Clouds and Earth's Radiant Energy System (CERES) project Edition-2 algorithms to 3.5 years of Tropical Rainfall Measuring Mission Visible and Infrared Scanner data and 5.5 and 8 years of MODerate Resolution Imaging Spectroradiometer (MODIS) data from Aqua and Terra, respectively. The cloud products are consistent quantitatively from all three imagers; the greatest discrepancies occur over ice-covered surfaces. The retrieved cloud cover ( 59%) is divided equally between liquid and ice clouds. Global mean cloud effective heights, optical depth, effective particle sizes, and water paths are 2.5 km, 9.9, 12.9 μm , and 80 g·m-2, respectively, for liquid clouds and 8.3 km, 12.7, 52.2 μm, and 230 g·m-2 for ice clouds. Cloud droplet effective radius is greater over ocean than land and has a pronounced seasonal cycle over southern oceans. Comparisons with independent measurements from surface sites, the Ice Cloud and Land Elevation Satellite, and the Aqua Advanced Microwave Scanning Radiometer-Earth Observing System are used to evaluate the results. The mean CERES and MODIS Atmosphere Science Team cloud properties have many similarities but exhibit large discrepancies in certain parameters due to differences in the algorithms and the number of unretrieved cloud pixels. Problem areas in the CERES algorithms are identified and discussed. Aqua Advanced Microwave Scanning Radiometer-Earth Observing System; Aqua MODIS Data; Atmospheric measurements; atmospheric precipitation; atmospheric techniques; CERES Edition-2; CERES project; climate; cloud; Cloud cover; cloud droplet effective radius; cloud effective height; Cloud optical depth; cloud product; cloud property retrieval; cloud remote sensing; clouds; Clouds and Earth's Radiant Energy System; Clouds and the Earth's Radiant Energy System (CERES); data acquisition; effective particle size; ice; Ice Cloud and Land Elevation Satellite; ice clouds; ice-covered surface; infrared imaging; Integrated optics; liquid clouds; Moderate Resolution Imaging Spectroradiometer; Moderate Resolution Imaging Spectroradiometer (MODIS); MODIS; MODIS Atmosphere Science Team; Pixel; radiometry; Remote sensing; Satellites; southern oceans; Terra MODIS Data; time 3.5 yr; time 5.5 yr; time 8 yr; TRMM VIRS; Tropical Rainfall Measuring Mission Visible and Infrared Scanner data; Visible and Infrare
Minnis, P.; Sun-Mack, Szedung; Young, D.F.; Heck, P.W.; Garber, D.P.; Chen, Yan; Spangenberg, D.A.; Arduini, R.F.; Trepte, Q.Z.; Smith, W.L.; Ayers, J.K.; Gibson, S.C.; Miller, W.F.; Hong, G.; Chakrapani, V.; Takano, Y.; Liou, Kuo-Nan; Xie, Yu; Yang, PingMinnis, P., S. Sun-Mack, D. Young, P. Heck, D. Garber, Y. Chen, D. Spangenberg, R. Arduini, Q. Trepte, W. Smith, J. Ayers, S. Gibson, W. Miller, G. Hong, V. Chakrapani, Y. Takano, K. Liou, Y. Xie, P. Yang, 2011: CERES Edition-2 Cloud Property Retrievals Using TRMM VIRS and Terra and Aqua MODIS Data #x2014;Part I: Algorithms. IEEE Transactions on Geoscience and Remote Sensing, 49(11), 4374-4400. doi: 10.1109/TGRS.2011.2144601. The National Aeronautics and Space Administration's Clouds and the Earth's Radiant Energy System (CERES) Project was designed to improve our understanding of the relationship between clouds and solar and longwave radiation. This is achieved using satellite broad-band instruments to map the top-of-atmosphere radiation fields with coincident data from satellite narrow-band imagers employed to retrieve the properties of clouds associated with those fields. This paper documents the CERES Edition-2 cloud property retrieval system used to analyze data from the Tropical Rainfall Measuring Mission Visible and Infrared Scanner and by the MODerate-resolution Imaging Spectrometer instruments on board the Terra and Aqua satellites covering the period 1998 through 2007. Two daytime retrieval methods are explained: the Visible Infrared Shortwave-infrared Split-window Technique for snow-free surfaces and the Shortwave-infrared Infrared Near-infrared Technique for snow or ice-covered surfaces. The Shortwave-infrared Infrared Split-window Technique is used for all surfaces at night. These methods, along with the ancillary data and empirical parameterizations of cloud thickness, are used to derive cloud boundaries, phase, optical depth, effective particle size, and condensed/frozen water path at both pixel and CERES footprint levels. Additional information is presented, detailing the potential effects of satellite calibration differences, highlighting methods to compensate for spectral differences and correct for atmospheric absorption and emissivity, and discussing known errors in the code. Because a consistent set of algorithms, auxiliary input, and calibrations across platforms are used, instrument and algorithm-induced changes in the data record are minimized. This facilitates the use of the CERES data products for studying climate-scale trends. AD 1998 to 2007; algorithm-induced change analysis; Aqua MODIS Data; Aqua satellite; atmospheric absorption; atmospheric radiation; atmospheric techniques; calibration; CERES data analysis; CERES Edition-2 cloud property retrieval system; climate; cloud; cloud remote sensing; clouds; Clouds and the Earth's Radiant Energy System (CERES); Clouds Earth's Radiant Energy System; condensed water path; Data analysis; frozen water path; ice-covered surface; Land surface; longwave radiation; Moderate-Resolution Imaging Spectrometer instrument; MODerate-resolution Imaging Spectrometer (MODIS); MODIS; National Aeronautics and Space Administration; Ocean temperature; particle size; Pixel; rain; satellite broad-band instrument; satellite calibration effect; satellite narrow-band image; Satellites; Sea surface; shortwave-infrared infrared near-infrared technique; snow; snow surface; Solar radiation; Terra MODIS Data; Terra satellite; top-of-atmosphere radiation field; TRMM VIRS; Tropical Rainfall Me


Chang, Fu-Lung; Minnis, Patrick; Ayers, J. Kirk; McGill, Matthew J.; Palikonda, Rabindra; Spangenberg, Douglas A.; Smith, William L.; Yost, Christopher R.Chang, F., P. Minnis, J. K. Ayers, M. J. McGill, R. Palikonda, D. A. Spangenberg, W. L. Smith, C. R. Yost, 2010: Evaluation of satellite-based upper troposphere cloud top height retrievals in multilayer cloud conditions during TC4. Journal of Geophysical Research: Atmospheres, 115(D10), D00J05. doi: 10.1029/2009JD013305. Upper troposphere cloud top heights (CTHs), restricted to cloud top pressures (CTPs) < 500 hPa, inferred using four satellite retrieval methods applied to Twelfth Geostationary Operational Environmental Satellite (GOES-12) data are evaluated using measurements during the July–August 2007 Tropical Composition, Cloud and Climate Coupling Experiment (TC4). The four methods are the single-layer CO2-absorption technique (SCO2AT), a modified CO2-absorption technique (MCO2AT) developed for improving both single-layered and multilayered cloud retrievals, a standard version of the Visible Infrared Solar-infrared Split-window Technique (old VISST), and a new version of VISST (new VISST) recently developed to improve cloud property retrievals. They are evaluated by comparing with ER-2 aircraft-based Cloud Physics Lidar (CPL) data taken during 9 days having extensive upper troposphere cirrus, anvil, and convective clouds. Compared to the 89% coverage by upper tropospheric clouds detected by the CPL, the SCO2AT, MCO2AT, old VISST, and new VISST retrieved CTPs < 500 hPa in 76, 76, 69, and 74% of the matched pixels, respectively. Most of the differences are due to subvisible and optically thin cirrus clouds occurring near the tropopause that were detected only by the CPL. The mean upper tropospheric CTHs for the 9 days are 14.2 (±2.1) km from the CPL and 10.7 (±2.1), 12.1 (±1.6), 9.7 (±2.9), and 11.4 (±2.8) km from the SCO2AT, MCO2AT, old VISST, and new VISST, respectively. Compared to the CPL, the MCO2AT CTHs had the smallest mean biases for semitransparent high clouds in both single-layered and multilayered situations whereas the new VISST CTHs had the smallest mean biases when upper clouds were opaque and optically thick. The biases for all techniques increased with increasing numbers of cloud layers. The transparency of the upper layer clouds tends to increase with the numbers of cloud layers. 3311 Clouds and aerosols; 3359 Radiative processes; 3394 Instruments and techniques; cloud top height; multilayer cloud; satellite cloud retrieval


Wang, D.; Minnis, P.; Charlock, T. P.; Zhou, D. K.; Rose, F. G.; Smith, W. L.; Jr, W. L. Smith; Nguyen, L.Wang, D., P. Minnis, T. P. Charlock, D. K. Zhou, F. G. Rose, W. L. Smith, W. L. S. Jr, L. Nguyen, 2007: Real-time mesoscale forecast support during the CLAMS field campaign. Advances in Atmospheric Sciences, 24(4), 599-605. doi: 10.1007/s00376-007-0599-3. This paper reports the use of a specialized, mesoscale, numerical weather prediction (NWP) system and a satellite imaging and prediction system that were set up to support the CLAMS (Chesapeake Lighthouse and Aircraft Measurements for Satellites) field campaign during the summer of 2001. The primary objective of CLAMS was to validate satellite-based retrievals of aerosol properties and vertical profiles of the radiative flux, temperature and water vapor. Six research aircraft were deployed to make detailed coincident measurements of the atmosphere and ocean surface with the research satellites that orbited overhead. The mesoscale weather modeling system runs in real-time to provide high spatial and temporal resolution for forecasts that are delivered via the World Wide Web along with a variety of satellite imagery and satellite location predictions. This system is a multi-purpose modeling system capable of both data analysis/assimilation and multi-scale NWP ranging from cloud-scale to larger than regional scale. This is a three-dimensional, nonhydrostatic compressible model in a terrain-following coordinate. The model employs advanced numerical techniques and contains detailed interactive physical processes. The utility of the forecasting system is illustrated throughout the discussion on the impact of the surface-wind forecast on BRDF (Bidirectional Reflectance Distribution Function) and the description of the cloud/moisture forecast versus the aircraft measurement. CLAMS field campaign; forecast support; Geophysics/Geodesy; mesoscale numerical weather prediction; Meteorology/Climatology


Rutledge, Charles K.; Schuster, Gregory L.; Charlock, Thomas P.; Denn, Frederick M.; Smith, William L.; Fabbri, Bryan E.; Madigan, James J.; Knapp, Robert J.Rutledge, C. K., G. L. Schuster, T. P. Charlock, F. M. Denn, W. L. Smith, B. E. Fabbri, J. J. Madigan, R. J. Knapp, 2006: Offshore Radiation Observations for Climate Research at the CERES Ocean Validation Experiment: A New “Laboratory” for Retrieval Algorithm Testing. Bull. Amer. Meteor. Soc., 87(9), 1211-1222. doi: 10.1175/BAMS-87-9-1211. Abstract When radiometers on satellites point toward Earth with the goal of sensing an important variable quantitatively, rather than just creating a pleasing image, the task at hand is often not simple. The electromagnetic energy detected by the radiometers is a puzzle of various signals; it must be solved to quantify the specific physical variable. This task, called the retrieval or remote-sensing process, is important to most satellite-based observation programs. It would be ideal to test the algorithms for retrieval processes in a sealed laboratory, where all the relevant parameters could be easily measured. The size and complexity of the Earth make this impractical. NASA's Clouds and the Earth's Radiant Energy System (CERES) project has done the next-best thing by developing a long-term radiation observation site over the ocean. The relatively low and homogeneous surface albedo of the ocean make this type of site a simpler environment for observing and validating radiation parameters from satellite-based instruments. To characterize components of the planet's energy budget, CERES uses a variety of retrievals associated with several satellite-based instruments onboard NASA's Earth Observing System (EOS). A new surface observation project called the CERES Ocean Validation Experiment (COVE), operating on a rigid ocean platform, is supplying data to validate some of these instruments and retrieval products. This article describes the ocean platform and the types of observations being performed there, and highlights of some scientific problems being addressed.


Redemann, J.; Schmid, B.; Eilers, J. A.; Kahn, R.; Levy, R. C.; Russell, P. B.; Livingston, J. M.; Hobbs, P. V.; Smith, W. L.; Holben, B. N.Redemann, J., B. Schmid, J. A. Eilers, R. Kahn, R. C. Levy, P. B. Russell, J. M. Livingston, P. V. Hobbs, W. L. Smith, B. N. Holben, 2005: Suborbital Measurements of Spectral Aerosol Optical Depth and Its Variability at Subsatellite Grid Scales in Support of CLAMS 2001. J. Atmos. Sci., 62(4), 993-1007. doi: 10.1175/JAS3387.1. Abstract As part of the Chesapeake Lighthouse and Aircraft Measurements for Satellites (CLAMS) experiment, 10 July–2 August 2001, off the central East Coast of the United States, the 14-channel NASA Ames Airborne Tracking Sunphotometer (AATS-14) was operated aboard the University of Washington’s Convair 580 (CV-580) research aircraft during 10 flights (∼45 flight hours). One of the main research goals in CLAMS was the validation of satellite-based retrievals of aerosol properties. The goal of this study in particular was to perform true over-ocean validations (rather than over-ocean validation with ground-based, coastal sites) at finer spatial scales and extending to longer wavelengths than those considered in previous studies. Comparisons of aerosol optical depth (AOD) between the Aerosol Robotic Network (AERONET) Cimel instrument at the Chesapeake Lighthouse and airborne measurements by AATS-14 in its vicinity showed good agreement with the largest r-square correlation coefficients at wavelengths of 0.38 and 0.5 μm (>0.99). Coordinated low-level flight tracks of the CV-580 during Terra overpass times permitted validation of over-ocean Moderate Resolution Imaging Spectroradiometer (MODIS) level 2 (MOD04_L2) multiwavelength AOD data (10 km × 10 km, nadir) in 16 cases on three separate days. While the correlation between AATS-14- and MODIS-derived AOD was weak with an r square of 0.55, almost 75% of all MODIS AOD measurements fell within the prelaunch estimated uncertainty range Δτ = ±0.03 ± 0.05τ. This weak correlation may be due to the small AODs (generally less than 0.1 at 0.5 μm) encountered in these comparison cases. An analogous coordination exercise resulted in seven coincident over-ocean matchups between AATS-14 and Multiangle Imaging Spectroradiometer (MISR) measurements. The comparison between AATS-14 and the MISR standard algorithm regional mean AODs showed a stronger correlation with an r square of 0.94. However, MISR AODs were systematically larger than the corresponding AATS values, with an rms difference of ∼0.06. AATS data collected during nine extended low-level CV-580 flight tracks were used to assess the spatial variability in AOD at horizontal scales up to 100 km. At UV and midvisible wavelengths, the largest absolute gradients in AOD were 0.1–0.2 per 50-km horizontal distance. In the near-IR, analogous gradients rarely reached 0.05. On any given day, the relative gradients in AOD were remarkably similar for all wavelengths, with maximum values of 70% (50 km)−1 and more typical values of 25% (50 km)−1. The implications of these unique measurements of AOD spatial variability for common validation practices of satellite data products and for comparisons to large-scale aerosol models are discussed.
Smith, W. L.; Charlock, T. P.; Kahn, R.; Martins, J. V.; Remer, L. A.; Hobbs, P. V.; Redemann, J.; Rutledge, C. K.Smith, W. L., T. P. Charlock, R. Kahn, J. V. Martins, L. A. Remer, P. V. Hobbs, J. Redemann, C. K. Rutledge, 2005: EOS Terra Aerosol and Radiative Flux Validation: An Overview of the Chesapeake Lighthouse and Aircraft Measurements for Satellites (CLAMS) Experiment. J. Atmos. Sci., 62(4), 903-918. doi: 10.1175/JAS3398.1. Abstract NASA developed an Earth Observing System (EOS) to study global change and reduce uncertainties associated with aerosols and other key parameters controlling climate. The first EOS satellite, Terra, was launched in December 1999. The Chesapeake Lighthouse and Aircraft Measurements for Satellites (CLAMS) field campaign was conducted from 10 July to 2 August 2001 to validate several Terra data products, including aerosol properties and radiative flux profiles derived from three complementary Terra instruments: the Clouds and the Earth’s Radiant Energy System (CERES), the Multiangle Imaging Spectroradiometer (MISR), and the Moderate Resolution Imaging Spectroradiometer (MODIS). CERES, MISR, and MODIS are being used to investigate the critical role aerosols play in modulating the radiative heat budget of the earth–atmosphere system. CLAMS’ primary objectives are to improve understanding of atmospheric aerosols, to validate and improve the satellite data products, and to test new instruments and measurement concepts. A variety of in situ sampling devices and passive remote sensing instruments were flown on six aircraft to characterize the state of the atmosphere, the composition of atmospheric aerosols, and the associated surface and atmospheric radiation parameters over the U.S. eastern seaboard. Aerosol particulate matter was measured at two ground stations established at Wallops Island, Virginia, and the Chesapeake Lighthouse, the site of an ongoing CERES Ocean Validation Experiment (COVE) where well-calibrated radiative fluxes and Aerosol Robotic Network (AERONET) aerosol properties have been measured since 1999. Nine coordinated aircraft missions and numerous additional sorties were flown under a variety of atmospheric conditions and aerosol loadings. On one “golden day” (17 July 2001), under moderately polluted conditions with midvisible optical depths near 0.5, all six aircraft flew coordinated patterns vertically stacked between 100 and 65 000 ft over the COVE site as Terra flew overhead. This overview presents a description of CLAMS objectives, measurements, and sampling strategies. Key results, reported in greater detail in the collection of papers found in this special issue, are also summarized.


Jin, Zhonghai; Charlock, Thomas P.; Smith, William L.; Rutledge, KenJin, Z., T. P. Charlock, W. L. Smith, K. Rutledge, 2004: A parameterization of ocean surface albedo. Geophysical Research Letters, 31(22), L22301. doi: 10.1029/2004GL021180. Measurements at a sea platform show that the ocean surface albedo is highly variable and is sensitive to four physical parameters: solar zenith angle, wind speed, transmission by atmospheric cloud/aerosol, and ocean chlorophyll concentration. Using a validated coupled ocean-atmosphere radiative transfer model, an ocean albedo look up table is created in terms of these four important parameters. A code to read the table is also provided; it gives spectral albedos for a range of oceanic and atmospheric conditions specified by the user. The result is a fast and accurate parameterization of ocean surface albedo for radiative transfer and climate modeling. 1610 Atmosphere; 1620 Climate dynamics; 3339 Meteorology and Atmospheric Dynamics: Ocean/atmosphere interactions; 3359 Meteorology and Atmospheric Dynamics: Radiative processes; 4264 Ocean optics


Dong, Xiquan; Mace, Gerald G.; Minnis, Patrick; Smith, William L.; Poellot, Michael; Marchand, Roger T.; Rapp, Anita D.Dong, X., G. G. Mace, P. Minnis, W. L. Smith, M. Poellot, R. T. Marchand, A. D. Rapp, 2002: Comparison of Stratus Cloud Properties Deduced from Surface, GOES, and Aircraft Data during the March 2000 ARM Cloud IOP. J. Atmos. Sci., 59(23), 3265-3284. doi: 10.1175/1520-0469(2002)059<3265:COSCPD>2.0.CO;2. Abstract Low-level stratus cloud microphysical properties derived from surface and Geostationary Operational Environmental Satellite (GOES) data during the March 2000 cloud intensive observational period (IOP) at the Atmospheric Radiation Measurement (ARM) program Southern Great Plains (SGP) site are compared with aircraft in situ measurements. For the surface retrievals, the cloud droplet effective radius and optical depth are retrieved from a δ2-stream radiative transfer model with the input of ground-based measurements, and the cloud liquid water path (LWP) is retrieved from ground-based microwave-radiometer-measured brightness temperature. The satellite results, retrieved from GOES visible, solar-infrared, and infrared radiances, are averaged in a 0.5° × 0.5° box centered on the ARM SGP site. The forward scattering spectrometer probe (FSSP) on the University of North Dakota Citation aircraft provided in situ measurements of the cloud microphysical properties. During the IOP, four low-level stratus cases were intensively observed by the ground- and satellite-based remote sensors and aircraft in situ instruments resulting in a total of 10 h of simultaneous data from the three platforms. In spite of the large differences in temporal and spatial resolution between surface, GOES, and aircraft, the surface retrievals have excellent agreement with the aircraft data overall for the entire 10-h period, and the GOES results agree reasonably well with the surface and aircraft data and have similar trends and magnitudes except for the GOES-derived effective radii, which are typically larger than the surface- and aircraft-derived values. The means and standard deviations of the differences between the surface and aircraft effective radius, LWP, and optical depth are −4% ± 20.1%, −1% ± 31.2%, and 8% ± 29.3%, respectively; while their correlation coefficients are 0.78, 0.92, and 0.89, respectively, during the 10-h period. The differences and correlations between the GOES-8 and aircraft results are of a similar magnitude, except for the droplet sizes. The averaged GOES-derived effective radius is 23% or 1.8 μm greater than the corresponding aircraft values, resulting in a much smaller correlation coefficient of 0.18. Additional surface–satellite datasets were analyzed for time periods when the aircraft was unavailable. When these additional results are combined with the retrievals from the four in situ cases, the means and standard deviations of the differences between the satellite-derived cloud droplet effective radius, LWP, and optical depth and their surface-based counterparts are 16% ± 31.2%, 4% ± 31.6%, and −6% ± 39.9%, respectively. The corresponding correlation coefficients are 0.24, 0.88, and 0.73. The frequency distributions of the two datasets are very similar indicating that the satellite retrieval method should be able to produce reliable statistics of boundary layer cloud properties for use in climate and cloud process models.


Minnis, P.; Mayor, S.; Smith, W.L.; Young, D.F.Minnis, P., S. Mayor, W. Smith, D. Young, 1997: Asymmetry in the diurnal variation of surface albedo. IEEE Transactions on Geoscience and Remote Sensing, 35(4), 879-890. doi: 10.1109/36.602530. Remote sensing of surface properties and estimation of clear-sky and surface albedo generally assume that the albedo depends only on the solar zenith angle. The effects of dew, frost, and precipitation as well as evaporation and wind can lead to some systematic diurnal variability resulting in an asymmetric diurnal cycle of albedo. This paper examines the symmetry of both surface-observed and top-of-the-atmosphere (TOA) albedos derived from satellite data. Broadband surface albedos were measured at the Department of Energy Atmospheric Radiation Measurement (ARM) Program Southern Great Plains Central Facility near Lamont, Oklahoma and several extended facilities. GOES satellite radiance data are converted to broadband albedo using bidirectional reflectance functions and an empirical narrowband-to-broadband relationship. The surface and top-of-atmosphere albedos vary in a consistent fashion during both the morning and afternoon. The initial results indicate that surface moisture, probably in the form of dew, has a significant effect and can change the albedo by 10% at a given solar zenith angle between the morning and afternoon. Wind speed is well correlated with the diurnal albedo asymmetry. Light winds and small dew point depressions are associated with the greatest morning/afternoon albedo differences. Aerosols tend to moderate those differences. Changes in the surface properties from dew may alter the bidirectional reflectance characteristics of the scene, affecting the interpretation of remote sensing data. Errors in the diurnally averaged albedos derived from Sun-synchronous satellite measurements that arise from albedo asymmetry are generally less than 3%. Further examination of surface albedo asymmetry is needed to assess its influence on satellite measurements and the surface energy budget over a range of land surface types 350 to 850 nm; aerosols; afternoon; albedo; asymmetric diurnal cycle; asymmetry; atmosphere; Atmospheric measurements; atmospheric optics; Bidirectional control; bidirectional reflectance functions; diurnal variation; Energy measurement; geophysical techniques; Lamont; Land surface; land surface properties; land surface types; Layout; Light scattering; Moisture; morning; Oklahoma; optics; Remote sensing; Satellites; Southern Great Plains; surface albedo; surface moisture; terrain; United States; USA; Wind speed