Spatiotemporal analysis of drought patterns and trends across Africa: a multi-scale SPEI approach (1960–2018)
Akinwale T. Ogunrinde, Paul Adigun, Xian Xue, Koji Dairaku, Qiqi Jing
Abstract
This study provides unprecedented insights into water scarcity dynamics across Africa's diverse climatic zones, utilizing the Standardized Precipitation-Evapotranspiration Index (SPEI) across multiple timescales from 1960 to 2018. Employing the Modified Mann-Kendall test, Sen's Slope estimator, and copula functions, we analyzed drought characteristics across eight African subregions using the CRU TS4.05 dataset. Key findings reveal significant spatial heterogeneity in drought trends, with increasing dryness particularly evident in the Mediterranean and Sahara regions. A pronounced shift towards drier conditions emerged post-1990, with mean drought duration expanding from 1.5 months (SPEI-3) to over 6 months (SPEI-24). Drought intensity increased by 0.2 unit annually, while frequency decreased by 20%. The Sahara region demonstrated the highest increasing drought trend across timescales. Return period analyses showed most sub-regions experiencing short-term droughts with low severity, while extreme events remained less frequent. These findings underscore the complex nature of African drought patterns, emphasizing the critical need for region-specific, adaptive climate strategies to address unique ecological challenges.