RESONANT INTERACTION OF SOUND-WAVE WITH INTERNAL SOLITONS IN THE COASTAL ZONE
RESONANT INTERACTION OF SOUND-WAVE WITH INTERNAL SOLITONS IN THE COASTAL ZONE
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DOI：
10.1121/1.401632
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发表时间：
1991-10-01
影响因子：
2.4
通讯作者：
ROGERS, PH
中科院分区：
文献类型：
--
作者：
ZHOU, JX;ZHANG, XZ;ROGERS, PH
在沿海地区经常观察到自然发生的内部孤立波列（孤子），但没有报道对这种孤立波的测量包括低频远程声音传播数据。本文探讨了夏季观测到的浅水声传播异常频率响应是由内波引起的可能性。观测到的传输损耗具有强烈的时间依赖性和各向异性，有时在某些频率范围内表现出异常大的衰减。采用抛物方程（PE）模型，数值模拟了存在强温跃层时浅水内波包对低频声传播的影响。发现声传输损耗对信号频率敏感，是孤子波长和包长的“共振”函数。声波与内波的强相互作用，以及沿海地区内波的已知特征，为夏季观测到的异常声传播提供了合理的解释。通过将PE码得到的声场分解为正模，分析了异常大的传输衰减是由与内波相互作用造成的“声模耦合”损失引起的。结果表明，PE分析预测的传输损耗的“类共振”行为与模耦合理论是一致的。作为一个逆问题，低频声学测量可以成为沿海地区内波活动遥感的潜在工具。
Naturally occurring internal solitary wave trains (solitons) have often been observed in the coastal zone, but no reported measurements of such solitary waves include low-frequency long-range sound propagation data. In this paper, the possibility that internal waves are responsible for the anomalous frequency response of shallow-water sound propagation observed in the summer is investigated. The observed transmission loss is strongly time dependent, anisotropic and sometimes exhibits an abnormally large attenuation over some frequency range. The parabolic equation (PE) model is used to numerically simulate the effect of internal wave packets on low-frequency sound propagation in shallow water when there is a strong thermocline. It is found that acoustic transmission loss is sensitive to the signal frequency and is a "resonancelike" function of the soliton wavelength and packet length. The strong interaction between acoustic waves and internal waves, together with the known characteristics of internal waves in the coastal zone, provides a plausible explanation for the observed anomalous sound propagation in the summer. By decomposing the acoustic field obtained from the PE code into normal modes, it is shown that the abnormally large transmission attenuation is caused by "acoustic mode-coupling" loss due to the interaction with the internal waves. It is also shown that the "resonancelike" behavior of transmission loss predicted by the PE analysis is consistent with mode coupling theory. As an inverse problem, low-frequency acoustic measurements could be a potential tool for remote-sensing of internal wave activity in the coastal zone.