Observations of Polarity Reversal in Shoaling Nonlinear Internal Waves
Observations of Polarity Reversal in Shoaling Nonlinear Internal Waves
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DOI：
10.1175/2008jpo3953.1
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发表时间：
2009-03
影响因子：
3.5
通讯作者：
E. Shroyer;J. Moum;J. Nash
中科院分区：
文献类型：
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作者：
E. Shroyer;J. Moum;J. Nash
新泽西海岸外的观测记录了三组超过35公里的非线性低压内波在大陆架上的浅化。每个波群都经历了沿其海岸中转的不断变化的背景条件。尽管有不同的波浪环境，但出现了一个明显的模式。传播到浅水中的近对称波形成不对称的形状；在波浪参考系中，前缘加速，导致前面加宽，而后面保持陡峭。这一趋势将持续下去，直到前一浪的前缘和前一面变得无法辨认，并出现一个接近底部的上升浪，它是由最初的下沉浪的尾部和下一浪的前部形成的。通过积分波涡度来诊断从低压波到高压波的转变，积分波涡度随着波极性的改变而改变符号。当使用观测的层结和速度剖面进行评估时，通过KdV方程中非线性项系数的符号变化来预测这种转变。
Observations off the New Jersey coast document the shoaling of three groups of nonlinear internal waves of depression over 35 km across the shelf. Each wave group experienced changing background conditions along its shoreward transit. Despite different wave environments, a clear pattern emerges. Nearly symmetric waves propagating into shallow water develop an asymmetric shape; in the wave reference frame, the leading edge accelerates causing the front face to broaden while the trailing face remains steep. This trend continues until the front edge and face of the leading depression wave become unidentifiable and a near-bottom elevation wave emerges, formed from the trailing face of the initial depression wave and the leading face of the following wave. The transition from depression to elevation waves is diagnosed by the integrated wave vorticity, which changes sign as the wave’s polarity changes sign. This transition is predicted by the sign change of the coefficient of the nonlinear term in the KdV equation, when evaluated using observed profiles of stratification and velocity.