Impact of fires on surface albedo dynamics over the African continent

Abstract

The seasonal variation analysis of a land surface albedo data set derived from 1‐year Meteosat observations reveals the high sensitivity of albedo to anthropogenic biomass burning activities during the dry season. At the beginning of this season, a rapid decrease of albedo is observed over fire‐prone areas. These low albedo values last during the entire dry season, increasing slowly at the end of this season. This paper focuses on a quantitative estimation of biomass burning impact on albedo seasonal variations. To this end, a conceptual method is proposed to detect pixels whose albedo seasonal cycle is affected by biomass burning. The performance of this approach is evaluated over the central Africa region, where the Experiment for Regional Sources and Sinks of Oxidants (EXPRESSO) field campaign took place in November 1996. Our results compare favorably with maps of fire‐affected areas derived from NOAA advanced very high resolution radiometer (AVHRR) observations. When applied over the entire African continent, the Northern Hemisphere appears much more affected by fire‐induced albedo decrease than the Southern Hemisphere. At a regional scale, Northern Hemisphere fires are responsible for a relative decrease of the albedo as large as 25% with respect to nonburnt areas. The amplitude of this large‐scale darkening phenomenon might locally affect the wind regime and associated rainfall.