Recent observed and simulated changes in precipitation over Africa

Abstract

Multiple observational data sets and atmosphere-only simulations from the Coupled Model Intercomparison Project Phase 5 are analyzed to characterize recent rainfall variability and trends over Africa focusing on 1983-2010. Data sets exhibiting spurious variability, linked in part to a reduction in rain gauge density, were identified. The remaining observations display coherent increases in annual Sahel rainfall (29 to 43 mm yr-1 per decade), decreases in March-May East African rainfall (-14 to -65 mm yr-1 per decade), and increases in annual Southern Africa rainfall (32 to 41 mm yr-1 per decade). However, Central Africa annual rainfall trends vary in sign (-10 to +39 mm yr-1 per decade). For Southern Africa, observed and sea surface temperature (SST)-forced model simulated rainfall variability are significantly correlated (r~0.5) and linked to SST patterns associated with recent strengthening of the Pacific Walker circulation. Key Points Rainfall trends from multiple observational data sets are not consistent in some regions Spurious rainfall trends are linked to changes in gauge density over time SST patterns play a strong role in determining Africa-wide rainfall trends since 1983