长江口杭州湾及邻近海区潮汐潮流场三维数值模拟

3-D Numerical Simulation of Tide and Tidal Current Fields in the Changjiang Estuary, Hangzhou Bay and Their Adjacent Sea

把长江河口、杭州湾及邻近海区作为整体 ,应用三维高分辨率非正交曲线网格河口海洋模式 ,模拟了 4个主要分潮M2 ,S2 ,K1,O1。在长江口外半日分潮M2 、S2 从东南方向传入长江口和杭州湾 ,全日分潮K1,O1从北向南传播。这 4个分潮的振幅在长江口南支向上游逐渐减小 ,但因杭州湾和长江口北支呈喇叭状 ,而向上游逐渐增加。计算潮差变化过程和实测值基本一致 ,4个分潮潮位振幅和位相的计算值与验潮站观测值相比 ,误差大部分在 10 %以内。结合 1996年 2—3月长江河口现场观测 ,考虑了径流的作用 ,三维数值模拟了计算域内流场。结果表明 ,即使在斜压效应不太明显的口门内 ,流速在垂直方向存在着明显的差异 ,上层流速明显大于下层流速 ;潮流具有不对称性 ,由于径流的作用 ,落潮时间明显大于涨潮时间 ,落潮流大于涨潮流 ,但在象北支涨潮槽中 ,涨潮流反而比落潮流大。模拟出的以上结论与观测结论较为一致。

In this paper, uniting the Yangtze Estuary, Hangzhou Bay and their adjacent sea , the 4 main tidal constituents M 2,S 2,K 1,O 1 are simulated using a non-orthogonal coordinate primitive equation model with high resolution. The semi-diurnal tides M 2,S 2 propagate from southeast into the Changjiang estuary and Hangzhou bay, but the diurnal tides K 1,O 1 propagate from north to south out of the Changjiang mouth. The tidal ranges decrease upstream in the South Branch of the Changjiang Estuary. The tidal ranges in the Hangzhou Bay and North Branch increase from the outer to the inner due to its funnel-shape. The simulated values of amplitude and phase of the M 2, S 2, K 1, O 1 tides are fairly consistent with the observations. Considering the river discharge, the 3-D current field is simulated. Combining with the observed data in Changjiang estuary from 15, February, 1996 to 1, March, 1996, the results indicate that the current velocity changed obviously in the vertical due to the bottom friction and vertical turbulent mixing. The current is asymmetric due to the river discharge, ebb current period longer than flood current period, the velocity of ebb current is stronger than that of flood current, but the situation is reverse in the flood current passage such as the North Branch.