The influence of soil moisture, coastline curvature, and land-breeze circulations on sea-breeze-initiated precipitation

Idealized numerical simulations of Florida convection are performed with a coupled atmosphere-land surface model to identify the roles of initial soil moisture, coastline curvature, and land-breeze circulations on sea-breeze- initiated precipitation. The 3D Goddard Cumulus Ensemble cloud-resolving mo del is coupled with the Goddard Parameterization for Land-Atmosphere-Cloud Exchange land surface model, thus providing a tool to simulate more realist ically land surface-atmosphere interaction and convective initiation. Eight simulations are conducted with either straight or curved coastlines, initi ally homogeneous soil moisture or initially variable soil moisture, and ini tially homogeneous horizontal winds or initially variable horizontal winds (land breezes). An additional simulation is performed to assess the role of Lake Okeechobee on convective development. All model simulations capture the diurnal evolution and general distributio n of sea-breeze-initiated precipitation over central Florida. The distribut ion of initial soil moisture influences the timing and location of subseque nt precipitation. Soil moisture acts as a moisture source for the atmospher e, increases the convectively available potential energy, and thus preferen tially focuses heavy precipitation over existing wet soil. Soil moisture-in duced mesoscale circulations do not produce heavy precipitation. Coastline curvature has a major impact on the timing and location of precipitation. E arlier low-level convergence occurs inland of convex coastlines, and subseq uent heavy precipitation occurs earlier in simulations with curved coastlin es. Early-morning land breezes influence the timing of precipitation by mod ifying low-level convergence. Because of nonlinear interaction between coas tline curvature and soil moisture, the highest peak accumulated rainfall an d highest peak rain rates occur in simulations with both coastline curvatur e and initial soil moisture variations. Lake Okeechobee influences the timi ng and location of precipitation because of strong lake-breeze circulations .