Atmospheric Chemistry and Physics Discussions www.atmos-chem-phys-discuss.net 1680-7367 1680-7375 7 5 2007 10.5194/acpd-7-13503-2007 http://www.atmos-chem-phys-discuss.net/7/13503/2007/ http://www.atmos-chem-phys-discuss.net/7/13503/2007/acpd-7-13503-2007.html http://www.atmos-chem-phys-discuss.net/7/13503/2007/acpd-7-13503-2007.pdf 13503 13535 2007-09-14 Estimation of the aerosol radiative forcing at ground level, over land, and in cloudless atmosphere, from METEOSAT-7 observation: method and first results T. Elias thierry.elias@lmd.polytechnique.fr J.-L. Roujean LMD, Ecole Polytechnique, 91128 Palaiseau cedex, France CNRM/GMME/MATIS, Meteo-France, 42, avenue G. Coriolis, 31057 Toulouse cedex, France A new method is proposed to estimate the spatial and temporal variability of the solar radiative flux reaching the surface (DSSF) over land, as well as the Aerosol Radiative Forcing (ARF), in cloud-free atmosphere. The objective of global applications of the method is fulfilled by using the visible broadband of METEOSAT-7 satellite which scans Europe and Africa on a half-hourly basis. The method relies on a selection of best correspondence between METEOSAT-7 radiance and DSSF computed with a radiative transfer code. The validation of DSSF is performed comparing retrievals with ground-based measurements acquired in two contrasted environments, i.e. an urban site near Paris and a continental background site in South East of France. The study is concentrated on aerosol episodes occurring around the 2003 summer heat wave, providing 42 cases of comparison for variable solar zenith angle (from 59° to 69°), variable aerosol type (biomass burning emissions and urban pollution), and variable aerosol optical thickness (a factor 6). The method reproduces measurements of DSSF within an accuracy assessment of 20 Wm−2 (5% in relative) in 70% of the cases, and within 40 Wm−2 in 90% of the cases. 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