Regional characterisation of meteorological drought and floods over west Africa

West Africa is characterised by diverse hydro-climatic divisions ranging from the humid equatorial climate to the semi-arid and arid climates that manifest in high space-time variability in rainfall. In this study, drought and floods in six delineated domains (Northern Sahel, Southern Sahel, Sudanian, Western Guinea Coast, Central Guinea Coast and Eastern Guinea Coast) of West Africa were illustrated using the Standardized Precipitation Index (SPI 3 months and 9 months) calculated from global CPC Merged Analysis of precipitation (CMAP 2.5 degrees by 2.5 degrees resolution) data from 1980 to 2017. The trend analysis shows that none of the domains exhibits a significant trend in the computed SPI. However, there is a significant trend in the annual rainfall rate for all the domains except the Eastern Guinea Coast. Again, there is a likelihood of an increasing trend of SPI-3 but a decreasing trend for the SPI-9. The drier areas have significant increasing rainfall trend while the highly humid regions show significant negative trend except for the Eastern Guinea Coast that shows a non-significant very weak positive trend. The most exposed area to extreme drought conditions occurs over the northern Sahel domain at SPI-3 though the frequency of occurrence is very low. The Western Guinea coast experiences the highest number of dry events of about 32% of the time followed by the Northern Sahel domain. Under SPI-9, the following domains: Eastern Guinea coast, Sudanian, Northern Sahel and Western Guinea coast are prone to flooding incidence as they had 40%, 37%, 29% and 26% of wet events, respectively. The study recommends apt and timely climate service delivery, adoption of ecosystem-based adaptation strategies that promote apt and sustainable water management practices in the region.