Journal of Tropical Oceanography >
Spatiotemporal characteristics of mesoscale eddies with transport capability of saline Kuroshio water in the northern South China Sea
Copy editor: LIN Qiang
Received date: 2022-07-05
Revised date: 2022-09-14
Online published: 2022-09-28
Supported by
Key Special Project for Introduced Talents Team of Southern Marine Science and Engineering Guangdong Laboratory (Guangzhou)(GML2019ZD0306)
National Natural Science Foundation of China(41676018)
Science and Technology Planning Project of Guangzhou City, China(202002030490)
Eddy-induced transport in the Luzon Strait significantly affects the thermo-salt balance in the northern South China Sea. Using the AVISO satellite data from 1993 to 2018, this paper identifies and screens 76 Kuroshio shedding anticyclic eddies, 46 Kuroshio associated cyclonic eddies, 29 South China Sea (SCS) locally-formed anticyclic eddies and 40 SCS locally-formed cyclonic eddies in the northern SCS. The average nonlinear coefficients of the four types of eddies are all much larger than 1, which confirms that the screening eddies do have the capacity of transporting the saline Kuroshio water. The propagation paths of the eddy are affected by the topography of the northern SCS, and shift to the southwest during the westward propagation process. Compared with the cyclonic eddy, the anticyclonic eddy moved farther to the northern part of the SCS. The eddies are mostly formed in the middle of the Luzon Strait, and the probability of formation gradually decreases with the increase or decrease of latitude. The shedding (associated) eddies are mostly formed in autumn and winter and the least in summer and the average number of anticyclonic eddies is 2.5 more than cyclonic eddies per month. The annual average number of shedding (associated) eddies is about 4.6, and cyclonic eddies do not form every year. Overall, the El Niño event increases the number of Kuroshio shedding or associated eddies by affecting the Kuroshio path.
Key words: northern South China Sea; Kuroshio; saline water; mesoscale eddy
YANG Yikai , ZENG Lili . Spatiotemporal characteristics of mesoscale eddies with transport capability of saline Kuroshio water in the northern South China Sea[J]. Journal of Tropical Oceanography, 2023 , 42(3) : 75 -85 . DOI: 10.11978/2022152
图1 吕宋海峡以西一个黑潮脱落反气旋涡在1993年1月1日的SSH与地转流(a)及SLA与地转流异常(b)绿色五角星代表涡旋中心, 绿色圆圈指示涡旋随后的移动路径。基于国家测绘地理信息局标准地图服务网站下载的审图号为GS(2016)1665号的标准地图制作 Fig. 1 SSH and geostrophic current (a) and SLA and geostrophic current anomaly (b) of a Kuroshio shedding anticyclonic eddy west of the Luzon Strait on January 1st, 1993. The green star represents the eddy center, and the green circle indicates the subsequent propagation path of the eddy |
表1 四类涡旋平均旋转速度、传播速度和非线性系数Tab. 1 Average rotational velocity, propagation velocity and nonlinear coefficient of four types of eddies |
参数 | 脱落反气旋涡 | 伴生气旋涡 | 局地反气旋涡 | 局地气旋涡 |
---|---|---|---|---|
平均旋转速度U/(m·s-1) | 0.38 | 0.32 | 0.34 | 0.34 |
平均传播速度c/(m·s-1) | 0.12 | 0.13 | 0.15 | 0.11 |
平均非线性系数 | 6.6 | 5.4 | 6.0 | 7.3 |
图3 筛选涡旋的标准化涡动能随标准化生命周期的演变红实线、蓝实线、红虚线和蓝虚线分别代表脱落反气旋涡、伴生气旋涡、局地反气旋涡和局地气旋涡。 Fig. 3 Evolution of normalized EKE of the screening eddies with normalized lifetime. The red solid line, blue solid line, red dashed line and blue dashed line represent shedding anticyclonic eddy, associated cyclonic eddy, locally formed anticyclonic eddy and locally formed cyclonic eddy, respectively |
图4 黑潮脱落(伴生)涡旋路径分布与沿吕宋海峡南北向的形成概率a、b为脱落反气旋涡; c、d为伴生气旋涡。黑线为涡旋移动路径; 红色和蓝色圆圈分别代表涡旋形成与消亡的位置。基于国家测绘地理信息局标准地图服务网站下载的审图号为GS(2016)1665号的标准地图制作 Fig. 4 The path distribution of associated eddy and their formation probability along the north-south direction of the Luzon Strait: (a) and (b) correspond to anticyclonic eddy, while (c) and (d) correspond to cyclonic eddy. The red and blue circles represent the location of eddy formation and extinction, respectively |
图5 南海局地涡旋路径分布与沿吕宋海峡南北向的形成概率a和b对应反气旋涡, c和d对应气旋涡。黑线为涡旋移动路径; 红色和蓝色圆圈分别代表涡旋形成与消亡的位置。基于国家测绘地理信息局标准地图服务网站下载的审图号为GS(2016)1665号的标准地图制作 Fig. 5 The path distribution of locally formed eddy and their formation probability along the north-south direction of the Luzon Strait, (a) and (b) correspond to anticyclonic eddy, while (c) and (d) correspond to cyclonic eddy. The red and blue circles represent the location of eddy formation and extinction, respectively |
图8 MEI(柱图)、KSI(橙线)与黑潮脱落(伴生)涡旋数目(绿线)的关系MEI正值指示暖的El Niño事件, 负值指示冷的La Niña事件 Fig. 8 The relationship between MEI (bar), KSI (orange line) and the number of Kuroshio shedding (associated) eddies (green line). Positive MEI values indicate the warm El Niño events and negative values indicate the cold La Niña events |
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