海表Ekman流不稳定性致新型次级环流

李燕; 乔方利; 戴德君; 马洪余

doi:10.3969/j.issn.0253-4193.2014.01.002

海表Ekman流不稳定性致新型次级环流

doi: 10.3969/j.issn.0253-4193.2014.01.002

1.
College of Physical and Environmental Oceanography, Ocean University of China, Qingdao 266003, China;Key Laboratory of Marine Science and Numerical Modeling (MASNUM), The First Institute of Oceanography, State Oceanic Administration, Qingdao 266061, China
2.
Key Laboratory of Marine Science and Numerical Modeling (MASNUM), The First Institute of Oceanography, State Oceanic Administration, Qingdao 266061, China

基金项目: 中华人民共和国科学技术部全球变化研究重大科学研究计划项目“南大洋-印度洋海气过程对东亚及全球气候变化的影响”（2010CB950303）。

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出版历程
- 收稿日期: 2012-12-24

Research on the new secondary circulation induced by the Ekman flow on the upper ocean

1.
College of Physical and Environmental Oceanography, Ocean University of China, Qingdao 266003, China;Key Laboratory of Marine Science and Numerical Modeling (MASNUM), The First Institute of Oceanography, State Oceanic Administration, Qingdao 266061, China
2.
Key Laboratory of Marine Science and Numerical Modeling (MASNUM), The First Institute of Oceanography, State Oceanic Administration, Qingdao 266061, China

摘要

摘要: 海洋上混合层中的次级环流可通过物质和能量的垂直输运和混合过程把海洋表层的热量、动量与物质携带到次表层，对海洋上层次级环流生成机制的研究可以丰富对上层海洋的理解和认识。文中利用线性稳定性理论讨论了经典海表Ekman流的不稳定性，提出Ekman流的不稳定性可生成一种新型的次级环流。这种次级环流的空间尺度与雷诺数、Ekman流的垂向衰减速率、水平湍黏性系数与垂向湍黏性系数比值等密切相关，尺度范围从数十米到数千米。数十米量级的次级环流其垂向结构以及次级环流流轴与主流场偏角都与Langmuir环流的特征极为相似，是Langmuir 环流形成机制的一种新解释。千米量级的次级环流能够解释黄海浒苔的条带分布。此外，所得次级环流的流轴与主流之间的偏角与科氏力有显著关系，北半球次级环流流轴偏向主流左侧，南半球反之。
- Ekman流 /
- 稳定性分析 /
- 次级环流(二次流)
Abstract: The secondary circulation in the mixed layer of the upper ocean can bring the heat, momentum and material from the upper ocean to the subsurface which affects the vertical transport, exchange and mixing in this layer. The studies on the secondary circulation, including its formation mechanism and the interaction with other dynamic process, can enrich our understanding of the ocean upper layer. In this study, we use the linear stability theory to analyze stability of classical Ekman flow on the upper ocean, and present the idea that the instability of the Ekman flow can induced a new kind of secondary circulation. The space scales of this secondary circulation are closely related with the Reynolds number, decaying rate of Ekman flow and the ratio between the horizontal and the vertical turbulent viscosity coefficients etc, and have a wide range from tens of meters to several kilometers. For the secondary circulation of tens of meters, its vertical structure and the deflection angle between the axis of secondary circulation and the main flow are very similar to that of the Langmuir circulation, so this is a new explanation of the formation mechanism for Langmuir circulation. For the secondary circulation of kilometers, it may be responsible for the band structure of surface drifting macroalgae in the western Yellow Sea. In addition, the deflection angle between the axis of the secondary circulation and the main flow is affected by the coriolis force, in the northern hemisphere the secondary circulation turns to the left of the main slow, and to the right in the southern hemisphere.
- upper mixed layer /
- Ekman flow /
- secondary circulation

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