The evolution of drought characteristics in semi-arid Africa over the last four decades

tudy region Semi-arid Africa, covering six subregions: the Mediterranean (MED), Sahel, North Eastern Africa (NEAF), South Eastern Africa (SEAF), Southern Africa (SAF), and Madagascar (MDG). Study focus We analyse drought duration, intensity, and severity from 1979 to 2024 across semi-arid Africa. Using Climate Prediction Center (CPC, 0.5°) precipitation and temperature, we compute the Standardized Precipitation Index (SPI) and the Standardized Precipitation Evapotranspiration Index (SPEI). Trends are detected with the Mann–Kendall test and Theil–Sen slope estimator. Short-term droughts (3–6 months), strongly influenced by temperature variability, are distinguished from 12-month events driven by cumulative hydrological deficits. New hydrological insights Three drought episodes emerge: the early 1990s, early 2000s, and the recent period beginning in 2022. Long time-scale indices (SPI-12, SPEI-12) capture the most persistent droughts, whereas short time-scale indices (SPEI-3, SPEI-6) reveal intense temperature-driven episodes. In MED, only 7–25 % of grid cells show significant SPI trends in duration, severity, and intensity, but up to 75 % exhibit drought intensification with SPEI, underscoring strong temperature sensitivity. Across NEAF, SEAF, SAF, and MDG, 25–55 % of pixels show significant increases in drought duration (up to +3 months per decade), severity (+3 units per decade), and intensity (+0.5 units per decade). Parts of the western Sahel and southern Madagascar display decreasing trends. Overall, the study delivers a continent-wide assessment of drought evolution and identifies hotspots where intensifying drought threatens water resources and food security.