Understanding Precipitation Extremes over West Africa: Characteristics, Drivers and Projections

Abstract

Extreme precipitation during the West African summer monsoon causes significant flooding and drought, impacting food security, infrastructure, and regional socioecological systems. This thesis examines monsoon precipitation's dynamics, variability, and future projections using gridded climate (1950–2022) and survey data. Results show spatially heterogeneous trends, with significant changes detected in monsoon precipitation variability, except in August. Two dominant precipitation modes were identified using season-reliant empirical orthogonal function (SEOF) analysis: the Sahel mode (16.3% variance) linked to equatorial Pacific, Mediterranean, Indian, and North Atlantic sea surface temperature (SST) anomalies and the Guinea coast mode (9.5% variance) influenced by equatorial and South Atlantic SST. Wet years exhibit strong low-level convergence over Africa and upper-level divergence over the Pacific, driven by Walker circulation changes. CMIP6 models perform better over the Sahel than the Guinea coast, projecting future drying trends. Extreme precipitation events impact agriculture, infrastructure, and food security, with adaptation hindered by poor infrastructure, technical capacity gaps, and funding constraints. These findings are crucial for climate adaptation, informing policymakers on resilient infrastructure and adaptive strategies to mitigate adverse impacts of climate extremes in West Africa