Response of Mature Storms to Soil Moisture State in Global Hotspot Regions

Mesoscale Convective Systems (MCSs) represent some of the most intense and destructive thunderstorms in the world. Understanding the physical processes that drive these storms and influence their characteristics is vital for hazard prediction and mitigation. 

A significant amount of research in the “natural laboratory” of West Africa has shown that soil moisture heterogeneity on different spatial scales can influence the location of convective initiation (10s of km) and the intensification of remotely triggered storms (100s of km).

Previous studies have demonstrated that the control of soil moisture state on convective initiation identified in West Africa is also important elsewhere in the world whereas very little is known about the influence of surface conditions on travelling storms in other regions.

In the current work we combine satellite observations and reanalysis data to characterise the impact of pre-storm soil moisture conditions on the atmospheric environment and characteristics of mature storms in seven MCS hotspot regions, West Africa, South Africa, South America, Great Plains, India, China and Australia. 

We observe a clear latitudinal dependence of the coupling signal with distinct differences between regions where convection is predominately driven by monsoonal or frontal dynamics. However our results suggest that in all regions, large-scale (100s of km) soil moisture gradients are having an impact on convection within mature MCSs through moderation of the climatological temperature gradient in the lower atmosphere, which influences factors that favour convection such as shear and convergence.