Numerical Simulations of Tropical C~yclone-()cean Interaction With a High-Resolution Coupled Model

The tropical cyclone-ocean interaction was investigated using a high-r(~solution tropical cyclone ocean coupled model. The model design consisted of the NOAA Geophysical Fluid Dynamics Laboratory tropical cyclone prediction model which was coupled with a multilayer primitive equation ocean model. Coupling between the hurricane and the ocean models was carried out by passing into the ocean model the wind stress, heat, and moisture fluxes computed in the !i1urricane model. The new sea surface temperature (SST) calculated by the ocean moClel was then used in the tropical cyclone model. A set of idealized numerical experiments were performed in which a tropical cyclone vortex was embedded in both easterly and westerly basic flows of 2.5, 5, and 7.5 m s -I with a fourth experiment run with no basic flow specified initially. The pr'ofile of the tan~:ential wind for Hurricane Gloria at 1200 UTC 22, September 1985 was used as the iruitial condition of the tropical cyclone for each of the experiments. The model ocean was initially horizontally homog(~nous and quiescent. To clarify the impact of the ocean response to the hurricane's be:havior, analogous experiments were also carried out with the SST kept constant (control cases). The experiments indicated that the cooling of the sea surface induced by the tropical cyclone resulted in a significant impact on the ultimate storm intensity due to the reduction of total heat flux directed into the tropical cy<:lone above the regions of decreased SST. The sea surface cooling produced by the tropical cyclones was found to be larger when the storms moved slower. In the experiments run without an initiaf basic flow, the maximum SST anomaly was about -5.6°C with a resulting difference in the minimum sea level pressure and maximum surface winds of 16.4 hPa and -7 m s -I, respectively. In contrast, in the experiments run with the 7.5 m s -I basic flow, the maximum SST anomalies ranged from about 2.6° to 3.0°C with a difference in the