scholarly journals Determination of Harmonic Parameters with Temporal Variations: An Enhanced Harmonic Analysis Algorithm and Application to Internal Tidal Currents in the South China Sea

2018 ◽  
Vol 35 (7) ◽  
pp. 1375-1398 ◽  
Author(s):  
Guangzhen Jin ◽  
Haidong Pan ◽  
Qilin Zhang ◽  
Xianqing Lv ◽  
Wei Zhao ◽  
...  
Keyword(s):  
South China Sea ◽  
Harmonic Analysis ◽  
South China ◽  
Spline Interpolation ◽  
Temporal Variations ◽  
Tidal Currents ◽  
The South China Sea ◽  
Internal Tides ◽  
The South ◽  
China Sea

AbstractAs an effective tool to distinguish different tidal components, classical tidal current harmonic analysis has been widely used to obtain harmonic parameters of internal tidal currents. However, harmonic parameters cannot exactly reveal the motion of internal tides, as the irregular temporal variations for internal tides are significant in many regions of the world’s oceans. An enhanced harmonic analysis (EHA) algorithm based on the independent point scheme and cubic spline interpolation is presented in this paper to obtain harmonic parameters with temporal variations for different tidal constituents of internal tides. Moreover, this algorithm is applied to analyze 14 months of current data obtained from a mooring located on the continental shelf in the northeastern region of the South China Sea. The obvious irregular temporal variations for the four principal constituents—M2, K1, S2, and O1—of internal tides in this region are indicated. It is hoped that this algorithm might present a brand-new view for researchers to investigate the irregular temporal motions of internal tides.

Oceanic crustal structures and temporal variations of magmatic budget during seafloor spreading in the East Sub-basin of the South China Sea

2021 ◽  
Vol 436 ◽  
pp. 106475
Author(s):  
Junhui Yu ◽  
Pin Yan ◽  
Yan Qiu ◽  
Matthias Delescluse ◽  
Wenkai Huang ◽  
...  
Keyword(s):  
South China Sea ◽  
South China ◽  
Temporal Variations ◽  
Seafloor Spreading ◽  
The South China Sea ◽  
The South ◽  
China Sea ◽  
Crustal Structures

Disintegration of the K1 internal tide in the South China Sea due to parametric subharmonic instability

2021 ◽  
Author(s):  
Kun Liu ◽  
Zhongxiang Zhao
Keyword(s):  
South China Sea ◽  
South China ◽  
Internal Tide ◽  
The South China Sea ◽  
Internal Tides ◽  
Upper Ocean ◽  
The South ◽  
China Sea ◽  
Parametric Subharmonic Instability ◽  
Critical Latitude

<p>The disintegration of the equatorward-propagating K<sub>1</sub> internal tide in the South China Sea (SCS) by parametric subharmonic instability (PSI) at its critical latitude of 14.52ºN is investigated numerically. The multiple-source generation and long-range propagation of K<sub>1</sub> internal tides are successfully reproduced. Using equilibrium analysis, the internal wave field near the critical latitude is found to experience two quasi-steady states, between which the subharmonic waves develop constantly. The simulated subharmonic waves agree well with classic PSI theoretical prediction. The PSI-induced near-inertial waves are of half the K<sub>1</sub> frequency and dominantly high modes, the vertical scales ranging from 50 to 180 m in the upper ocean. From an energy perspective, PSI mainly occurs in the critical latitudinal zone from 13–15ºN. In this zone, the incident internal tide loses ~14% energy in the mature state of PSI. PSI triggers a mixing elevation of O(10<sup>-5</sup>–10<sup>-4</sup> m<sup>2</sup>/s) in the upper ocean at the critical latitude, which is several times larger than the background value. The contribution of PSI to the internal tide energy loss and associated enhanced mixing may differ regionally and is closely dependent on the intensity and duration of background internal tide. The results elucidate the far-field dissipation mechanism by PSI in connecting interior mixing with remotely generated K<sub>1</sub> internal tides in the Luzon Strait.</p>

Effects of tidal currents on nonlinear internal solitary waves in the South China Sea

2013 ◽  
Vol 12 (1) ◽  
pp. 13-22 ◽  
Author(s):  
Zhisong Fan ◽  
Xingang Shi ◽  
Antony K. Liu ◽  
Hailong Liu ◽  
Peiliang Li
Keyword(s):  
South China Sea ◽  
Solitary Waves ◽  
South China ◽  
Tidal Currents ◽  
The South China Sea ◽  
Internal Solitary Waves ◽  
The South ◽  
China Sea

scholarly journals Long-range propagation and associated variability of internal tides in the South China Sea

2016 ◽  
Vol 121 (11) ◽  
pp. 8268-8286 ◽  
Author(s):  
Zhenhua Xu ◽  
Kun Liu ◽  
Baoshu Yin ◽  
Zhongxiang Zhao ◽  
Yang Wang ◽  
...  
Keyword(s):  
South China Sea ◽  
Long Range ◽  
South China ◽  
The South China Sea ◽  
Internal Tides ◽  
The South ◽  
China Sea

scholarly journals Influence of Remote Internal Tides on the Locally Generated Internal Tides upon the Continental Slope in the South China Sea

2021 ◽  
Vol 9 (11) ◽  
pp. 1268
Author(s):  
Zheng Guo ◽  
Anzhou Cao ◽  
Shuya Wang
Keyword(s):  
South China Sea ◽  
Continental Slope ◽  
South China ◽  
Maximum Energy ◽  
The South China Sea ◽  
Internal Tides ◽  
The South ◽  
China Sea ◽  
The Taiwan Strait ◽  
Local Generation

In this paper, the M2 internal tides (ITs) originating from the continental slope in the South China Sea are studied using the CROCO model. The simulation results show that there are two origins of ITs on the continental slope: at 118°–119.5° E along 22° N near the southern entrance of the Taiwan Strait and at 117°–118° E along 20° N near Dongsha Island. The local generation of ITs is greatly influenced by the ITs that radiate from the Luzon Strait (LS). The integrated conversion at the first generation site is increased by 31% to 0.42 GW compared to the case where the LS is excluded from the simulation region. Its maximum energy flux almost doubles to 2.5 kW/m, which is 10% of the westward component. The existence of the other IT beams from Dongsha Island is attributed to the ITs from the LS. The local generation on the continental slope changes when remotely generated ITs alter the amplitudes and phases of the bottom pressure perturbation. These results indicate that the ITs originating from the LS contribute to the spatial variation of ITs in the SCS by modulating the IT generation on the continental slope.

scholarly journals Application of Three-Dimensional Interpolation in Estimating Diapycnal Diffusivity in the South China Sea

2020 ◽  
Vol 8 (11) ◽  
pp. 832
Author(s):  
Junting Guo ◽  
Yafei Nie ◽  
Shuang Li ◽  
Xianqing Lv
Keyword(s):  
South China Sea ◽  
South China ◽  
Spline Interpolation ◽  
Three Dimensional ◽  
The South China Sea ◽  
Field Observations ◽  
The South ◽  
China Sea ◽  
Study Results ◽  
Diapycnal Diffusivity

Diapycnal diffusivity is an important parameter to characterize oceanic turbulent mixing and vertical transport. However, due to the challenging accessibility of field observations, the observation of diapycnal diffusivity in the South China Sea (SCS) is rare. In this study, a three-dimensional field of diapycnal diffusivity in the SCS with high spatial resolution is performed by interpolating the rare field observations, which aims to provide a reference for the value of diapycnal diffusivity in ocean models. Given the anisotropy of diapycnal diffusivity and its rapid change in the magnitude in the vertical direction, several typical interpolation methods are compared in this study. Results of two cross-validation methods demonstrate that the three-dimensional (3D) thin-plate spline interpolation method yields the most reasonable and accurate results among a total of five typical methods used in this study.

scholarly journals On the consistency in variations of chlorophyll <i>a</i> concentration in the South China Sea as revealed by three remote sensing datasets

2013 ◽  
Vol 10 (5) ◽  
pp. 7549-7578
Author(s):  
S. L. Shang ◽  
Q. Dong ◽  
C. M. Hu ◽  
G. Lin ◽  
Y. H. Li ◽  
...  
Keyword(s):  
South China Sea ◽  
South China ◽  
Environmental Changes ◽  
Temporal Variations ◽  
The South China Sea ◽  
Percentage Error ◽  
The South ◽  
Study Region ◽  
Average Percentage ◽  
China Sea

Abstract. Chlorophyll a (Chl) concentrations derived from satellite measurements have been used in oceanographic research, for example to interpret eco-responses to environmental changes on global and regional scales. However, it is unclear how existing Chl products compare with each other in terms of accuracy and consistency in revealing temporal and spatial patterns, especially in the optically complex marginal seas. In this study, we examined three MODIS Chl data products that have been made available to the community by the US NASA using community-accepted algorithms and default parameterization. These included the products derived from the OC3M, GSM and GIOP algorithms. We compared their temporal variations and spatial distributions in the South China Sea. We found that the three products appeared to capture general features such as unique winter peak at the Southeast Asian Time-series Study station (SEATS, 18° N, 116° E), strong upwelling induced bloom off the Vietnam and the Pearl River plume associated bloom in summer, their absolute magnitude, however, may be questionable. Further error statistics using field measured Chl as the truth demonstrated that the three MODIS Chl products may contain high degree of uncertainties in the study region. Root mean square error (RMSE) of the products from OC3M and GSM (on a log scale) was about 0.4 and average percentage error (ε) was ~150% (Chl between 0.03–7.67 mg m–3, n = 63). In contrast, the GIOP with default parameterization led to higher errors (&amp;varepsilon; = 349%). This study thus advocates more careful interpretation of Chl spatio-temporal variations when using standard Chl products, and also points to the need of local tuning of algorithm parameterization for the study region.

Spatial–Temporal Variations and Mechanisms of the Upper Ocean Heat Content in the South China Sea

2018 ◽  
Vol 176 (4) ◽  
pp. 1847-1861
Author(s):  
Hongwei Liu ◽  
Qilong Zhang ◽  
Chongguang Pang ◽  
Rongshuo Cai ◽  
Qinghua Qi ◽  
...  
Keyword(s):  
South China Sea ◽  
South China ◽  
Heat Content ◽  
Temporal Variations ◽  
The South China Sea ◽  
Ocean Heat Content ◽  
Upper Ocean ◽  
The South ◽  
Upper Ocean Heat Content ◽  
China Sea

Disintegration of the K1 Internal Tide in the South China Sea due to Parametric Subharmonic Instability

2020 ◽  
Vol 50 (12) ◽  
pp. 3605-3622
Author(s):  
Kun Liu ◽  
Zhongxiang Zhao
Keyword(s):  
South China Sea ◽  
South China ◽  
Internal Tide ◽  
The South China Sea ◽  
Internal Tides ◽  
Upper Ocean ◽  
The South ◽  
China Sea ◽  
Parametric Subharmonic Instability ◽  
Critical Latitude

AbstractThe disintegration of the equatorward-propagating K1 internal tide in the South China Sea (SCS) by parametric subharmonic instability (PSI) at its critical latitude of 14.52°N is investigated numerically. The multiple-source generation and long-range propagation of K1 internal tides are successfully reproduced. Using equilibrium analysis, the internal wave field near the critical latitude is found to experience two quasi-steady states, between which the subharmonic waves develop constantly. The simulated subharmonic waves agree well with classic PSI theoretical prediction. The PSI-induced near-inertial waves are of half the K1 frequency and dominantly high modes, the vertical scales ranging from 50 to 180 m in the upper ocean. From an energy perspective, PSI mainly occurs in the critical latitudinal zone from 13° to 15°N. In this zone, the incident internal tide loses ~14% energy in the mature state of PSI. PSI triggers a mixing elevation of O(10−5–10−4) m2 s−1 in the upper ocean at the critical latitude, which is several times larger than the background value. The contribution of PSI to the internal tide energy loss and associated enhanced mixing may differ regionally and is closely dependent on the intensity and duration of background internal tide. The results elucidate the far-field dissipation mechanism by PSI in connecting interior mixing with remotely generated K1 internal tides in the Luzon Strait.

scholarly journals Tidal Mixing in the South China Sea: An Estimate Based on the Internal Tide Energetics

2016 ◽  
Vol 46 (1) ◽  
pp. 107-124 ◽  
Author(s):  
Xiaowei Wang ◽  
Shiqiu Peng ◽  
Zhiyu Liu ◽  
Rui Xin Huang ◽  
Yu-Kun Qian ◽  
...  
Keyword(s):  
South China Sea ◽  
South China ◽  
Dissipation Rate ◽  
Internal Tide ◽  
The South China Sea ◽  
Internal Tides ◽  
Tidal Mixing ◽  
The South ◽  
China Sea ◽  
Diapycnal Diffusivity

AbstractBy taking into account the contributions of both locally and remotely generated internal tides, the tidal mixing in the Luzon Strait (LS) and the South China Sea (SCS) is investigated through internal-tide simulation and energetics analysis. A three-dimensional nonhydrostatic high-resolution model driven by four primary tidal constituents (M2, S2, K1, and O1) is used for the internal-tide simulation. The baroclinic energy budget analysis reveals that the internal tides radiated from the LS are the dominant energy source for the tidal dissipation in the SCS. In the LS, the estimated depth-integrated turbulent kinetic energy dissipation exceeds O(1) W m−2 atop the two subsurface ridges, with a dissipation rate of >O(10−7) W kg−1 and diapycnal diffusivity of ~O(10−2) m2 s−1. In the SCS, the most intense turbulence occurs in the deep-water basin with a dissipation rate of O(10−8–10−6) W kg−1 and diapycnal diffusivity of O(10−3–10−1) m2 s−1 within the ~2000-m water column above the seafloor as well as in the shelfbreak region with a dissipation rate of O(10−7–10−6) W kg−1 and diapycnal diffusivity of O(10−4–10−3) m2 s−1. These estimated values are consistent with observations reported in previous studies and are at least one order of magnitude larger than those based solely on locally generated internal tides.

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