Land‐Atmosphere Coupling Regimes in a Future Climate in Africa: From Model Evaluation to Projections Based on CORDEX‐Africa

Abstract

Land‐atmosphere coupling plays a crucial role in determining the evolution of weather and climate. In the current study, the full ensemble of CORDEX‐Africa climate change simulations is used to understand how strong and weak coupling regions in Africa will evolve in the future. The ability of the regional climate models to capture the coupling signal relies on a reasonable representation of near surface air temperature, precipitation, surface fluxes, and soil moisture. A thorough model evaluation reveals typical shortcomings in the representation of the African climate, in particular seasonal precipitation. The multimodel ensemble mean outperforms the individual models and is therefore used for the investigation of the land‐atmosphere coupling. This ensemble mean shows a widespread warming in Africa and changes in precipitation, such as a decrease in the Sahel during summer and an increase in western Africa during summer and autumn. The coupling analysis relies on surface fluxes, the related evaporative fraction and their correlations as well as the correlation between evaporative fraction and soil moisture. Overall, water‐limited regions that exhibit a strong land‐atmosphere coupling are projected to expand further southward in West Africa and further northward in southern Africa. This is particularly true over the Sahel during spring and summer, when the strong coupling region shifts southward, indicating a potential expansion of the semiarid and arid regions. A transition of energy limited regimes, with weak coupling, to water‐limited regimes where soil moisture plays a more important role, is projected for the end of the 21st century as drying continues.