Numerical Study on the Coastal Upwelling and Its Seasonal Variation in the East China Sea

The upwelling structure and its seasonal variation along Zhejiang and Fujian coast of the East China Sea are studied using a three-dimensional baroclinic nonlinear numerical model forced by QuikSCAT winds over 20002004, in which other important factors such as realistic topography, boundary currents (Taiwan Warm Current, Kuroshio and Changjiang Discharge) and heat flux are all included. Numerical model results indicate that there exist obvious upwellings in the coastal area along Zhejiang and Fujian coast during every season and their intensity and spatial distribution have distinct seasonal variability. The stronger upwelling centres are mostly located in the vicinity of Zhoushan Islands and Yushan Archipelago of Zhejiang coast, Haitan Island and Mazu Archipelago of Fujian coast. In addition, the mean upwelling velocity is about 0.3 x 10(-3) cm/s and the magnitude of upwelling intensity is 10(-3) cm/s in winter, while in summer they are about 0.3 x 10(-2) cm/s and 10(-2) cm/s, respectively. The modelling results also show that the change rate of upwelling intensity is less in wintertime with the weaker coastal upwelling but quite to the contrary in summertime.