Role of Land Surface Processes and Boundary Layer Clouds on

Numerous observational and modeling studies have examined the role of land surface processes in convection initiation. This in depth study looked at the role of surface sensible heat flux gradients on convection initiation using observations from several stations with a spacing of 50 to 100 km in the Southern Great Plains (SGP) region of the United States. Observations used in this study were provided by the U.S. Department of Energy Atmospheric Radiation Measurement (ARM) Program. Data used included measurements of surface turbulent fluxes using eddy correlation method, surface energy budget components, and precipitation on different summer days when large scale effects are minimal and boundary layer processes are dominant. Six stations were selected with four in the corners of a rectangle and two in between. A time history of surface sensible heat fluxes and their gradients was constructed and then correlated with hourly observations of precipitation. Results show the direct role of surface heat flux gradients on convection initiation and precipitation. Role of soil moisture and soil temperature on convection initiation was also investigated. Second part of this study involved the investigation of diurnal variation of precipitation and the role of boundary layer cloud – radiation feed back processes during nights in two regions, SGP and Sand hills region of the Carolinas. Results from this study will also be presented.