WEST-AFRICAN PRECIPITATION AND DOMINANT ATMOSPHERIC MECHANISMS

Latitude-time cross-sections of precipitation across the West African region indicate that a strong relation exists between the May-September cycle of precipitation in the Sahel and the January-December cycle in the moist Southern sector. It is demonstrated that while the promiment precipitation band moves with the Inter-tropical discontinuity (ITD) in its South-North annual course, another important atmospheric mechanism, the Walker circulation (WC) influences the precipitation in the South where the ITD control breaks down. The effects, on the Sahel region's precipitation, of these atmospheric mechanisms, along with albedo variation are associated with a bio-physical feed-back mechanism forced, in the main, by ocean-atmosphere interaction. © 1978 Springer-Verlag.