资源环境科技发展态势分析平台

Climate model simulations of the mid-Holocene (MH) consistently underestimate northern African rainfall for reasons not fully understood. While most models incorporate orbital forcing and vegetation feedbacks, they neglect dust reductions associated with greater vegetation cover. Here we simulate the MH climate response to reduced Saharan dust using CESM CAM5-chem, which resolves direct and indirect dust aerosol effects. Direct aerosol effects increase Saharan and Sahel convective rainfall by similar to 16% and 8%. In contrast, indirect aerosol effects decrease stratiform rainfall, damping the dust-induced total rainfall increase by similar to 13% in the Sahara and similar to 59% in the Sahel. Sensitivity experiments indicate the dust-induced precipitation anomaly in the Sahara and Sahel (0.27 and 0.18 mm/day) is smaller than the anomaly from MH vegetation cover (1.19 and 1.08 mm/day). Although sensitive to dust radiative properties, sea surface temperatures, and indirect aerosol effect parameterization, our results suggest that dust reductions had competing effects on MH African rainfall.