海洋环流与波动重点实验室知识库

       内潮在层化海洋中普遍存在， 它是由正压潮流与大陆坡， 海脊，海底峡谷等复杂海底地形相互作用产生。内潮的破碎和耗散会在局地和深海海盆引起强垂向混合，这对维持经向翻转环流起着重要作用。背景环流通过改变层结，调制着内潮的生成和传播。由于背景环流场存在着不同时间与空间尺度的信号，内潮在其调制作用下也会存在时空变化。我们通过高分辨率的三维数值模式来研究在印太环流系统的影响下， M2 内潮的能量收支与辐射路径的变化。同时，我们进一步研究内潮不同时间尺度的演化与变异，并探讨局地耗散效率q的季节与年际变化。

       我们利用高精度数值模式， 揭示了在台湾东北海域黑潮调制作用下，M2 内潮的能量收支和演化过程。研究发现，内潮生成在大陆坡的陡峭地形，特别是 ILan 海脊和 Mien-Hua 峡谷处，这两个海域首次被确定为 M2 内潮的生成源区。黑潮通过调制层结分布影响着 M2 内潮能量的生成。当模式的初始场考虑黑潮时，与水平均一的理想层结的模拟结果相比， I-Lan 海脊处生成的斜压能量降低了约30%，而在 Mien-Hua 峡谷和北部陆坡提高了约 10%。来自多个源区的内潮发生相互干涉，形成一个复杂、 不均匀的三维斜压场。 在 I-Lan 海脊生成一束南向、逆黑潮传播的能量射线，并且能量沿等深线的方向辐射。复杂的地形特征和背景环流增强了内潮的能量耗散。

       印尼海域内潮和印尼贯穿流（ITF）之间的相互作用过程并不为人所知。在该海域，我们围绕印尼龙目海峡进行了一系列高分辨率的数值模拟，探讨了在ITF 调制作用下，龙目海峡区 M2 内潮的时空变化。龙目海峡内潮在 ITF 背景层结和流场调制作用下呈现出南北不对称性。同时由季风和 ITF 引起的表层盐度变化调制 M2 内潮能量的季节信号； 由 ITF 和 El Niño 调制海气淡水通量进而影响局地层化， 使得内潮的生成和耗散存在年际变化。局部耗散效率 q 表现出明显的季节和年际信号， 这会对低纬度赤道的海洋气候过程提供有效的反馈。

       我们进一步研究了印尼-澳大利亚海盆海域 M2 内潮在南赤道流系影响下能量辐射传递过程。 我们通过高精度数值模式发现，该海域 M2 内潮在多个源区生成， 包括龙目海峡、帝汶周边海区和澳大利亚西北陆架。在龙目海峡附近，印尼贯穿流调节了 M2 内潮生成的斜压能量， 其能量通量在南向辐射过程中受南赤道流折射效应发生偏折，并且可以穿过南赤道流后传播超过 500 公里，最终到达澳大利亚的西北陆坡。来自澳大利亚西北陆架的内潮能量向深海海盆传播，并且与来自龙目海峡的内潮发生相互干涉。背景流场和多源区干涉作用会增加内潮的能量耗散，导致在海盆内部形成空间不均匀能量耗散场。

    Internal tides are ubiquitous in the stratified ocean where barotropic tidal currents flow over various topographical features, including continental slopes, sea-mountains, ridges and submarine canyons. Internal tidal breaking and dissipation can induce strong diapycnal mixing both in local rough topographical features and deep basin areas, which is found to play an important role in sustaining global meridional overturning circulation. The background subtidal currents modulate the horizontally varying stratification, which could influence the generation and propagation of internal tides. The subtidal circulation fields vary significantly on different spatiotemporal scales, so their interactions with internal tides may change in time and space. We use a highresolution numerical model to investigate the variability of M2 internal tides during their generation and propagation through the Indo-Pacific circulation system. We further detect the variability of internal tide evolution in different time scales. Special attention is directed to the seasonal and interannual variability of the local dissipation efficiency  q.

    The variability and energetics of M2 internal tides during their generation and propagation through the Kuroshio flows northeast of Taiwan are investigated using a high-resolution numerical model. The corrugated continental slopes, particularly the ILan Ridge and Mien-Hua Canyon, are first identified as the energetic sources of M2 internal tides. The M2 internal tide generation is influenced by horizontally varying, zonally tilting stratification associated with the Kuroshio. In this situation, the conversion rate decrease by ~30% at the I-Lan Ridge but increase within ~10% at the Mien-Hua Canyon and north shelf, in comparison to the ideal simulation initiated with horizontal homogeneous stratification. Internal tides from multiple sources interfere to form a three-dimensional baroclinic field. An energetic along-slope tidal beam from the I-Lan Ridge radiates southward, against the northward Kuroshio flows, causing strong vertical displacement. Complex topographic features and background currents enhance the internal tide dissipation, which induces strong, inhomogeneous vertical mixing.

    The interaction between the energetic internal tides in the Indonesian Seas and the Indonesian Throughflow (ITF) is not well known. Here we conduct a series of highresolution numerical simulations surrounding the Lombok Strait, Indonesia, which is an important exit channel for the ITF, to explore the influences of the ITF on the spatiotemporal variations of M2 internal tides generated from the Strait. The ITF enhances the north-south asymmetry of internal tide propagation from the Lombok Strait. Seasonal variations of internal tide generation are associated with the surface salinity variations induced by the monsoon and ITF. Interannual variability of internal tide generation and dissipation are due to ITF and air-sea freshwater flux induced stratification variations associated with El Niño-Southern Oscillation. The local dissipation efficiency q exhibits substantial seasonal and interannual variations, which may provide effective feedback to the climate processes in the low-latitude equatorial
oceans.
    We further examines the effects of the South Equatorial Current (SEC) system on the generation and propagation of the M2 internal tides. We firstly investigate the dynamics and mechanism of the M2 internal tides in the Indo-Australian (IA) basin based on a high-resolution numerical model. M2 internal tides in the entire basin are originated from multiple source sites, including the Lombok Strait (LS), the region around Timor Island and Australian west shelf (AWS). In the near field of the LS, the Indonesian Throughflow modulates M2 internal tides generated energy. In the mid-field, M2 internal tides are refracted by the SEC system. After propagating across the SEC system, the remaining energy travels into the IA basin over a distance of ~500km and finally arrives at the northwest slope of Australia. Another beam radiated from the AWS can interfere with this long-range beam from the LS, forming an inhomogeneous baroclinic field which can be reproduced by an improved line source model. The influence of the SEC system and multi-sources interference can increase internal tide dissipation, resulting in a nonuniform distribution.

摘 要 .................................................... I
Abstract ............................................... III
第 1 章 引言 ............................................ 1
1.1 内潮及研究意义 ...........................................1
1.2 内潮的研究进展 ...........................................3
1.2.1 内潮的研究方法........................................3
1.2.2 全球海洋内潮研究进展..................................5
1.2.3 台湾东北内潮研究现状..................................8
1.2.4 印尼-澳大利亚海域内潮研究现状........................10
1.3 问题的提出 ..............................................13
第 2 章 ROMS 模式和相关方程介绍......................... 15
2.1 ROMS 模式简介............................................15
2.2 模式控制方程及边界条件 ..................................15
2.2.1 控制方程.............................................16
2.2.2 边界条件.............................................16
2.2.3 网格与随底坐标.......................................18
2.3 能量平衡方程 ............................................20
2.4 内潮混合参数化方案 ......................................21
第 3 章 台湾东北 M2内潮受黑潮调制下的生成与传播 ......... 23
3.1 引言 ....................................................23
3.2 方法 ....................................................25
3.2.1 模式设置.............................................25
3.2.2 模式验证.............................................28
3.3 模式结果分析 ............................................30
3.3.1 M2内潮的能量收支.....................................30
3.3.2 M2内潮的传播路径.....................................33
3.3.3 黑潮对 M2内潮能量收支的影响 ..........................36
3.3.4 内潮的传播变化和多源区干涉...........................40
3.3.5 M2内潮耗散和混合.....................................47
3.4 总结和讨论 ..............................................49
第 4 章 龙目海峡印尼贯穿流对 M2内潮调制作用研究 ......... 51
4.1 引言 ....................................................51
4.2 模式设置 ................................................53
4.3 模式结果分析 ............................................54
4.3.1 M2内潮的源区分布和能量收支...........................54
4.3.2 M2内潮南北不对称分布.................................58
4.3.3 M2内潮的季节变化.....................................59
4.3.4 M2内潮的年际变化.....................................62
4.4 本章总结与讨论 ..........................................63
第 5 章 印尼-澳大利亚海盆南赤道流系对 M2内潮的折射效应 .. 65
5.1 引言 ....................................................65
5.2 模式设置与验证 ..........................................65
5.2.1 模式设置.............................................66
5.2.2 模式验证.............................................66
5.3 模式结果分析 ............................................68
5.3.1 M2内潮的多源区分布...................................68
5.3.2 南赤道流对 M2内潮能量传播的调制作用 ..................71
5.3.3 M2内潮能量的耗散与混合...............................76
5.4 本章总结与讨论 ..........................................78
第 6 章 总结与展望 ..................................... 81
6.1 本文主要结论及创新点 ....................................81
6.2 本文工作展望 ............................................82
参考文献 ................................................ 83
致 谢 ................................................... 99
作者简历及攻读学位期间发表的学术论文与研究成果 ......... 100