Trends and discontinuities in regional rainfall of West and Central Africa: 1951-1989

Standardized regional mean annual rainfall series are analysed over the period 1951-1989 from a data set of 891 rainfall stations which covers 23 countries of West and Central Africa. Missing values are estimated by using regionalized indexes computed on the basis of a morpho-climatic delimitation of 44 homogeneous climatic units. Searches for statistical discontinuities in rainfall series show no discontinuity for most units of Central Africa. For several units of West Africa the first discontinuity occurs at the end of the 1950s. The main discontinuity period occurs between 1968 and 1970, followed by a second one at the beginning of the 1980s. Rainfall deficit is greater north of 10 degreesN, and is also important in the Guinean Mountains and on the northern coast of the Gulf of Guinea, west of the Atakora Mountains. Regions leeward of mountainous areas experienced moderate rainfall decrease.