Impact of Climate Change on Rainfall Characteristics over West Africa

Abstract

The impact of climate change and variability on West African precipitation has significant consequences for the socio-economic activities of the region. In this study Global Precipitation Climatology Center (GPCC), Climate Hazard Group Infrared Precipitation with Station data (CHIRPS) and Coupled Model Intercomparison Project (CMIP5 and CMIP6) are used to study rainfall patterns over West Africa during Monsoon months (JJAS). The study aimed to determine which of the models best reproduced the observation data over West Africa by comparing biases of each model and their ensembles over each subregion and the entire West Africa. This study utilized various datasets, including GPCC, CHIRPS, CMIP5, and CMIP6, to analyze the spatial distribution, variability, and trends of rainfall in West Africa during the summer months of June to September (JJAS). The analysis focused on the Sahelian, Savannah, and Guinean zones, using daily rainfall indices such as consecutive dry days (CDD) and wet days (CWD. The daily data has been processed over West Africa during the period (1983 to 2012) for historical, (2021 to 2050) for near forecasting and (2071 to 2100) for far future trends. The indices are, maximum 5 days (RX5DAY), heavy and very heavy rainfall (R10MM and R20MM), the percentile (R75p, R90p, and R95p) and simple daily intensity (SDII). The findings revealed a stronger correlation between CMIP6 model and the observation dataset, indicating that CMIP6 better reproduced the rainfall patterns over the region compared to CMIP5. The study indicated a change in the western and northeastern areas of West Africa. Central West Africa showed a dynamic influence on precipitation indices under various climate change scenarios. The SSP5-8.5 scenario from CMIP6 model predicted significant increases in R10MM, R20MM, and RX5DAY compared to the current climate. The study's findings have implications for flood modeling and watershed management.