scholarly journals Features of Intraseasonal Variability Observed in the Upper-Layer Current in the Northern South China Sea

2021 ◽  
Vol 8 ◽  
Author(s):  
Wen Xu ◽  
Yeqiang Shu ◽  
Dongxiao Wang ◽  
Ju Chen ◽  
Jinghong Wang ◽  
...  
Keyword(s):  
South China Sea ◽  
South China ◽  
Northern South China Sea ◽  
Intraseasonal Variability ◽  
Mesoscale Eddy ◽  
Luzon Strait ◽  
Altimeter Data ◽  
China Sea ◽  
Spatial Differences ◽  
Long Time

This study reveals the features of the strong intraseasonal variability (ISV) of the upper-layer current in the northern South China Sea (NSCS) based on four long-time mooring observations and altimeter data. The ISV of the upper-layer current in the NSCS consists of two dominant periods of 10–65 days and 65–110 days. The ISV with period of 10–65 days is much strong in the Luzon Strait and decays rapidly westward along the slope. The ISV with the period of 65–110 days is relatively strong along the slope with two high cores at 115 and 119°E, whereas it is weak in the Luzon Strait. The 10–65-day ISV can propagate directly from the western Pacific into the NSCS for most of the time. However, due to its long wavelength, the 65–110-day ISV propagates into the NSCS indirectly, possibly similar to the wave diffraction phenomenon. The spatial differences between the two main frequency bands are primarily due to the baroclinic and barotropic instabilities. The spatial distribution of the upper-layer ISV is closely associated with the mesoscale eddy radius of the NSCS. The eddy radius is directly proportional to the strength of 65–110-day ISV, but it is inversely proportional to the strength of 10–65-day ISV.

Evolution and propagation of a mesoscale eddy in the northern South China Sea during winter

2013 ◽  
Vol 32 (7) ◽  
pp. 1-7 ◽  
Author(s):  
Changjian Liu ◽  
Yan Du ◽  
Wei Zhuang ◽  
Huayong Xia ◽  
Qiang Xie
Keyword(s):  
South China Sea ◽  
South China ◽  
Northern South China Sea ◽  
Mesoscale Eddy ◽  
China Sea

Spatial structure of turbulent mixing of an anticyclonic mesoscale eddy in the northern South China Sea

2020 ◽  
Vol 39 (11) ◽  
pp. 69-81
Author(s):  
Yongfeng Qi ◽  
Chenjing Shang ◽  
Huabin Mao ◽  
Chunhua Qiu ◽  
Changrong Liang ◽  
...  
Keyword(s):  
South China Sea ◽  
Spatial Structure ◽  
South China ◽  
Turbulent Mixing ◽  
Northern South China Sea ◽  
Mesoscale Eddy ◽  
China Sea

scholarly journals Suppressed Thermocline Mixing in the Center of Anticyclonic Eddy in the North South China Sea

2021 ◽  
Vol 9 (10) ◽  
pp. 1149
Author(s):  
Yongfeng Qi ◽  
Huabin Mao ◽  
Xia Wang ◽  
Linhui Yu ◽  
Shumin Lian ◽  
...  
Keyword(s):  
South China Sea ◽  
Internal Waves ◽  
South China ◽  
Northern South China Sea ◽  
Mesoscale Eddy ◽  
Fine Scale ◽  
Mean Flow ◽  
China Sea ◽  
Flow Interactions ◽  
Background Shear

Direct microstructure observations and fine-scale measurements of an anticyclonic mesoscale eddy were conducted in the northern South China Sea in July 2020. An important finding was that suppressed turbulent mixing in the thermocline existed at the center of the eddy, with an averaged diapycnal diffusivity at least threefold smaller than the peripheral diffusivity. Despite the strong background shear and significant wave–mean flow interactions, the results indicated that the lack of internal wave energy in the corresponding neap tide period during measurement of the eddy’s center was the main reason for the suppressed turbulent mixing in the thermocline. The applicability of the fine-scale parameterization method in the presence of significant wave–mean flow interactions in a mesoscale eddy was evaluated. Overprediction via fine-scale parameterization occurred in the center of the eddy, where the internal waves were inactive; however, the parameterization results were consistent with microstructure observations along the eddy’s periphery, where active internal waves existed. This indicates that the strong background shear and wave–mean flow interactions affected by the mesoscale eddy were not the main contributing factors that affected the applicability of fine-scale parameterization in the northern South China Sea. Instead, our results showed that the activity of internal waves is the most important consideration.

scholarly journals Seasonal SSH Variability of the Northern South China Sea

2015 ◽  
Vol 45 (6) ◽  
pp. 1595-1609 ◽  
Author(s):  
Fang-Hua Xu ◽  
Lie-Yauw Oey
Keyword(s):  
South China Sea ◽  
South China ◽  
North Pacific Ocean ◽  
Northern South China Sea ◽  
Luzon Strait ◽  
Height Anomaly ◽  
Ekman Pumping ◽  
Wind Stress Curl ◽  
China Sea ◽  
The North

AbstractThe seasonal response of sea surface height anomaly (SSHA) to wind stress curl (WSC) in the northern South China Sea (NSCS) and the Kuroshio intrusion through the Luzon Strait is analyzed using observations and models. The dominant response to WSC is through simple Ekman pumping, while effects of β appear as the weaker second empirical orthogonal function mode. The Luzon Strait intrusion is shown to be largely deterministic using a model forced by realistic wind in the North Pacific Ocean, and it contributes significantly to the SSH variability in the NSCS. The WSC accounts for 62%, while intrusion 38% of the total forcing, but the latter alters the forced Rossby wave response. Without the intrusion, westward propagation is too fast, resulting in incorrect balance and erroneous annual SSH variability in the NSCS.

scholarly journals Simulations of Internal Solitary Wave Interactions with Mesoscale Eddies in the Northeastern South China Sea

2015 ◽  
Vol 45 (12) ◽  
pp. 2959-2978 ◽  
Author(s):  
Jieshuo Xie ◽  
Yinghui He ◽  
Zhiwu Chen ◽  
Jiexin Xu ◽  
Shuqun Cai
Keyword(s):  
South China Sea ◽  
Solitary Wave ◽  
South China ◽  
Mesoscale Eddy ◽  
Synthetic Aperture Radar Image ◽  
Satellite Observations ◽  
Internal Solitary Wave ◽  
Altimeter Data ◽  
China Sea ◽  
Northeastern South China Sea

AbstractWith the combined analysis of synthetic aperture radar image and satellite altimeter data collected in the northeastern South China Sea (SCS), this study found one type of distorted phenomenon of internal solitary wave (ISW) with the long front caused by the oceanic mesoscale eddy. Motivated by these satellite observations, the authors carried out numerical experiments using the fully nonhydrostatic and nonlinear MITgcm to investigate the perturbation of ISWs by an isolated cyclonic or anticyclonic eddy. The results show that the ISW front is distorted by these oceanic eddies due to the retardation and acceleration effects at their two sides. The ISW energy along the front is focused onto (scattered from) the wave fragment where a concave (convex) pattern is formed, and the previously accumulated energy in the focusing region is gradually released after the ISW propagates away from the eddies. The ISW amplitude is modulated greatly by the eddies due to the energy redistribution along the front. Sensitivity results indicate that the magnitude of the modulated ISW amplitude in the focusing region can reach twice the incident ISW amplitude, while in the scattering region it can be reduced by more than a half. These results therefore suggest that models with eddies included, especially the energetic eddies, could further improve the amplitude predictions in the northeastern SCS. Additionally, the internal gravity wave formed behind the energy-focusing region by the anticyclonic eddies can steepen and break with the consequent formation of a secondary trailing ISW packet. Finally, this study shows that the model results of the distorted front and trailing packet are in qualitative agreement with that of the satellite observations in the northeastern SCS.

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