Convection intertropicale et pluviometrie — Essai de mise en relation pour l'Afrique de l'ouest du 11 Mai au 20 Aout 1985

Relationship between deep convection and rainfall in West Africa May 11 – August 20 1981From May 11 to August 20, an attempt at monitoring convective clouds over West Africa was carried out in Lannion by ORSTOM and the “Centre de Météorologie Spatiale”. Since most of the rain in sudanese countries is the result of convective activity, it was assumed that the measure of occurrences of cold top clouds with infrared Meteosat II data could give us a good relation with synoptic stations rainfall data. The comparison of visible and infrared data gave us a threshold of −40°C. Five scenes were computed daily (9h, 12h, 15h, 18h, 24h) during 102 days. This attempt led us to discover homogeneous areas according to zonal climatic features and topography. Further research including the use of radar data, the setting up of a better network for rainfall measurements, special experiments to improve the threshold efficiency are expected to be carried out next year. Several French research laboratories are involved in this program. Good results are also expected in the field of crop monitoring.