| LI Guojing,WANG Dongxiao,CHEN Ju,YAO Jinglong,ZENG Lili,SHU Yeqiang,SUI Dandan. 2015. Contrasting dynamic characteristics of shear turbulence and Langmuir circulation in the surface mixed layer. Acta Oceanologica Sinica, 34(5):1－11 |
| Contrasting dynamic characteristics of shear turbulence and Langmuir circulation in the surface mixed layer |
| 上混合中剪切湍流和朗缪尔环流动力特征差异 |
| Received:August 07, 2013 Revised:December 21, 2014 |
| DOI：10.1007/s13131-015-0661-4 |
| Key words:surface mixed layer Langmuir circulation shear turbulence large eddy simulation |
| 中文关键词: 上混合层 朗缪尔环流 剪切湍流 大涡模拟 |
| 基金项目:The National Basic Research Program of China (973 Program) under contract No. 2011CB403504; the China Postdoctoral Science Foundation under contract No. 2013M542216; the National Natural Science Foundation of China under contract No. 41206011. |
| Author Name | Affiliation | E-mail | | LI Guojing | State Key Laboratory of Tropical Oceanography, South China Sea Institute of Oceanology, Chinese Academy of Sciences, Guangzhou 510301, China | | | WANG Dongxiao | State Key Laboratory of Tropical Oceanography, South China Sea Institute of Oceanology, Chinese Academy of Sciences, Guangzhou 510301, China | | | CHEN Ju | State Key Laboratory of Tropical Oceanography, South China Sea Institute of Oceanology, Chinese Academy of Sciences, Guangzhou 510301, China | | | YAO Jinglong | State Key Laboratory of Tropical Oceanography, South China Sea Institute of Oceanology, Chinese Academy of Sciences, Guangzhou 510301, China | yaojl@scsio.ac.cn | | ZENG Lili | State Key Laboratory of Tropical Oceanography, South China Sea Institute of Oceanology, Chinese Academy of Sciences, Guangzhou 510301, China | | | SHU Yeqiang | State Key Laboratory of Tropical Oceanography, South China Sea Institute of Oceanology, Chinese Academy of Sciences, Guangzhou 510301, China | | | SUI Dandan | State Key Laboratory of Tropical Oceanography, South China Sea Institute of Oceanology, Chinese Academy of Sciences, Guangzhou 510301, China | |
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| Abstract: |
| Large eddy simulation (LES) is used to investigate contrasting dynamic characteristics of shear turbulence (ST) and Langmuir circulation (LC) in the surface mixed layer (SML). ST is usually induced by wind forcing in SML. LC can be driven by wave-current interaction that includes the roles of wind, wave and vortex forcing. The LES results show that LC suppresses the horizontal velocity and greatly modifies the downwind velocity profile, but increases the vertical velocity. The strong downwelling jets of LC accelerate and increase the downward transport of energy as compared to ST. The vertical eddy viscosity Km of LC is much larger than that of ST. Strong mixing induced by LC has two locations. They are located in the 2δs-3δs(Stokes depth scale) and the lower layer of the SML, respectively. Its value and position change periodically with time. In contrast, maximum Km induced by ST is located in the middle depth of the SML. The turbulent kinetic energy (TKE) generated by LC is larger than that by ST. The differences in vertical distributions of TKE and Km are evident. Therefore, the parameterization of LC cannot be solely based on TKE. For deep SML, the convection of large-scale eddies in LC plays a main role in downward transport of energy and LC can induce stronger velocity shear (S2) near the SML base. In addition, the large-scale eddies and S2 induced by LC is changing all the time, which needs to be fully considered in the parameterization of LC. |
| 中文摘要: |
| 采用大涡模拟研究了上混合层中剪切湍流和朗缪尔环流动力特征的差异。风诱导了剪切湍流，波流相互作用诱导了朗缪尔环流-也称风积丘。研究结果表明朗缪尔环流与剪切湍流相比抑制了水平速度，极大地改变顺风方向的速度分布，增加了垂向速度。朗缪尔环流诱导了强的向下射流，其加速并增加了能量的向下输运。朗缪尔环流诱导的垂向涡粘系数远大于剪切湍流诱导的垂向涡粘系数。朗缪尔环流诱导了两个强混合区域，分别位于二到三倍的斯托克斯深度和靠近上混合层底部，并且其大小和位置随着时间成周期性变化。朗缪尔环流的湍动能远大于剪切湍流的湍动能。朗缪尔环流的湍动能和垂向涡粘系数的垂向分布存在着十分明显的差异，其参数化不能仅以湍动能特征为依据。对于深的上混合层，朗缪尔环流中的大尺度涡在能量垂向输运中起着主导作用，并且朗缪尔环流增强了混合层底部的速度剪切。此外，朗缪尔环流诱导的大尺度涡和速度剪切均随着时间不断改变，这需要在朗缪尔环流参数化中充分考虑。 |
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