Influence of initial soil moisture in a regional climate model study over West Africa – Part 1: Impact on the climate mean

Abstract. The impact of soil moisture initial conditions on the mean climate over West Africa was examined using latest version regional model International Centre for Theoretical Physics (RegCM4) at a 25 km horizontal resolution. reanalysis European Medium-Range Weather Forecasts (ECMWF) 20th century (ERA-20C) used to initialize control experiment, while its minimum and maximum values entire domain were establish respective dry wet (hereafter referred as experiments, respectively). For control, an ensemble five runs from June September performed. In each we analyzed two idealized simulations most sensitive conditions. precipitation in is linear Central Sahel regions, where (wet) experiments lead rainfall decrease (increase). strongest increase found with change value approximately 40 %, whereas Sahel, peak −4 %. sensitivity can persist 3–4 months (90–120 d) depending region. However, influence no longer than 1 month (between 15 30 d). temperature located −1.5 ∘C Guinea coast around 0.6 ∘C. A significant surface energy fluxes noted: (dry) cooling (warming) associated (increase) sensible heat flux, (decrease) latent flux boundary layer depth. Part 2 this study (Koné et al., 2022) investigates extremes.