海洋环流与波动重点实验室知识库

内潮（斜压潮）是发生在稳定层化海洋中潮频段的内波，由正压潮流与海脊、岛弧、海沟等复杂海底地形相互作用生成。内潮破碎引起的跨等密度面混合是大洋子午环流维持和变异的关键驱动因子。西北太平洋具有全球最典型的脊-沟-弧-盆复杂海底地形结构，也是全球最强的内潮发生区之一，对该海域内潮能量学和动力学的研究对于理解该海域海洋多尺度能量串级具有重要意义。本文基于精细化数值模拟，系统研究了西北太平洋主要是菲律宾海海盆半日内潮和全日内潮能量生成、辐射及耗散过程。

基于三维精细化数值模型揭示了西北太平洋半日M2内潮长距离能量传递和多源内潮波干涉过程，给出了西北太平洋多源M2内潮能量传递路径图。研究发现，除吕宋海峡外，位于第一岛链的琉球群岛和位于第二岛链的马里亚纳岛弧及小笠原海脊都是内潮强源区，首次揭示了位于海盆内部的局地源区（大东群岛和帕劳海脊）。发现源自多源区的第一模态内潮和第二模态内潮可在菲律宾深海海盆长距离传递并相互干涉形成复杂内潮场，使得斜压能量场呈现非常强的不均一特性。重点分析了两个多源内潮干涉过程，其中吕宋海峡和南琉球岛链宫古海峡的内潮干涉产生几支东南方向的增强能通量分支，这与之前的高度计观测结果一致。而源自吐噶喇海峡和小笠原海脊的内潮波干涉形态则受到局地源区和地形的显著影响，呈现出多尺度空间分布特征。半日内潮在源区和深海海盆都有显著能量耗散，干涉过程导致的强能通量分支对应了较强的局地耗散，对于海盆内部的局地混合具有重要贡献。

通过潮-流耦合数值模拟，进一步研究了西北太平洋菲律宾海海域复杂背景层结和环流条件下全日K1内潮能量辐射传递过程，发现全日内潮源区分布显著区别于半日内潮，吕宋海峡和桑托斯海峡是菲律宾海两个主导源区，而在小笠原海脊-马里亚纳岛弧全日内潮生成则很弱。在全日内潮临界纬度的伊豆海脊和吐噶喇海峡也有相对显著的全日内潮信号生成。来自吕宋海峡的全日内潮能量可以长距离传递超过2500公里并跨越马里亚纳岛弧。全日内潮传递过程中受到地转效应，出现显著的向赤道偏折现象。吕宋全日内潮和桑托斯海峡全日内潮在马里亚纳西侧海盆相遇并相互干涉，形成向东南方向传播的能量通量分支。全日内潮干涉增强分支同样对应了较强的局地耗散，进一步说明了干涉过程对多频段内潮能量耗散分布的重要作用。

建立了线源波动理论模型，成功再现了半日M2内潮多源干涉形态，通过在线源波动模型加入科氏效应，成功模拟出了全日K1内潮的干涉过程和向赤道偏转现象，从而在理论上解释了多源内潮干涉过程和科氏效应对于内潮能量传递路径的关键作用。建立了射线追踪理论模型，研究了背景环流场对全日内潮辐射路径的调制作用，发现黑潮、北赤道流系等能够显著影响全日内潮的传递路径。

Internal tides (baroclinic tides) are internal waves within the tidal frequency band and they are generated by barotropic tidal currents flowing over rough topographic feature such as such as mid-ocean ridges, seamounts and trenches. The diapycanal mixing caused by internal tide is a key driving factor for the maintenance and variation of the oceanic meridional circulation. The northwestern Pacific Ocean has the most typical ridge-trench-arc-basin topography features in the world oceans. It is also one of the strongest internal tide occurrence areas. The study of the energetics and dynamics of internal tides could lead to the in-depth understanding of the multi-scale energy cascade in this area. Based on high-resolution numerical simulation, this paper systematically studies the generation, radiation and dissipation processes of tidal energy in the northwestern Pacific Ocean (mainly in the Philippine Sea).

Long-range radiation and interference of M2 internal tides from multiple sources in the Northwestern Pacific are examined by driving a high-resolution numerical model. The M2 internal tides are effectively generated around the boundary area of the Philippine Sea basin, which includes the Luzon Strait, Ryukyu Island chain, Bonin Ridge, Mariana Arc and Izu Ridge, favouring the occurrence of complex interference patterns. The mode-1 and mode-2 M2 tidal beams from boundary sources radiate a long distance into the basin but exhibit different interference-modulated geography variations. Two notable interference cases are investigated: 1) the superposition of internal tides from Luzon Strait and Miyako Strait bifurcates into several southeastward beams, consistent with previous numerical simulations and altimeter measurements, and 2) the interference between Tokara Strait and Bonin Ridge exhibits a multi-scale spatial pattern, which is modulated by the local generated energy and bathymetry features. Energetic dissipation occurs both near the boundary sources and in the basin. Enhanced dissipation is found to coincide closely with the interference-modulated flux field in the deep basin.

We further study the diurnal internal tide radiation process under subtidal backgrounds circulation in the Northwestern Pacific. It is found that the distribution of generation sites of the diurnal internal tide is significantly different from the semi-diurnal tide. The Luzon Strait and the Santos Strait are the two dominant source of the Philippine Sea, while the tide generation in the Bonin ridge-Mariana Island Arc is weak. There are also relatively significant diurnal tide signals in the Izu ridge and the Tokara Strait which exceed the critical latitude of the diurnal internal tide. The diurnal internal tide energy from the Luzon Strait can propagate over 2500 kilometers, even crossing over the Mariana Island arc. Due to the effects of earth rotation, the diurnal internal tides tend to bend equatorward notably during the propagation. The diurnal internal tide from Luzon Strait and Santos Strait encounter in the basin of the western Mariana basin and interfered with each other, forming southeastwardly branches of energy flux. The enhanced branches also correspond to strong local dissipation, further illustrating the important role of the interference process in the multi-band internal tide energy dissipation distribution.

The theoretical line-source model is established, and the multi-source interference pattern of semidiurnal internal tide is successfully reproduced. The earth rotation effect is then added into the line-source model. The interference process and bending equatorward phenomenon of the diurnal internal tide are also well reproduced. The important roles of interference process and the Coriolis effect in the internal tide energy propagation are therefore theoretically explained. The modulation effect of the background circulation field on the diurnal internal tide radiation path is studied by conducting the ray tracing theory model. It is found that the Kuroshio, the northern equatorial current system and the Mindanao eddy can significantly affect the transmission path of the diurnal internal tide.

摘  要... II

Abstract IV

第1章  引言... 9

1.1  研究背景及意义... 9

1.2 研究现状... 12

1.2.1 全球海洋内潮研究进展... 12

1.2.2 西北太平洋内潮研究现状... 15

1.3 科学问题的提出... 19

第2章 理论和模型介绍... 21

2.1 线性内波理论... 21

2.2 内潮生成理论... 23

2.3 内波本征方程... 25

2.4 斜压能量方程... 29

2.5 模式介绍... 30

第3章 西北太平洋半日M2内潮的长距离辐射及干涉过程... 33

3.1  引言... 33

3.2  方法... 35

3.2.1 模型设置... 35

3.2.2 模态分解方法... 36

3.2.3 模型验证... 37

3.3  模式结果分析... 39

3.3.1 M2内潮的多源区分布... 39

3.3.2 内潮传播和能量通量整体形态... 41

3.3.2 多源内潮干涉过程... 46

3.3.3 M2内潮能量耗散... 51

3.4 本章总结与讨论... 56

3.5模拟的内潮对各种模式参数的敏感性... 59

第4章  西北太平洋环流调制下的全日K1内潮能量辐射过程... 61

4.1 引言... 61

4.2  方法介绍... 62

4.2.1 模式区域选择... 62

4.2.2 Data-driven 数值模拟... 63

4.2.3 改进的线源波动模型... 63

4.2.4 模式有效性验证... 64

4.3 模拟结果分析... 67

4.3.1 全日K1内潮生成与传递的整体形态分布... 67

4.3.2 多源内潮波相互干涉... 71

4.3.3 低频背景场和层化对内潮能量传递的调制... 74

4.3.4 背景层化和环流下的全日K1内潮射线追踪... 75

4.3.5 全日K1内潮能量耗散过程... 77

4.3 本章总结与讨论... 78

第5章  结论和展望... 81

5.1 本文的主要结论... 81

5.3 本文的主要创新点... 82

5.3 未来工作展望... 82

参考文献... 85

致  谢... 97

作者简历及攻读学位期间发表的学术论文与研究成果    99