scholarly journals Tropical Cyclone–Induced Ocean Response: A Comparative Study of the South China Sea and Tropical Northwest Pacific*,+

2015 ◽  
Vol 28 (15) ◽  
pp. 5952-5968 ◽  
Author(s):  
Wei Mei ◽  
Chun-Chi Lien ◽  
I.-I. Lin ◽  
Shang-Ping Xie
Keyword(s):  
South China Sea ◽  
Mixed Layer ◽  
South China ◽  
Regional Difference ◽  
Chlorophyll Concentration ◽  
The South China Sea ◽  
Northwest Pacific ◽  
The South ◽  
China Sea ◽  
Sst Cooling

Abstract The thermocline shoals in the South China Sea (SCS) relative to the tropical northwest Pacific Ocean (NWP), as required by geostrophic balance with the Kuroshio. The present study examines the effect of this difference in ocean state on the response of sea surface temperature (SST) and chlorophyll concentration to tropical cyclones (TCs), using both satellite-derived measurements and three-dimensional numerical simulations. In both regions, TC-produced SST cooling strongly depends on TC characteristics (including intensity as measured by the maximum surface wind speed, translation speed, and size). When subject to identical TC forcing, the SST cooling in the SCS is more than 1.5 times that in the NWP, which may partially explain weaker TC intensity on average observed in the SCS. Both a shallower mixed layer and stronger subsurface thermal stratification in the SCS contribute to this regional difference in SST cooling. The mixed layer effect dominates when TCs are weak, fast-moving, and/or small; and for strong and slow-moving TCs or strong and large TCs, both factors are equally important. In both regions, TCs tend to elevate surface chlorophyll concentration. For identical TC forcing, the surface chlorophyll increase in the SCS is around 10 times that in the NWP, a difference much stronger than that in SST cooling. This large regional difference in the surface chlorophyll response is at least partially due to a shallower nutricline and stronger vertical nutrient gradient in the SCS. The effect of regional difference in upper-ocean density stratification on the surface nutrient response is negligible. The total annual primary production increase associated with the TC passage estimated using the vertically generalized production model in the SCS is nearly 3 times that in the NWP (i.e., 6.4 ± 0.4 × 1012 versus 2.2 ± 0.2 × 1012 g C), despite the weaker TC activity in the SCS.

scholarly journals Estimate of Ocean Mixed Layer Deepening after a Typhoon Passage over the South China Sea by Using Satellite Data

2013 ◽  
Vol 43 (3) ◽  
pp. 498-506 ◽  
Author(s):  
Jiayi Pan ◽  
Yujuan Sun
Keyword(s):  
South China Sea ◽  
Surface Temperature ◽  
Mixed Layer ◽  
South China ◽  
The South China Sea ◽  
Temperature Profiles ◽  
The South ◽  
Translation Speed ◽  
China Sea ◽  
Sst Cooling

Abstract The ocean responses to Typhoon Cimaron, which influenced the South China Sea (SCS) from 1 to 8 November 2006, are analyzed. Based on satellite-observed sea surface temperature (SST) and climatological temperature profiles in the SCS, mixed layer deepening, an important parameter characterizing turbulent mixing and upwelling driven by strong typhoon winds, is derived. Corresponding to the SST drop of 4.4°C on 3 November 2006, the mixed layer deepened by 104.5 m relative to the undisturbed depth of 43.2 m, which is consistent with a simulation result from a mixed layer model. Furthermore, baroclinic geostrophic velocity and vorticity are calculated from the surface temperature gradient caused by the typhoon. The negative vorticity, associated with the typhoon cooling, indicated an anticyclonic baroclinic circulation strongest at the base of the mixed layer and at the depth of 50 m, the geostrophic speed reached as high as 0.2 m s−1. Typhoon Cimaron proceeded slowly (1.7 m s−1) when it was making a southwestward turn on 3 November 2006, resulting in a subcritical condition with a Froude number (the ratio of typhoon translation speed to first baroclinic mode speed) of 0.6 around the maximum SST drop location and facilitating high SST cooling and mixed layer deepening because of the absence of inertial-gravity waves in the wake of the typhoon. Comparison of Argo buoy data with the climatological temperature suggests that the average uncertainty in the mixed layer deepening estimation caused by the difference between Argo and climatological temperature profiles is less than 10 m.

scholarly journals Influence of the Size of Supertyphoon Megi (2010) on SST Cooling

2018 ◽  
Vol 146 (3) ◽  
pp. 661-677 ◽  
Author(s):  
Iam-Fei Pun ◽  
I.-I. Lin ◽  
Chun-Chi Lien ◽  
Chun-Chieh Wu
Keyword(s):  
South China Sea ◽  
Size Effect ◽  
South China ◽  
Thermal Structure ◽  
The South China Sea ◽  
The South ◽  
Translation Speed ◽  
China Sea ◽  
Philippine Sea ◽  
Sst Cooling

Supertyphoon Megi (2010) left behind two very contrasting SST cold-wake cooling patterns between the Philippine Sea (1.5°C) and the South China Sea (7°C). Based on various radii of radial winds, the authors found that the size of Megi doubles over the South China Sea when it curves northward. On average, the radius of maximum wind (RMW) increased from 18.8 km over the Philippine Sea to 43.1 km over the South China Sea; the radius of 64-kt (33 m s−1) typhoon-force wind (R64) increased from 52.6 to 119.7 km; the radius of 50-kt (25.7 m s−1) damaging-force wind (R50) increased from 91.8 to 210 km; and the radius of 34-kt (17.5 m s−1) gale-force wind (R34) increased from 162.3 to 358.5 km. To investigate the typhoon size effect, the authors conduct a series of numerical experiments on Megi-induced SST cooling by keeping other factors unchanged, that is, typhoon translation speed and ocean subsurface thermal structure. The results show that if it were not for Megi’s size increase over the South China Sea, the during-Megi SST cooling magnitude would have been 52% less (reduced from 4° to 1.9°C), the right bias in cooling would have been 60% (or 30 km) less, and the width of the cooling would have been 61% (or 52 km) less, suggesting that typhoon size is as important as other well-known factors on SST cooling. Aside from the size effect, the authors also conduct a straight-track experiment and find that the curvature of Megi contributes up to 30% (or 1.2°C) of cooling over the South China Sea.

scholarly journals Deep Circulation in the South China Sea Simulated in a Regional Model

2019 ◽  
Author(s):  
Xiaolong Zhao ◽  
Chun Zhou ◽  
Xiaobiao Xu ◽  
Ruijie Ye ◽  
Jiwei Tian ◽  
...  
Keyword(s):  
South China Sea ◽  
Spatial Structure ◽  
South China ◽  
The South China Sea ◽  
Northwest Pacific ◽  
The South ◽  
China Sea ◽  
Deep Circulation ◽  
Mixing Parameters ◽  
Circulation In The Scs

Abstract. The South China Sea (SCS) is the largest marginal sea in the northwest Pacific Ocean. In this study, deep circulation in the SCS is investigated using results from eddy-resolving, regional simulations using the Hybrid Coordinate Ocean Model (HYCOM) verified by continuous current-meter observations. Analysis of these results provides a detailed spatial structure and temporal variability of the deep circulation in the SCS. The major features of the SCS deep circulation are a basin-scale cyclonic gyre and a concentrated deep western boundary current (DWBC). Transport of the DWBC is ∼ 2 Sv at 16.5° N with a width of ∼53 km. Flowing southwestward, the narrow DWBC becomes weaker with a wider range. The model results reveal the existence of 80- to 120-day oscillation in the deep northeastern circulation and the DWBC, which are also the areas with elevated eddy kinetic energy. This intraseasonal oscillation propagates northwestward with a velocity amplitude of ∼ 1.0 to 1.5 cm s-1. The distribution of mixing parameters in the deep SCS plays a role in both spatial structure and volume transport of the deep circulation. Compared with the northern shelf of the SCS with the Luzon Strait, deep circulation in the SCS is more sensitive to the large vertical mixing parameters of the Zhongsha Island Chain area.

Multi-decadal changes in the South China Sea mixed layer salinity

2021 ◽  
Author(s):  
Lili Zeng ◽  
Eric P. Chassignet ◽  
Xiaobiao Xu ◽  
Dongxiao Wang
Keyword(s):  
South China Sea ◽  
Mixed Layer ◽  
South China ◽  
The South China Sea ◽  
The South ◽  
China Sea
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