Changes in seasonal descriptors of precipitation in Burkina Faso associated with late 20th century drought and recovery in West Africa

Daily rainfall records of 39 stations spanning the different agro—climatic zones of Burkina Faso were analyzed to describe the evolution of five seasonal rainfall descriptors over time. The period from1941 to 2000, including the two most contrasted periods in the recent history of the Sahelian climate, i.e. the wet decades (1941–1970) and the dry decades (1971–2000), were considered. It was found that certain seasonal descriptors—namely total seasonal rainfall, number of rain-days and cessation dates of the rainy season—when aggregated into annual and national means manifested almost the same evolution pattern; while others, notably average rainfall per rain-day and onset date of the growing period, showed different patterns of evolution. It was concluded that the recent reduction in seasonal precipitation amount was related to a reduced number of rain-days in August and September, with precocious cessation of the rainy season as a consequence. However, all the seasonal descriptors showed recovery trends since the end of the 1980s, with the mean rainfall per rain-day, exhibiting the steadiest trend. But, the descriptors were more volatile during that recovery time according to the upward trends in their interannual variability. Importantly, the links between the seasonal descriptors and two sea surface