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 temperature indexes were discussed in light of climate change impacts on rain-fed agriculture, the main source of food for the population of Burkina Faso. The results should be incorporated in alleviation strategies of climate change impacts in the Sahel region.

► Drought has started in Burkina Faso at the end of 1960s and lasted up to 2000.
► Seasonal descriptors in Burkina Faso are recovering from the drought since the end of 1980s.
► Rainfall amount per rain-day is the only seasonal descriptor with a significant upward trend.
► Onset date of the growing season showed an unclear trend from 1970 to 2000.
► Seasonal descriptors are increasingly volatile since the beginning of the 1970s.