Ballooning of River-Plume Bulge and Its Stabilization by Tidal Currents
Ballooning of River-Plume Bulge and Its Stabilization by Tidal Currents
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DOI：
10.1175/jpo2837.1
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发表时间：
2005-12
影响因子：
3.5
通讯作者：
A. Isobe
中科院分区：
文献类型：
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作者：
A. Isobe
当淡水流入邻近的海洋时，在河口前形成反气旋涡流（凸起）。众所周知，在没有周围洋流或风力的情况下，近海的隆起物（气球）很难达到稳定状态。本研究通过对沿海淡水源诱导的河流羽流进行数值实验，为河流羽流膨胀提供了物理解释。释放到模型海洋的部分淡水经历了惯性不稳定性。在河流羽流的周围水域中，当扰动不被强迫时，近惯性振荡是主要的。这些各向同性的扰动被惯性不稳定性放大，因此不稳定的淡水可以向任意方向移动。因此，不稳定的淡水不需要向河口右侧的海岸边界流移动。长时间不稳定的淡水可以在凸起中停留很长时间。不稳定的淡水在凸起处逐渐积聚，于是就发生了膨胀。当周围水域的扰动方向被规定时，不稳定的淡水被迫向同一方向移动。因此，当沿岸潮流引起背景扰动时，不稳定淡水在沿岸方向的运动受到限制。由此得出结论，潮流在稳定沿海和陆架水域的河羽隆起的近海生长中起作用。
When freshwater debouches into an adjacent ocean, an anticyclonic eddy (bulge) is formed in front of the river mouth. It is well known that a bulge growing offshore (ballooning) hardly reaches a steady state in the absence of either ambient currents or wind forcing. This study provides a physical interpretation for the ballooning of river-plume bulges by conducting numerical experiments in which a river plume is induced by a coastal freshwater source. Part of the freshwater released to the model ocean undergoes inertial instability. Near-inertial oscillations are predominant when disturbances are not forced in ambient waters of the river plume. These isotropic disturbances are amplified by inertial instability, so that unstabilized freshwater can move in arbitrary directions. Thus, unstabilized freshwater does not need to move toward the coastal boundary current on the right-hand side of the river mouth. Freshwater unstabilized for a long time can stay in the bulge for a long time. Unstabilized freshwater accumulates gradually in the bulge, and so ballooning occurs. When the direction of disturbances is prescribed in ambient waters, unstabilized freshwater is forced to move in the same direction. Thereby, the motion of unstabilized freshwater is restricted in the alongshore direction when background disturbances are induced by alongshore tidal currents. It is therefore concluded that tidal currents play a role in stabilizing the offshore growth of river-plume bulges in coastal and shelf waters.