SIMULATING IMPACT OF MINERAL DUST ON THE WEST AFRICAN SUMMER MONSOON EVOLUTION

Abstract

Mineral dust over West Africa region modulates summer monsoon through direct and indirect radiative forcing. This study examined the impact of mineral dust on West Africa Monsoon variability with the aid of Regional Climate Model (RegCM4) at 50km grid resolution driven by ERA Interim reanalysis. Three experiments were performed; first with the non-dust aerosol version of the model (CONTROL), second with the dust aerosol module (DUST) and with an increase in the dust concentration (DOUBLE DUST). The simulation was run from October, 2004 to December, 2005 over West Africa domain with the first three months taken as spin up for model stability. The results shows that with DUST experiment, outgoing Long wave Radiation (OLR) flux changes from 2.0 W/m2 to 4.0 W/m2 indicating reduction in convective formation in the Sahel. The precipitation increases from 4.0 - 8.0 mm/day in the Guinea coast region while there were decrease in precipitation of 2.0 - 0.0 mm/day in the Sahel. There was strengthening of TEJ core and weakening of AEJ as dust concentration increases in some parts of the region during the monsoon period. It was concluded that increase in mineral dust concentration could results in enhancement of precipitation amount in the Guinea coast and reduction of precipitation amount in the Sahel region of West Africa but it is not yet clear whether the increase in AOD of dust will enhance or delay onset of precipitation in the region.