The 23rd Conference on Hurricanes and Tropical Meteorology

2A.8
A NUMERICAL SIMULATION OF THE SOUTH CHINA SEA RESPONSE TO TROPICAL CYCLONE ERNIE 1996

Peter C. Chu, NPS, Monterey, CA; and J. M. Veneziano

We study the response of the South China Sea (SCS) to a tropical cyclone using the Princeton Ocean Model (POM) with 20 km horizontal resolution and 23 sigma levels conforming to a realistic bottom topography. A high-resolution surface wind field was established to represent Tropical Cyclone Ernie (1996) over the SCS. Its translational velocity is determined using the best track storm course and speed from post-storm analysis by the United States Navy Joint Typhoon Warning Center at Guam (JTWC), and its relative velocity to the storm center is determined using a recently developed tropical cyclone wind profile model (TCWPM). To obtain the wind field both inside and outside a tropical storm, a background (climatological) wind field is blended. The calculated wind field is verified using the JTWC analyzed wind profile data. The integration of the POM model was divided into pre-experimental and experimental stages. During the pre-experimental stage, the model was integrated for 34 months and three days from an initial at rest state with three-dimensional climatological January temperature and salinity fields, forced by the climatological monthly mean wind stress. The final state from the pre-experimental run was taken as the SCS condition for 4 November 1996, the initial condition for the experimental stage. During the experimental stage, the POM model was forced by TCWPM modeled wind field, simulating Tropical Cyclone Ernie, for eighteen days. Our results show that the POM adequately simulated ocean responses to tropical cyclone forcing. Near-surface ocean responses simulated by the POM included strong asymmetrical divergent currents with near-inertial oscillations, significant sea surface temperature cooling, biased to the right of the storm track, and sea surface depressions in the wake of the storm. Subsurface responses included intense upwelling and cooling at the base of the mixed layer to the right of the storm track. Several unique features, caused by coastal interactions with storm forcing, were also simulated by the model. Along the coast of Luzon a sub-surface alongshore jet was formed, a warm anomaly off the northern tip of Luzon was significantly enhanced by surface layer convergence and storm surges simulated along the coasts of Luzon and Vietnam.


The 23rd Conference on Hurricanes and Tropical Meteorology