| Cheng Zi,Zhou Meng,Zhong Yisen,Zhang Zhaoru,Liu Hailong,Zhou Lei. 2020. Statistical characteristics of mesoscale eddies on the continental slope in the northern South China Sea. Acta Oceanologica Sinica, 39(3):36－44 |
| Statistical characteristics of mesoscale eddies on the continental slope in the northern South China Sea |
| 南海北部陆坡中尺度涡的演化及传播规律分析 |
| Received:November 15, 2018 |
| DOI：10.1007/s13131-019-1530-3 |
| Key words:the South China Sea continental slope Dongsha Islands eddy statistics eddy propagation |
| 中文关键词: 南海 陆坡 东沙岛 涡旋统计 涡旋传播 |
| 基金项目:The National Basic Research Program of China under contract Nos 2014CB441500 and 2014CB441506, the National Natural Science Fundation of China under contract No. 41706014; the Shanghai Jiao Tong University Fund under contract No. 2019 SJTU-HKUST. |
| Author Name | Affiliation | E-mail | | Cheng Zi | School of Oceanography, Shanghai Jiao Tong University, Shanghai 200030, China | | | Zhou Meng | School of Oceanography, Shanghai Jiao Tong University, Shanghai 200030, China | meng.zhou@sjtu.edu.cn | | Zhong Yisen | School of Oceanography, Shanghai Jiao Tong University, Shanghai 200030, China | | | Zhang Zhaoru | School of Oceanography, Shanghai Jiao Tong University, Shanghai 200030, China | | | Liu Hailong | School of Oceanography, Shanghai Jiao Tong University, Shanghai 200030, China | | | Zhou Lei | School of Oceanography, Shanghai Jiao Tong University, Shanghai 200030, China | |
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| Abstract: |
| The continental slope in the northern South China Sea (SCS) is rich in mesoscale eddies which play an important role in transport and retention of nutrients and biota. In this study, we investigate the statistical properties of eddy distributions and propagation in a period of 24 years between 1993 and 2016 by using the altimeter data. A total of 147 eddies are found in the continental slope region (CSR), including 70 cyclonic eddies (CEs) and 77 anticyclonic eddies (ACEs). For those eddies that appear in the CSR, the surrounding areas of Dongsha Islands (DS) and southwest of Taiwan (SWT) are considered as the primary sources, where eddies generated contribute more than 60% of the total. According to the spatial distribution of eddy relative vorticity, eddies are weakening as propagating westward. Although both CEs and ACEs roughly propagate along the slope isobaths, there are discrepancies between CEs and ACEs. The ACEs move slightly faster in the zonal direction, while the CEs tend to cross the isobaths with large bottom depth change. The ACEs generally move further into the basin areas after leaving the CSR while CEs remain around the CSR. The eddy propagation on the continental slope is likely to be associated with mean flow at a certain degree because the eddy trajectories have notable seasonal signals that are consistent with the seasonal cycle of geostrophic current. The results indicate that the eddy translation speed is statistically consistent with geostrophic velocity in both magnitude and direction. |
| 中文摘要: |
| 南海北部陆坡一直以来都是中尺度涡非常活跃的区域，但由于缺乏系统统计，人们对该区域内中尺度涡的生成和运动规律的认识还不够深刻。本文使用高度计数据和欧拉型涡旋检测方法研究了南海北部陆坡24年（1993-2016）间涡旋的统计特征，在陆坡研究区域（Continental Slope Region, CSR）内共发现了147个中尺度涡旋，其中有70个气旋（CE）和77个反气旋（ACE）。这些涡旋有两个十分重要的生成地，东沙群岛（DS）周围海域和台湾岛西南侧（SWT）海域，来源于上述两处区域的涡旋占CSR中出现的中尺度涡旋总数的60％以上。根据涡旋相对涡度的空间分布，本文发现当涡旋向西传播时其强度会逐渐减弱，并且ACE的强度比CE更强。虽然涡旋大都沿陆坡等深线传播，但不同极性的涡旋涡度对于地形的响应也有差异。在CSR中，ACE在沿陆坡的方向上运动得稍快，而CE比ACE更容易出现跨越等深线的运动；离开CSR之后，ACE通常会进一步向海盆深处运动，而CE则会徘徊在陆坡边缘。此外，涡旋的传播很可能受到平均流的很大影响。对应于陆坡地转流的季节性周期变化，涡旋的轨迹也具有显著的季节信号。进一步的研究表明，涡旋的传播速度在大小和方向上与地转流速高度一致。 |
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