Atlantic Hurricanes Using a Coupled Regional Climate Model

To improve understanding of the role of air-sea interactions in the formation and development of tropical storms in the Atlantic, a coupled regional climate model (CRCM) is developed by coupling the Advanced Weather Research & Forecasting Model (WRF-ARW 3.1) to the Regional Ocean Modeling System (ROMS 3.0). The coupling between WRF and ROMS is conducted by exchanging the surface heat & momentum fluxes with sea surface temperature (SST) between these two models every hour of time integration. The model domain covering the entire Atlantic domain from 130°W to 40°E in longitude and 33°S to 52°N in latitude. WRF has a horizontal resolution of 27 km, while ROMS features a 9 km grid. Both models use the Mercator projection and the Arakawa C-grid for horizontal discretization and are readily configured to share a common land mask.

Preliminary results have demonstrated the ability of the CRCM to realistically capture the major climate and weather features over the Atlantic ocean, including the inter-tropical convergent zone (ITCZ), SST distribution and the formation of tropical storms (hurricanes) from African easterly waves. The animation shows a simulated Category 1 hurricane passing through Gulf of Mexico in a coupled simulation of the CRCM. The simulated storm encounters a warm Loop Current Eddy in the Gulf before making landfall on Texas coast. The warm eddy may provide a key source of energy to fuel rapid intensification of hurricanes that cross the Gulf, as it happened in 2005 when Hurricane Katrina passed over a Loop Current Eddy and underwent a rapid intensification before making landfall. The bottom right panel shows the oceanic response along the track of the storm. The intense surface cooling and large air-sea exchange along the hurricane track, which bear a considerable resemblance to observations (e.g., McPhaden et al. 2009), are indicative of strong air-sea coupling. These simulation results offer us an opportunity to analyze the interaction between hurricanes and oceanic mesoscale eddies.