海洋环流与波动重点实验室知识库

在空间均匀和各向同性的假定下，地转湍流理论认为涡旋动能随尺度分布遵循k^-n定律，k为波数，并在中尺度区间逆向向大尺度流动。但实际海洋受边界、地形、层结等，具有明显的非均匀、各向异性特征。同时，了解海洋不同尺度之间的能量传递是理解海洋能量平衡和动力演化过程的基础。鉴于此，我们基于近30年卫星高度计资料，分别计算了热带、副热带、中高纬度等海洋涡旋强度不同区域的海面高度异常(SSHA)波数谱，进而利用线性回归拟合方法估算出中尺度波段上SSHA波数谱的谱斜率，并与地转湍流理论预测进行了对比。同时，通过结合观测数据和分辨率更高以及不同海域的数值模拟数据集，我们计算了典型高涡旋动能区域动能谱通量以及不同波数壳之间的动能传递。我们的研究发现，SSHA波数谱从赤道到中高纬度逐渐变陡，其斜率由-4减到-5，基本符合赤道线性波动理论和准地转湍流理论的预测。SSHA波数谱斜率存在纬向与经向差异，例如在赤道地区，纬向谱比相应的经向谱陡；而在南极绕极流区域，经向谱斜率大于纬向谱斜率。海洋表层流场能谱通量对数据分辨率具有较强的依赖性，其由逆向传递转向正向串级的0值点随分辨率增加而向小尺度转移，并最终固定在30 km；动能串级主要由二维运动主导，在中尺度到次中尺度的波数范围内动能在临近尺度之间发生正向串级，具有局域性特征。相反，逆向动能传递出现在比第一次变形半径更大的尺度上，并发生在尺度差异较大的运动之间，具有非局域性特征。两者共同作用导致的净效应为在中尺度区间内动能的逆向传递以及在次中尺度区间上的正向串级；三维湍流与理论预测一致，具有局域性特征。海洋上表层存在动能的双向流动，即动能同时向大尺度和小尺度转移。以上结果表明，海洋中尺度运动受beta效应影响，具有明显的经向和纬向差异，海洋中尺度运动介于准二维和三维之间，不能用一个全球普适的湍流理论模型来描述。这项研究为了解海洋不同尺度过程之间能量转移的复杂性提供了有价值的见解。

Under the assumption of homogeneity and isotropy, geostrophic turbulence theory holds that the eddy kinetic energy follows the power law k^-n with the scale distribution, where k is the wavenumber, and the kinetic energy flows inversely to the large-scale in the mesoscale region. However, the actual ocean is affected by boundary, topography, stratification and so on, which has obvious non-uniform and anisotropic characteristics. At the same time, understanding the energy transfer between different scales of the ocean is the basis for understanding the energy balance and dynamic evolution of the ocean. In view of this, based on the satellite altimeter data of the last 30 years, we calculated the wave number spectrum of sea surface height anomaly (SSHA) in different regions of tropical, subtropical and mid-high latitudes, respectively, and then estimated the spectral slope of SSHA wave number spectrum in the mesoscale band by linear regression fitting method, and compared it with the prediction of geostrophic turbulence theory. At the same time, kinetic energy fluxes in typical high vortex kinetic energy regions and kinetic energy transfer between different wave number shells are calculated by combining observational data with numerical simulation datasets of higher resolution and different sea areas. Our study shows that the SSHA wave number spectrum gradually steepens from equator to middle and high latitudes, and its slope decreases from -4 to -5, which basically accords with the prediction of equatorial linear wave theory and quasi-geostrophic turbulence theory. There is a zonal and meridional difference in the slope of SSHA wave number spectrum. For example, in the equatorial region, the zonal spectrum is steeper than the corresponding meridional spectrum. In the circumpolar current region of the South Pole, the slope of the meridional spectrum is greater than that of the zonal spectrum. The energy spectrum flux of the ocean surface flow field has a strong dependence on the data resolution, and the 0 value point of the forward cascade shifts from the reverse transfer to the small scale with the increase of the resolution, and finally fixed at 30 km. The kinetic energy cascades are mainly dominated by two-dimensional motion. In the range of wave number from mesoscale to submesoscale, the kinetic energy cascades forward between comparable scales, which has local characteristics. On the contrary, the inverse kinetic energy transfer appears at scales larger than the first deformation radius, and occurs between scales with large scale differences, and has non-local characteristics. The net effect of the two is the reverse transfer of kinetic energy in the mesoscale interval and the positive cascade in the submesoscale interval. The three-dimensional turbulence is consistent with the theoretical prediction and only contributes to the local kinetic energy cascade. There is a bidirectional flow of kinetic energy in the upper surface of the ocean, that is, kinetic energy transfers to large scale and small scale at the same time. The above results show that the mesoscale motion of the ocean is affected by the beta-effect and has obvious meridional and zonal differences. The mesoscale motion of the ocean is between quasi-two-dimensional and three-dimensional, and cannot be described by a global turbulence theoretical model. The study provides valuable insights into the complexity of energy transfer between processes at different scales in the ocean.

目 录

第1章 绪论 1

1.1 研究意义 1

1.2 研究背景 1

1.3 本文工作 4

第2章 资料与方法 6

2.1 资料介绍 6

2.1.1 OFES Model Data 6

2.1.2 AVISO altimetry data 6

2.1.3 GLORYS12V1 6

2.1.4 Atlantic-European North West Shelf-Ocean Physics Analysis and Forecast Product 7

2.1.5 预处理方法 7

2.1.6 谱分析以及谱斜率计算 8

2.1.7 谱的不确定性分析 10

2.2 能量串级 11

2.2.1 地转速度场计算 11

2.2.2 能谱通量计算 12

2.2.3 波数壳能量传递 13

2.3 Helmholtz分解 14

第3章 能谱分析 16

3.1 一维波数谱分析 16

3.2 各向同性波数谱分析 17

3.3 波数频率谱分析 19

3.4 小结 20

第4章 能谱通量及其局域性分析 22

4.1 能谱通量计算结果 22

4.2 波数壳能量传递分析 24

4.3 Helmholtz分解 29

4.4 小结 32

第5章 全文总结与讨论 34

5.1 主要结论 34

5.2 本文创新点 35

5.3 未来工作展望 36

参考文献 38

致 谢 42

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 43