潮汐作用下北黄海跃层波动的数值研究

NUMERICAL SIMULATION OF THE THERMOCLINE UNDULATION IN THE NORTH YELLOW SEA UNDER THE EFFECT OF TIDE

跃层除有季节性的变化外 ,还时刻受到潮汐、风、降水等诸多因素扰动而引起波动与起伏。文章研究潮汐 (4大分潮M2 ,S2 ,K1,O1同时输入 )作用下渤海跃层起伏与波动的三维数值模型 (将海洋分为 3层 ,即上混和层 ,跃层和下混和层 ) ,揭示了整个海区跃层上下界面处跃层起伏的地理分布及叠加在起伏之上的潮周期波动的时空变化 ,模拟出跃层波动与实测基本一致。跃层波动既与潮汐运动有关 ,又与潮汐有很大区别。从波动位相、波高来看 ,两者均不相同 ,甚至周期有时也不同。跃层上下界面的波动周期、位相、波高在很多地区也不一致。中下层余流大小和方向几乎一致。大振幅的跃层波动均发生在近海地形突变之处。海水运动的激发与地形相互作用以及海岸海底摩擦可能是跃层波动与起伏的重要因素。

Besides the seasonal variation, the instantaneous wave of thermocline may occur under the effects of tide, wind mixing and rainfall,etc. In this paper, the numerical simulation has been carried out for the fluctuation and the undulation of thermal layer under the influence of tide (simultaneous input 4 principal tidal components, such as M 2,S 2,K 1,O 1) by using three\|dimensional nonlinear model (in the vertical direction,the sea is separated into three layers,such as the upper mixed layer,the thermal layer and the lower mixed layer).The result shows that the wave of the thermocline is consistent with the observations. The distribution of undulation of the thermal layer is given and the temporal spatial variation characteristics of the thermocline undulation are also analyzed. Although the wave of the thermal layer and tide are related to each other in a certain degree,but they are different in the phase, amplitude and even period. Meanwhile, the waves in the upper and lower surface of thermocline are also different in the phase, amplitude and period in many positions.In the middle and lower layer,the mean current possesses almost the same direction and magnitude. The waves of large amplitude always occur in the sea areas with a convex coastline and complex variation of depth.It may be possible that the causes are the bottom friction and complex geography.