海洋环流与波动重点实验室知识库

        热带西太平洋暖池及其周边海域表层和次表层海洋环流复杂、多变，由数支赤道流和西边界流组成的环流系统，直接影响和调制暖池自身变异和暖池区海洋-大气相互作用过程，在全球气候系统中扮演重要角色；同时复杂的环流系统在海洋纬向和经向热量和质量输送、热带印度洋-太平洋水交换、南北半球水交换等过程中均起关键作用。近些年来，基于现场观测资料发现海流的季节内变率在热带西太平洋海流多尺度变异中占有很大贡献，但是对于其中关键物理过程、动力机制目前尚不清晰。因此，开展西太平洋海流季节内变异研究，关注最基础的环流动力学问题，对认识西太平洋环流多尺度变异规律、理解全球海洋热盐循环及物质能量再分配具有重要意义。
        本文基于潜标系统获取的现场观测数据，结合多种海洋模式输出再分析数，以关键区域海流流速为切入点，着眼于上层海流和深层海流两个方面展开研究。吕宋岛以东的三套潜标观测揭示了吕宋岛以东黑潮速度、体积输运和空间结构的季节内变异特征及其机制，指出其空间结构与台湾以东黑潮不同，以经向输运为主，提升了对不同区域黑潮变率结构的认知。基于一套全水深潜标系统观测的流速数据，揭示了菲律宾海全水深海流季节内变异垂向结构，进一步探究了上层和深层海流的季节内变异特征及其相关物理机制。
        首先基于18°N 断面三套潜标系统ADCP 观测数据和HYCOM 再分析数据，本文揭示了吕宋以东黑潮流速和体积输运具有50–60 天和100 天两个显著的季节内变异周期。进一步分析表明吕宋以东黑潮的季节内变率是由黑潮经向输运模态主导的，而非黑潮的纬向迁徙模态。与被认为主要是以纬向迁徙变异为主的台湾以东黑潮截然不同，表明同受中尺度涡旋的调节，但是不同区域黑潮的主要变异结构存在差异。此外根据三套潜标观测在122.7°–123.3°E，0 到50 米层估算得的黑潮体积输运为6.5±2.6 Sv (Sverdrup)。
        结合卫星高度计数据，进一步研究表明来自不同区域的涡旋在吕宋以东黑潮季节内变异中扮演着不同角色。吕宋以东黑潮50–60 天的变率是受产生于大洋内部沿18°N 平行向西传播的涡旋调制，其传播速度约为13 cm/s，周期为56.6 天，波长约为635 km。涡旋的生成机制为北赤道流和副热带逆流系统的斜压不稳定。另一个主要的季节内变率——100 天周期，则是受到生成于北赤道流区域（129°E，15°N）涡旋的调制，其移动路径在背景流场的平流作用下先向西平行传播，随后向西北方向传播至吕宋岛以东。
        对深层海流季节内变率的认知受限于观测资料的缺乏，目前知之甚少。本文基于布放在130°E，11°N 的一套全水深潜标观测数据和GLORYS2V4 再分析数据对此展开研究。以深层海流变异相对显著的经向速度流场展开分析，结果表明菲律宾海海流存在两个主要的季节内变率周期，分别是45 天和62 天，并表现出从海面到海底的正压变异结构。具体表现为250–5000 米的整层海流都具有显著的45 天的变率，在1500 米以上和2500 米以下海流中可见62 天的变异信号。值得注意的是，在深层5000 米处观测到存在较强的季节性波动信号。
        结合卫星高度计数据进一步研究表明，上层海流62 天的季节内变率是受到大洋第一斜压Rossby 波的调制，其纬向波长为684 km。此外，我们发现ENSO事件对西太平洋上层海洋季节内波动有调节作用，体现在2015/16 年和2018/19年厄尔尼诺事件半年之后，在西太平洋的上层海洋分别出现了两次超强的季节内波动。由厄尔尼诺事件主导的正风应力旋度异常激发出的斜压Rossby 波，以负的SLA 信号形式向西传播，从太平洋中东部传到西太平洋，调制西太平洋菲律宾海域上层海洋的季节内变率。
        而对于近乎于全水深存在的45 天季节内变率和深层海洋的62 天变率则主要是受到海盆正压Rossby 模调制。海盆正压模理论表明菲律宾海盆内存在由海盆纬向尺度所决定的固有周期振荡。较为规则的菲律宾海深海海盆，其在11°N东西向宽度为921 km，相应存在约45 天的季节内振荡的正压Rossby 波信号；而在5000 米以下的深海，对应的东西向宽度为640 km，对应深层海洋中62 天的正压Rossby 波波动变率。进一步初探海盆正压Rossby 模态振荡的激发源，发现对于45 天的变率而言，菲律宾海南部区域（126°–140°E，5°–13°N）的风场变率对其更为重要；对于62 天的变率而言，菲律宾海北部（15–20°N）的风场似乎是为海盆内共振的季节内波动提供能量。此外，利用GLORYS2V4 再分析数据对菲律宾海深层海洋经向流速验证表明，整个菲律宾海深层海洋确实存在显著的季节内变率信号，具体周期也有与潜标观测结果比较吻合，因此可确认菲律宾海存在海盆正压Rossby 模态调制的季节内波动。
        综上所述，基于西太平洋两个关键区域的潜标观测揭示了上层和中深层海流季节内变率的特征及其相关物理机制。在靠近西边界区域，吕宋以东黑潮（18°Ｎ，123°E 附近）的季节内变异是受到传播而来的涡旋的调制；而在开阔大洋中（11°N，130°E），上层海洋海流的季节内变异主要是大尺度的Rossby 波主导，海盆内深层海流的季节内变异主要受海盆正压Rossby 波的调制。同时，西太平洋上层海流季节内波动对ENSO 事件存在强的响应，滞后时长为半年。以上结论丰富了我们对西太平洋环流变异规律和驱动机制的认知。

    The surface and subsurface ocean circulation in the western tropical Pacific Ocean and the sea around the warm pool is complex and variable, consisting of several equatorial currents and western boundary currents, which directly influence and modulate the variability of the warm pool itself and the air-sea interaction process in the warm pool, which play an important role in the global climate system and have an impact on the climate environment of Asian. At the same time, the current system plays a key role in the zonal and meridional heat and mass transport of the ocean, the water exchange between the Indo-Pacific tropical water and northern and southern hemisphere water. In recent years, intra-seasonal variability of currents has been found to contribute significantly to the variability of currents in the western tropical Pacific based on in-situ observations. Therefore, it is important to study the intra-seasonal variability of the western Pacific currents to understand the multi-scale variability of the western Pacific current and to understand the global ocean heat and salt variability and material-energy redistribution.
    Based on the in-situ observation data obtained from the mooring system and various ocean models outputs reanalysis data, this study focuses on the upper and deep currents variability of current velocities in key regions. An array of three profiler moorings observations east of Luzon Island revealed the intra-seasonal variability of Kuroshio meridional velocity, volume transport and spatial structure east of Luzon Island and their driven mechanisms, which spatial structure different from that of east of Taiwan Island and is dominated by the meridional transport mode, which enhance the knowledge of the Kuroshio variability structure in different regions. Based on the current velocity data observed by a full-depth mooring system, we revealed the vertical structure of multi-layer currents in the Philippine Sea, and the intra-seasonal variability of upper and deep currents, and their related physical mechanisms are further investigated.
    Based on the ADCP data and HYCOM reanalysis data from three mooring systems at 18°N, this study reveals two significant intra-seasonal variability cycles of 50–60 days and 100 days of the Kuroshio meridional velocity and volume transport east of Luzon Island. Further analysis shows that the intra-seasonal variability of the Kuroshio east of Luzon Island is dominated by the meridional transport mode of the Kuroshio rather than the zonal migration mode. This is different from the Kuroshio east of Taiwan Island, which is thought to be dominated by the zonal migration variability. In addition, the volume transport of Kuroshio at 122.7°–123.3°E, 0–50 m, estimated from three mooring observations was 6.5±2.6 Sv (Sverdrup).
    Combined with satellite altimeter data, further investigation shows that eddies of different regional play different roles in the intra-seasonal variability of the Kuroshio east of Luzon Island. The 50–60-day variability of the Kuroshio east of Luzon Island is modulated by eddies generated in the open ocean along the 18°N parallel to the west with a propagation speed of about 13 cm/s, a period of 56.6 days, and a wavelength of about 635 km. These eddies are generated by the baroclinic instability of the North Equatorial Current and the Subtropical Countercurrent system. The other major intra-seasonal variability, the 100-day period, is modulated by eddies generated in the North Equatorial Current regions (129°E, 15°N), which first propagates parallel to the west and then move northwest to the east of Luzon Island under the advection of the background flow field.
    Intra-seasonal variability of deep currents was studied based on one near full-water depth mooing observations deployed at 130°E, 11°N from September 19, 2015 to October 22, 2019, and GLORYS2V4 reanalysis data. The results show that there are two major intra-seasonal variability period in the Philippine sea, 45 and 62 days, respectively, which exhibit a barotropic structure from the surface to the bottom. Specifically, the whole layer of currents from 250–5000 m has a significant 45-day variability, and a 62-day variability signal shown above 1500 m and below 2500 m layers. It is noteworthy that there has a strong intra-seasonal fluctuation at the depths of 5000 m.
    Further studies combined with satellite altimeter data indicate that the 62-day intra-seasonal variability of the upper ocean current is modulated by the first baroclinic Rossby wave with a zonal wavelength of 684 km. In addition, the ENSO events have a significant effect on the intra-seasonal fluctuations of the upper ocean in the western Pacific. There are two super-strong intra-seasonal fluctuations in the western Pacific upper ocean, lagging the 2015/16 and 2018/19 El Niño events by 6 months, respectively. The baroclinic Rossby waves, excited by the positive wind stress vorticity anomaly in the eastern Pacific dominated by the El Niño event, propagate westward in the form of a negative SLA signal from the east-central Pacific to the western Pacific, modulating the intra-seasonal variability of the upper ocean in the Philippine Sea of the western Pacific.
    The 45-day intra-seasonal variability present near full water depth and the 62-day variability in the deep ocean are mainly modulated by the barotropic Rossby mode in the basin. The intrinsic oscillation period in the Philippine basin depends on the actual topography. The more regular deep ocean basin in the Philippine Sea, with an east-west width of 900 km, excites the barotropic Rossby wave signal with about 45 days of intra-seasonal oscillations, while in the deep ocean below 5000 m, the corresponding basin has an east-west width of 640 km, which corresponds to 62 days of barotropic Rossby wave fluctuation variability in the deeper ocean. The trigger source of the basin barotropic Rossby mode oscillations in the deep ocean basin is further investigated, and it is found that for the 45-day variability, the wind field variability in the southern Philippine Sea region (126°–140°E, 5°–13°N) is more important. For the 62-day variability, the wind field in the northern Philippine Sea (15°–20°N) seems to be energizing the intra-seasonal fluctuations of resonances within the basin. In addition, verification of the deep ocean meridional flow velocity in the Philippine Sea using GLORYS2V4 reanalysis data shows that there is indeed a significant intra-seasonal variability signal throughout the deep ocean, and the period is in good agreement with the mooring observations, thus confirming the existence of intra-seasonal fluctuations of the basin barotropic Rossby mode modulation in the Philippine Sea.
    In summary, the mooring observations in two key regions of the western Pacific Ocean revealed the characteristics of the intra-seasonal variability of different layers of currents and their associated physical mechanisms. Near the western boundary, the intra-seasonal variability of the Kuroshio east of Luzon Island (18°N, 123°E) is modulated by the propagating eddies, while in the open ocean (11°N, 130°E), the intra-seasonal variability of the upper ocean currents is mainly dominated by large-scale Rossby waves, and the intra-seasonal variability of the deep currents in the basin is mainly modulated by the basin barotropic Rossby modes. Meanwhile, the intra-seasonal fluctuations of the western Pacific upper ocean currents respond to ENSO events with a lag time of six months.

第1 章 绪论 ............................................................................................ 1
1.1 研究背景和意义 ................................................................................................. 1
1.2 研究现状 ............................................................................................................. 3
1.2.1 上层海洋海流变率 ...................................................................................... 3
1.2.2 深层海洋海流变率 ...................................................................................... 7
1.3 科学问题的提出 ................................................................................................. 8
1.4 本文主要研究内容及章节安排 ......................................................................... 9
第2 章 数据和方法 ............................................................................. 11
2.1 数据资料 ........................................................................................................... 11
2.1.1 18°N 断面潜标观测 ................................................................................... 11
2.1.2 130°E，11°N 深海潜标观测 ..................................................................... 13
2.1.3 HYCOM 再分析数据 ................................................................................. 14
2.1.4 GLORYS2V4 再分析数据 ......................................................................... 15
2.1.5 卫星高度计数据 ........................................................................................ 16
2.1.6 其他数据集 ................................................................................................ 16
2.2 研究方法 ........................................................................................................... 16
2.2.1 输运体积计算 ............................................................................................ 16
2.2.2 海盆正压Rossby 模理论 .......................................................................... 17
2.2.3 常规分析方法 ............................................................................................ 18
第3 章 吕宋岛以东黑潮的季节内变异 .............................................20
3.1 潜标ADCP 观测结果 ...................................................................................... 20
3.1.1 吕宋以东黑潮结构 .................................................................................... 20
3.1.2 经向速度的季节内变率 ............................................................................ 22
3.1.3 体积输运特征以及其变率 ........................................................................ 25
3.2 HYCOM 再分析数据结果 ................................................................................ 28
3.2.1 完整黑潮结构 ............................................................................................ 28
3.2.2 经向速度的季节内变率 ............................................................................ 30
3.2.3 黑潮输运及其变率 .................................................................................... 31
3.3 吕宋岛以东黑潮主要变率——经向输运模态 ............................................... 34
3.3.1 经向输运模态和纬向迁徙模态 ................................................................ 34
3.3.2 吕宋以东黑潮与台湾以东黑潮的主导模态对比 .................................... 39
3.4 季节内变率机制 ............................................................................................... 41                
3.4.1 吕宋以东黑潮50–60 天季节内变率 ........................................................ 42
3.4.2 吕宋以东黑潮100 天季节内变率 ............................................................ 46
3.5 本章总结 ........................................................................................................... 49
第4 章 菲律宾海全海深环流的季节内变率 .....................................51
4.1 潜标观测结果 ................................................................................................... 51
4.2 速度季节内变率特征 ....................................................................................... 55
4.3 机制讨论 ........................................................................................................... 57
4.3.1 上层62 天变率机制 .................................................................................. 57
4.3.2 全水深45 天变率机制 .............................................................................. 61
4.3.3 深层海流62 天变率机制 ......................................................................... 66
4.3.4 海盆Rossby 正压模触发源 ...................................................................... 67
4.4 海盆正压Rossby 模在菲律宾海盆的适用性 ................................................. 68
4.5 西太平洋季节内振荡对ENSO 的响应 .......................................................... 71
4.6 本章总结与讨论 ............................................................................................... 74
4.6.1 本章小结 .................................................................................................... 74
4.6.2 存在问题 .................................................................................................... 75
第5 章 总结与展望 .............................................................................76
5.1 主要结论 ........................................................................................................... 76
5.2 本文创新点 ....................................................................................................... 78
5.3 对未来工作的展望 ........................................................................................... 78
参考文献 ...................................................................................................81
致 谢 .......................................................................................................91
作者简历及攻读学位期间发表的学术论文与其他相关学术成果 ......94