scholarly journals Eddy characteristics in the Northern South China Sea as inferred from Lagrangian drifter data

2011 ◽  
Vol 8 (4) ◽  
pp. 1575-1599 ◽  
Author(s):  
J. X. Li ◽  
R. Zhang ◽  
B. Jin
Keyword(s):  
South China Sea ◽  
South China ◽  
Large Scale ◽  
Northern South China Sea ◽  
Temporal Distribution ◽  
Spatial And Temporal Patterns ◽  
China Sea ◽  
Eddy Characteristics ◽  
Anticyclonic Eddies ◽  
Lagrangian Drifter

Abstract. Cyclones and anticyclones from large scale to submesoscale on the Northern South China Sea (NSCS) have been statistically characterized based on the satellite-tracked Lagrangian drifter data using a geometric eddy identification method. There are totally 1972 eddies identified, 4/5 of which are anticyclonic eddies. If the submesoscale eddies are eliminated, the other eddies in the NSCS will show a 1.1–1 dominance with the number (133) of anticyclones over the number (122) of cyclones. The spatial distribution of all the eddies are: in Zone Z1, the number of anticyclones dominate the number of cyclones, most of which are the submesoscale anticyclonic eddies with small radii; whereas, in Zone Z2, cyclonic eddies are a little more than anticyclonic eddies. The temporal distribution of eddy number in the NSCS has a close relation with monsoon. The number of the large eddies peaks during the winter monsoon, while they tend to decrease quickly in the transition periods of monsoon. In contrast, submesoscale eddies are likely to generate in the summer monsoon, which may be related to the baroclinic instability in the NSCS. The spatial and temporal patterns have a good agreement with the results of SSHA. The maximum and mean tangential velocities of anticyclones (cyclones) are 45 (30) cm s−1 and 30 (15) cm s−1, respectively. Large scale eddies can be considered in geostrophic balance, but ageostrophic dynamics may be important for the submesoscale eddies where centrifugal effects cannot be ignored in the NSCS.

scholarly journals Eddy characteristics in the northern South China Sea as inferred from Lagrangian drifter data

Ocean Science ◽  
2011 ◽  
Vol 7 (5) ◽  
pp. 661-669 ◽  
Author(s):  
◽  
◽  
Keyword(s):  
South China Sea ◽  
South China ◽  
Large Scale ◽  
Northern South China Sea ◽  
Temporal Distribution ◽  
Height Anomaly ◽  
Spatial And Temporal Patterns ◽  
China Sea ◽  
Eddy Characteristics ◽  
Anticyclonic Eddies

Abstract. Cyclonic and anticyclonic eddies from large scale to submesoscale in the northern South China Sea (NSCS) have been statistically characterized based on the satellite-tracked Lagrangian drifters using our developed geometric eddy identification method. There are in total 2208 eddies identified, 70% of which are anticyclonic eddies. If the submesoscale eddies are eliminated, the other eddies in the NSCS will show a 1.2:1 ratio of the number of anticyclones (210) to the number of cyclones (171). The spatial distribution of the eddies is regional: in southwest of Taiwan, the number of anticyclones dominates the number of cyclones, and most of them are the submesoscale anticyclones with small radii; in contrast, the large and medium cyclonic eddies are a little more than the same scale anticyclonic eddies in northwest of Luzon. The temporal distribution of eddy number in the NSCS has a close relation with the Asian monsoon. The number of the large and medium eddies peaks during the winter monsoon, while the submesoscale eddies are apt to generate in the summer monsoon. The spatial and temporal patterns have a good agreement with the results of the sea surface height anomaly (SSHA). The maximum and mean tangential velocities of anticyclones (cyclones) are 40 (30) cm s−1 and 25 (15) cm s−1, respectively. The calculated normalized vorticities from drifters suggest that although the mesoscale eddies may be considered in geostrophic balance, ageostrophic dynamics and centrifugal effects may play an important role for the growth and decay of the mesoscale cores.

scholarly journals Could the two anticyclonic eddies during winter 2003/2004 be reproduced and predicted in the northern South China Sea?

Ocean Science ◽  
2019 ◽  
Vol 15 (1) ◽  
pp. 97-111 ◽  
Author(s):  
Dazhi Xu ◽  
Wei Zhuang ◽  
Youfang Yan
Keyword(s):  
South China Sea ◽  
South China ◽  
Large Scale ◽  
Numerical Models ◽  
Northern South China Sea ◽  
Mesoscale Eddies ◽  
Nonlinearity Parameter ◽  
Observation Data ◽  
China Sea ◽  
Anticyclonic Eddies

Abstract. Great progress has been made in understanding the mesoscale eddies and their role on the large-scale structure and circulation of the oceans. However, many questions still remain to be resolved, especially with regard to the reproductivity and predictability of mesoscale eddies. In this study, the reproductivity and predictability of mesoscale eddies in the northern South China Sea (NSCS), a region with strong eddy activity, are investigated with a focus on two typical anticyclonic eddies (AE1 and AE2) based on a HYCOM–EnOI assimilated system. The comparisons of assimilated results and observations suggest that generation, evolution, and propagation paths of AE1 and AE2 can be well reproduced and forecasted when the observed amplitude is >8 cm (or the advective nonlinearity parameter U∕c is >2), although their forcing mechanisms are quite different. However, when their amplitudes are less than 8 cm, the generation and decay of these two mesoscale eddies cannot be well reproduced and predicted by the system. This result suggests, in addition to dynamical mechanisms, that the spatial resolution of assimilation observation data and numerical models must be taken into account in reproducing and predicting mesoscale eddies in the NSCS.

Spatial and temporal distribution of nanoflagellates in the northern South China Sea

Hydrobiologia ◽  
2008 ◽  
Vol 605 (1) ◽  
pp. 143-157 ◽  
Author(s):  
Bangqin Huang ◽  
Wenlu Lan ◽  
Zhenrui Cao ◽  
Minhan Dai ◽  
Lingfeng Huang ◽  
...  
Keyword(s):  
South China Sea ◽  
South China ◽  
Northern South China Sea ◽  
Temporal Distribution ◽  
Spatial And Temporal Distribution ◽  
China Sea

Formation and Dynamics of a Long-Lived Eddy Train in the South China Sea: A Modeling Study

2017 ◽  
Vol 47 (11) ◽  
pp. 2793-2810 ◽  
Author(s):  
Zhongya Cai ◽  
Jianping Gan
Keyword(s):  
South China Sea ◽  
Wind Stress ◽  
South China ◽  
Northern South China Sea ◽  
Anticyclonic Eddy ◽  
The South China Sea ◽  
The South ◽  
Wind Stress Curl ◽  
China Sea ◽  
Anticyclonic Eddies

AbstractA process-oriented numerical modeling study was conducted to investigate the formation and underlying forcing of an anticyclonic eddy train observed in the northern South China Sea. Observations showed that long-lived anticyclonic eddies formed an eddy train along an eastward separated jet across the northern South China Sea in summer. The eddy train plays a critical role in regulating ocean circulation in the region. Forced by the southwesterly monsoon and prevailing dipole wind stress curl in the summer, the northward coastal jet separates from the west boundary of the South China Sea basin and overshoots northeastward into the basin. The anticyclonic recirculation of the separated jet forms the first anticyclonic eddy in the eddy train. The jet meanders downstream with a strong negative shear vorticity that forms a second and a third anticyclonic eddy along the jet’s path. These three eddies form the eddy train. These eddies weaken gradually with depth from surface, but they can extend to approximately 500 m deep. The inherent stratification in the region regulates the three-dimensional scale of the anticyclonic eddies and constrains their intensity vertical extension by weakening the geostrophic balance within these eddies. Analyses of the vorticity balance indicate that the eddy train’s negative vorticity originates from the beta effect of northward western boundary current and from the subsequent downstream vorticity advection in the jet. The jet separation is a necessary condition for the formation of the eddy train, and the enhanced stratification, increased summer wind stress, and associated negative wind stress curl are favorable conditions for the formation of the anticyclonic eddies.

Polarity Variations of Internal Solitary Waves over the Continental Shelf of the Northern South China Sea: Impacts of Seasonal Stratification, Mesoscale Eddies, and Internal Tides

2018 ◽  
Vol 48 (6) ◽  
pp. 1349-1365 ◽  
Author(s):  
Xiaojiang Zhang ◽  
Xiaodong Huang ◽  
Zhiwei Zhang ◽  
Chun Zhou ◽  
Jiwei Tian ◽  
...  
Keyword(s):  
South China Sea ◽  
Continental Shelf ◽  
South China ◽  
Northern South China Sea ◽  
Internal Tides ◽  
Thermocline Depth ◽  
China Sea ◽  
Seasonal Stratification ◽  
Anticyclonic Eddies ◽  
The Impact

AbstractSpatiotemporal variations in internal solitary wave (ISW) polarity over the continental shelf of the northern South China Sea (SCS) were examined based on mooring-array observations from October 2013 to June 2014. Depression ISWs were observed at the easternmost mooring, where the water depth is 323 m. Then, they evolved into elevation ISWs at the westernmost mooring, with a depth of 149 m. At the central mooring, with a depth of 250 m, the ISWs generally appeared as depression waves in autumn and spring but were elevation waves in winter. Seasonal variations in stratification caused this seasonality in polarity. On the intraseasonal time scales, anticyclonic eddies can modulate ISW polarity at the central mooring by deepening the thermocline depth for periods of approximately 8 days. During some days in autumn and spring, depression ISWs and ISWs in the process of changing polarity from depression to elevation appeared at time intervals of 10–12 h because of the thermocline deepening caused by internal tides. Isotherm anomalies associated with eddies and internal tides have a more significant contribution to determining the polarity of ISWs than do the background currents. The observational results reported here highlight the impact of multiscale processes on the evolution of ISWs.

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