Tests of a Mesoscale Model Coupled with a Boundary Layer/Soil Model

A meso-beta grid point model with a detailed microphysics parameterization of warm-cold processes is briefly described. The model is initialized with a mesoscale data set beginning 12Z on 27 March 1982 at a location centered over north-central Texas. Parameters from subsequent 6-h forecasts are compared with observations. Velocity, temperature and moisture parameters generally appeared to be forecast well. The model was additionally run without any pBLsoil model physics to evaluate the effect that the processes have on the forecast. The most noticeable effects were observed near the surface where forecast temperatures were too cold and wind were too high. This run also yielded about 20-50 percent less precipitation. The models soil physics parameterization appears to be essential to represent realistically the supply to the lower atmosphere of the moisture necessary for the precipitating clouds. Sensitivity tests with the PBLsoil model revealed that, at least for this case, the effect of soil moisture on ground temperature is approximately as important as the effect of clouds on ground temperature. However, when the effects of clouds were removed from the model atmosphere, the ground temperature and PBL height tended to exhibit unusual oscillations. The reasons for this are not yet known.