This study aims to investigate characteristics of continental shelf wave(CSW)on the northwestern continental shelf of the South China Sea(SCS)induced by winter storms in 2021.Mooring and cruise observations,tidal gaug...This study aims to investigate characteristics of continental shelf wave(CSW)on the northwestern continental shelf of the South China Sea(SCS)induced by winter storms in 2021.Mooring and cruise observations,tidal gauge data at stations Hong Kong,Zhapo and Qinglan and sea surface wind data from January 1 to February 28,2021 are used to examine the relationship between along-shelf wind and sea level fluctuation.Two events of CSWs driven by the along-shelf sea surface wind are detected from wavelet spectra of tidal gauge data.The signals are triply peaked at periods of 56 h,94 h and 180 h,propagating along the coast with phase speed ranging from 6.9 m/s to18.9 m/s.The dispersion relation shows their property of the Kelvin mode of CSW.We develop a simple method to estimate amplitude of sea surface fluctuation by along-shelf wind.The results are comparable with the observation data,suggesting it is effective.The mode 2 CSWs fits very well with the mooring current velocity data.The results from rare current help to understand wave-current interaction in the northwestern SCS.展开更多
This study is the fi rst to depict typhoon-induced continental shelf wave(CSW)propagation in the eastern Taiwan Strait(TWS)during the passage of Typhoon Meranti in 2016 using tidal gauge data and along-track satellite...This study is the fi rst to depict typhoon-induced continental shelf wave(CSW)propagation in the eastern Taiwan Strait(TWS)during the passage of Typhoon Meranti in 2016 using tidal gauge data and along-track satellite altimeter data.The strong amplitude response of sea level oscillations(within the range of 0.30–0.54 m)as a free,barotropic CSW after Meranti,which impacted the TWS,was clearly detected in time and frequency(in bands of 64–81 h)using wavelet and cross-wavelet analyses.The measured group and phase speeds were consistent with the dispersion curves for CSW with the fi rst-mode derived from the cross-shelf sections of the eastern TWS,with the mean speeds reaching 3 and 5.6±0.7 m/s,respectively.Coincidentally,the typhoon-induced sea level anomaly(SLA)was also captured by the satellite altimeter before this CSW entered into the TWS.Using the theoretical cross-shore CSW modes to fi t the SLA data,the results indicated that the fi rst three wave modes can interpret this CSW event appeared in the southern TWS very well,with the fi rst mode being the dominant one.展开更多
The free shelf wave theory is applied to the practical case of the continental shelf in the East China Sea to analyse the effects of the shelf wave on the Kuroshio. The results indicate that the shelf wave in lower fr...The free shelf wave theory is applied to the practical case of the continental shelf in the East China Sea to analyse the effects of the shelf wave on the Kuroshio. The results indicate that the shelf wave in lower frequency travels from north to south and its phase velocity is proportional to the Kuroshio's current velocity) the maximum current velocity of the Kuroshio lies at the continental margin. The analytical solutions obtained indicate that the hydrodynamic characters of the sea region over the shelf present band structure. The horizontal motion ( x -component) caused by the shelf wave at the margin may be one of the causes for generating wavy pattern of the Kuroshio's axis .展开更多
Sand waves on the northern South China Sea shelf had been considered as stable relict bed form. For the industry use of sea bed between stations LF13-2 and LF13-1, a new round of explorations were conducted. The newly...Sand waves on the northern South China Sea shelf had been considered as stable relict bed form. For the industry use of sea bed between stations LF13-2 and LF13-1, a new round of explorations were conducted. The newly obtained data show that both spacings and amplitudes of sand waves are all systematically changing with water depth. Repeated observations since 2003 to 2004 showed that the sea bed is currently active. Due to strong erosion of surface sediment since Dongsha （东沙） uplifting, there are almost no modern sediments on the shelf of Dongsha area. Sand materials in the study area mainly originate from the erosion of the bed sediment formation. The water depth increment revealed by repeated echo sounder data is mainly due to erosion. Bottom currents are quite complex in the area of Dongsha underwater plateaus. At site 9MKH, the southward ebb current is stronger than the north- ward flood current, while at site AEM-HR, the WNW-ward flood current is slightly stronger than the ESE-ward ebb current. At site 9MKII, the maximum bottom current speed is 48 cm/s, and 22% of the observed bottom current speeds are larger than 20 cm/s, which meet the minimum bottom current speed required for the creation of sand wave. This article points out that present-day oceanographic condition couples well with the sand-wave morphologies, and that the sand waves are to a great extent in equilibrium with the ongoing present-day oceanographic bottom current condition and active.展开更多
Various aspects of studies on internal tides are reviewed .Both beam-like structure and modal structure of internal tides may exist in the ocean . Bottom intensifications are caused by many factors .e.g. upstream bloc...Various aspects of studies on internal tides are reviewed .Both beam-like structure and modal structure of internal tides may exist in the ocean . Bottom intensifications are caused by many factors .e.g. upstream blocking , which is the result of nonlinear interaction among waves . The energy may decay very fast so that internal tides are mostly locally generated .Internal tides may have considerable residual currents.In a 3-D frame, numerical study revealed that internal waves may interfere with each other to cause strong motions fer from the generation sources.The mechanism that determines how the lee waves break to form various nonlinear waves such as solitary waves, hydraulic jumps and internal surges or bores remains unclear. Analytic study is difficult , so numerical method may be effective . A radiation condition on the open boundary must be employed. A complete 3-D model may gain interesting result.Study on internal tides in China is limited to field observations and data analysis .展开更多
Abstract. Due to the incapability of high frequency surface wave radar （HFSWR） to detect undercurrent parameters, a new algorithm is proposed to apply a three-dimensional （3D） nonlinear barotropic shallow sea and ...Abstract. Due to the incapability of high frequency surface wave radar （HFSWR） to detect undercurrent parameters, a new algorithm is proposed to apply a three-dimensional （3D） nonlinear barotropic shallow sea and continental shelf model in coordinate system to the inversion of undercurrent. The calculation domain of this model is the area detected by HFSWR. Considering the benthal topography of the detected area and the ocean dynamic parameters, such as surface current, wind and wave detected by HFSWR, the relation between surface current and undercurrent is established in this model, Accordingly, the undercurrent parameters of corresponding area are obtained. The inversion results agree with the law of ocean dynamics and reproduce the movement of undercurrent.展开更多
Observations and numeric modeling of internal wave generation and transformation in the shelf zone of sea show that the main part of tidal energy is transported to shores in form of internal gravitational waves. Long-...Observations and numeric modeling of internal wave generation and transformation in the shelf zone of sea show that the main part of tidal energy is transported to shores in form of internal gravitational waves. Long-term measurements of temperature and current velocity fluctuations at many levels in the near-bottom thermocline were carried out during the periods when stable seasonal thermocline was present. Analysis of the measurements permits us to understand mechanisms of internal wave destruction with turbulent motion generation and corresponding rebuilding of velocity and density mean fields in the stratified near-bottom layer. Spectral analysis of temperature fluctuations shows that in shoaling internal waves the low-frequency maxima disappear, maxima at higher frequencies appear, and the spectra slope in the high frequency range changes with depth. Taking into account the concurrent analysis of near-bottom pressure fluctuations and current velocity fluctuations from surface till bottom we come to the conclusion that breaking internal waves in a near-bottom thermocline generate not only small-scale three-dimensional turbulence, but also quasi-horizontal turbulence of larger scales, which considerably contributes into mixing and sediments, alluvium, and nutrients transport in the shelf zone of sea.展开更多
基金The National Key R&D Program of China under contract No.2022YFC3104805the National Natural Science Foundation of China under contract Nos 42276019,41706025 and 41976200+4 种基金the Innovation Team Plan for Universities in Guangdong Province under contract No.2019KCXTF021the First-class Discipline Plan of Guangdong Province under contract Nos 080503032101and 231420003the Program for Scientific Research Start-up Funds of Guangdong Ocean University under contract No.060302032106the Open Fund Project of Key Laboratory of Marine Environmental Information Technology(2019)Ministry of Natural Resources。
文摘This study aims to investigate characteristics of continental shelf wave(CSW)on the northwestern continental shelf of the South China Sea(SCS)induced by winter storms in 2021.Mooring and cruise observations,tidal gauge data at stations Hong Kong,Zhapo and Qinglan and sea surface wind data from January 1 to February 28,2021 are used to examine the relationship between along-shelf wind and sea level fluctuation.Two events of CSWs driven by the along-shelf sea surface wind are detected from wavelet spectra of tidal gauge data.The signals are triply peaked at periods of 56 h,94 h and 180 h,propagating along the coast with phase speed ranging from 6.9 m/s to18.9 m/s.The dispersion relation shows their property of the Kelvin mode of CSW.We develop a simple method to estimate amplitude of sea surface fluctuation by along-shelf wind.The results are comparable with the observation data,suggesting it is effective.The mode 2 CSWs fits very well with the mooring current velocity data.The results from rare current help to understand wave-current interaction in the northwestern SCS.
基金Supported by the Science Foundation of Fujian Province(No.2019J01119)the Scientifi c Research Foundation of Third Institute of Oceanography,MNR(Nos.2017011,2019018)+1 种基金the National Natural Science Foundation of China(No.41506014)the National Key Research and Development Program of China(No.2016YFC1402607)。
文摘This study is the fi rst to depict typhoon-induced continental shelf wave(CSW)propagation in the eastern Taiwan Strait(TWS)during the passage of Typhoon Meranti in 2016 using tidal gauge data and along-track satellite altimeter data.The strong amplitude response of sea level oscillations(within the range of 0.30–0.54 m)as a free,barotropic CSW after Meranti,which impacted the TWS,was clearly detected in time and frequency(in bands of 64–81 h)using wavelet and cross-wavelet analyses.The measured group and phase speeds were consistent with the dispersion curves for CSW with the fi rst-mode derived from the cross-shelf sections of the eastern TWS,with the mean speeds reaching 3 and 5.6±0.7 m/s,respectively.Coincidentally,the typhoon-induced sea level anomaly(SLA)was also captured by the satellite altimeter before this CSW entered into the TWS.Using the theoretical cross-shore CSW modes to fi t the SLA data,the results indicated that the fi rst three wave modes can interpret this CSW event appeared in the southern TWS very well,with the fi rst mode being the dominant one.
文摘The free shelf wave theory is applied to the practical case of the continental shelf in the East China Sea to analyse the effects of the shelf wave on the Kuroshio. The results indicate that the shelf wave in lower frequency travels from north to south and its phase velocity is proportional to the Kuroshio's current velocity) the maximum current velocity of the Kuroshio lies at the continental margin. The analytical solutions obtained indicate that the hydrodynamic characters of the sea region over the shelf present band structure. The horizontal motion ( x -component) caused by the shelf wave at the margin may be one of the causes for generating wavy pattern of the Kuroshio's axis .
基金supported by the National Basic Research Pro-gram of China (973 Program) (No. 2007CB411702)the National Natural Science Foundation of China (Nos. 40572067, 40776032)
文摘Sand waves on the northern South China Sea shelf had been considered as stable relict bed form. For the industry use of sea bed between stations LF13-2 and LF13-1, a new round of explorations were conducted. The newly obtained data show that both spacings and amplitudes of sand waves are all systematically changing with water depth. Repeated observations since 2003 to 2004 showed that the sea bed is currently active. Due to strong erosion of surface sediment since Dongsha （东沙） uplifting, there are almost no modern sediments on the shelf of Dongsha area. Sand materials in the study area mainly originate from the erosion of the bed sediment formation. The water depth increment revealed by repeated echo sounder data is mainly due to erosion. Bottom currents are quite complex in the area of Dongsha underwater plateaus. At site 9MKH, the southward ebb current is stronger than the north- ward flood current, while at site AEM-HR, the WNW-ward flood current is slightly stronger than the ESE-ward ebb current. At site 9MKII, the maximum bottom current speed is 48 cm/s, and 22% of the observed bottom current speeds are larger than 20 cm/s, which meet the minimum bottom current speed required for the creation of sand wave. This article points out that present-day oceanographic condition couples well with the sand-wave morphologies, and that the sand waves are to a great extent in equilibrium with the ongoing present-day oceanographic bottom current condition and active.
文摘Various aspects of studies on internal tides are reviewed .Both beam-like structure and modal structure of internal tides may exist in the ocean . Bottom intensifications are caused by many factors .e.g. upstream blocking , which is the result of nonlinear interaction among waves . The energy may decay very fast so that internal tides are mostly locally generated .Internal tides may have considerable residual currents.In a 3-D frame, numerical study revealed that internal waves may interfere with each other to cause strong motions fer from the generation sources.The mechanism that determines how the lee waves break to form various nonlinear waves such as solitary waves, hydraulic jumps and internal surges or bores remains unclear. Analytic study is difficult , so numerical method may be effective . A radiation condition on the open boundary must be employed. A complete 3-D model may gain interesting result.Study on internal tides in China is limited to field observations and data analysis .
文摘Abstract. Due to the incapability of high frequency surface wave radar （HFSWR） to detect undercurrent parameters, a new algorithm is proposed to apply a three-dimensional （3D） nonlinear barotropic shallow sea and continental shelf model in coordinate system to the inversion of undercurrent. The calculation domain of this model is the area detected by HFSWR. Considering the benthal topography of the detected area and the ocean dynamic parameters, such as surface current, wind and wave detected by HFSWR, the relation between surface current and undercurrent is established in this model, Accordingly, the undercurrent parameters of corresponding area are obtained. The inversion results agree with the law of ocean dynamics and reproduce the movement of undercurrent.
文摘Observations and numeric modeling of internal wave generation and transformation in the shelf zone of sea show that the main part of tidal energy is transported to shores in form of internal gravitational waves. Long-term measurements of temperature and current velocity fluctuations at many levels in the near-bottom thermocline were carried out during the periods when stable seasonal thermocline was present. Analysis of the measurements permits us to understand mechanisms of internal wave destruction with turbulent motion generation and corresponding rebuilding of velocity and density mean fields in the stratified near-bottom layer. Spectral analysis of temperature fluctuations shows that in shoaling internal waves the low-frequency maxima disappear, maxima at higher frequencies appear, and the spectra slope in the high frequency range changes with depth. Taking into account the concurrent analysis of near-bottom pressure fluctuations and current velocity fluctuations from surface till bottom we come to the conclusion that breaking internal waves in a near-bottom thermocline generate not only small-scale three-dimensional turbulence, but also quasi-horizontal turbulence of larger scales, which considerably contributes into mixing and sediments, alluvium, and nutrients transport in the shelf zone of sea.
