A 3-DIMENSIONAL NUMERICAL SENSITIVITY STUDY OF CONVECTION OVER THE FLORIDA PENINSULA

The Florida peninsula has the highest annual number of days with thunderstorms in the United States, partly due to sea breeze convergence. A three-dimensional mesoscale planetary boundary layer (PBL) model with the E-epsilon turbulence closure is used to investigate the relationship between sea breeze convergence and convection over the peninsula for two ambient wind cases during typical summer days. It is found that the spatial and temporal variation of the sea breeze convergence zones and the associated convective activities depend to a large extent on the direction and magnitude of the ambient wind. For the case of southeasterly ambient winds, a strong convergence zone and hence significant rainfall occur primarily along the west coast of the peninsula. The convergence zone and the associated rainfall shift towards the east coast for the case of southwesterly ambient winds. These are in agreement with the observations. In contrast to the southeasterly and southwesterly ambient winds, an intense convergence zone and rainfall occur near both coastlines of the peninsula under light ambient winds. It is also found that lake Okeechobee has a substantial influence on south Florida's mesoscale weather. A cloudless region is always present over the lake at least until late afternoon due to its own lake breeze circulation. Finally, increased roughness of the land surface appears to influence the temporal and spatial variation of the convection by determining the intensity of the vertical turbulent transport of heat and momentum.