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首页> 外文期刊>Journal of Physical Oceanography >The Effect of a Bottom Shelf Front upon the Generation and Propagation of Near-Inertial Internal Waves in the Coastal Ocean
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The Effect of a Bottom Shelf Front upon the Generation and Propagation of Near-Inertial Internal Waves in the Coastal Ocean

机译：底架前缘对近海内惯性内波的产生和传播的影响

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A three-dimensional nonlinear baroclinic model in cross-sectional form is used to study the generation and propagation of wind-forced near-inertial internal waves in a coastal region in the presence of a bottom front. Initially calculations are performed with the front in an infinite domain region. By this means coastal effects are removed. The initial response is in terms of inertial oscillations in the surface layer. However, in the frontal area these are modified by interaction through the nonlinear momentum terms with regions of positive and negative vorticity associated with the alongfront flow. This leads to a change in amplitude, phase, and frequency of the inertial current, and a resulting Ekman pumping that drives near-inertial internal waves in the frontal region. On the positive vorticity side of the front these waves are at the superinertial frequency and rapidly propagate away. On the negative side they are at the subinertial frequency and are trapped and inertial energy leaks to depth. Calculations with a coastal boundary and no front show that the offshore propagation of near-inertial waves is similar to that found on the positive vorticity side of the front. This shows that in terms of superinertial internal wave generation and propagation the front acts in a similar manner to a coastal boundary. However, with a coastal boundary, inertial currents below the thermocline are phase shifted by 180° from those above. This phase shift is only found in the frontal case when the front is adjacent to a coast and is due to the no-normal-flow condition at the coast. For the case of a stratified region between the coast and the front, near-inertial energy is trapped in this region and is dissipated at a rate depending upon the local value of vertical eddy viscosity. The offshore spatial distribution of near-inertial internal waves is found to be independent of whether the coastal region is represented by a vertical wall or a more realistic sloping seabed. However, in the case of a weak coastal front, the near-frontal distribution of near-inertial energy is influenced by the horizontal spatial variability of stratification within the front.
机译：截面形式的三维非线性斜压模型用于研究存在底部前缘的沿海地区风力近惯性内波的产生和传播。最初，计算是在无限域区域中进行的。通过这种方式，消除了沿海影响。初始响应是根据表面层中的惯性振动来进行的。但是，在额叶区域，这些变化通过非线性动量项与与沿流流动相关的正涡旋和负涡旋区域的相互作用而被修改。这导致惯性电流的幅度，相位和频率发生变化，并导致驱动额叶区域中接近惯性内部波的埃克曼泵浦。在正面的正涡度侧，这些波处于超惯性频率，并迅速传播开。在负的一面，它们处于亚惯性频率并被捕获，惯性能量泄漏到深度。在没有边界的情况下进行的海岸边界计算表明，近惯性波的近海传播与在前沿的正涡度侧的相似。这表明，在超惯性内波的产生和传播方面，前锋的作用与沿海边界相似。然而，在沿海边界，温跃层以下的惯性电流与上方的惯性电流相移了180°。这种相移仅在前部靠近海岸时才在额部情况下发现，这是由于海岸的非正常流动条件所致。对于海岸和前缘之间的分层区域，近惯性能量被困在该区域中，并以取决于垂直涡流粘度的局部值的速率消散。发现近惯性内波的离岸空间分布与沿岸区域是垂直壁还是更现实的倾斜海床无关。然而，在沿海锋线较弱的情况下，近惯性能量的近锋线分布受锋线内分层的水平空间变异性影响。

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