Sulfate Production and Deposition in Midlatitude Continental Cumulus Clouds. Part I: Cloud Model Formulation and Base Run Analysis

Abstract

We have developed a 1.5 dimensional Eulerian cumulus cloud model which incorporates: (i) two in-cloud regions, (ii) a bulk water parameterization including the ice phase, (iii) an entrainment formulation based on the turbulent kinetic energy, (iv) a sustained subcloud forcing, and (v) a flux-corrected transport algorithm in the numerical advection scheme. This model formulation was chosen in order to provide a simple dynamic framework which permits simultaneous up- and downdrafts in-cloud. The model is compared against aircraft and radar data for clouds observed during the Cooperative Convective Precipitation Experiment (CCOPE) held in south-central Montana during the summer of 1981. The overall dynamic, thermodynamic and microphysical agreement is good. Sensitivity analysis of adjustable parameters indicates that model response is not overly sensitive to the characteristic entrainment mixing length used, but fairly sensitive to parameters used in the ice phase microphysics.