Collective Impacts of Orography and Soil Moisture on the Soil Moisture‐Precipitation Feedback

Abstract

Abstract Ensembles of convection‐resolving simulations with a simplified land surface are conducted to dissect the isolated and combined impacts of soil moisture and orography on deep‐convective precipitation under weak synoptic forcing. In particular, the deep‐convective precipitation response to a uniform and a nonuniform soil moisture perturbation is investigated both in settings with and without orography. In the case of horizontally uniform perturbations, we find a consistently positive soil moisture‐precipitation feedback, irrespective of the presence of low orography. On the other hand, a negative feedback emerges with localized perturbations: a dry soil heterogeneity substantially enhances rain amounts that scale linearly with the dryness of the soil, while a moist heterogeneity suppresses rain amounts. If the heterogeneity is located in a mountainous region, the relative importance of soil moisture heterogeneity decreases with increasing mountain height: A mountain 500 m in height is sufficient to neutralize the local soil moisture‐precipitation feedback.