Analyses of pluviometric grids and main features of the changes occurring in West and Central Africa during the 20th century

Using monthly grids of rainfall data provided by the Climate Research Unit (CRU) of the University of East Anglia, UK, we have undertaken analysis of the main features of the changes in rainfall regime that they highlight in West and Central Africa during the 20th century. From these data grids, and using robust statistical analysis tools, it is shown that during the last century West and Central Africa experienced alternations of dry and rainy seasons with very variable spatial and temporal extent. North of the Equator, the clearest climatic changes were droughts, while south of the Equator; a series of much wetter periods occurred. During the first half of the century, the changes tended to correspond to an increase in the annual rainfall, whilst the inverse tendency was seen afterwards, with a peak at the end of the 1960s and the beginning of the 1970s. The latter period is marked by an agricultural, hydrological and climatic drought that is the greatest in significance and intensity both statistically and in human memory. Numerous studies carried out at smaller scales confirm this overall analysis, even if, sometimes, they may highlight some local or regional characteristics that the data used by the CRU and the spatial resolution of the grids cannot always reveal. Nevertheless, these grids can be of good utility in regional hydrology.