Soil Moisture Gradient Interactions with Convective Precipitation for the Midwestern United States Corn Belt

Recent climatic research for mid-latitude agricultural regions (e.g., U.S. Great Plains, southwest Australia, Midwest Corn Belt: CB) suggests a land surface influence on warm-season convective precipitation (CVP). Soil moisture (SM) content and associated spatial gradients have been implicated in CVP development through the formation of mesoscale circulations arising from variations in surface heat fluxes, set within the framework of synoptic atmospheric conditions. However, in comparison to other agricultural mid-latitude regions, SM-CVP relationships for the humid lowlands of the CB have received less attention, particularly on climatological (i.e., weekly to interannual) time scales. Accordingly, we correlate surface radar-retrieved CVP initiation locations and timing to reanalyzed SM data for the CB region, both for categories of SM content (low, medium, high) and their associated spatial gradients, for the 11 warm-seasons (May-September) 2013-2023. These data are processed for all isolated (i.e., non-synoptically forced) CVP occurrences. CVP events are then correlated with SM for the entire period, as well as for three subseasons (early, middle, and late). This procedure is conducted for two domains: a topographically-varied portion of south-central Indiana, and a flatter area in central Illinois. Subsequent numerical comparison between these two sub-regions provides insights into SM-deep convection interactions for different topographic settings under broadly similar climatic conditions. Additionally, composite mapping of key atmospheric variables (e.g., wind velocity, humidity) for categories of SM-CVP association reveals the synoptic environments that may further aid precipitation forecasting in the CB.