Recent Rainfall Decline in West Africa Due to Enhanced Biomass Burning and Dust Emission

Abstract

Rainfall in West Africa during boreal summer is primarily controlled by the low-level southerly monsoon flow that transports moisture from the Gulf of Guinea to the region and the African Easterly Jet that modulates the convective systems. However, the role of aerosols in rainfall variability of this region, despite the large emissions of dust and black carbon in Africa, is not well-understood. Our study reveals a decline in precipitation over Southern West Africa (SWA) in the past two decades that its trend and interannual variability present an indirect relationship with the aerosols loadings. Examining the local and remote sources of aerosols, we found that the latter have a larger contribution. We have used MERRA-2 large scale atmospheric dynamics and physics data to determine the mechanisms responsible for aerosol-rainfall interactions in the region. Our results have important implications for the people and ecosystem as the increasing rates of land use change, deforestation and urbanization in the continent are expected to enhance the aerosols. This will result in an increase in the frequency and intensity of the extreme events including droughts.