Less frequent and more intense rainfall along the coast of the Gulf of Guinea in West and Central Africa (1981-2014)

Abstract

Since the 1990s, rainfall has been reported to increase over the Gulf of Guinea. In light of the devastating floods that have occurred since then over the coastal areas of this region, this study aims to better characterize the recent trends in precipitation there. We used the Climate Hazards Group InfraRed Precipitation with Station (CHIRPS) product, a new observational rainfall dataset that covers the period 1981-2014 at high resolution and daily time steps. During the first rainy season (April-June), we find that the lack of significant trend observed in mean precipitation hides a trend towards less frequent but more intense rainfall along the coast of the Gulf of Guinea, which is expected to increase the likelihood of flooding and droughts, and fits with the recent increase in devastating floods. Over the north however (be tween 7° and 12.5° N), rainfall has become more frequent and less intense, which is expected to decrease the likelihood of flooding and droughts. During the second rainy season (September-November), we find that the clear increase in mean precipitation observed between 5° and 12.5°N results from an increase in precipitation intensity and frequency, while over southern Cameroon, the decrease in mean precipitation hides a trend towards less frequent but more intense rainfall. In both seasons, the average duration of wet spells has greatly decreased along the coast, in favor of more numerous and more intense isolated wet days.