Dry years and wet years in the Sahel: quo vadimus?

The Sahelian rainfall deficit over the past 30 years is usually analysed globally, which does not allow its impact upon the hydrological cycle to be studied. Using both the AGRHYMET data and a high space-time resolution data set in the area of Niamey (the AMMA-CATCH Niger data set), allows analysis of the significant factors that differentiate between dry and wet years. This analysis explores the rainfall variability at different temporal scales for dry and wet years: at the annual scale, through the rainfall index sensitivity to the size of the area considered; at the event scale, through the variation of two parameters defining the rainfall regime, namely the mean event depth and the mean number of events per day; and at a smaller scale, by studying distributions of rainfall intensities.