Science et changements planétaires / Sécheresse


Synthesis and evaluation of the seasonal forecasts in West Africa Volume 15, issue 3, JUILLET-AOÛT-SEPTEMBRE 2004


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Centre régional de formation et d’application en agrométéorologie hydorlogie et météorologie (AGRHYMET), BP 11011, Niamey, Niger, Unité mixte de recherche HydroSciences, Institut de recherche pour le développement (IRD), Maison des sciences de l’eau, BP 64501, 34394 Montpellier cedex 5, France

Our objective is to evaluate seasonal weather forecasts in West Africa since the beginning of the PRESAO process in 1998 and then to highlight any other oceanic or continental parameters which may possibly correlate with the flows of the large rivers and to the rainfall in West Africa. Four countries are considered in this study: Benin, Guinea, Mali and Chad. The models used within the framework of PRESAO being generally gauged over the period 1961-1990, the evaluation is related to the period 1991-1997. This evaluation shows the insufficiency of the sea surface temperatures used up to now at the time of the PRESAO, to explain precipitations in West Africa. But improvements remain possible. For example, the use of the area 8°W-12°W/2°N-2°S through the anomalies of sea surface temperatures improves the performances of the models, therefore the scores of the forecast. This indicates strong connections between precipitations in West Africa and the oceanic zones of the Atlantic frontage of Africa located on the course of the African monsoon which brings rainfall in the aforementioned area. This encourages the exploration of other predictors in order to improve the forecasts.