Cloud-land surface interactions and water recycling in the Southern Great Plains: observations and regional simulations

Description

Locally generated continental cumulus convection, a cloud type showing particular sensitivity to the underlying land surface, is an important component of the atmospheric radiation budget and hydrologic cycle in the Southern Great Plains (SGP), particularly during the summertime growing season. Modeling and observational studies have shown that the configuration of the land surface can significantly impact the formation and structure of the cumulus cloud by determining the partitioning of surface sensible heat (SH) and latent heat (LH) fluxes, which affects the evolution of the convective boundary layer. Clouds, in turn, impact the responses of the land surface by altering the incident radiative fluxes and precipitation. In this study, we conduct two regional simulations over SGP from May to September of 2006 and 2007, a typical dry and a wet summer respectively, based on the WRF regional model coupled with the NOAH land surface model. We first evaluate various components of the modeled water cycle and energy budgets against observations, including SH, LH, shortwave and longwave radiative fluxes, precipitation, evapotranspiration, soil moisture, and atmospheric moisture flux divergences, and calculate the bulk moisture budget and water recycling ratio over SGP for 2006 and 2007. We also examine the relationships between soil moisture, SH/LH partitioning, cloud base height, cloud depth, cloud cover fraction, convective available potential energy (CAPE), based on observations and model results, and discuss how land surface properties affect the formation and structure of cumulus cloud under a typical dry or wet condition. The results could potentially advance our understanding of the physics of cumulus cloud convection and its interaction with land surface over the study region.