Can we use surface wind fields from meteorological reanalyses for Sahelian dust emission simulations?

The Sahel is prone to intense soil erosion, and the dust emission flux is very sensitive to the surface wind speed. In this study, we use high-frequency observations acquired across the Sahel to assess the ability of three global reanalyses (ERA-interim, NCEP-CFSR and MERRA) to capture the observed surface wind events that are critical to wind erosion. ERA-Interim is shown to perform best. However, all three reanalyses present a too flat annual cycle, with important season-dependent biases: they overestimate the surface wind during dry season nights and underestimate it during spring and monsoon season days. More importantly, the strongest wind speeds, observed in the morning and during deep convective events, are systematically underestimated. As analyzed wind fields are one of the main inputs of many dust emission models, their too low fraction of high wind speeds will lead to major errors in dust emission simulations.