Continental Active Surface-Forced Shallow Cumulus (CASS)—Large Eddy Simulation Coupled with Land Surface Model

The case “Continental Active Surface-forced Shallow cumulus (CASS)” is developed based on decade-long warm-season observations at DOE ARM US Southern Great Plains (SGP) site and aims to represent the daytime evolution of non-precipitating fair-weather shallow cumulus clouds purely forced by land surface heat fluxes and local atmospheric environment and least subject to synoptic forcings such as dry lines, fronts and deep convections. CASS may serve as a new test case for both the cloud-scale large-eddy simulation (LES) studies and the development of convection and cloud parameterizations in large-scale models. CASS data is available to public via http://portal.nersc.gov/project/capt/CASS/

CASS is originally forced with prescribed land surface heat fluxes. In this study, we further develop the land surface component forcing data set. Soil moisture, soil temperature, soil/vegetation type, leaf area index are all derived based on longterm observations at SGP site. Their impacts on shallow cumulus cloud properties are systematically assessed using large eddy simulation coupled with a land surface model. This work extends CASS’ capability as a test case strongly constrained by observational data in land-atmosphere interaction studies.

This work is performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under Contract DE-AC52-07NA27344. LLNL-ABS-755327