Typhoon process and its impact on the surface circulation in the northern South China Sea

A severe typhoon Utor, occurring between July 3 and 8, 2001, brought heavy rainfall, strong wind and storm surge. Utor was responsible for tremendous destruction and economic losses in Philippines, Taiwan and Guangdong. An air-sea model system (MM5 and Princeton Ocean Model (POM)) was built to simulate meteorological dynamics and ocean circulation in the South China Sea (SCS). In the POM the output of MM5 was used as the input data. With an increased number of vertical levels, a high-resolution planetary boundary layer scheme and updated landuse/vegetation data, the accuracy of computing wind, temperature and other meteorological fields are improved in near surface and upper levels in MM5 simulations. The simulated trajectory and wind speed of Utor are close to the observed results. The simulated distribution of rainfall is accorded well with measured data in the Pearl River Delta (PRD) area. At different meteorological stations in Hong Kong, the wind, temperature and sea surface pressure are well simulated. The simulated ocean surface current and surface temperature fields have an obvious rightward-biased response to the typhoon Utor, and the maximum velocity and the lowest temperature region appear in the 30 km of the right side of the typhoon track. The typhoon Utor could make the water 50m under the surface ocean unwell to surface and the ocean surface temperature decrease by about 2°C.