A numerical study of the generation mechanism of internal solitary waves in the Luzon Strait
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摘要: 中国南海由于地势环境的复杂性, 成为海洋内波的多发区, 其中中国南海北部大部分内波发源于吕宋海峡。本文通过调制不稳定探讨吕宋海峡内波生成机理。依据完全非线性薛定谔方程, 推导内潮波调制不稳定性的增益。从层化、内潮波的波长和初始振幅等方面计算了内潮波在吕宋海峡处增益峰值的变化, 从而分析吕宋海峡区域内潮波调制不稳定性的特点, 发现了吕宋海峡内潮波演变成内孤立波的条件。研究结果表明:内潮波在吕宋海峡处能够产生调制不稳定性, 其增益的峰值发生在东部山脊处, 内潮波在此处获得最大增益, 开始分裂成孤立波列。峰值增益的大小和范围与层化、内潮波初始条件有关。数值计算结果与实际观测结果吻合。
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关键词:
- 调制不稳定性 /
- 增益 /
- 海洋内波 /
- 完全非线性薛定谔方程 /
- 吕宋海峡
Abstract: The South China Sea (SCS) is a hot spot for oceanic internal solitary waves due to many factors, such as the complexity of the terrain environment. The internal solitary waves in the northern SCS mainly originate in the Luzon Strait. The generation mechanism of the internal solitary waves in the Luzon Strait is discussed using a modulation instability. The energy gain of the modulation instability is derived based on the fully nonlinear Schrödinger equation. The peak value of the gain is calculated under different conditions of stratification, wavelength and the initial amplitude of an internal tidal wave. The characteristics of the modulation instability in the Luzon Strait are investigated. The conditions that make the internal tidal wave evolve into an internal solitary wave in the Luzon strait are also obtained. The results show that the internal tide waves can generate the modulation instability in the Luzon Strait and that the maximum gain occur at the eastern sill of the Luzon Strait, where the internal tide waves start to break up into internal solitary trains. The magnitude and the scope of the peak gain are relevant to the stratification and the initial conditions of the internal tide waves. The numerical simulation results are consistent with the in-situ data.-
Key words:
- modulation instability /
- energy gain /
- internal solitary wave /
- fully nonlinear Schrö /
- dinger equation
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