Evaluating the influence of African dust in West African rainfall through Earth observation

Abstract

<p>Food and economic safety in West Africa rely heavily on rainfed agriculture and are threatened by climate change and demographic growth. Accurate rainfall information is therefore crucial to ensure safety against these challenges. However, existing rainfall models fail to accurately represent the highly variable and sparsely monitored West African rainfall distribution. Satellite rainfall products show a poor correlation with ground-based rainfall measurements and literature suggests that atmospheric aerosols are partly to blame for this poor performance.</p> <p>West Africa presents higher airborne aerosol concentrations than other regions of the world, mainly originating from dust outbreaks in the Sahara Desert and biomass burning across the Atlantic Ocean in South and Central Africa. Furthermore, climate in West Africa is modulated by the movement of the Intertropical Convergence Zone (ITCZ), that separates a hot, dry and dusty air mass from the Sahara Desert from a cold and humid air mass from the Atlantic Ocean. The ITCZ marks the transition between the dry and the rainy season in the reigon.</p> <p>In this work we study the relationship between atmospheric dust during the dry and the rainy season and precipitation in West Africa using Google Earth Engine. We employ IMERG precipitation data for West Africa and aerosol data from the TROPOMI instrument on-board Sentinel 5P over the whole of Africa between 2018 and 2022, to capture the largest sources of airborne aerosols reaching West Africa throughout the year. We investigate precipitation on a 0.5 degree resolution grid covering West Africa and part of the adjacent Atlantic Ocean and spanning over all West African climatic regions, from the Sahara in the North to the Guinean and Guinean-Congolian regions in the South. We analyze regional and remote aerosol-precipitation connections at different temporal and spatial scales and for the different climatic regions.</p> <p>The aim of this research is to further the knowledge about the relationship between African dust and West African rainfall so we can better account for and reproduce these processes in satellite rainfall retrieval models.  </p>