Simulation of the Effects of Bathymetry and Land–Sea Contrasts on Hurricane Development Using a Coupled Ocean–Atmosphere Model

Abstract

A version of the Naval Research Laboratory Limited Area Dynamical Weather Prediction Model is coupled with the DieCAST ocean circulation model, which is particularly well suited for the specification of realistic bathymetry. The resulting coupled model, with 11 levels in the atmosphere and 20 in the ocean, is used to study the sensitivity of hurricane formation, intensification, and weakening in the Gulf of Mexico and the Carribean region to the presence of land?sea contrasts and bathymetry in this region. Numerical simulations with the fully coupled model, Gulf of Mexico, and Carribean geography and bathymetry are compared with simulations with coupling and no geometry or bathymetry and also with simulations using the uncoupled atmospheric model. The primary finding is that land?sea contrast and bathymetry reduce the intensification of the tropical disturbance, even when the hurricane is far from shore. The effect of drier air coming off the land masses surrounding the Gulf, which can penetrate to the storm center in a day, is to reduce the moisture supply and thereby decrease the rate of intensification of the storm. This is true in both the coupled and uncoupled model integrations. In the coupled model simulations, inertia currents and vertical mixing and upwelling on the continental shelf cause more intense and more widespread sea surface cooling in the presence of land?sea contrasts and bathymetry than in its absence, further reducing the rate of intensification.