Numerical Study Of The Seasonal Variation And Dynamic Mechanism Of The Beginning Of The Kuroshio

The Kuroshion is a strong Western boundary Current in Pacific, its state has a significant change through the Luzon Strait. The Kuroshio whose seasonal and interannual changes will play a decisive role in the structure of the circulation and thermohaline distribution in China's coastal waters has a feature of high temperature,high salinity and high velocity.Because of the paucity of direct current measurements of Luzon strait, it has many different points of the flow pattern and dynamic mechanism in Luzon strait. In this paper, on the basis of previous studies, with the POM2K edition of Princeton Ocean Model, we build a three dimensional baroclinic model which includes the whole north Pacific, the model in an orthogonal curvilinear coordinate has a higher precision and well fitting of the coastline in East China Sea.The results better reproduce the seasonal variation features of the flow in the East China Sea(ECS) and the South China Sea(SCS), such as the Kuroshio,Taiwan warm current and the Tsushima warm current. The discharge comparison from several key sections of the ECS and measured data shows the high consistency and credibility.After discussing the sea surface height anomalies(SSHA) of the model and the comparison with the satellite data, the results prove the credibility once again. And then, we discuss the relationship between the seasonal variation of the location of North Equatorial Current(NEC) bifurcation and the discharge of the beginning of the Kuroshio, the results confide us that the discharge is bigger when the location of NEC bifurcation is norther in autumn and winter, but the otherwise in spring and summer.On this basis, several numerical experiments are employed to study the dynamic mechanism of the beginning of the Kuroshio .The results show that the seasonal changes in wind stress is the main driving forces to the seasonal variation of the net discharge in Luzon Strait , and the same to the seasonal variation of the upper flow; The nonlinearity in the equation shows a little contribution to the net discharge in Luzon Strait, but more significant impact to the upper flow; The strong baroclinicity exists in the Luzon Strait all the year, the net flow of Luzon Strait and the upper flow are sensitive to the calculation of baroclinic gradient force.