Contribution of the Sahel region to precipitation over the African continent

Redistribution of evapotranspiration from land via atmospheric circulation is an important Earth system process. Globally, evapotranspiration contributes significantly to terrestrial rainfall, on both regional and more remote scales. In wet, tropical regions (e.g. the Congo basin), transpiration and interception loss from the dense forest cover are the primary drivers of moisture recycling, which plays a crucial role in preserving regional ecosystem functioning. However, for semi-arid and arid regions, our knowledge on the extent and significance of evapotranspiration for moisture recycling is still very limited, despite the significance this may have for addressing challenges of desertification in times of rapid environmental change. Considering this, we are taking the Sahel region as a case study and investigate its contribution to precipitation in the African continent. In addition, we specifically study what fraction of the precipitation originates from vegetation in the Sahel through transpiration and interception loss. Our study is based on simulated atmospheric moisture trajectories derived from the Lagrangian model FLEXPART with a 1-degree resolution, driven by ECMWF reanalysis data over 1980–2016. Preliminary results show (1) the temporal variability in the contribution of the region to precipitation in African drylands, and (2) a significant contribution of local precipitation recycling. We conclude that consideration of the naturally and anthropogenically-driven greening of the Sahel, as well as land use and land cover changes in the region, may have both local and far-reaching impacts via the transport of moisture through the atmosphere.