Recent trends in the daily rainfall regime in Southern West Africa

Abstract

Extreme climate events, either being linked to dry spells or extreme precipitation, are of major concern in Africa, a region in which the economy and population are highly vulnerable to climate hazards. However, recent trends in climate events are not often documented in this poorly surveyed continent. This study makes use of a large set of daily rain gauge data covering Southern West Africa (extending from 10° Wto 10° E and from 4° N to 12° N) from 1950 to 2014. The evolution of the number and the intensity of daily rainfall events, especially the most extremes, were analyzed at the annual and seasonal scales. During the first rainy season (April-July), mean annual rainfall is observed to have a minor trend due to less frequent but more intense rainfall mainly along the coast of SouthernWest Africa (SWA) over the last two decades. The north-south seasonal changes exhibit an increase in mean annual rainfall over the last decade during the second rainy season (September-November) linked by both an increase in the frequency of occurrence of rainy days as well as an increase in the mean intensity and extreme events over the last decade. The study also provides evidence of a disparity that exists between the west and east of SWA, with the east recording a stronger increase in the mean intensity of wet days and extreme rainfall during the second rainy season (September-November).