{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,4,10]],"date-time":"2026-04-10T22:45:33Z","timestamp":1775861133579,"version":"3.50.1"},"reference-count":50,"publisher":"MDPI AG","issue":"9","license":[{"start":{"date-parts":[[2021,4,23]],"date-time":"2021-04-23T00:00:00Z","timestamp":1619136000000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["Remote Sensing"],"abstract":"<jats:p>Geostationary observations offer the unique opportunity to resolve the diurnal cycle of the Earth\u2019s Radiation Budget at the top of the atmosphere (TOA), crucial for climate-change studies. However, a drawback of the continuous temporal coverage of the geostationary orbit is the fixed viewing geometry. As a consequence, imperfections in the angular distribution models (ADMs) used in the radiance-to-flux conversion process or residual angular-dependent narrowband-to-broadband conversion errors can result in systematic errors of the estimated radiative fluxes. In this work, focusing on clear-sky reflected TOA observations, we compare the overlapping views from Meteosat Second Generation satellites at 0\u00b0 and 41.5\u00b0E longitude which enable a quantification of viewing-angle-dependent differences. Using data derived from the Spinning Enhanced Visible and InfraRed Imager (SEVIRI), we identify some of the main sources of discrepancies, and show that they can be significantly reduced at the level of one month. This is achieved, separately for each satellite, via a masking procedure followed by an empirical fit at the pixel-level that takes into account all the clear-sky data from that satellite, calculated separately per timeslot of the day, over the month of November 2016. The method is then applied to each month of 2017, and gives a quadratic mean of the albedo root-mean squared difference over the dual-view region which is comparable from month to month, with a 2017 average value of 0.01. Sources of discrepancies include the difficulty to estimate the flux over the sunglint ocean region close to the limbs, the fact that the data processing does not include dedicated angular distribution models for the aerosol-over-ocean case, and the existence of an observer-dependent diurnal-asymmetry artefact affecting the clear-sky-albedo dependence on the solar zenith angle particularly over land areas.<\/jats:p>","DOI":"10.3390\/rs13091655","type":"journal-article","created":{"date-parts":[[2021,4,25]],"date-time":"2021-04-25T02:12:57Z","timestamp":1619316777000},"page":"1655","update-policy":"https:\/\/doi.org\/10.3390\/mdpi_crossmark_policy","source":"Crossref","is-referenced-by-count":5,"title":["Dual View on Clear-Sky Top-of-Atmosphere Albedos from Meteosat Second Generation Satellites"],"prefix":"10.3390","volume":"13","author":[{"ORCID":"https:\/\/orcid.org\/0000-0002-4746-7797","authenticated-orcid":false,"given":"Alexandre","family":"Payez","sequence":"first","affiliation":[{"name":"Royal Meteorological Institute of Belgium, Ringlaan 3 Avenue Circulaire, B-1180 Brussels, Belgium"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-4571-1450","authenticated-orcid":false,"given":"Steven","family":"Dewitte","sequence":"additional","affiliation":[{"name":"Royal Meteorological Institute of Belgium, Ringlaan 3 Avenue Circulaire, B-1180 Brussels, Belgium"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"ORCID":"https:\/\/orcid.org\/0000-0003-2195-8253","authenticated-orcid":false,"given":"Nicolas","family":"Clerbaux","sequence":"additional","affiliation":[{"name":"Royal Meteorological Institute of Belgium, Ringlaan 3 Avenue Circulaire, B-1180 Brussels, Belgium"}],"role":[{"role":"author","vocabulary":"crossref"}]}],"member":"1968","published-online":{"date-parts":[[2021,4,23]]},"reference":[{"key":"ref_1","doi-asserted-by":"crossref","first-page":"1431","DOI":"10.1175\/BAMS-D-13-00047.1","article-title":"The Concept of Essential Climate Variables in Support of Climate Research, Applications, and Policy","volume":"95","author":"Bojinski","year":"2014","journal-title":"Bull. Am. Meteorol. Soc."},{"key":"ref_2","unstructured":"Pachauri, R., Allen, M., Barros, V., Broome, J., Cramer, W., Christ, R., Church, J., Clarke, L., Dahe, Q., and Dasqupta, P. (2021, April 22). Climate Change 2014: Synthesis Report. Contribution of Working Groups I, II and III to the Fifth Assessment Report of the Intergovernmental Panel on Climate Change, Available online: https:\/\/www.ipcc.ch\/report\/ar5\/syr\/."},{"key":"ref_3","unstructured":"Note that wide-field-of-view instruments, which cannot provide spatial information, are not considered in this work."},{"key":"ref_4","doi-asserted-by":"crossref","first-page":"851","DOI":"10.1175\/1520-0426(1996)013<0851:VOESR>2.0.CO;2","article-title":"Validation of ERBS Scanner Radiances","volume":"13","author":"Green","year":"1996","journal-title":"J. Atmos. Ocean. Technol."},{"key":"ref_5","doi-asserted-by":"crossref","first-page":"784","DOI":"10.1175\/1520-0450(1992)031<0784:TOARFV>2.0.CO;2","article-title":"Top-of-Atmosphere Radiative Fluxes: Validation of ERBE Scanner Inversion Algorithm Using Nimbus-7 ERB Data","volume":"31","author":"Suttles","year":"1992","journal-title":"J. Appl. Meteorol."},{"key":"ref_6","doi-asserted-by":"crossref","first-page":"240","DOI":"10.1175\/1520-0450(2003)042<0240:ADMFTO>2.0.CO;2","article-title":"Angular Distribution Models for Top-of-Atmosphere Radiative Flux Estimation from the Clouds and the Earth\u2019s Radiant Energy System Instrument on the Tropical Rainfall Measuring Mission Satellite. Part I: Methodology","volume":"42","author":"Loeb","year":"2003","journal-title":"J. Appl. Meteorol."},{"key":"ref_7","unstructured":"Suttles, J.T., Green, R.N., Minnis, P., Smith, G.L., Staylor, W.F., Wielicki, B.A., Walker, I.J., Young, D.F., Taylor, V.R., and Stowe, L.L. (1988). Angular Radiation Models for Earth\u2013Atmosphere System, Volume 1\u2014Shortwave Radiation."},{"key":"ref_8","doi-asserted-by":"crossref","first-page":"25","DOI":"10.3847\/0004-637X\/830\/1\/25","article-title":"The total solar irradiance climate data record","volume":"830","author":"Dewitte","year":"2016","journal-title":"Astrophys. J."},{"key":"ref_9","first-page":"309","article-title":"Planetary Theories in rectangular and spherical variables: VSOP87 solutions","volume":"202","author":"Bretagnon","year":"1988","journal-title":"Astron. Astrophys."},{"key":"ref_10","doi-asserted-by":"crossref","first-page":"784","DOI":"10.1175\/1520-0493(2001)129<0784:TDCITT>2.0.CO;2","article-title":"The diurnal cycle in the tropics","volume":"129","author":"Yang","year":"2001","journal-title":"Mon. Weather. Rev."},{"key":"ref_11","doi-asserted-by":"crossref","first-page":"853","DOI":"10.1175\/1520-0477(1996)077<0853:CATERE>2.0.CO;2","article-title":"Clouds and the Earth\u2019s Radiant Energy System (CERES): An Earth Observing System Experiment","volume":"77","author":"Wielicki","year":"1996","journal-title":"Bull. Am. Meteorol. Soc."},{"key":"ref_12","doi-asserted-by":"crossref","first-page":"977","DOI":"10.1175\/BAMS-83-7-Schmetz-2","article-title":"An Introduction to Meteosat Second Generation (MSG)","volume":"83","author":"Schmetz","year":"2002","journal-title":"Bull. Am. Meteorol. Soc."},{"key":"ref_13","doi-asserted-by":"crossref","first-page":"945","DOI":"10.1175\/BAMS-86-7-945","article-title":"The Geostationary Earth Radiation Budget Project","volume":"86","author":"Harries","year":"2005","journal-title":"Bull. Am. Meteorol. Soc."},{"key":"ref_14","unstructured":"Ratier, A. (2021, April 22). EUMETSAT Programmes and Future Plans, September 2020. EUM\/DG\/VWG\/20\/1191556 v2, Available online: https:\/\/www.nesdis.noaa.gov\/content\/2020-community-meetings-presentations."},{"key":"ref_15","doi-asserted-by":"crossref","first-page":"1906","DOI":"10.1016\/j.asr.2007.07.042","article-title":"The Geostationary Earth Radiation Budget Edition 1 data processing algorithms","volume":"41","author":"Dewitte","year":"2008","journal-title":"Adv. Space Res."},{"key":"ref_16","unstructured":"(2021, April 22). We Use What Are, at the Time of Writing, the Very Latest Available Products Covering the Dual-View Period: GL-SEV HR V003. Available online: https:\/\/gerb.oma.be."},{"key":"ref_17","doi-asserted-by":"crossref","first-page":"1087","DOI":"10.1175\/2007JTECHA1001.1","article-title":"Unfiltering of the Geostationary Earth Radiation Budget (GERB) Data. Part I: Shortwave Radiation","volume":"25","author":"Clerbaux","year":"2008","journal-title":"J. Atmos. Ocean. Technol."},{"key":"ref_18","doi-asserted-by":"crossref","first-page":"611","DOI":"10.5194\/amt-8-611-2015","article-title":"Next-generation angular distribution models for top-of-atmosphere radiative flux calculation from CERES instruments: Methodology","volume":"8","author":"Su","year":"2015","journal-title":"Atmos. Meas. Tech."},{"key":"ref_19","doi-asserted-by":"crossref","first-page":"503","DOI":"10.1175\/JTECH-D-15-0147.1","article-title":"Advances in Geostationary-Derived Longwave Fluxes for the CERES Synoptic (SYN1deg) Product","volume":"33","author":"Doelling","year":"2016","journal-title":"J. Atmos. Ocean. Technol."},{"key":"ref_20","doi-asserted-by":"crossref","unstructured":"Urbain, M., Clerbaux, N., Ipe, A., Tornow, F., Hollmann, R., Baudrez, E., Velazquez Blazquez, A., and Moreels, J. (2017). The CM SAF TOA Radiation Data Record Using MVIRI and SEVIRI. Remote Sens., 9.","DOI":"10.3390\/rs9050466"},{"key":"ref_21","unstructured":"Clerbaux, N., Urbain, M., Ipe, A., Baudrez, E., Velazquez-Blazquez, A., Akkermans, T., Hollmann, R., Fuchs, P., Selbach, N., and Werscheck, M. (2021, April 22). CMSAF TOARadiationGERB\/SEVIRIData Record-Edition 2. Available online: https:\/\/wui.cmsaf.eu\/safira\/action\/viewDoiDetails?acronym=TOA_GERB_V002."},{"key":"ref_22","doi-asserted-by":"crossref","first-page":"1741","DOI":"10.1080\/01431160500107015","article-title":"Angular distribution models anisotropic correction factors and sun glint: A sensitivity study","volume":"27","author":"Bertrand","year":"2006","journal-title":"Int. J. Remote Sens."},{"key":"ref_23","unstructured":"The albedo is set to 1 where it exceeds this value. Such pixels are not masked, to help identify and address potential issues."},{"key":"ref_24","unstructured":"Russell, J. (2017). Quality Summary: GERB L2 Edition 1 Products, Available online: http:\/\/cedadocs.ceda.ac.uk\/1358\/."},{"key":"ref_25","doi-asserted-by":"crossref","first-page":"31255","DOI":"10.1029\/1999JD900935","article-title":"Top-of-atmosphere albedo estimation from angular distribution models: A comparison between two approaches","volume":"104","author":"Loeb","year":"1999","journal-title":"J. Geophys. Res. Atmos."},{"key":"ref_26","unstructured":"For consistency with an aerosol-optical-depth mask applied in the following, as there is no retrieval at larger zenith angles."},{"key":"ref_27","unstructured":"The sunglint angle is defined via: cos(sunglintangle)=sin(\u03b8\u2299)sin(\u03b8vz)cos(\u03d5rel)+cos(\u03b8\u2299)cos(\u03b8vz)."},{"key":"ref_28","unstructured":"Note that the CERES team proposes a method to account for aerosols in the clear-sky ocean ADM; see ref. [6]. However, this correction is not actually applied in the GL-SEV processing."},{"key":"ref_29","unstructured":"The presence of aerosols results in a quite diffuse reflection; very different from the strong specular reflection in the clear-sky ocean case. The use of clear-sky ocean ADMs that do not take aerosols into account is therefore particularly problematic."},{"key":"ref_30","doi-asserted-by":"crossref","first-page":"2455","DOI":"10.1016\/j.rse.2007.11.005","article-title":"Aerosol retrieval over ocean from SEVIRI for the use in GERB Earth\u2019s radiation budget analyses","volume":"112","author":"Ignatov","year":"2008","journal-title":"Remote Sens. Environ."},{"key":"ref_31","first-page":"D10S23","article-title":"Shortwave aerosol radiative forcing over cloud-free oceans from Terra: 1. Angular models for aerosols","volume":"110","author":"Zhang","year":"2005","journal-title":"J. Geophys. Res. Atmos."},{"key":"ref_32","doi-asserted-by":"crossref","first-page":"3585","DOI":"10.1109\/TGRS.2006.881119","article-title":"Diurnal Asymmetry in the GERB SW Fluxes","volume":"44","author":"Bertrand","year":"2006","journal-title":"IEEE Trans. Geosci. Remote Sens."},{"key":"ref_33","doi-asserted-by":"crossref","first-page":"895","DOI":"10.1175\/JCLI-D-17-0208.1","article-title":"Clouds and the Earth\u2019s Radiant Energy System (CERES) Energy Balanced and Filled (EBAF) Top-of-Atmosphere (TOA) Edition-4.0 Data Product","volume":"31","author":"Loeb","year":"2018","journal-title":"J. Clim."},{"key":"ref_34","doi-asserted-by":"crossref","first-page":"879","DOI":"10.1109\/36.602530","article-title":"Asymmetry in the diurnal variation of surface albedo","volume":"35","author":"Minnis","year":"1997","journal-title":"IEEE Trans. Geosci. Remote Sens."},{"key":"ref_35","doi-asserted-by":"crossref","first-page":"305","DOI":"10.1016\/S0065-2687(08)60176-4","article-title":"Land Surface Processes and Climate-Surface Albedos and Energy Balance","volume":"25","author":"Dickinson","year":"1983","journal-title":"Adv. Geophys."},{"key":"ref_36","doi-asserted-by":"crossref","first-page":"214","DOI":"10.1175\/1520-0450(1986)025<0214:CORCSA>2.0.CO;2","article-title":"Comparison of Regional Clear-Sky Albedos Inferred from Satellite Observations and Model Computations","volume":"25","author":"Briegleb","year":"1986","journal-title":"J. Clim. Appl. Meteorol."},{"key":"ref_37","doi-asserted-by":"crossref","first-page":"2963","DOI":"10.1175\/2008JAMC1843.1","article-title":"Dependence of Land Surface Albedo on Solar Zenith Angle: Observations and Model Parameterization","volume":"47","author":"Yang","year":"2008","journal-title":"J. Appl. Meteorol. Climatol."},{"key":"ref_38","unstructured":"While the branches themselves cannot be physical, one can notice the presence of overimposed instantaneous patterns. In contrast to the branches, those are actually consistent between the two satellites at corresponding times and likely of physical origin. They are in fact already present in SEVIRI narrowband radiances."},{"key":"ref_39","unstructured":"Although an effect due to residual narrowband-to-broadband errors in GL-SEV cannot be excluded, this would not be sufficient to explain the diurnal-asymmetry artefact, which also appears in pure broadband GERB data."},{"key":"ref_40","unstructured":"Further note that any actual observer-independent physical effect with a significant impact on the albedo should remain clearly visible even with swapped branches from MSG-3 to MSG-1. If there were dew [34] in the early morning for instance, the shape of the two morning branches would then be similarly skewed upwards and the apparent symmetry seen here when swapping the morning and afternoon branches would be lost."},{"key":"ref_41","unstructured":"(2021, April 22). The NLopt Free and Open Source Nonlinear-Optimization Library. Available online: http:\/\/github.com\/stevengj\/nlopt."},{"key":"ref_42","unstructured":"Powell, M.J.D. (July, January 22). The NEWUOA software for unconstrained optimization without derivatives. Technical report, DAMTP 2004\/NA08, Department of Applied Mathematics and Theoretical Physics, University of Cambridge, 2004. Proceedings of the 40th Workshop on Large Scale Nonlinear Optimization, Erice, Italy."},{"key":"ref_43","doi-asserted-by":"crossref","first-page":"262","DOI":"10.1145\/192115.192124","article-title":"Algorithm 733: TOMP-Fortran modules for optimal control calculations","volume":"20","author":"Kraft","year":"1994","journal-title":"ACM Trans. Math. Soft"},{"key":"ref_44","unstructured":"One could also further include a minimum requested range in cos(\u03b8\u2299), especially for high latitudes in winter."},{"key":"ref_45","unstructured":"Dewitte, S., Clerbaux, N., Ipe, A., Baudrez, E., and Moreels, J. (2017). Dual view Geostationary Earth Radiation Budget from the Meteosat Second Generation satellites. EGU General Assembly Conference Abstracts, EGU."},{"key":"ref_46","unstructured":"A few aerosol-loaded pixels remain west of Africa in the dual-view region, even in Figure 9d. Correctly masked when seen from MSG-3, they were not identified from MSG-1 (being close to the viewing-zenith limit), and thus reintroduced."},{"key":"ref_47","unstructured":"For each pixel, we define the branches themselves with respect to the local noon, determined as the UTC timeslot with the largest mean cos(\u03b8\u2299) value (akin to ref. [32]); the local midnight is calculated as local noon plus 12 h, modulo 24 h."},{"key":"ref_48","unstructured":"Due to the tip, we can expect higher branches to be slightly steeper, and lower branches, flatter. While this can artificially increase the difference between branches for each pixel, it will not affect the qualitative result (i.e., which is higher or lower)."},{"key":"ref_49","unstructured":"The large afternoon effect in South America is similarly due to a cloud-detection issue. Note that trying to address it with masks and cuts ultimately creates an imbalance between the branches (artificially giving more weight to one of them). This issue should preferably be dealt with within the GL-SEV data processing itself."},{"key":"ref_50","unstructured":"As a corollary, this of course also means that, together with ref. [37], we do not find that the morning albedo is systematically larger than the afternoon one when such a diurnal asymmetry is present\u2014i.e., what one might have expected if an actual phenomenon such as dew was at play [34]."}],"container-title":["Remote Sensing"],"original-title":[],"language":"en","link":[{"URL":"https:\/\/www.mdpi.com\/2072-4292\/13\/9\/1655\/pdf","content-type":"unspecified","content-version":"vor","intended-application":"similarity-checking"}],"deposited":{"date-parts":[[2025,10,11]],"date-time":"2025-10-11T05:52:01Z","timestamp":1760161921000},"score":1,"resource":{"primary":{"URL":"https:\/\/www.mdpi.com\/2072-4292\/13\/9\/1655"}},"subtitle":[],"short-title":[],"issued":{"date-parts":[[2021,4,23]]},"references-count":50,"journal-issue":{"issue":"9","published-online":{"date-parts":[[2021,5]]}},"alternative-id":["rs13091655"],"URL":"https:\/\/doi.org\/10.3390\/rs13091655","relation":{},"ISSN":["2072-4292"],"issn-type":[{"value":"2072-4292","type":"electronic"}],"subject":[],"published":{"date-parts":[[2021,4,23]]}}}