Verification Analysis of the University of Virginia Three-Dimensional Mesoscale Model Prediction over South Florida for 1 July 1973

Abstract

An improved version of the mesoscale model, originally developed by Pielke (1974), is used to predict the sea breeze circulations over south Florida for a synoptically undisturbed day during the summer of 1973. Radar and surface observations are used to quantitatively verify the model results and to improve our understanding of the physical processes which occur over the region. Among the improvements to the model are the incorporation of a surface heat budget, longwave and shortwave radiative fluxes, a prognostic equation for the depth of the planetary boundary layer, as well as a more accurate numerical representation of the advective and diffusive terms in the model. Despite these significant changes in the model, however, the predicted sea breeze circulation pattern is still quite similar to the earlier simulations. Among the conclusions of this study are the following: 1) As shown in earlier experiments, the agreement between predicted convergence zones and shower distribution improves during most of the afternoon. Although the specific locations of shower occurrence cannot be predicted, the general regions of preferred convective rain activity are simulated with skill by the model. 2) The surface winds and temperature predictions have some skill except in or near regions of showers where local cumulonimbus circulations dominate. 3) Mesoscale moisture flux through the approximate cloud-base level is shown to precede the occurrence of rain in the NOAA south Florida cloud seeding area during the morning and early afternoon.