Soil Moisture Impact on Convective Initiation

Abstract

The influence of soil moisture on convective storm initiation remains an open question, with previous studies showing conflicting results regarding whether storms preferentially form over wet or dry soils. Here, we analyze the soil moisture‐convection relationship using satellite observations across North America, Africa, and Australia from 2015 to 2020. Unlike previous studies that used precipitation as a proxy for convection, we directly track convective initiation using cloud‐top temperatures from geostationary satellites. By combining this with satellite retrievals of soil moisture and atmospheric conditions, we find that the preference for storm initiation systematically varies with regional aridity. In arid regions, convection preferentially initiates over soils that are, on average, 25% wetter than climatology and exhibit positive soil moisture gradients, whereas more humid regions show weaker or slightly negative anomalies. The relationship with aridity is strongest for soil moisture anomalies (, ) and weaker for soil moisture gradient anomalies (, ). Time series analysis shows that convective initiation in arid and semi‐arid regions is generally preceded by positive soil moisture anomalies, indicating that moisture preconditioning is associated with subsequent local convection. These results indicate that the soil moisture‐convection feedback depends strongly on the background climate state.