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热带海洋学报

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基于湾流海域船载ADCP观测资料的地转平衡态和非地转动能分析

刘余亿1,2，曹海锦3，经志友1   

  1. 1. 热带海洋环境国家重点实验室(中国科学院南海海洋研究所), 广东 广州 510301;

    2. 中国科学院大学, 北京 100049;

    3. 河海大学海洋学院，江苏 南京 210098

  • 收稿日期:2022-02-17 修回日期:2022-04-17 出版日期:2022-04-19 发布日期:2022-04-19
  • 通讯作者: 经志友

Analysis of kinetic energy of balanced geostrophic motions and unbalanced wave motions based on ship-board ADCP observation data in the Gulf Stream

LIU Yuyi1, 2, CAO Haijin3, JING Zhiyou1   

  1. 1. State Key Laboratory of Tropical Oceanography (South China Sea Institute of Oceanology, Chinese Academy of Sciences), Guangzhou 510301, China;

    2. University of Chinese Academy of Sciences, Beijing 100049, China;

    3. College of Oceanography, Hohai University, Nanjing 210098, China

  • Received:2022-02-17 Revised:2022-04-17 Online:2022-04-19 Published:2022-04-19
  • Contact: Zhiyou JING

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摘要： 本研究基于湾流海域14年(2005-2018年)船载ADCP观测的水平流速数据，利用Helmholtz分解和波数谱分析等方法，分离了海域内的地转平衡态涡旋运动和非地转内波运动，分析了两者的动能在连续波数谱空间的转换尺度，并初步探讨了影响湾流海域转换尺度的潜在因素。研究结果表明，湾流强流区的地转平衡态运动活跃，其转换尺度小于10km，且季节性差异较小；弱流区的非地转运动显著强于强流区，其转换尺度约为15km，夏季(~28km)明显大于冬季(~13km)；且湾流海域的转换尺度受夏秋季频繁发生的飓风向海洋输入的近惯性波动能量影响。同时，该海域转换尺度的深度变化结果表明，转换尺度与亚中尺度范围内地转平衡态运动的动能水平呈负相关关系，当地转平衡态运动的动能占主导时，转换尺度相应减小，较小的转换尺度对应较弱的非地转内波动能和较强的地转平衡态动能，本研究关于地转运动和非地转运动的有效分离有助于理解海洋不同尺度的动力过程及其能量转化。

关键词: 湾流, 波谱分解, 地转平衡态运动, 非地转内波运动, 转换尺度

Abstract: Based on the horizontal velocity data observed by ship-board ADCP in the Gulf Stream for 14 years (2005-2018), we use the methods of Helmholtz decomposition and wavenumber spectrum analysis to decompose the balanced geostrophic motions and unbalanced wave motions of the ocean, and analyze the transition scale between them. We also discuss the main factors affecting the transition scale of the Gulf Stream. The results show that the balanced geostrophic motions in the strong current region of the Gulf stream is more active, its transition scale is less than 10 km with small seasonal difference. The unbalanced motions in the weak current region are significantly stronger than that in the strong, and its transition scale is about 15 km, which is significantly larger in summer (~28 km) than in winter (~13 km). The transition scale of the Gulf Stream is affected by the near-inertial wave energy input by frequent hurricanes in summer and autumn. Also, the results of transition scale dependence on depth show that the transition scale is negatively correlated with the kinetic energy level of the balanced geostrophic motions at submesoscale. When the kinetic energy of balanced geostrophic is active, the transition scale decreases accordingly. The smaller transition scale corresponds to the smaller kinetic energy level of unbalanced wave motions and the larger of balanced geostrophic motions. The effective separation of balanced geostrophic motions and unbalanced wave motions in this study is helpful to understand the dynamic processes and the energy transformation at different scales.

Key words: Gulf Stream, spectral decomposition, balanced geostrophic motion, unbalanced motion, transition scale