Abstract
In general, a mesoscale cyclonic (anticyclonic) eddy has a colder (warmer) core, and it is considered as a cold (warm) eddy. However, recently research found that there are a number of “abnormal” mesoscale cyclonic (anticyclonic) eddies associated with warm (cold) cores in the South China Sea (SCS). These “abnormal” eddies pose a challenge to previous works on eddy detection, characteristic analysis, eddy-induced heat and salt transports, and even on mesoscale eddy dynamics. Based on a 9-year (2000–2008) numerical modelling data, the cyclonic warm-core eddies (CWEs) and anticyclonic cold-core eddies (ACEs) in the SCS are analyzed. This study found that the highest incidence area of the “abnormal” eddies is the northwest of Luzon Strait. In terms of the eddy snapshot counting method, 8 620 CWEs and 9 879 ACEs are detected, accounting for 14.6% and 15.8% of the total eddy number, respectively. The size of the “abnormal” eddies is usually smaller than that of the “normal” eddies, with the radius only around 50 km. In the generation time aspect, they usually appear within the 0.1–0.3 interval in the normalized eddy lifespan. The survival time of CWEs (ACEs) occupies 16.3% (17.1%) of the total eddy lifespan. Based on two case studies, the intrusion of Kuroshio warm water is considered as a key mechanism for the generation of these “abnormal” eddies near the northeastern SCS.
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Acknowledgements
The altimeter data are obtained from the AVISO Website, and the AVHRR SST product data were obtained from the NASA JPL Website. The wind forcing and lateral open boundary conditions are from the NOAA and SODA product, respectively. We thank the editor and two anonymous reviewers for their constructive comments and helpful suggestions on an earlier version of the manuscript.
Funding
Foundation item: The National Natural Science Foundation of China under contract Nos 41906008, 41806039, 41806030, 42076021, 41676010 and 41706205; the State Key Laboratory of Tropical Oceanography, South China Sea Institute of Oceanology, Chinese Academy of Sciences under contract Nos LTO1902 and LTO1807; the Strategic Priority Research Program of Chinese Academy of Sciences under contract No. XDB42000000; the Youth Innovation Promotion Association CAS under contract No. 2017397; the Pearl River S&T Nova Program of Guangzhou under contract No. 201806010105; the Open Fund of State Key Laboratory of Satellite Ocean Environment Dynamics, Second Institute of Oceanography, MNR under contract No. QNHX2022; the Startup Foundation for Introducing Talent of Nanjing University of Information Science & Technology under contract No. 2019r049; the Startup Foundation for Introducing Talent of Zhejiang Ocean University; the National Key Research Programs of China under contract Nos 2016YFC1401407 and 2017YFA0604100; the National Programme on Global Change and Air-Sea Interaction under contract Nos GASI-IPOVAI-03 and GASI-IPOVAI-05; the Innovation Group Project of Southern Marine Science and Engineering Guangdong Laboratory (Zhuhai) under contract No. 311020004.
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Sun, W., Liu, Y., Chen, G. et al. Three-dimensional properties of mesoscale cyclonic warm-core and anticyclonic cold-core eddies in the South China Sea. Acta Oceanol. Sin. 40, 17–29 (2021). https://doi.org/10.1007/s13131-021-1770-x
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DOI: https://doi.org/10.1007/s13131-021-1770-x