Numerical Simulation of the Evolution of a Three-Dimensional Field of Cumulus Clouds. Part I: Model Description, Comparison with Observations and Sensitivity Studies.

Abstract A surface boundary layer model was developed which utilizes the single-level surface mesonet data and the results of a surface energy and moisture budget calculation. The heat and moisture fluxes calculated using this model were employed in the three-dimensional simulation of a cumulus cloud field. The analytical treatment of the surface layer represents a significant computational advantage. The cloud field simulation represents seven hours of the 20 June 1981 case of the Cooperative Convective Precipitation Experiment (CCOPE) conducted in Montana. The model results are compared .with the available radar and aircraft data, with the record of hourly surface observations and with the available cloud photographs. The results of the numerical experiments suggest that dynamical inhomogeneities imposed on the flow by the terrain plays a leading role in the rate of development of the convective cloud field. The thermodynamical inhomogeneities generated by such things as the type of soil and vegetation ...