Comparison of top of the atmosphere GERB measured radiances with independent radiative transfer simulations obtained at the Valencia Anchor Station area

The purpose of this work is to compare top of the atmosphere (TOA) radiances as measured by the Geostationary Earth Radiation Budget (GERB) instrument on board the METEOSAT-8 ( METEOSAT Second Generation ) satellite to equivalent independent radiances obtained from radiative transfer simulations performed using surface and atmospheric measured parameters gathered during the GERB Surface Ground Validation Campaign at the Valencia Anchor Station (VAS) reference area in February 2004. In this paper we try to extend the methodology previously developed and tested for the NASA Clouds and the Earth's Radiant Energy System (CERES) instrument in the framework of the SEVIRI and GERB Cal/val Area for Large scale field ExperimentS (SCALES) project, to validate GERB much lower spatial resolution data (pixel size of the order of 60 x 60 km 2 over the VAS). The study also includes the selection of atmospheric profiles from on-purpose radiosonde and GPS ( Global Positioning System ) data, a BRDF ( Bidirectional Reflectance Distribution Function ) estimation for the large-scale study area and Streamer radiative transfer simulations of TOA shortwave and longwave radiances.