Characterizing Northeast Africa Drought and Its Drivers

Abstract

This study explores the drivers of drought over northeast (NE) Africa as represented by monthly ERA5 potential evaporation during 1970–2022. The comparisons with surface heat flux and A-pan measurements suggest that potential evaporation quantifies moisture deficits that lead to drought. A principal component (PC) analysis of potential evaporation has the following leading modes: PC-1 in the Nile Basin and PC-2 in the Rift Valley. Time scores were filtered and regressed onto fields of SST, netOLR, and 500 hPa zonal wind to find teleconnections, and drought composites were analyzed for anomalous structure. The results identify that cold-phase Indian Ocean Dipole (IOD) couples with the overlying zonal Walker circulation. Deep easterly winds subside at −0.1 m/s over the west Indian Ocean and NE Africa, causing desiccation that spreads westward from the Rift Valley via diurnal heat fluxes. Insights are gained on IOD modulation based on the Pacific ENSO, but long-range forecasts remain elusive.