2000年秋季东沙冷涡的三维结构及其演化过程*

doi:10.11978/j.issn.1009-5470.2013.02.006

摘要/Abstract

摘要：

根据AVISO(Archiving Validation and Interpolation of Satellite Oceanographic Data)高度计资料，用区域海洋模式(ROMS)再现和分析了2000年9月4日—10月11日生命周期为36天的一个东沙冷涡过程。该冷涡的平均半径为77km，移动路程为487km。模式结果表明，该冷涡的平均移动速度为15cm·s^-1，冷涡的移动方向几乎沿着1000—2000m陆坡等深线，除了地形的影响外，东北季风也对该冷涡移动方向的转换有作用。冷涡的形变与效应有密切的关系，趋势是导致其形状为长轴位于东北-西南方向的椭圆。其次，对该冷涡的半径、涡度、能量密度、形变和散度等进行时间序列计算分析，得到其平均涡度为3.997×10^-6s^-1，平均能量密度为2.42×10^-2cm²·s^-2·km^-2，涡度与半径具有近似正相关关系，而平均能量密度与半径呈负相关关系；平均的剪切形变、拉伸形变和散度的平均值分别为1.801×10^-6s^-1、4.612×10^-7s^-1、3.269×10^-8s^-1。数值结果表明, 在这次东沙冷涡过程中，整个生命周期共出现过两种不同的三维结构，在生成阶段涡旋形状为表层和底部小、中间大的腰鼓状；成熟期为表层大、底部小的碗状；消亡阶段只能在表层看到信号。该东沙冷涡的深度在不同的生存阶段也不同，大部分时刻小于50m水深，但最深可达到水深450m处。最后，文中给出了速度、温度和盐度的垂向分布情况。其中，东沙冷涡的切向速度在40—50cm·s^-1间，高值区位于水深小于100m处，在100—200m速度递减率较大；温度分布具有一个位于60—100m水深处的低温拱起结构，该冷涡造成了10—20m左右的等温线抬升；高盐核心的拱起结构比低温拱起结构更深，大致位于100—150m，高盐核心区盐度≥34.6‰。

关键词: 海北部, 东沙冷涡, 运动特征, 三维结构, 垂向速度特性, 垂向温盐特性

Abstract:

Using the Regional Ocean Modeling System (ROMS) product and Archiving Validation and Interpolation of Satellite Oceanographic Data (AVISO) satellite altimeter data，we revealed some characteristics of one Dongsha Cold Eddy (DCE) during autumn 2000. This DCE survived 36 days, from September 4 to October 11. The average radius of the DCE was 77 km, travel distance was about 487 km, mean moving speed from model output was 15 cm·s^-1; eddy moving direction indicated it interacted with topography during its life time, and moved along the continental slope at depth of 1000-2000 m. The winter monsoon contributed to eddy’s direction change as well. The deformation of the DCE’s shape was related to the effect. The trend was to lead its shape to become an ellipse, with the long axis located along the northeast to southwest direction. Furthermore, analysis of eddy radius, vorticity, energy density (EI), shear deformation rate (SHD), the stretching deformation rate (STD), and the divergence was carried out. The average vorticity was 3.997×10^-6s^-1, and the mean EI was 2.42×10^-2cm²·s^-2·km^-2. The vorticity was positively correlated with radius, while the energy was negatively correlated with radius. The averaged shear deformation, stretching deformation rate, and divergence were 1.801×10^-6s^-1, 4.612×10^-7s^-1, and 3.269×10^-8s^-1, respectively. We applied three-dimensional eddy detection method to ROMS model output. There were two types of three-dimensional structures of this DCE during its lifetime. During generation, the DCE was lens-shaped and had the largest radius in the stratified layer; when it matured, the shape was like a bowl and had the largest radius at the surface; during the termination, it could only be detected at the surface. In most occasions, the DCE could reach 50 m or less, but sometimes it could reach 450 m. Finally, we also analyzed vertical distributions of velocity, temperature, and salinity. It shows that the range of tangential velocity is from -40 to 50cm·s^-1, its velocity core was located at the depth no more than 100m, and the velocity decreased sharply at 100-200 m. There was a low temperature dome between the depth of 60 and 100m, where the DCE caused 10-20m rise of the 22℃ isotherm. Similarly, there was also a high salinity dome at 100-150m, with salinity greater than 34.6‰.

Key words: northern South China Sea, Dongsha cold eddy, kinetic characteristic, three-dimensional structure, vertical profile of tangential velocity, vertical distributions of temperature and salinity

中图分类号:

P731

林夏艳，管玉平，刘宇. 2000年秋季东沙冷涡的三维结构及其演化过程^*[J]. 热带海洋学报, 2013, 32(2): 55-65.

LIN Xia-yan, GUAN Yu-ping, LIU Yu. Three-dimensional structure and evolution process of Dongsha Cold Eddy during autumn 2000[J]. Journal of Tropical Oceanography, 2013, 32(2): 55-65.

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