Generation of internal waves by a supercritical stratified plume
Generation of internal waves by a supercritical stratified plume
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DOI：
10.1029/2008jc004851
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发表时间：
2009-05
影响因子：
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通讯作者：
N. Stashchuk;V. Vlasenko
中科院分区：
文献类型：
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作者：
N. Stashchuk;V. Vlasenko
[1]利用完全非线性非静力数值模式研究了河流羽流内波的产生。垂直流体分层，潮汐参数，河流流量，和底部地形接近观察到的哥伦比亚河口附近。结果表明，在落潮初期，入海的河水表现为表面急流。它与停滞的陆架沃茨碰撞，并在羽流外边界区域下沉，形成重力流的头部。在通常在落潮相的第一阶段实现的超临界条件下，内波在重力流的头部被捕，因为它们的相速度小于羽流的速度。当减速锋的速度小于内波相速度时，它们从羽流中释放并辐射。波浪产生的这种机制对周围陆架沃茨的分层很敏感。有人发现，从表面到底部的浮力频率曲线的急剧衰减提供了最有利的条件，有效的解体的头部的重力流成一个包的内波和他们的快速分离的羽流。在陆架流体层结接近单调的情况下，重力流的头部分解成孤立内波包是不可能的。
[1] The generation of internal waves by a propagating river plume is studied in the framework of a fully nonlinear nonhydrostatic numerical model. The vertical fluid stratification, parameters of tide, river discharge, and the bottom topography were taken close to those observed near the Columbia River mouth. It was found that in the beginning of the ebb tidal phase the river water intruding into the sea behaves as a surface jet stream. It collides with the stagnant shelf waters and sinks down in the area of the outer plume boundary, forming a head of the gravity current. In supercritical conditions which are normally realized at the first stage of the ebb tidal phase, internal waves are arrested in the head of the gravity current because their phase speed is smaller than the velocity of the plume. They are released and radiate from the plume when the speed of the decelerating front becomes smaller than the internal wave phase speed. This mechanism of the wave generation is sensitive to the stratification of the ambient shelf waters. It was found that dramatic decay of the buoyancy frequency profile from the surface to the bottom provides the most favorable conditions for the efficient disintegration of the head of the gravity current into a packet of internal waves and their fast separation from the plume. In the case when the fluid stratification on the shelf is close to monotonous, the disintegration of the head of the gravity current into a packet of solitary internal waves is not expected.