Numerical Simulations with a Three-Dimensional Cloud Model: Lateral Boundary Condition Experiments and Multicellular Severe Storm Simulations

Simulations with a three-dimensional numerical cloud model are presented for airflow over a bell-shaped mountain and for a multicellular severe storm. A comparison of results using the Orlanski (1976) and Klemp and Wilhelmson (1978) treatments for the normal velocities shows that physical modes can be computationally excited using the latter's treatment with the result of very large horizontally averaged vertical velocities. Cell splitting occurs for the model calculations and the analysis indicates the splitting is caused by an entrainment effect which may be an artifact of the experimental design. An analysis of subgrid/resolved scale kinetic energy shows that this ratio is much smaller for the current severe storm simulations than that found by Lipps (1977) for his trade wind cumuli simulations. A comparison of some general features of the multicellular severe storm with observational data is presented.