Top of the Atmosphere Reflected Shortwave Radiative Fluxes from GOES-R

Abstract. Under the GOES-R activity, new algorithms are being developed at the National Oceanic and Atmospheric Administration (NOAA)/Center for Satellite Applications and Research (STAR) to derive surface and Top of the Atmosphere (TOA) shortwave (SW) radiative fluxes from the Advanced Baseline Imager (ABI), the primary instrument on GOES-R. This paper describes a support effort in the development and evaluation of the ABI instrument capabilities to derive such fluxes. Specifically, scene dependent narrow-to-broadband (NTB) transformations are developed to facilitate the use of observations from ABI at the TOA. Simulations of NTB transformations have been performed with MODTRAN4.3 using an updated selection of atmospheric profiles as implemented with the final ABI specifications. These are combined with Angular Distribution Models (ADMs), which are a synergy of ADMs from the Clouds and the Earth's Radiant Energy System (CERES) and from simulations. Surface condition at the scale of the ABI products as needed to compute the TOA radiative fluxes come from the International Geosphere-Biosphere Programme (IGBP). Land classification at 1/6° resolution for 18 surface types are converted to the ABI 2-km grid over the (CONtiguous States of the United States) (CONUS) and subsequently re-grouped to 12 IGBP types to match the classification of the CERES ADMs. In the simulations, default information on aerosols and clouds is based on the ones used in MODTRAN. Comparison of derived fluxes at the TOA is made with those from the CERES and/or the Fast Longwave and Shortwave Radiative Flux (FLASHFlux) data. A satisfactory agreement between the fluxes was observed and possible reasons for differences have been identified; the agreement of the fluxes at the TOA for predominantly clear sky conditions was found to be better than for cloudy sky due to possible time shift in observation times between the two observing systems that might have affected the position of the clouds during such periods.

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Next-generation angular distribution models for top-of-atmosphere radiative flux calculation from the CERES instruments: validation

Atmospheric Measurement Techniques Discussions ◽

10.5194/amtd-8-4489-2015 ◽

2015 ◽

Vol 8 (5) ◽

pp. 4489-4536 ◽

Cited By ~ 4

Author(s):

W. Su ◽

J. Corbett ◽

Z. Eitzen ◽

L. Liang

Keyword(s):

Angular Distribution ◽

Radiant Energy ◽

Energy System ◽

Direct Integration ◽

Distribution Models ◽

Radiative Fluxes ◽

Rms Error ◽

Sky Conditions ◽

Along Track ◽

Scene Identification

Abstract. Radiative fluxes at the top of the atmosphere (TOA) from the Clouds and the Earth's Radiant Energy System (CERES) instrument are fundamental variables for understanding the Earth's energy balance and how it changes with time. TOA radiative fluxes are derived from the CERES radiance measurements using empirical angular distribution models (ADMs). This paper evaluates the accuracy of CERES TOA fluxes using direct integration and flux consistency tests. Direct integration tests show that the overall bias in regional monthly mean TOA shortwave (SW) flux is less than 0.2 W m−2 and the RMS error is less than 1.1 W m−2. The bias and RMS error are very similar between Terra and Aqua. The bias in regional monthly mean TOA LW fluxes is less than 0.5 W m−2 and the RMS error is less than 0.8 W m−2 for both Terra and Aqua. The accuracy of the TOA instantaneous flux is assessed by performing tests using fluxes inverted from nadir- and oblique-viewing angles using CERES along-track observations and temporally- and spatially-matched MODIS observations, and using fluxes inverted from multi-angle MISR observations. The TOA instantaneous SW flux uncertainties are about 2.3% (1.9 W m−2) over clear ocean, 1.6% (4.5 W m−2) over clear land, and 2.0% (6.0 W m−2) over clear snow/ice; and are about 3.3% (9.0 W m−2), 2.7% (8.4 W m−2), and 3.7% (9.9 W m−2) over ocean, land, and snow/ice under all-sky conditions. The TOA SW flux uncertainties are generally larger for thin broken clouds than for moderate and thick overcast clouds. The TOA instantaneous daytime LW flux uncertainties are 0.5% (1.5 W m−2), 0.8% (2.4 W m−2), and 0.7 % (1.3 W m−2) over clear ocean, land, and snow/ice; and are about 1.5% (3.5 W m−2), 1.0% (2.9 W m−2), and 1.1 % (2.1 W m−2) over ocean, land, and snow/ice under all-sky conditions. The TOA instantaneous nighttime LW flux uncertainties are about 0.5–1% (< 2.0 W m−2) for all surface types. Flux uncertainties caused by errors in scene identification are also assessed by using the collocated CALIPSO, CloudSat, CERES and MODIS data product. Errors in scene identification tend to underestimate TOA SW flux by about 0.6 W m−2 and overestimate TOA daytime (nighttime) LW flux by 0.4 (0.2) W m−2 when all CERES viewing angles are considered.

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Next-generation angular distribution models for top-of-atmosphere radiative flux calculation from CERES instruments: validation

Atmospheric Measurement Techniques ◽

10.5194/amt-8-3297-2015 ◽

2015 ◽

Vol 8 (8) ◽

pp. 3297-3313 ◽

Cited By ~ 21

Author(s):

W. Su ◽

J. Corbett ◽

Z. Eitzen ◽

L. Liang

Keyword(s):

Angular Distribution ◽

Energy Balance ◽

Radiant Energy ◽

Energy System ◽

Direct Integration ◽

Distribution Models ◽

Radiative Fluxes ◽

Sky Conditions ◽

Along Track ◽

Scene Identification

Abstract. Radiative fluxes at the top of the atmosphere (TOA) from the Clouds and the Earth's Radiant Energy System (CERES) instrument are fundamental variables for understanding the Earth's energy balance and how it changes with time. TOA radiative fluxes are derived from the CERES radiance measurements using empirical angular distribution models (ADMs). This paper evaluates the accuracy of CERES TOA fluxes using direct integration and flux consistency tests. Direct integration tests show that the overall bias in regional monthly mean TOA shortwave (SW) flux is less than 0.2 Wm−2 and the RMSE is less than 1.1 Wm−2. The bias and RMSE are very similar between Terra and Aqua. The bias in regional monthly mean TOA LW fluxes is less than 0.5 Wm−2 and the RMSE is less than 0.8 Wm−2 for both Terra and Aqua. The accuracy of the TOA instantaneous flux is assessed by performing tests using fluxes inverted from nadir- and oblique-viewing angles using CERES along-track observations and temporally and spatially matched MODIS observations, and using fluxes inverted from multi-angle MISR observations. The averaged TOA instantaneous SW flux uncertainties from these two tests are about 2.3 % (1.9 Wm−2) over clear ocean, 1.6 % (4.5 Wm−2) over clear land, and 2.0 % (6.0 Wm−2) over clear snow/ice; and are about 3.3 % (9.0 Wm−2), 2.7 % (8.4 Wm−2), and 3.7 % (9.9 Wm−2) over ocean, land, and snow/ice under all-sky conditions. The TOA SW flux uncertainties are generally larger for thin broken clouds than for moderate and thick overcast clouds. The TOA instantaneous daytime LW flux uncertainties derived from the CERES-MODIS test are 0.5 % (1.5 Wm−2), 0.8 % (2.4 Wm−2), and 0.7 % (1.3 Wm−2) over clear ocean, land, and snow/ice; and are about 1.5 % (3.5 Wm−2), 1.0 % (2.9 Wm−2), and 1.1 % (2.1 Wm−2) over ocean, land, and snow/ice under all-sky conditions. The TOA instantaneous nighttime LW flux uncertainties are about 0.5–1 % (< 2.0 Wm−2) for all surface types. Flux uncertainties caused by errors in scene identification are also assessed by using the collocated CALIPSO, CloudSat, CERES and MODIS data product. Errors in scene identification tend to underestimate TOA SW flux by about 0.6 Wm−2 and overestimate TOA daytime (nighttime) LW flux by 0.4 (0.2) Wm−2 when all CERES viewing angles are considered.

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Angular Distribution Models for Top-of-Atmosphere Radiative Flux Estimation from the Clouds and the Earth’s Radiant Energy System Instrument on the Terra Satellite. Part I: Methodology

Journal of Atmospheric and Oceanic Technology ◽

10.1175/jtech1712.1 ◽

2005 ◽

Vol 22 (4) ◽

pp. 338-351 ◽

Cited By ~ 207

Author(s):

Norman G. Loeb ◽

Seiji Kato ◽

Konstantin Loukachine ◽

Natividad Manalo-Smith

Keyword(s):

Angular Distribution ◽

Radiant Energy ◽

Tropical Rainfall Measuring Mission ◽

Energy System ◽

Distribution Models ◽

Radiative Fluxes ◽

Earth Observing System ◽

Moderate Resolution ◽

Moderate Resolution Imaging Spectroradiometer ◽

Terra Satellite

Abstract The Clouds and Earth’s Radiant Energy System (CERES) provides coincident global cloud and aerosol properties together with reflected solar, emitted terrestrial longwave, and infrared window radiative fluxes. These data are needed to improve the understanding and modeling of the interaction between clouds, aerosols, and radiation at the top of the atmosphere, surface, and within the atmosphere. This paper describes the approach used to estimate top-of-atmosphere (TOA) radiative fluxes from instantaneous CERES radiance measurements on the Terra satellite. A key component involves the development of empirical angular distribution models (ADMs) that account for the angular dependence of the earth’s radiation field at the TOA. The CERES Terra ADMs are developed using 24 months of CERES radiances, coincident cloud and aerosol retrievals from the Moderate Resolution Imaging Spectroradiometer (MODIS), and meteorological parameters from the Global Modeling and Assimilation Office (GMAO)’s Goddard Earth Observing System (GEOS) Data Assimilation System (DAS) V4.0.3 product. Scene information for the ADMs is from MODIS retrievals and GEOS DAS V4.0.3 properties over the ocean, land, desert, and snow for both clear and cloudy conditions. Because the CERES Terra ADMs are global, and far more CERES data are available on Terra than were available from CERES on the Tropical Rainfall Measuring Mission (TRMM), the methodology used to define CERES Terra ADMs is different in many respects from that used to develop CERES TRMM ADMs, particularly over snow/sea ice, under cloudy conditions, and for clear scenes over land and desert.

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Top-of-Atmosphere Direct Radiative Effect of Aerosols over Global Oceans from Merged CERES and MODIS Observations

Journal of Climate ◽

10.1175/jcli3504.1 ◽

2005 ◽

Vol 18 (17) ◽

pp. 3506-3526 ◽

Cited By ~ 139

Author(s):

Norman G. Loeb ◽

Natividad Manalo-Smith

Keyword(s):

Information Service ◽

Radiant Energy ◽

Energy System ◽

Surface Fluxes ◽

Radiative Effect ◽

Distribution Models ◽

Radiative Fluxes ◽

Clear Sky ◽

Moderate Resolution Imaging Spectroradiometer ◽

Global Oceans

Abstract The direct radiative effect of aerosols (DREA) is defined as the difference between radiative fluxes in the absence and presence of aerosols. In this study, the direct radiative effect of aerosols is estimated for 46 months (March 2000–December 2003) of merged Clouds and the Earth’s Radiant Energy System (CERES) and Moderate Resolution Imaging Spectroradiometer (MODIS) Terra global measurements over ocean. This analysis includes the contribution from clear regions in both clear and partly cloudy CERES footprints. MODIS–CERES narrow-to-broadband regressions are developed to convert clear-sky MODIS narrowband radiances to broadband shortwave (SW) radiances, and CERES clear-sky angular distribution models (ADMs) are used to estimate the corresponding top-of-atmosphere (TOA) radiative fluxes that are needed to determine the DREA. Clear-sky MODIS pixels are identified using two independent cloud masks: (i) the NOAA/National Environmental Satellite, Data, and Information Service (NESDIS) algorithm that is used for inferring aerosol properties from MODIS on the CERES Single Scanner Footprint TOA/Surface Fluxes and Clouds (SSF) product (NOAA SSF); and (ii) the standard algorithm that is used by the MODIS aerosol group to produce the MODIS aerosol product (MOD04). Over global oceans, direct radiative cooling by aerosols for clear scenes that are identified from MOD04 is estimated to be 40% larger than for clear scenes from NOAA SSF (5.5 compared to 3.8 W m−2). Regionally, differences are largest in areas that are affected by dust aerosol, such as oceanic regions that are adjacent to the Sahara and Saudi Arabian deserts, and in northern Pacific Ocean regions that are influenced by dust transported from Asia. The net total-sky (clear and cloudy) DREA is negative (cooling) and is estimated to be −2.0 W m−2 from MOD04, and −1.6 W m−2 from NOAA SSF. The DREA is shown to have pronounced seasonal cycles in the Northern Hemisphere and large year-to-year fluctuations near deserts. However, no systematic trend in deseasonalized anomalies of the DREA is observed over the 46-month time series that is considered.

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Evaluation of net shortwave radiation over China with a regional climate model

Climate Research ◽

10.3354/cr01598 ◽

2020 ◽

Vol 80 (2) ◽

pp. 147-163

Author(s):

X Liu ◽

Y Kang ◽

Q Liu ◽

Z Guo ◽

Y Chen ◽

...

Keyword(s):

Regional Climate Model ◽

Climate Model ◽

Regional Climate ◽

Radiant Energy ◽

Energy System ◽

Radiation Budget ◽

Shortwave Radiation ◽

Monsoon Region ◽

Clear Sky ◽

Sky Conditions

The regional climate model RegCM version 4.6, developed by the European Centre for Medium-Range Weather Forecasts Reanalysis, was used to simulate the radiation budget over China. Clouds and the Earth’s Radiant Energy System (CERES) satellite data were utilized to evaluate the simulation results based on 4 radiative components: net shortwave (NSW) radiation at the surface of the earth and top of the atmosphere (TOA) under all-sky and clear-sky conditions. The performance of the model for low-value areas of NSW was superior to that for high-value areas. NSW at the surface and TOA under all-sky conditions was significantly underestimated; the spatial distribution of the bias was negative in the north and positive in the south, bounded by 25°N for the annual and seasonal averaged difference maps. Compared with the all-sky condition, the simulation effect under clear-sky conditions was significantly better, which indicates that the cloud fraction is the key factor affecting the accuracy of the simulation. In particular, the bias of the TOA NSW under the clear-sky condition was <±10 W m-2 in the eastern areas. The performance of the model was better over the eastern monsoon region in winter and autumn for surface NSW under clear-sky conditions, which may be related to different levels of air pollution during each season. Among the 3 areas, the regional average biases overall were largest (negative) over the Qinghai-Tibet alpine region and smallest over the eastern monsoon region.

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On the Use of Geophysical Parameters for the Top-of-Atmosphere Shortwave Clear-Sky Radiance-to-Flux Conversion in EarthCARE

Journal of Atmospheric and Oceanic Technology ◽

10.1175/jtech-d-18-0087.1 ◽

2019 ◽

Vol 36 (4) ◽

pp. 717-732 ◽

Cited By ~ 1

Author(s):

F. Tornow ◽

C. Domenech ◽

J. Fischer

Keyword(s):

Permutation Test ◽

Climate Modeling ◽

Radiant Energy ◽

Energy System ◽

Max Planck ◽

Distribution Models ◽

Dynamic Surface ◽

Clear Sky ◽

Fresh Snow ◽

Bidirectional Reflectance Distribution

AbstractWe 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.

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Next-generation angular distribution models for top-of-atmosphere radiative flux calculation from CERES instruments: methodology

Atmospheric Measurement Techniques ◽

10.5194/amt-8-611-2015 ◽

2015 ◽

Vol 8 (2) ◽

pp. 611-632 ◽

Cited By ~ 46

Author(s):

W. Su ◽

J. Corbett ◽

Z. Eitzen ◽

L. Liang

Keyword(s):

Angular Distribution ◽

Sea Ice ◽

Regional Scale ◽

Radiant Energy ◽

Energy System ◽

Continuous Functions ◽

Climate Feedback ◽

Radiative Energy ◽

Next Generation ◽

Distribution Models

Abstract. The top-of-atmosphere (TOA) radiative fluxes are critical components to advancing our understanding of the Earth's radiative energy balance, radiative effects of clouds and aerosols, and climate feedback. The Clouds and the Earth's Radiant Energy System (CERES) instruments provide broadband shortwave and longwave radiance measurements. These radiances are converted to fluxes by using scene-type-dependent angular distribution models (ADMs). This paper describes the next-generation ADMs that are developed for Terra and Aqua using all available CERES rotating azimuth plane radiance measurements. Coincident cloud and aerosol retrievals, and radiance measurements from the Moderate Resolution Imaging Spectroradiometer (MODIS), and meteorological parameters from Goddard Earth Observing System (GEOS) data assimilation version 5.4.1 are used to define scene type. CERES radiance measurements are stratified by scene type and by other parameters that are important for determining the anisotropy of the given scene type. Anisotropic factors are then defined either for discrete intervals of relevant parameters or as a continuous functions of combined parameters, depending on the scene type. Significant differences between the ADMs described in this paper and the existing ADMs are over clear-sky scene types and polar scene types. Over clear ocean, we developed a set of shortwave (SW) ADMs that explicitly account for aerosols. Over clear land, the SW ADMs are developed for every 1° latitude × 1° longitude region for every calendar month using a kernel-based bidirectional reflectance model. Over clear Antarctic scenes, SW ADMs are developed by accounting the effects of sastrugi on anisotropy. Over sea ice, a sea-ice brightness index is used to classify the scene type. Under cloudy conditions over all surface types, the longwave (LW) and window (WN) ADMs are developed by combining surface and cloud-top temperature, surface and cloud emissivity, cloud fraction, and precipitable water. Compared to the existing ADMs, the new ADMs change the monthly mean instantaneous fluxes by up to 5 W m−2 on a regional scale of 1° latitude × 1° longitude, but the flux changes are less than 0.5 W m−2 on a global scale.

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A Study of the Longer Term Variation of Aerosol Optical Thickness and Direct Shortwave Aerosol Radiative Effect Trends Using MODIS and CERES

10.5194/acp-2017-365 ◽

2017 ◽

Author(s):

Ricardo Alfaro-Contreras ◽

Jianglong Zhang ◽

Jeffrey S. Reid ◽

Sundar Christopher

Keyword(s):

Optical Thickness ◽

Broad Band ◽

Radiant Energy ◽

Energy System ◽

Short Wave ◽

Aerosol Optical Thickness ◽

Radiative Effect ◽

Distribution Models ◽

Direct Forcing ◽

Aerosol Radiative

Abstract. By combining Collection 6 Moderate Resolution and Imaging Spectroradiometer (MODIS) and Version 22 Multi-angle Imaging Spectroradiometer (MISR) aerosol products with Cloud and Earth’s Radiant Energy System (CERES) flux products, the aerosol optical thickness (AOT, at 0.55 µm) and Short-Wave Aerosol Radiative Effect (SWARE) trends are studied over ocean for the near full Terra (2000–2015) and Aqua (2002–2015) data records. Despite differences in sampling methods, regional SWARE and AOT trends are highly correlated with one another. Over global oceans, weak SWARE (cloud free SW flux) and AOT trends of 0.5–0.6 W m−2 (−0.5 to −0.6 W m−2) and 0.002 AOT decade−1 were found using Terra data. Near zero AOT and SWARE trends are also found for using Aqua data, regardless of Angular Distribution Models (ADMs) used. Regionally, positive SWARE and AOT trends are found over the Bay of Bengal, Arabian Sea, Arabian/Persian Gulf and the Red Sea, while statistically significant negative trends are derived over the Mediterranean Sea and the eastern US coast. In addition, the global mean instantaneous SW aerosol direct forcing efficiencies are found to be ~ −60 W m−2 per AOT, with corresponding SWARE values of ~ −7 W m−2 from both Aqua and Terra data, and again, regardless of CERES ADMs used. Regionally, SW aerosol direct forcing efficiency values of ~ −40 W m−2 per AOT are found over the southwest coast of Africa where smoke aerosol particles dominate in summer. Larger (in magnitude) SW aerosol direct forcing efficiency values of −50 to −80 W m−2 per AOT are found over several other dust and pollutant aerosol dominated regions. Lastly, the AOT and SWARE trends from this study are also inter-compared with aerosol trends (such as active-based) from several previous studies. Findings suggest that a cohesive understanding of the changing aerosol skies can be achieved through the analysis of observations from both passive- and active-based analyses, as well as at both narrow-band and broad-band data sets.

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Determining the Daytime Earth Radiative Flux from National Institute of Standards and Technology Advanced Radiometer (NISTAR) Measurements

10.5194/amt-2019-214 ◽

2019 ◽

Author(s):

Wenying Su ◽

Patrick Minnis ◽

Lusheng Liang ◽

David P. Duda ◽

Konstantin Khlopenkov ◽

...

Keyword(s):

Near Infrared ◽

Radiant Energy ◽

Correlation Coefficients ◽

Energy System ◽

Low Earth Orbit ◽

Spectral Radiance ◽

Daily Maximum ◽

Distribution Models ◽

The Earth ◽

Highly Correlated

Abstract. The National Institute of Standards and Technology Advanced Radiometer (NISTAR) onboard Deep Space Climate Observatory (DSCOVR) provides continuous full disc global broadband irradiance measurements over most of the sunlit side of the Earth. The three active cavity radiometers measures the total radiant energy from the sun-lit 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 data base 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 and 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 about 3 % greater than those from CERES, but the correlation between them is only about 0.38.

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Decomposing Shortwave Top-of-Atmosphere and Surface Radiative Flux Variations in Terms of Surface and Atmospheric Contributions

Journal of Climate ◽

10.1175/jcli-d-18-0826.1 ◽

2019 ◽

Vol 32 (16) ◽

pp. 5003-5019 ◽

Cited By ~ 1

Author(s):

Norman G. Loeb ◽

Hailan Wang ◽

Fred G. Rose ◽

Seiji Kato ◽

William L. Smith ◽

...

Keyword(s):

Regional Distribution ◽

Radiant Energy ◽

Surface Flux ◽

Energy System ◽

The Arctic ◽

Radiative Fluxes ◽

The Difference ◽

Atmospheric Variations ◽

Modern Era ◽

Global Mean

AbstractA 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) Edition 4.0 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—the 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.

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