海洋环流与波动重点实验室知识库

海洋涡旋对全球大洋内部温盐能量的传播起着至关重要的作用，并且是连接大尺度环流和小尺度湍流的重要纽带。本文首先利用卫星高度计Chelton涡旋数据集和浮标漂流轨迹Argos探测的涡旋轨迹，对于全球1993年至2015年的海洋涡旋进行了特征信息（半径、生命周期等）的分析对比，比对结果表明，高度计涡旋数据集提供的欧拉涡旋和浮标漂流轨迹Argos探测的拉格朗日涡旋的配对成功率在全球范围内空间分布上波动较为明显，在南北半球中纬度地区内（20~60度）两种不同数据源的涡旋配对成功率为最大值，最大可达25%，反观在低纬度海区内两种不同数据源的配对成功率普遍低于10%。由于地转效应引发的科氏力在低纬度海区内趋近于零值，因而在该处采用卫星高度计将无法有效对涡旋进行信息提取，造成高度计提取的欧拉涡旋的数据缺失。但在近赤道海区内，漂流浮标Argos轨迹识别出的拉格朗日涡旋依旧大量存在，并不受地转科氏力趋近于零的影响。这说明在近赤道海区内，采用漂流浮标Argos手段提取的涡旋信息，可以非常有效的填补卫星高度计在该海区识别提取涡旋的限制。对这两种不同数据源的匹配成功的涡旋信息进一步比对分析，我们发现总体上在全球海洋内，利用高度计提取的欧拉涡旋半径普遍大于对应匹配的Argos拉格朗日涡旋闭合回路半径，而两种数据源探测的涡旋（闭合回路）在太平洋内部海区、大西洋内部海区等区域内半径基本差别不大；但是在靠近赤道海区、中高纬度西边界强流海域和靠近极地的高纬度海域，欧拉涡旋半径可达对应匹配的拉格朗日涡旋闭合回路半径的三倍或更多。此外，对两者匹配涡旋的涡旋内部平均Rossby数的统计分析表明，通常拉格朗日涡旋内面积越小的漂流浮标闭合轨迹对应较高的涡旋平均相对涡度，表明Argos浮标在被海洋当中已经存在的中尺度涡俘获之后，更容易在中尺度涡内部相对涡度较高的区域内（如中尺度涡旋中心和边缘带区域等）形成漂流浮标轨迹的闭合。

进一步我们将研究区域集中在东海黑潮区域，漂流浮标和模式输出结果表明黑潮两侧产生的涡旋绝大多数位于黑潮边界之外，其生命周期远远短于大洋内部的涡旋，半径集中分布在200km以内。此处涡旋的半径和生命周期近似成正比例关系，且涡旋Rossby数越大，对应半径越小、生命周期越短。且基本位于上50m水层左右，且半径随着水深增加而减小，呈现碗状结构，并随着时间推移涡旋沿着黑潮向下游移动。

此外通过对台湾东北海域的一套从2017年5月开始近一年的潜标声学多普勒海流剖面仪(ADCP)测流数据，结果表明，该海区正压潮流以半日潮流占主导地位，以M₂分潮为主，在该处半日内潮明显强于全日内潮能量，且半日能量有较为明显的季节变化，冬半年半日内潮能量超过夏半年内潮能量的两倍。为了研究造成内潮季节变化的原因，我们发现该处相对于夏半年，在地形不变的情形下，在冬半年正压振幅和海水层结都有减弱，这原本应该导致该处内潮能量在冬半年较小。进一步研究表明，由于潜标位置台湾东北部涡旋的影响，在夏半年主要受到气旋涡控制，背景流速主要朝西南方向，沿着等深线流动；而在冬半年主要受到反气旋涡旋控制，背景流速朝西北方向，垂直于等深线流动，在跨越等深线时，通过正压潮和地形的相互作用产生内潮，导致该处在冬半年内潮能量增强。

Oceanic eddy plays an inmportant role in transportation of mass, energy in the ocean, which is a connection of large scale currents to small scale turbulence. In this paper, based on the eddy data set released by Chelton and the buoy drifting trajectory from 1993 to 2015, we match the Euler eddy extracted from satellite altimeter and Lagrange eddy extracted from buoy drifting trajectory in the same period. The paired-eddy indicates that the pairing success rate of the Euler eddies and the Lagrange eddies is not uniform in the spatial and time distribution. Between 20 and 60 degrees in both north and south latitudes, the eddy pairing success rate reaches 25%, but in the equatorial region, this value is less than 10%.  Due to the Coriolis effect in the low latitude area is insignificant, the satellite altimeter observations could not be effective to the Euler eddy; however, the Lagrange eddies identified by the buoy trajectory are abundant, which indicates that the eddy observation by the drifting buoy in the low latitude region could effectively overcome the area limitation of the satellite altimeter observation. Upon further analysis, the Euler eddy radius (closed loop) is generally larger than that of the paired Lagrange eddy. The eddy radius obtained by the two identification methods is roughly equivalent inside the ocean, but between 20 degrees in the north and south of the equator (especially near the equatorial region), high latitude regions, and western boundary current regions, the Euler eddy radius is more than triple the radius of the simultaneous Lagrange eddy closed loop. In addition, when analyzing the global distribution of the ratio of the Euler eddy Rossby number and the corresponding Lagrange eddy Rossby number, it is observed that the closed loop with smaller Lagrange eddy corresponds to a larger average relative vorticity. That is, after the buoy is captured by the meso-scale vortex, it is easier to form a closed loop where the relative vorticity is larger (such as meso-scale eddy centers, mesos-cale eddy edges, etc.).

Then we focus our research area on the Kuroshio region in the East China Sea using buoy drifting trajectory and ROMS model. Most of oceanic eddies generated on both sides of the Kuroshio is outside the boundary of the Kuroshio, the life cycle is much shorter than eddies inside the ocean, and the radius is concentrated within 200km. The radius of the eddy is approximately proportional to the life cycle, and the larger the eddy Rossby number, the smaller the corresponding radius and the shorter the life cycle. The eddy is basically located in the upper 50m water layer, and the radius decreases as the depth increases, showing a bowl-like structure, and the eddy moves downstream along the Kuroshio over time.

The spatial-temporal characteristics of the barotropic tides and internal tides (ITs) northeast of Taiwan Island are examined, based on a 1-year mooring current observations from May 2017. The results of harmonic tidal analysis show that the barotropic tides are dominated by semidiurnal tides, which was mainly controlled by M2 tidal components. Moreover, the vertical structures of diurnal and semidiurnal ITs show that seasonal variations of the diurnal IT energy is not significant, whereas the semidiurnal IT shows notable seasonal variation. The semidiurnal IT energy in winter half year is twice that in summer half year. The seasonal variation of semidiurnal IT is mainly modulated by the direction change of the flow field rather than by the topography and stratification. In summer (winter) half year cyclonic (anti-cyclonic) eddies meanly control at this point, so the flow direction is mainly in the southwest (northeast) direction, causing the background flow to flow along (perpendicular) the isobath. When crossing the isobath, the ITs are generated by the interaction of the barotropic tide and the topography, resulting in the increase of the tidal energy in the winter half year.

第一章 绪论... 1

1.1 研究背景及研究意义... 1

1.2 海洋涡旋国内外研究进展... 3

1.3 本文的主要研究内容... 10

第二章 研究数据与方法以及模式介绍... 13

2.1 表层漂流浮标数据... 13

2.2全球涡旋数据集... 14

2.3 高度计数据... 15

2.3.1 基于流场几何特征的涡旋探测... 15

2.3.2 基于改进的特征线法的黑潮主轴及边界提取... 16

2.4 锚定潜标观测... 18

2.5 CFSR数据集... 20

2.6 WOA 13数据集... 20

2.7 OEFS数据... 20

2.8 Regional Ocean Modeling System (ROMS) 模式简介... 20

2.8.1 ROMS控制方程及边界条件... 21

2.8.2 坐标系统... 23

2.8.3垂向混合参数化方案... 25

2.8.4东海区域模式设置... 25

第三章 基于卫星高度计和浮标漂流轨迹的海洋涡旋对比分析... 27

3.1 引言... 27

3.2涡旋匹配成功率的全球空间分布... 29

3.3 配对涡旋半径的空间分布变化... 31

3.4 配对涡旋Rossby数的空间分布特征... 33

3.5 配对涡旋归一化结果... 35

3.6 本章小结... 42

第四章 东海黑潮海洋涡旋的基本特征研究... 45

4.1 引言... 45

4.2东海黑潮涡旋的漂流浮标提取结果... 45

4.3东海黑潮涡旋的ROMS模式输出结果... 52

4.3.1 模式验证... 52

4.3.2 基于模式结果的涡旋提取... 56

4.4 本章小结... 70

第五章 台湾东北部涡旋对于内潮的影响... 73

5.1 引言... 73

5.2观测点的背景水文信息... 73

5.3潜标观测结果分析... 76

5.3.1正压特征... 76

5.3.2斜压特征... 79

5.4 正/斜压季节分析... 81

5.5内潮季节变化特征... 83

5.6季节变化的机制讨论... 85

5.7 本章小结... 89

第六章 结论与展望... 91

6.1 论文总结... 91

6.2 未来工作展望    93