The evolution of energy, energy flux and modal structure of the internal tides (ITs) in the northeastern South China Sea is examined using the measurements at two moorings along a cross-slope section from the deep con...The evolution of energy, energy flux and modal structure of the internal tides (ITs) in the northeastern South China Sea is examined using the measurements at two moorings along a cross-slope section from the deep continental slope to the shallow continental shelf. The energy of both diurnal and semidiurnal ITs clearly shows a ~14-day spring-neap cycle, but their phases lag that of barotropic tides, indicating that ITs are not generated on the continental slope. Observations of internal tidal energy flux suggest that they may be generated at the Luzon Strait and propagate west-northwest to the continental slope in the northwestern SCS. Because the continental slope is critical-supercritical with respect to diurnal ITs, about 4.6 kJ/m^2 of the incident energy and 8.7 kW/m of energy flux of diurnal ITs are reduced from the continental slope to the continental shelf. In contrast, the semidiurnal internal tides enter the shelf because of the sub-critical topography with respect to semidiurnal ITs. From the continental slope to the shelf, the vertical structure of diurnal ITs shows significant variation, with dominant Mode 1 on the deep slope and dominant higher modes on the shelf. On the contrary, the vertical structure of the semidiurnal ITs is stable, with dominant Mode 1.展开更多
On the basis of the theoretical research results by the author and the literature published up to date, the analysis and the justification presented in this paper show that the breaking products of oceanic internal wa...On the basis of the theoretical research results by the author and the literature published up to date, the analysis and the justification presented in this paper show that the breaking products of oceanic internal waves are not only turbulence, but also the fine-scale near-inertial internal waves （the oceanic reversible finestructure） for inertial waves and the internal solitary waves for internal tides respectively. It was found that the oceanic reversible finestructure may be induced by the effect of the horizontal component f （f = 2Ωcosφ） of the rotation vector on inertial waves. And a new instability of the theoretical shear and strain spectra due to the effect of f occurs at critical vertical wavenumber β c ≈ 0.1 cpm. It happens when the levels of shear and strain of the reversible finestructure are higher than those of inertial waves, which is induced by the effect of f along an ＂iso-potential-pycnal＂ of internal wave. If all breaking products of internal waves are taken into account, the average kinetic energy dissipation rate is an order of magnitude larger than the values of turbulence observed by microstructure measurements. The author’s theoretical research results are basically in agreement with those observed in IWEX, DRIFTER and PATCHEX experiments. An important impersonal fact is that on the mean temporal scale of thermohaline circulation these breaking products of internal waves exist simultaneously with turbulence. Because inertial waves are generated by winds at the surface, and internal tides are generated by strong tide-topography interactions, the analysis and justification in this paper support in principle the abyssal recipes Ⅱ：energetics of tidal and wind mixing by Munk Wunsch in 1998, in despite of the results of microstructure measurements for the turbulent kinetic energy dissipation rate and the diapycnal turbulent eddy diffusivity.展开更多
在全球的海洋中,中国东海和临近海域是最显著的内潮生成地之一。本文采用NODC(Levitus) World Ocean Atlas 1998提供的季平均温、盐资料,计算海水的密度,并计算垂向密度梯度的最大值点,得到一个较符合海水实际的密度分层。使用三维非线...在全球的海洋中,中国东海和临近海域是最显著的内潮生成地之一。本文采用NODC(Levitus) World Ocean Atlas 1998提供的季平均温、盐资料,计算海水的密度,并计算垂向密度梯度的最大值点,得到一个较符合海水实际的密度分层。使用三维非线性数值模型(将海洋分为2层)研究了潮汐(M2,S2,K1,O1分潮)作用下渤黄东海的内潮,揭示了整个海区内潮起伏的空间分布,结果发现大振幅的波动均发生在台湾东北(冲绳海槽)海域和中国近海地形突变之处,其中前者更显著。对于各分潮模拟得到的表面潮与TOPEX/Poseidon高度计资料基本一致。研究结果表明上层海水的深度和厚度的梯度对内潮有一定的影响;冬季分布区域比夏季小,强度比夏季大。展开更多
On the basis of the time series observations from a temperature chain and an acoustic Doppler current profiler on the continental shelf of the northern South China Sea, a sequence of internal solitary waves （ISWs） a...On the basis of the time series observations from a temperature chain and an acoustic Doppler current profiler on the continental shelf of the northern South China Sea, a sequence of internal solitary waves （ISWs） and background waves （BWs, including internal tides and near-inertial waves） on the continental shelf were captured simultaneously after the transit of Typhoon Neast in October 2011. These measurementsprovided a unique opportunity to explore the influence of BWs on the ISWs. The BWs appeared a conversion on the current strength and vertical mode structure during the observational period. The BWs were dominated by weak and mode-one waves before October 2 and then turned to strong and high-mode waves after that time. Meanwhile, the ISWs displayed different wave structures before and after October 2, which was closely related to BWs＇ changes. According to the current profiles of BWs, the high-mode wave structure with strong current could significantly strengthen the vertical shear of ISWs in the near-surface layer and promote the breaking of ISWs, and thus it may play an important role in affecting the background current condition.展开更多
By analyzing a data set collected using a moored instrument array and CTD during TOGA-COARE, it is found that there exist remarkable internal tides in the western equatorial Pacific Ocean around 1°45′S, 156°...By analyzing a data set collected using a moored instrument array and CTD during TOGA-COARE, it is found that there exist remarkable internal tides in the western equatorial Pacific Ocean around 1°45′S, 156°E, whose horizontal wavenumber （wavelength）, vertical wavenumber, h 156° orizontal propagation speed and vertical propagation speed are 3.3×10^-2 km^-1 （210 km）, - 1.6×10^-3m, 2.0 m/s and -3.8 cm/s, respectively, that is, the waveform propagates downwards slantingly. Moreover, the propagating direction rotates statistically clockwise as the depth increases and its cause is unclear.展开更多
By using a coordinate transformation,an exact solution of internal tides is obtained when the bot- tom slope is linear and the V(?)is(?)la frequency is constant.Consequently the dispersion relations of free waves are ...By using a coordinate transformation,an exact solution of internal tides is obtained when the bot- tom slope is linear and the V(?)is(?)la frequency is constant.Consequently the dispersion relations of free waves are presented.Compared with Baines solution,the solution derived here is more consistent with展开更多
The water column structure of the ice shelf cavity outflow from under Pine Island Glacier and its temporal variability were investigated using a hourly time series of yo-yo CTD and LADCP data collected over -24 h at t...The water column structure of the ice shelf cavity outflow from under Pine Island Glacier and its temporal variability were investigated using a hourly time series of yo-yo CTD and LADCP data collected over -24 h at the southern end of the ice shelf front. The primary water types present over the continental shelf off Pine Island Bay were Circumpolar Deep Water （CDW）, modified Circumpolar Deep Water （mCDW）, Shelf Water （SW）, and Ice Shelf Water （ISW）. As CDW transited the shelf, it transitioned into cooler, mCDW. In the upper 200 m, ISW dominated within 100 km of the ice shelf and SW further offshore. Within Pine Island Bay, the water column was partitioned into two primary layers based on their behavior： an upper outflowing layer from 100 m to 450 m composed of ISW with a significant meltwater component, 1%-2%, over an inflowing layer from -550 m to the sea bed composed of mCDW. Due to the small cavity extent, the outflowing water was warmer than the seawater freezing point. The upper ISW layer was further split into upper ISW layer #1 （100-300 m） and upper ISW layer #2 （320450 m） with the transition coinciding with the ice shelf draft. Small step-like features with heights from 1-50 m existed within both the ISW layers and were more prominent in upper ISW layer #1. A baroclinic signal at the semidiurnal frequency existed within both primary layers with the strongest signal, - 10 cm·s^-1, propagating vertically in the upper ISW layer.展开更多
The layered model in Part I was used to simulate the internal tide in a stratified, two layer, and rectangular sea area with step like topography. The internal tide current velocities of the upper and lower layers and...The layered model in Part I was used to simulate the internal tide in a stratified, two layer, and rectangular sea area with step like topography. The internal tide current velocities of the upper and lower layers and the interfacial elevations were computed and the effect of the upper layer water depth and density difference were studied. Numerical experiments verified that the model can correctly simulate internal tides. The model was also applied to the northwestern part of the South China Sea to simulate the internal tides there with real topography. The distributions of internal tide amplitude in interfaces were delineated.展开更多
A two-dimensional spectral-difference mode (with vorticity and density equations) of internal tides isdeveloped for studying the genration and propagration of internal tides generated at the continentalshelf/slope. In...A two-dimensional spectral-difference mode (with vorticity and density equations) of internal tides isdeveloped for studying the genration and propagration of internal tides generated at the continentalshelf/slope. In general, internal tides propagate seaward in deep sea regions and shoreward on the shelf,and are dissipated rapidly. When the Vaisala frequency decreases vertically, waves may be mostly limited to thecontinental slope region. in deep sea region, motions may have either boam-like structure or modal structure,depending on the stratification strerigth and structure, whereas a modal structure may always exist onthe shelf. Waves show strong bottom intensification on the slope when strong stratification exists on thebottom. The barotropic tidal advection may affed the temporal character of internal tides at thecontinental slope, shelf break and shelf regions. but may have little influence on the energy density and energy flux of internal tides. ln the case of strong stratification, waverforms展开更多
基金The State Key Laboratory of Tropical Oceanography,South China Sea Institute of Oceanology,Chinese Academy of Sciences under contract No.LTO1915the National Natural Science Foundation of China under contract Nos 41630970,41876016,41676022 and 41521005the Instrument Developing Project of the CAS under contract No.YZ201432
文摘The evolution of energy, energy flux and modal structure of the internal tides (ITs) in the northeastern South China Sea is examined using the measurements at two moorings along a cross-slope section from the deep continental slope to the shallow continental shelf. The energy of both diurnal and semidiurnal ITs clearly shows a ~14-day spring-neap cycle, but their phases lag that of barotropic tides, indicating that ITs are not generated on the continental slope. Observations of internal tidal energy flux suggest that they may be generated at the Luzon Strait and propagate west-northwest to the continental slope in the northwestern SCS. Because the continental slope is critical-supercritical with respect to diurnal ITs, about 4.6 kJ/m^2 of the incident energy and 8.7 kW/m of energy flux of diurnal ITs are reduced from the continental slope to the continental shelf. In contrast, the semidiurnal internal tides enter the shelf because of the sub-critical topography with respect to semidiurnal ITs. From the continental slope to the shelf, the vertical structure of diurnal ITs shows significant variation, with dominant Mode 1 on the deep slope and dominant higher modes on the shelf. On the contrary, the vertical structure of the semidiurnal ITs is stable, with dominant Mode 1.
基金The Key Program of National Natural Science Foundation of China under contract No.41030855
文摘On the basis of the theoretical research results by the author and the literature published up to date, the analysis and the justification presented in this paper show that the breaking products of oceanic internal waves are not only turbulence, but also the fine-scale near-inertial internal waves （the oceanic reversible finestructure） for inertial waves and the internal solitary waves for internal tides respectively. It was found that the oceanic reversible finestructure may be induced by the effect of the horizontal component f （f = 2Ωcosφ） of the rotation vector on inertial waves. And a new instability of the theoretical shear and strain spectra due to the effect of f occurs at critical vertical wavenumber β c ≈ 0.1 cpm. It happens when the levels of shear and strain of the reversible finestructure are higher than those of inertial waves, which is induced by the effect of f along an ＂iso-potential-pycnal＂ of internal wave. If all breaking products of internal waves are taken into account, the average kinetic energy dissipation rate is an order of magnitude larger than the values of turbulence observed by microstructure measurements. The author’s theoretical research results are basically in agreement with those observed in IWEX, DRIFTER and PATCHEX experiments. An important impersonal fact is that on the mean temporal scale of thermohaline circulation these breaking products of internal waves exist simultaneously with turbulence. Because inertial waves are generated by winds at the surface, and internal tides are generated by strong tide-topography interactions, the analysis and justification in this paper support in principle the abyssal recipes Ⅱ：energetics of tidal and wind mixing by Munk Wunsch in 1998, in despite of the results of microstructure measurements for the turbulent kinetic energy dissipation rate and the diapycnal turbulent eddy diffusivity.
文摘在全球的海洋中,中国东海和临近海域是最显著的内潮生成地之一。本文采用NODC(Levitus) World Ocean Atlas 1998提供的季平均温、盐资料,计算海水的密度,并计算垂向密度梯度的最大值点,得到一个较符合海水实际的密度分层。使用三维非线性数值模型(将海洋分为2层)研究了潮汐(M2,S2,K1,O1分潮)作用下渤黄东海的内潮,揭示了整个海区内潮起伏的空间分布,结果发现大振幅的波动均发生在台湾东北(冲绳海槽)海域和中国近海地形突变之处,其中前者更显著。对于各分潮模拟得到的表面潮与TOPEX/Poseidon高度计资料基本一致。研究结果表明上层海水的深度和厚度的梯度对内潮有一定的影响;冬季分布区域比夏季小,强度比夏季大。
基金The National Nature Science Foundation of China under contract Nos U1133001,41030855 and 2013AA09A502
文摘On the basis of the time series observations from a temperature chain and an acoustic Doppler current profiler on the continental shelf of the northern South China Sea, a sequence of internal solitary waves （ISWs） and background waves （BWs, including internal tides and near-inertial waves） on the continental shelf were captured simultaneously after the transit of Typhoon Neast in October 2011. These measurementsprovided a unique opportunity to explore the influence of BWs on the ISWs. The BWs appeared a conversion on the current strength and vertical mode structure during the observational period. The BWs were dominated by weak and mode-one waves before October 2 and then turned to strong and high-mode waves after that time. Meanwhile, the ISWs displayed different wave structures before and after October 2, which was closely related to BWs＇ changes. According to the current profiles of BWs, the high-mode wave structure with strong current could significantly strengthen the vertical shear of ISWs in the near-surface layer and promote the breaking of ISWs, and thus it may play an important role in affecting the background current condition.
基金supported by the National Natural Science Foundation of China under contract Nos 49676275 and 49976002the Microwave Imaging National Key Laboratory Foundation under contract No.51442020103JW1002.
文摘By analyzing a data set collected using a moored instrument array and CTD during TOGA-COARE, it is found that there exist remarkable internal tides in the western equatorial Pacific Ocean around 1°45′S, 156°E, whose horizontal wavenumber （wavelength）, vertical wavenumber, h 156° orizontal propagation speed and vertical propagation speed are 3.3×10^-2 km^-1 （210 km）, - 1.6×10^-3m, 2.0 m/s and -3.8 cm/s, respectively, that is, the waveform propagates downwards slantingly. Moreover, the propagating direction rotates statistically clockwise as the depth increases and its cause is unclear.
基金National Education Committee Foundation Programs 9142305 and 9342305National Natural Science Foundation Program 49376257National Special Research Program 85-927-05-03
文摘By using a coordinate transformation,an exact solution of internal tides is obtained when the bot- tom slope is linear and the V(?)is(?)la frequency is constant.Consequently the dispersion relations of free waves are presented.Compared with Baines solution,the solution derived here is more consistent with
基金support personnel on the RVIB Nathaniel B.Palmer during NPB0901funded partially by both the Australian Antarctic Division,project 2944
文摘The water column structure of the ice shelf cavity outflow from under Pine Island Glacier and its temporal variability were investigated using a hourly time series of yo-yo CTD and LADCP data collected over -24 h at the southern end of the ice shelf front. The primary water types present over the continental shelf off Pine Island Bay were Circumpolar Deep Water （CDW）, modified Circumpolar Deep Water （mCDW）, Shelf Water （SW）, and Ice Shelf Water （ISW）. As CDW transited the shelf, it transitioned into cooler, mCDW. In the upper 200 m, ISW dominated within 100 km of the ice shelf and SW further offshore. Within Pine Island Bay, the water column was partitioned into two primary layers based on their behavior： an upper outflowing layer from 100 m to 450 m composed of ISW with a significant meltwater component, 1%-2%, over an inflowing layer from -550 m to the sea bed composed of mCDW. Due to the small cavity extent, the outflowing water was warmer than the seawater freezing point. The upper ISW layer was further split into upper ISW layer #1 （100-300 m） and upper ISW layer #2 （320450 m） with the transition coinciding with the ice shelf draft. Small step-like features with heights from 1-50 m existed within both the ISW layers and were more prominent in upper ISW layer #1. A baroclinic signal at the semidiurnal frequency existed within both primary layers with the strongest signal, - 10 cm·s^-1, propagating vertically in the upper ISW layer.
文摘The layered model in Part I was used to simulate the internal tide in a stratified, two layer, and rectangular sea area with step like topography. The internal tide current velocities of the upper and lower layers and the interfacial elevations were computed and the effect of the upper layer water depth and density difference were studied. Numerical experiments verified that the model can correctly simulate internal tides. The model was also applied to the northwestern part of the South China Sea to simulate the internal tides there with real topography. The distributions of internal tide amplitude in interfaces were delineated.
基金National Education Committee Foundation Program(9142305)National Science Foundation Program(49376257)
文摘A two-dimensional spectral-difference mode (with vorticity and density equations) of internal tides isdeveloped for studying the genration and propagration of internal tides generated at the continentalshelf/slope. In general, internal tides propagate seaward in deep sea regions and shoreward on the shelf,and are dissipated rapidly. When the Vaisala frequency decreases vertically, waves may be mostly limited to thecontinental slope region. in deep sea region, motions may have either boam-like structure or modal structure,depending on the stratification strerigth and structure, whereas a modal structure may always exist onthe shelf. Waves show strong bottom intensification on the slope when strong stratification exists on thebottom. The barotropic tidal advection may affed the temporal character of internal tides at thecontinental slope, shelf break and shelf regions. but may have little influence on the energy density and energy flux of internal tides. ln the case of strong stratification, waverforms
