Vegetation index trends for the African Sahel 1982-1999

Abstract

Pathfinder AVHRR NDVI data have been analyzed for the African Sahel to study recent trends in vegetation greenness. A strong increase in seasonal NDVI was observed over large areas in the Sahel during the period 1982-1999. The increase is interpreted as a vegetation recovery from the drought periods of the 1980's. Although strong shifts in satellite overpass times have led to shifting solar zenith angles (SZA) over the time period, only minimal influence of SZA's on the Pathfinder NDVI was found in our data. A preliminary analysis of rainfall data indicates increasing rainfall during the period. The observed trends may have important implications to the Sahel including changes to the water cycle, energy exchange and carbon storage.