Projected Drought Events over West Africa Using RCA4 Regional Climate Model

This study presents projected drought trend by Standardized Precipitation Evapotranspiration Index (SPEI) and Standardized Precipitation Index (SPI) under RCP4.5 and RCP8.5 scenarios. The Rossby Center Atmospheric Regional Model (RCA4) datasets obtained from the Coordinated Regional Climate Downscaling Experiment over West Africa were used for the study for projected period between 2011 and 2100. The ability of the RCA4 to reproduce the past climate was evaluated using Climate Research Unit (CRU) dataset. Drought classification and trends in seasonal and annual variability using Mann-Kendall trend test at 95% confidence level were also examined. The results show that RCA4 replicates observed climate of West Africa, evident by strong correlation between the output of the model and CRU dataset. Strong correlation exists between SPI and SPEI at 95% confidence level. The RCA4 model projects a distinct humid period between 2011 and 2060 and drier period from the early 2060s till the year 2100 under RCP4.5 and 8.5 pathways. Projected drought events by the two indices show that areas north of 12 degrees N of West Africa will be hot spot area for mildly and moderately dry events, while the southern part of West Africa will witness pronounced severe and extreme dry events under the two RCPs. Under RCP4.5, SPI trend shows an insignificant increase in almost all the seasons, while the increase is significant in SPEI. At RCP8.5 scenario, SPEI projects a significant decreasing trend in drought events over the three climatic zones and in almost all seasons. The result may be applied to a sustainable climate change adaptation plan.