Large-scale features of Africa's diurnal climate

This study explores the structure and modulation of the mean diurnal climate of Africa with a focus on satellite rainfall. Solar heating over tropical mountains and land-sea temperature gradients initiate moisture convergence in the afternoon-evening. The diurnal temperature range is from 5 degrees C along the coast to 20 degrees C in arid zones with low vegetation fraction. NCEP2 reanalysis reveals the diurnal circulation via continental-scale drainage and seabreeze flows. Factors modulating the diurnal cycle vary across four sub-regions: South Africa, East Congo, Ethiopia, and Guinea. In the Congo and Guinea coast the surface moisture and heat fluxes are important, while in South Africa convective available potential energy and vertical motion are influential. Ethiopia's evening orographic convection is out of phase with surface fluxes. The diurnal residual calculated from NCEP2 fields exhibits a 2 km depth for thermal gradients and 200 km inland penetration of onshore flow by evening.