Exploitation of Surface Albedo Derived From the Meteosat Data to Characterize Land Surface Changes

Abstract

Land surface albedo constitutes a critical climatic variable, since it largely controls the actual amount of solar energy available to the Earth system. From a mathematical point of view, the determination of the surface albedo corresponds to the estimation of a boundary condition for the radiation transfer problem in the coupled surface-atmosphere system. A relatively large database of 10 years or more of Meteosat data has been accumulated by EUMETSAT. These data, collected at half-hourly intervals over the entire Earth disk visible from longitude 0 degree, constitute a unique resource to describe the anisotropy of the coupled surface-atmosphere system, and provide the opportunity to document changes in surface albedo which may have occurred in these regions over that period. An advanced algorithm to retrieve the radiative properties of terrestrial surfaces sampled by the Meteosat visible instrument has been derived and a preliminary analysis of a one-year (1996) set of Meteosat data was performed. The accumulation of results in 10-day periods permits evaluating the seasonal albedo changes occurring at a continental scale. These first results, supported by additional radiation transfer simulations, suggest that anthropogenic fire activities induce significant perturbations of the surface albedo values in the inter-tropical zones at that scale.