The Role of Air-Sea Interaction in the Rapid Intensity Changes of Hurricane Rita (2005) as Simulated with WRF-HYCOM

A cloud-resolving, ocean-coupled hurricane modeling system is developed under the Earth System Modeling Framework (ESMF) using the state-of-the-art numerical forecasting models of atmosphere (WRF) and ocean (HYCOM). With this system, the impact of coupling to an eddy-resolving ocean model and the atmospheric model resolution on the intensity simulation of Hurricane Rita (2005) are firstly examined through a set of numerical experiments. Coupling to the ocean model eliminates the erroneous intensification during last several hours of simulation, as occurred in the uncoupled experiments. However, the rapid intensification and the following weakening process of Rita can only be simulated with the resolution of WRF model increased to near 1-km aside from coupling to the ocean model. The system is capable of reproducing the realistic response of upper-ocean. The ocean upwelling strongly depends on the spatial distribution of the geostrophic vorticity associated with the (warm and cold) ocean eddies. The area and value of extreme SST cooling simulated by the coupled system are similar to those observed. The surface latent heat flux is reduced by 30% when Rita left Loop Current and entered the colder water area, which contributed to the weakening of Rita after maximum intensity. The high resolution, coupled system also reproduced the concentric eyewall cycle during the weakening phase of Rita.