潮汐作用下渤海温跃层波动与起伏的数值研究

研究了潮汐(四大分潮 M₂,S₂,K₁,O₁同时输入)作用下渤海温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),揭示了整个海区温跃层上界面处跃层起伏(在文中指每个时刻跃层波高的周期平均值)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.结果发现大振幅的跃层波动均发生在海峡及近海地形突变之处.一般界面波动的波高大于甚至远远大于同一位置的表层潮波.从位相以及周期来看,潮波和跃层上下界面波动相互之间,有些海域一致,有些地方则相差甚远.跃层上界深度及厚度的梯度,对跃层起伏分布有一定的影响.跃层起伏还可能与海岸海底摩擦有关.

The interface waves of thermocline excited by the principal tidal constituents in the Bohai Sea

In this study, interface waves of thermocline layer are simulated by the model in the Bohai Sea. The waves are excited by tidal oscillation. The numerical model is three-dimensional nonlinear. In the vertical direction, the sea is separated into three layers, namely, upper mixing layer, thermal layer and lower mixing layer. Four principal tidal components, which are M2, S2, K1, O1, are considered in the model. So the surface waves are tidal ones. Not only the temporal varied internal waves have been analyzed, but time-mean values of them, which are called undulation in the paper, have been did. The result shows that the wave of the thermocline is consistent with observations. The waves in the upper and lower surface of thermocline are different in the phase, amplitude, even period in many places. The interface waves of large amplitude occur in the areas with a convex coastline and complex variation of depth. Compared with tidal residual elevation, the undulations of thermocline are larger. And higher absolute values also lie in the near coastline and the areas with complex topography. The bottom friction and topography play a major role for the undulation and interface-wave height.