| 摘要: |
| 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)。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。鉴于此,我们基于近30 a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波数谱的斜率,并与地转湍流理论预测进行了对比。研究结果显示: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。SSHA波数谱斜率的各向异性表明海洋中尺度运动受?效应影响,具有明显的经向和纬向差异。以上结果表明,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。 |
| 关键词: 海面高度 中尺度涡旋 地转湍流 波数-频率谱 谱斜 |
| DOI：10.11759/hykx20220921003 |
| 分类号:P731 |
| 基金项目:国家自然科学基金项目(41776035);山东省自然科学基金项目(ZR2021MD024);崂山实验室科技创新项目(LSKJ202202400) |
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| Power spectra analysis of Pacific Ocean eddies based on sat-ellite altimeter data |
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HUA Junwei1,2,3, WANG Faming1,2,3,4
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1.Institute of Oceanology, the Chinese Academy of Sciences, Qingdao 266071, China;2.University of the Chinese Academy of Sciences, Beijing 100049, China;3.Key Laboratory of Ocean Circulation and Wave, the Chinese Academy of Sciences, Qingdao 266071, China;4.Laboratory for Ocean and Climate Dynamics, Pilot National Laboratory for Marine Science and Technology(Qingdao), Qingdao 266237, China
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| Abstract: |
| Assuming homogeneity and isotropy, geostrophic turbulence theory proposes that the eddy kinetic energy follows a power law k–n with the scale distribution. However, the actual ocean is affected by various factors, such as boundaries, topography, and stratification. These elements introduce nonhomogeneous and anisotropic characteristics. To reconcile theory with observations, we conducted an analysis based on 30 years of altimeter data. We estimated the wavenumber spectrum of sea surface height anomalies (SSHAs) in different regions:tropical, subtropical, and mid-high latitudes. Following this, we evaluated the spectral slope using linear regression in the mesoscale band. The results reveal that the SSHA wavenumber spectrum steepens from the equator toward middle and high latitudes. Simultaneously, its slope decreases from -4 to -5, which agrees well with the equatorial linear wave theory. We found a zonal and meridional difference in the slope of the SSHA wavenumber spectrum. For instance, in the equatorial region, the zonal spectrum appears steeper than the corresponding meridional spectrum. Conversely, in the Antarctic Circumpolar Current region, the meridional spectrum slope exceeds that of the zonal spectrum. This anisotropy in the slope of the SSHA wavenumber spectrum indicates that the mesoscale motion of the ocean is affected by the beta effect, resulting in considerable meridional and zonal differences. In conclusion, our results demonstrate that the mesoscale motion of the ocean oscillates between quasi-two-dimensional and three-dimensional states. Therefore, it cannot be adequately described by a global turbulence theoretical model. |
| Key words: sea surface height mesoscale eddy geostrophic turbulence wavenumber-frequency spectrum spectral slope |
