海洋环流与波动重点实验室知识库

内重力波是海洋中普遍存在的现象，发生在海洋中的层结水体中。其频率在f<σ 的范围内，其中f是局地科氏频率，N是浮力频率。根据内重力波的特征和形成原因，在海洋中被分为内潮、近惯性波和孤立波等。西北太平洋作为近惯性振荡的高发区域，科研意义十分重要。然而，由于缺乏观测资料，目前人们对近惯性波的传播机制，其受到背景环境的影响仍然了解很少。本文应用在西北太平洋的潜标数据以及在南海北部的着陆器数据，结合ARGO的温盐数据、卫星的海表高度计数据以及台风的气象数据，对单台风影响下的近惯性振荡信号、多台风影响的近惯性振荡信号，以及对非台风影响的近惯性振荡信号进行分析。解释了西北太平洋以及南海海域的近惯性振荡的信号特征。

通过对西北太平洋三次单台风影响的近惯性振荡现象的特征进行了分析，我们发现：三次近惯性振荡的垂向群速度比前人的研究结果小，同时近惯性流具有高垂向波数的特征。经过理论推导发现，高垂向波数对应小的垂向群速度，这解释了为什么此处垂向群速度比较小。三个近惯性振荡信号发生红移现象，同时红移出现在EOF第一第二模态，第三和第四模态的分解结果却呈现出蓝移的特征。通过与非台风期间的近惯性振荡信号EOF分解结果进行对比，发现台风在此处可以激发EOF前两模态的近惯性振荡信号，三四模态的近惯性振荡信号是在台风期间增强的局地近惯性信号。

对此区域六次台风影响下的近惯性振荡信号分析，发现在台风未激发近惯性振荡时，近惯性振荡生成于台风最接近潜标日期的两天之后。但是当近惯性振荡已经生成，新的台风可以在距离最近日期之前增强近惯性振荡。对比于单次台风的效应，该海域在受到多台风影响之后能量可以下传到更深的位置。

对着陆器流场进行分析，发现南海具有强烈的半日分潮和全日分潮信号。此处的近惯性信号比潮汐信号小一个量级，但是存在一支传到600米水深以下的蓝移强近惯性振荡信号。该信号强度与潮信号同量级，持续时间从11月3日至16日。谱分析发现垂向流速呈现出五个不同的流核，最强流核发生在600米至650米位置。近惯性能量下传速度为67±5 m d^-1，从600米下传到1000米的位置能量耗散18%。EOF分解结果显示，这次近惯性振荡信号开始是第一模态占主导，随后不稳定变成高阶模态。卫星的海表高度异常显示此时的正涡度有利于此次近惯性振荡发生蓝移。

Internal gravity waves are common phenomenon in the ocean. They occur in stratified waters, with the frequency in the range of f < σ < N, where f is the local Coriolis frequency and N is the buoyancy frequency. According to the characteristics and formation causes of the internal gravity wave, the wave is divided into internal tide (IT), near inertial wave (NIW) and solitary wave (SW). As the northwestern Pacific Ocean is high-incidence of the typhoon and mesoscale eddy, scientific research here is very important. However, due to the lack of observational data, the current mechanisms of transmission of NIWs, which are affected by water feature, are still poorly understood. The mooring data in the Northwest Pacific and the lander data in the northern part of the South China Sea were applied in this paper. Combined with the temperature data, salinity data by ARGO, the sea surface altimeter data by satellites and the typhoon meteorological data, the NIW signal influenced by one single typhoon and the multiple of five typhoons. The NIW signal in the deep water are analyzed in this research. The signal characteristics of NIW in the South China Sea and the Northwest Pacific Ocean are explained.

By analyzing the characteristics of the NIWs affecting the three typhoons in the western North Pacific, we find that the vertical group velocity of the three NIWs is smaller than that of the previous studies. Near inertial current has the characteristics of high vertical wavenumber. After theoretical analysis, we find that the high vertical wave number corresponds to a small vertical group velocity, which explains that the vertical group velocity is relatively small here. The three NIW signals are red-shifted. The red shift occurs in the first and second modes of EOF, and the third and fourth modes exhibit a blue-shifting. Since the NIW signals during non-typhoon are blue-shifted. Therefore, the typhoon can excite the NIW signal of the first two modes of EOF, and the near-inertial oscillation signal of the three-four mode is resonantly enhanced during the typhoon.

The analysis of the NIW signal under the influence of six typhoons in this area shows that when NIW signal is not exist, near-inertial oscillations were generated two days after the date during the typhoon was closest to of the mooring. But when NIW signal is exist, the new typhoon can enhance NIW before the closest date. Compared to the effect of a single typhoon, the energy can be transmitted to a deeper position after being affected by multiple typhoons.

Analysis of the lander flow field revealed that the South China Sea has a strong diurnal tide and semidiurnal tide signal. The near-inertial signal here is one order of magnitude smaller than the tidal signal, but there is a blue-shifted near-inertial oscillation signal that passes below 600 meters of water depth. The signal strength is of the same magnitude as the tidal signal and lasts from November 3 to 16. Spectral analysis revealed that the vertical flow rate exhibited five different current cores, with the strongest current cores occurring between 600 and 650 meters. The near-inertial energy transmission speed is 67±5 m d^-1, and the energy dissipation from the 600-meter to the 1000-meter position is 18%. The EOF analysis results show that the NIW signal begins to dominate the first mode, and then becomes unstable to become a higher-order mode. Combined with the typhoon information, we found that the cause of the NIW signal was not caused by the typhoon. The sea surface height anomaly of the satellite data shows that the positive vorticity is favorable for the blue shift of the NIW during this time.

目录

第一章 绪论. 1

1.1 海洋中的近惯性振荡现象. 1

1.2 海洋对热带气旋的响应. 2

1.3 近惯性振荡的生成、发展及耗散过程. 4

1.4 近惯性的研究意义. 9

1.5 本研究主要解决的问题. 12

第二章 数据介绍、方法介绍和近惯性振荡的理论推导. 15

2.1 数据介绍. 15

2.1.1 AVISO卫星数据. 15

2.1.2 台风数据介绍. 16

2.1.3 南海着陆器数据介绍. 17

2.1.4 潜标观测数据介绍. 19

2.1.5 温度/盐度剖面浮标. 22

2.2 方法介绍. 23

2.2.1谱密度估计. 23

2.2.2 带通滤波. 25

2.2.3 经验正交函数分析. 26

2.2.4 旋转谱分析. 27

2.3 近惯性振荡的理论推导. 29

2.3.1 近惯性振荡的垂直模态. 29

2.3.2近惯性振荡能量传播的群速度. 33

2.3.3 近惯性振荡垂向群速度与水体层化的关系. 34

2.3.4 近惯性振荡的频移现象. 34

第三章 台风影响下的西北太平洋的近惯性振荡特征. 37

3.1 单台风影响的近惯性振荡. 37

3.1.1 台风基本情况. 37

3.1.2 三次台风期间的流场特征. 40

3.1.3 近惯性振荡信号分析. 47

3.1.4 结果讨论. 61

3.2多次台风引起的近惯性振荡. 67

3.2.1 近惯性振荡期间的流场特征. 67

3.2.2 六次台风的基本信息. 68

3.2.3 近惯性流特征. 71

3.3 本章小结. 74

第四章 非台风影响的近惯性振荡特征分析. 77

4.1着陆器期间的海底水文要素分析水体特征. 77

4.1.1 海底的温盐数据. 77

4.1.2 背景流数据. 80

4.1.3 背景环境下的浮力频率. 83

4.2 流场的振动特征. 84

4.2.1 顺时针和逆时针的功率谱密度. 84

4.2.2 各个频率内波的振动特征. 86

4.3 11月份强近惯性振荡的特征分析. 90

4.3.1 强近惯性振荡期间背景流特征. 90

4.3.2 近惯性流场特征分析. 91

4.3.3近惯性振荡的垂向模态. 93

4.3.4 秋季强近惯性振荡信号的生成原因与位置. 95

4.3.5 近惯性振荡蓝移原因分析. 96

4.4内潮与近惯性振荡的非线性相互作用. 97

4.4.1 非线性波波相互作用理论基础. 97

4.4.2 波动的垂向剪切. 98

4.4.3 fM2次级波动的垂向结构. 102

4.5 本章小结. 104

4.5.1 600米以下内波与近惯性信号的相互作用. 104

4.5.2 南海11月份近惯性振荡特征. 106

第五章 结论与展望. 109

5.1 研究工作总结. 109

5.2 今后的工作展望. 110

参考文献. 111

致谢. 123

个人简历. 127

已发表文章. 127