Mesoscale Associations Between Midwest Land Surface Properties and Convective Cloud Development in the Warm Season

Abstract

The study of land surface-atmosphere interactions is vital to understanding climatic variations in the Earth's planetary boundary layer, particularly given continual land cover modifications by humans on local to regional scales. An agriculturally important region ideal for the study of land surface-atmosphere interactions is the Midwest United States "Corn Belt." To evaluate the mesoscale relationships between Corn Belt land surface properties and a key indicator of the surface-atmosphere feedback in humid climates—warm-season convective cloud development—conventional meteorological data, digital maps of land surface properties, and satellite data were examined in a GIS framework for the May-September periods of 1991 through 1999. The results indicate associations between the surface and atmospheric moisture content and the formation of convective clouds: cumulus clouds initiate first and persist longer over a dry (moist) surface with an initially dry (moist) atmosphere. These relationships are evident when forcing from the free atmosphere is either extremely weak (i.e., when fronts and other disturbances are absent and 500 mb winds are <7 ms-1), weak (same as extremely weak, except 500 mb winds are 7-13 ms-1), or strong (same as extremely weak, except 500 mb winds >18 ms-1). However, the association between convective cloud development and other land surface properties (e.g., land use-land cover [LULC], soil order, elevation, and slope) is not consistent spatially. We find that a surface moisture-convective cloud relationship dominates Corn Belt land surface-atmosphere interactions across a range of barotropic synoptic conditions under different atmospheric moisture contents. The study results can help lead to improved prediction of convective cloud formation, and more realistic modeling of land surface-atmospheric interactions for weather and climate forecasting.