Dry soils can intensify mesoscale convective systems

Significance Soil moisture plays a key role in the climate system by affecting rainfall and drought over land. Through its impact on temperature, humidity, and wind in the lower atmosphere, it can influence where thunderstorms initiate. However, in many regions of the world, traveling storm clusters known as mesoscale convective systems (MCSs) are the dominant source of rainfall, and very little is known about their response to surface conditions once triggered. We use satellite observations to demonstrate that dry soils at scales ≥ 200 km frequently create atmospheric conditions that intensify mature MCSs in the Sahel, long after their initiation. This surface-driven predictability of hazardous weather has potentially important applications, particularly in Africa, where the population is increasingly exposed to flood risk.