Numerical Simulation Of Circulation And Sea Temperature In The Northwest Pacific With Vertical S Coordinate Model

In this paper, making using of a three dimensional high resolution numerical model, Ecom-si, which includes various dynamical factors, such as the water flux at the lateral open boundaries, the sea surface wind stress, the heat flux, the evaporation and precipitation at sea surface, the circulation and sea temperature in the Northwest Pacific are simulated for a whole year in this model. Meanwhile, a vertical stretchable coordinate, S coordinate, is applied to this model. The vertical S coordinate has the advantage not only in making the model surface closer to the physical plane and behaving like z coordinate but also in fitting the bottom topographic changes. Then based on the model results which were run for about two year with the initial elevation and current condition, the changes of the circulation and sea temperature in the Northwest Pacific are analyzed.The model validation shows that the simulated sea temperatures are consistent with the section data, which were measured by Japan in the Northwest Pacific in each month of 2008. Including several factors, the circulation numerical experiment in the Northwest Pacific reconstructed the North Equatorial Current,the Kuroshio,the ocean circulation in South China Sea,the Taiwan Warm Current,the Tsushima Warm Current,the Yellow Sea Warm Current and coast currents fairly well. The place of the Kuroshio entering into the Continental shelf is always at the northeast area of Taiwan. Under the impact of the season wind, the flows of the Kuroshio at sea surface in summer is bigger than in winter. The surface and mid flows of the Taiwan Warm Current are moving in the nearshore of Fujian and Zhejiang, their directions turn east obviously for one time. The turning east place of the surface flow which goes further in summer changes seasonally in the year. In addition, under the influence of the seasonal wind, the flow of the Taiwan Warm Current is bigger in summer than in winter. The circulation in the South China Sea also changes seasonally. In winter, the counterclockwise circulation occurs in the South China Sea in which there exist a branch of the Kuroshio. While, in summer, the circulation flows clockwise and the branch of the Kuroshio is disappeared. As to the seasonal variations of the sea temperature in the Northwest Pacific, the model results show that in the South China Sea, the sea temperature is always high. The average temperature in winter is about 22-24℃and 28℃in summer. Along the latitude within the east china sea shelf, the sea temperature varies intensely in winter from 14℃to 22 while in summer, it changes smaller with about 28℃in average. Among the area of the Yellow Sea and the East China Sea, there exists a higher temperature gradient in winter because of the warm water carried by the Yellow Sea Warm Current. Opposite to the winter, the temperature in summer is almost the same with no obvious gradient. Compared with theσcoordinate model, the ocean model with vertical S coordinate can simulate the temperature better because in theσmodel, the horizontal changes of the model depth are included in theσlevel which means its resolution at sea surface is lower than the s coordinate. In addition, the horizontal distribution of sea temperature in theσmodel is more likely impacted by the model depth.