Atmospheric Measurement Techniques Discussions www.atmos-meas-tech-discuss.net 1867-8610 3 2 2010 10.5194/amtd-3-1023-2010 http://www.atmos-meas-tech-discuss.net/3/1023/2010/ http://www.atmos-meas-tech-discuss.net/3/1023/2010/amtd-3-1023-2010.html http://www.atmos-meas-tech-discuss.net/3/1023/2010/amtd-3-1023-2010.pdf 1023 1098 2010-03-18 A sea surface reflectance model for (A)ATSR, and application to aerosol retrievals A. M. Sayer sayer@atm.ox.ac.uk G. E. Thomas R. G. Grainger Atmospheric, Oceanic & Planetary Physics, Clarendon Laboratory, Parks Road, Oxford, OX1 3PU, UK A model of the sea surface bidirectional reflectance distribution function (BRDF) is presented for the visible and near-IR channels (over the spectral range 550 nm to 1.6 &mu;m) of the dual-viewing Along-Track Scanning Radiometers (ATSRs). The intended application is as part of the Oxford-RAL Aerosols and Clouds (ORAC) retrieval scheme. The model accounts for contributions to the observed reflectance from whitecaps, sun-glint and underlight. Uncertainties in the parametrisations used in the BRDF model are propagated through into the forward model and retrieved state. The new BRDF model offers improved coverage over previous methods, as retrievals are possible into the sun-glint region, through the ATSR dual-viewing system. The new model has been applied in the ORAC aerosol retrieval algorithm to process Advanced ATSR (AATSR) data from September 2004 over the south-eastern Pacific. The assumed error budget is shown to be generally appropriate, meaning the retrieved states are consistent with the measurements and a priori assumptions. The resulting field of aerosol optical depth (AOD) is compared with colocated MODIS-Terra observations, AERONET observations at Tahiti, and cruises over the oceanic region. 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