夏季长江冲淡水扩展的数值模拟

建立一个σ坐标系下三维非线性斜压陆架模式,研究夏季径流量、台湾暖流、黄海冷水团、风场对长江冲淡水扩展的影响。数值试验基本再现了夏季长江冲淡水低盐水舌伸向东北的现象和渤、黄、东海的环流结构。长江径流量只影响近口门附近冲淡木朝东南方向扩展势力和整个冲淡水扩展范围的大小。台湾暖流深受底形的影响,流动路径稳定,且不受自身强度的影响,又主流远离长江口,对长江冲淡水扩展的影响不大。黄海冷水团产生的余流在长江口海区阻碍着冲淡水沿岸向南扩展,在远离长江口海区诱导冲淡水向东南运动。总的黄海冷水团的作用是使长江冲淡水低盐水舌伸向东北。黄海冷水团越强,这种作用就越明显。夏季风场在冲淡水转向东北的过程中作用显着。

Numerical model simulation of expansion of Changjiang diluted water in summer

A three-dimensional nonlinear baroclinic estuary and ocean model with primitive equation in o- coordination system is developed to study the impacts of the factors of runoff, the Taiwan Warm Current (TWC), the Huanghai Sea Cold Water Mass (HSCWM) and wind field on the expansion of Changjiang diluted water (CDW). Numerical experiments show the northeast expansion of freshwater tongue of CDW and the cir- culation structure of the East China Sea. Runoff has an effect only on the trend of southeast expansion of CDW and the extent of expansion. As greatly affected by topography, TWC has a stable flow path that is in- dependent of its strength. And also because of the long distance of TWC from the Changjiang Estuary, TWC has a very little effect on the expansion of CDW. The residual current induced by HSCWM blocks the CDW's southward expansion along the coast. In sea area far from the Changjiang Estuary, HSCWM induces the CDW expand southeast. The HSCWM has a significant influence on the northeast turning direction of the CDW. The stronger the HSCWM is, the greater the effect of the HSCWM's induced residual currents and the more obvious the northeast turning of the CDW.