Towards the prediction of Sahelian rainfall from sea surface temperatures in the Gulf of Guinea

Abstract

The possible link between sea surface temperature (SST) in specific areas of the Gulf of Guinea and summer Sahelian rainfall is investigated for the purpose of forecasting Sahelian rainfall. Analyses of data series of rainfall in the Sahel and SST in the Eastern Tropical Atlantic reveal that summer Sahelian rainfall is dependent on SST distribution, according to the period (dry or wet) and/or the specific oceanic area (coastal, equatorial or intermediate zone) under consideration. The occurrence of warm surface waters in the Gulf of Guinea is coincident with reduction of summer rainfall in the Sahel, mainly during dry periods. The same relationship does not hold during wet periods. It is suggested that summer Sahelian rainfall could be predicted: (a) from SST in the intermediate warm waters area and the equatorial upwelling zone 1–2 months earlier; (b) from previous quarterly rainfall data in the Sahel.