Surface waves have a considerable effect on vertical mixing in the upper ocean.In the past two decades,the vertical mixing induced through nonbreaking surface waves has been used in ocean and climate models to improve...Surface waves have a considerable effect on vertical mixing in the upper ocean.In the past two decades,the vertical mixing induced through nonbreaking surface waves has been used in ocean and climate models to improve the simulation of the upper ocean.Thus far,several nonbreaking wave-induced mixing parameterization schemes have been proposed;however,no quantitative comparison has been performed among them.In this paper,a one-dimensional ocean model was used to compare the performances of five schemes,including those of Qiao et al.(Q),Hu and Wang(HW),Huang and Qiao(HQ),Pleskachevsky et al.(P),and Ghantous and Babanin(GB).Similar to previous studies,all of these schemes can decrease the simulated sea surface temperature(SST),increase the subsurface temperature,and deepen the mixed layer,thereby alleviating the common thermal deviation problem of the ocean model for upper ocean simulation.Among these schemes,the HQ scheme exhibited the weakest wave-induced mixing effect,and the HW scheme exhibited the strongest effect;the other three schemes exhibited roughly the same effect.In particular,the Q and P schemes exhibited nearly the same effect.In the simulation based on observations from the Ocean Weather Station Papa,the HQ scheme exhibited the best performance,followed by the Q scheme.In the experiment with the HQ scheme,the root-mean-square deviation of the simulated SST from the observations was 0.43℃,and the mixed layer depth(MLD)was 2.0 m.As a contrast,the deviations of the SST and MLD reached 1.25℃ and 8.4 m,respectively,in the experiment without wave-induced mixing.展开更多
Diapycnal mixing plays an important role in the ocean circulation.Internal waves are a kind of bridge relating the diapycnal mixing to external sources of mechanical energy.Difficulty in obtaining eigen solutions of i...Diapycnal mixing plays an important role in the ocean circulation.Internal waves are a kind of bridge relating the diapycnal mixing to external sources of mechanical energy.Difficulty in obtaining eigen solutions of internal waves over curved topography is a limitation for further theoretical study on the generation problem and scattering process.In this study,a kind of transform method is put forward to derive the eigen solutions of internal waves over subcritical topography in twodimensional and linear framework.The transform converts the curved topography in physical space to flat bottom in transform space while the governing equation of internal waves is still hyperbolic if proper transform function is selected.Thus,one can obtain eigen solutions of internal waves in the transform space.Several examples of transform functions,which convert the linear slope,the convex slope,and the concave slope to flat bottom,and the corresponding eigen solutions are illustrated.A method,using a polynomial to approximate the transform function and least squares method to estimate the undetermined coefficients in the polynomial,is introduced to calculate the approximate expression of the transform function for the given subcritical topography.展开更多
The scattering process, which means the redistribution of energy fluy in modenumber space, is analyzed for internal waves propagating from the abyssal ocean onto a subcritical strait slope and then a shelf region. In ...The scattering process, which means the redistribution of energy fluy in modenumber space, is analyzed for internal waves propagating from the abyssal ocean onto a subcritical strait slope and then a shelf region. In light of Wunsch＇s work, the waves are analytically expressed as superimposition of eigensolutions distribution of energy flux in the shelf region： one is the ratio of water depth in and the other is the ratio of the slope of the internal tide rays to the topographic energy flux distribution： the energy flux is focused around one modenumber or case, the range of modenumbers where energy flux is distributed is narrow. Two parameters have evident effects on the the shelf region to that in the abyssal ocean slope. Generally, there are two patterns of focused around two modenumbers. In any case, the range of modenumbers where energy flux is distributed is narrow.展开更多
Continuous observation of sea water temperature and current was made at Wenchang Station(19°35′N,112°E) in 2005. The data collected indicate vigorous internal waves of both short periods and tidal and near-...Continuous observation of sea water temperature and current was made at Wenchang Station(19°35′N,112°E) in 2005. The data collected indicate vigorous internal waves of both short periods and tidal and near-inertial periods. The temperature and current time series during 18-30 September were examined to describe the upper ocean internal wave field response to Typhoon Damrey(0518) . The strong wind associated with the typhoon,which passed over the sea area about 45 km south of Wenchang Station on 25 September,deepened the mixed layer depth remarkably. It decreased the mixed layer temperature while increasing the deep layer temperature,and intensified the near-inertial and high-frequency fluctuations of temperature and current. Power spectra of temperature and current time series indicate significant deviations from those obtained by using the deep ocean internal wave models characterized by a power law. The frequency spectra were dominated by three energetic bands:around the inertial frequency(7.75× 10-6 Hz) ,tidal frequencies(1.0×10-5 to 2.4×10-5 Hz) ,and between 1.4×10-4 and 8.3×10-4 Hz. Dividing the field data into three phases(before,during and after the typhoon) ,we found that the typhoon enhanced the kinetic energy in nearly all the frequency bands,especially in the surface water. The passage of Damrey made a major contribution to the horizontal kinetic energy of the total surface current variances. The vertical energy density distribution,with its peak value at the surface,was an indication that the energy injected by the strong wind into the surface current could penetrate downward to the thermocline.展开更多
Insufficient vertical mixing in the upper ocean during summer is a common problem of oceanic circulation and climate models.The turbulence associated with non-breaking waves is widely believed to effectively solve thi...Insufficient vertical mixing in the upper ocean during summer is a common problem of oceanic circulation and climate models.The turbulence associated with non-breaking waves is widely believed to effectively solve this problem.In many studies,non-breaking surface wave processes are attributed to the effects of Langmuir circulations(LCs).In the present work,the influences of LCs on the upper-ocean thermal structure are examined by using one-and three-dimensional ocean circulation,as well as climate,models.The results indicated that the effect of vertical mixing enhanced by LCs is limited to the upper ocean.The models evaluated,including those considering LC effects alone and the combined effects of LCs and wave breaking,failed to produce a reasonable summertime thermocline,resulting in a large cold bias in the subsurface layer.Therefore,while they can slightly reduce the biases of mixed layer depths and sea surface temperatures in models,LCs are insufficient to solve the problem of insufficient vertical mixing.Moreover,restriction of non-breaking surface wave-induced processes in LCs may be questionable.展开更多
Internal waves propagate along wave beams that are inclined with respect to the horizontal plane. It is conjectured that the internal waves generated in the Luzon Strait may be confined between the double ridges in th...Internal waves propagate along wave beams that are inclined with respect to the horizontal plane. It is conjectured that the internal waves generated in the Luzon Strait may be confined between the double ridges in the strait and concentrate to a closed trajectory, the so-called internal wave attractor, due to the reflection of wave beams from the lateral boundaries, sea surface and bottom. This work carried out two experiments using a three dimensional non-hydrostatic general circulation model, MITgcm, to investigate the possibility that the ridges in the Lnzon Strait allows for internal wave attractors. Baroclinic current in both of the experiments demonstrate the forming of ring-like patterns in some section around 20° and 21°N, indicating that the development of the internal wave attractors are allowed in the Luzon Strait. The different resolutions and initial conditions in the two experiments also reveal that the internal-wave-attractor phenomenon is robust in this region.展开更多
Laboratory experiments and field observations show that the equilibrium range of wind wave spectra presents a – 4 power law when it is scaled properly. This feature has been attributed to energy balance in spectral s...Laboratory experiments and field observations show that the equilibrium range of wind wave spectra presents a – 4 power law when it is scaled properly. This feature has been attributed to energy balance in spectral space by many researchers. In this paper we point out that white noise on an oscillation system can also lead to a similar inverse power law in the corresponding displacement spectrum, implying that the – 4 power law for the equilibrium range of wind wave spectra may probably only reflect the randomicity of the wind waves rather than any other dynamical processes in physical space. This explanation may shed light on the mechanism of other physical processes with spectra also showing an inverse power law, such as isotropic turbulence, internal waves, etc.展开更多
Diapycnal mixing is important in oceanic circulation. An inverse method in which a semi-explicit scheme is applied to discretize the one-dimensional temperature diffusion equation is established to estimate the vertic...Diapycnal mixing is important in oceanic circulation. An inverse method in which a semi-explicit scheme is applied to discretize the one-dimensional temperature diffusion equation is established to estimate the vertical temperature diffusion coefficient based on the observed temperature profiles. The sensitivity of the inverse model in the idealized and actual conditions is tested in detail. It can be found that this inverse model has high feasibility under multiple situations ensuring the stability of the inverse model, and can be considered as an efficient way to estimate the temperature diffusion coefficient in the weak current regions of the ocean. Here, the hydrographic profiles from Argo floats are used to estimate the temporal and spatial distribution of the vertical mixing in the north central Pacific based on this inverse method. It is further found that the vertical mixing in the upper ocean displays a distinct seasonal variation with the amplitude decreasing with depth, and the vertical mixing over rough topography is stronger than that over smooth topography It is suggested that the high-resolution profiles from Argo floats and a more reasonable design of the inverse scheme will serve to understand mixing processes.展开更多
Continuous observation in late April 2005 on the northwestern shelf of the South China Sea reveals vigorous strong currents, the maximum velocity of which exceeds 3.8 m/s. The strong currents occurred around spring ti...Continuous observation in late April 2005 on the northwestern shelf of the South China Sea reveals vigorous strong currents, the maximum velocity of which exceeds 3.8 m/s. The strong currents occurred around spring tide period, when the internal tide waves were also expected to be vigorous. Analysis shows that the major peaks of the current power spectrum are in low frequency band. Using a numerical method applied to the actual ocean stratification, we find that the amplitude profiles of the strong current are similar to that of the currents induced by some low-mode internal waves （at diurnal or semi-diurnal frequency）. It indicates that the temporal and spatial features of strong currents were possibly induced by low frequency internal waves.展开更多
In order to investigate the aggregation mechanism of green macroalgae(Enteromorpha prolifera)on the Qingdao coastline,the macroalgal drift characteristics in the Yellow Sea during June and July in 2008 and 2010 were s...In order to investigate the aggregation mechanism of green macroalgae(Enteromorpha prolifera)on the Qingdao coastline,the macroalgal drift characteristics in the Yellow Sea during June and July in 2008 and 2010 were simulated using a three-dimensional wave-tide-circulation coupled model.In June 2008,the monthly-mean surface current flowed onshore and its direction was almost perpendicular to the Qingdao coastline,which was identified as the main reason for a huge accumulation of algae in the coastal waters off Qingdao.The current became parallel to the coastline in July 2008;this shift in current direction led to little accumulation of algae near Qingdao and thus relieved the environmental pressure on the Olympic sailing events.By using the coupled model,we predicted that there would be no serious algal accumulation at Qingdao in late June 2010,which was later confirmed by observations.This study demonstrated that the drift path of macroalgae near Qingdao is mainly controlled by the surface current,which is primarily driven by wind.Regional climate change is therefore one of the means by which physical processes affect marine ecosystems.展开更多
The classical Ekman theory tells us that the ocean surface current turns to the right(left) side of wind direction with 45° in the north(south) hemisphere,but the observation and research results show that the su...The classical Ekman theory tells us that the ocean surface current turns to the right(left) side of wind direction with 45° in the north(south) hemisphere,but the observation and research results show that the surface current deflexion angle is smaller than 45° in the Arctic and high latitude areas while larger than 45° in the low latitude areas.In order to explain these phenomena,a series of idealized numerical experiments are designed to investigate the influence of vertical viscosity coefficients with different vertical distribution characteristics on the classical and steady Ekman spiral structure.Results show that when the vertical viscosity coefficient decreases with water depth,the surface current deflexion angle is larger than 45°,whereas the angle is smaller than 45° when the vertical viscosity coefficient increases with water depth.So the different observed surface current deflexion angles in low latitude sea areas and the Arctic regions should be attributed to the different vertical distribution characteristics of vertical viscosity coefficients in the upper ocean.The flatness of the Ekman spiral is not equal to one and does not show regular behaviors for the numerical experiments with different distribution of vertical viscosity.However,the magnitudes and directions of volume transport of Ekman spirals are almost the same as the results of classical Ekman theory,i.e.,vertical viscosity coefficient distributions have no effect on the magnitudes and directions of volume transport.展开更多
基金supported by the Laoshan Laboratory(No.LSKJ202201600)the National Key Research and Development Program of China(No.2022YFC2808304).
文摘Surface waves have a considerable effect on vertical mixing in the upper ocean.In the past two decades,the vertical mixing induced through nonbreaking surface waves has been used in ocean and climate models to improve the simulation of the upper ocean.Thus far,several nonbreaking wave-induced mixing parameterization schemes have been proposed;however,no quantitative comparison has been performed among them.In this paper,a one-dimensional ocean model was used to compare the performances of five schemes,including those of Qiao et al.(Q),Hu and Wang(HW),Huang and Qiao(HQ),Pleskachevsky et al.(P),and Ghantous and Babanin(GB).Similar to previous studies,all of these schemes can decrease the simulated sea surface temperature(SST),increase the subsurface temperature,and deepen the mixed layer,thereby alleviating the common thermal deviation problem of the ocean model for upper ocean simulation.Among these schemes,the HQ scheme exhibited the weakest wave-induced mixing effect,and the HW scheme exhibited the strongest effect;the other three schemes exhibited roughly the same effect.In particular,the Q and P schemes exhibited nearly the same effect.In the simulation based on observations from the Ocean Weather Station Papa,the HQ scheme exhibited the best performance,followed by the Q scheme.In the experiment with the HQ scheme,the root-mean-square deviation of the simulated SST from the observations was 0.43℃,and the mixed layer depth(MLD)was 2.0 m.As a contrast,the deviations of the SST and MLD reached 1.25℃ and 8.4 m,respectively,in the experiment without wave-induced mixing.
基金the National Nature Science Foundation of China under contract No. 40876015the National High Technology Research and Development Program of China (863 Program) under contract No. 2008AA09A402
文摘Diapycnal mixing plays an important role in the ocean circulation.Internal waves are a kind of bridge relating the diapycnal mixing to external sources of mechanical energy.Difficulty in obtaining eigen solutions of internal waves over curved topography is a limitation for further theoretical study on the generation problem and scattering process.In this study,a kind of transform method is put forward to derive the eigen solutions of internal waves over subcritical topography in twodimensional and linear framework.The transform converts the curved topography in physical space to flat bottom in transform space while the governing equation of internal waves is still hyperbolic if proper transform function is selected.Thus,one can obtain eigen solutions of internal waves in the transform space.Several examples of transform functions,which convert the linear slope,the convex slope,and the concave slope to flat bottom,and the corresponding eigen solutions are illustrated.A method,using a polynomial to approximate the transform function and least squares method to estimate the undetermined coefficients in the polynomial,is introduced to calculate the approximate expression of the transform function for the given subcritical topography.
基金This study was financially supported by the National Nature Science Foundation of China(Grant No.40406008)the Foundation for Open Proiects of the Key Lab of Physical Oceanography,Ministry of Education,China(Grant No.200309).
文摘The scattering process, which means the redistribution of energy fluy in modenumber space, is analyzed for internal waves propagating from the abyssal ocean onto a subcritical strait slope and then a shelf region. In light of Wunsch＇s work, the waves are analytically expressed as superimposition of eigensolutions distribution of energy flux in the shelf region： one is the ratio of water depth in and the other is the ratio of the slope of the internal tide rays to the topographic energy flux distribution： the energy flux is focused around one modenumber or case, the range of modenumbers where energy flux is distributed is narrow. Two parameters have evident effects on the the shelf region to that in the abyssal ocean slope. Generally, there are two patterns of focused around two modenumbers. In any case, the range of modenumbers where energy flux is distributed is narrow.
基金This study is supported by the National Natural Science Foundation of China(Grant No.40476017)the Knowledge Innovation Program of the Chinese Academy of Sciences(Grant No.KZCX2-YW-201).
文摘Continuous observation of sea water temperature and current was made at Wenchang Station(19°35′N,112°E) in 2005. The data collected indicate vigorous internal waves of both short periods and tidal and near-inertial periods. The temperature and current time series during 18-30 September were examined to describe the upper ocean internal wave field response to Typhoon Damrey(0518) . The strong wind associated with the typhoon,which passed over the sea area about 45 km south of Wenchang Station on 25 September,deepened the mixed layer depth remarkably. It decreased the mixed layer temperature while increasing the deep layer temperature,and intensified the near-inertial and high-frequency fluctuations of temperature and current. Power spectra of temperature and current time series indicate significant deviations from those obtained by using the deep ocean internal wave models characterized by a power law. The frequency spectra were dominated by three energetic bands:around the inertial frequency(7.75× 10-6 Hz) ,tidal frequencies(1.0×10-5 to 2.4×10-5 Hz) ,and between 1.4×10-4 and 8.3×10-4 Hz. Dividing the field data into three phases(before,during and after the typhoon) ,we found that the typhoon enhanced the kinetic energy in nearly all the frequency bands,especially in the surface water. The passage of Damrey made a major contribution to the horizontal kinetic energy of the total surface current variances. The vertical energy density distribution,with its peak value at the surface,was an indication that the energy injected by the strong wind into the surface current could penetrate downward to the thermocline.
基金the National Key Research and Development Program of China(No.2017YFC1404000)the Basic Scientific Fund for National Public Research Institutes of China(No.2018S03)+1 种基金the National Natural Science Foundation of China(Nos.41776038 and 41376036)Dr.Fangli Qiao was supported by the Natural Science Foundation of China(Nos.41821004).
文摘Insufficient vertical mixing in the upper ocean during summer is a common problem of oceanic circulation and climate models.The turbulence associated with non-breaking waves is widely believed to effectively solve this problem.In many studies,non-breaking surface wave processes are attributed to the effects of Langmuir circulations(LCs).In the present work,the influences of LCs on the upper-ocean thermal structure are examined by using one-and three-dimensional ocean circulation,as well as climate,models.The results indicated that the effect of vertical mixing enhanced by LCs is limited to the upper ocean.The models evaluated,including those considering LC effects alone and the combined effects of LCs and wave breaking,failed to produce a reasonable summertime thermocline,resulting in a large cold bias in the subsurface layer.Therefore,while they can slightly reduce the biases of mixed layer depths and sea surface temperatures in models,LCs are insufficient to solve the problem of insufficient vertical mixing.Moreover,restriction of non-breaking surface wave-induced processes in LCs may be questionable.
基金The National Basic Research Program(973 Program) of China under contract No.2011CB403502the Major National Scientific Research Projects of China under contract No.2012CB957803+2 种基金the National Natural Science Foundation of China under contract No41476024the National Natural Science Foundation of China-Shandong Joint Fund of Marine Science Research Centers of China under contract No.U1406404the Foundation for Outstanding Young and Middle-aged Scientists in Shandong Province of China under contract No.BS2011HZ019
文摘Internal waves propagate along wave beams that are inclined with respect to the horizontal plane. It is conjectured that the internal waves generated in the Luzon Strait may be confined between the double ridges in the strait and concentrate to a closed trajectory, the so-called internal wave attractor, due to the reflection of wave beams from the lateral boundaries, sea surface and bottom. This work carried out two experiments using a three dimensional non-hydrostatic general circulation model, MITgcm, to investigate the possibility that the ridges in the Lnzon Strait allows for internal wave attractors. Baroclinic current in both of the experiments demonstrate the forming of ring-like patterns in some section around 20° and 21°N, indicating that the development of the internal wave attractors are allowed in the Luzon Strait. The different resolutions and initial conditions in the two experiments also reveal that the internal-wave-attractor phenomenon is robust in this region.
基金This study was financially supported by the National Natural Science Foundation of China （Grant No. 40406008）the Foundation for 0pen Projects of the Key Lab of Physical 0ceanography, the Ministry of Education, China （Grant No. 200309）.
文摘Laboratory experiments and field observations show that the equilibrium range of wind wave spectra presents a – 4 power law when it is scaled properly. This feature has been attributed to energy balance in spectral space by many researchers. In this paper we point out that white noise on an oscillation system can also lead to a similar inverse power law in the corresponding displacement spectrum, implying that the – 4 power law for the equilibrium range of wind wave spectra may probably only reflect the randomicity of the wind waves rather than any other dynamical processes in physical space. This explanation may shed light on the mechanism of other physical processes with spectra also showing an inverse power law, such as isotropic turbulence, internal waves, etc.
基金The Program for New Century Excellent Talents in University of the Ministry of Education under contract No.NCET-10-0764the National High Technology Research and Development Program of China(863 Program)under contract No.2013AA09A502the National Natural Science Foundation of China under contract Nos 40876015 and 41176010
文摘Diapycnal mixing is important in oceanic circulation. An inverse method in which a semi-explicit scheme is applied to discretize the one-dimensional temperature diffusion equation is established to estimate the vertical temperature diffusion coefficient based on the observed temperature profiles. The sensitivity of the inverse model in the idealized and actual conditions is tested in detail. It can be found that this inverse model has high feasibility under multiple situations ensuring the stability of the inverse model, and can be considered as an efficient way to estimate the temperature diffusion coefficient in the weak current regions of the ocean. Here, the hydrographic profiles from Argo floats are used to estimate the temporal and spatial distribution of the vertical mixing in the north central Pacific based on this inverse method. It is further found that the vertical mixing in the upper ocean displays a distinct seasonal variation with the amplitude decreasing with depth, and the vertical mixing over rough topography is stronger than that over smooth topography It is suggested that the high-resolution profiles from Argo floats and a more reasonable design of the inverse scheme will serve to understand mixing processes.
基金the National Natural Science Foundation of China under contract Nos 41006018 and 40730842The National Basic Research Program(973 Program)of China under contract No.2011CB403502+2 种基金the National High Technology Research and Development Program(863 Program)of China under contract No.2008AA09A402Open Fund of the Key Laboratory of Ocean Circulation and WavesChinese Academy of Sciences under contract No.KLOCAW0905
文摘Continuous observation in late April 2005 on the northwestern shelf of the South China Sea reveals vigorous strong currents, the maximum velocity of which exceeds 3.8 m/s. The strong currents occurred around spring tide period, when the internal tide waves were also expected to be vigorous. Analysis shows that the major peaks of the current power spectrum are in low frequency band. Using a numerical method applied to the actual ocean stratification, we find that the amplitude profiles of the strong current are similar to that of the currents induced by some low-mode internal waves （at diurnal or semi-diurnal frequency）. It indicates that the temporal and spatial features of strong currents were possibly induced by low frequency internal waves.
基金supported by the National 908 Project of China(908-02-01-04)the National Key Technology R&D Special Program(2008 BAC49B02)
文摘In order to investigate the aggregation mechanism of green macroalgae(Enteromorpha prolifera)on the Qingdao coastline,the macroalgal drift characteristics in the Yellow Sea during June and July in 2008 and 2010 were simulated using a three-dimensional wave-tide-circulation coupled model.In June 2008,the monthly-mean surface current flowed onshore and its direction was almost perpendicular to the Qingdao coastline,which was identified as the main reason for a huge accumulation of algae in the coastal waters off Qingdao.The current became parallel to the coastline in July 2008;this shift in current direction led to little accumulation of algae near Qingdao and thus relieved the environmental pressure on the Olympic sailing events.By using the coupled model,we predicted that there would be no serious algal accumulation at Qingdao in late June 2010,which was later confirmed by observations.This study demonstrated that the drift path of macroalgae near Qingdao is mainly controlled by the surface current,which is primarily driven by wind.Regional climate change is therefore one of the means by which physical processes affect marine ecosystems.
基金supported by the National Natural Science Foundation of China(Grant No.40876015)the Project of Comprehensive Evaluation of Polar Areas on Global and Regional Climate Changes(Grant No.CHINARE2012-04-04)
文摘The classical Ekman theory tells us that the ocean surface current turns to the right(left) side of wind direction with 45° in the north(south) hemisphere,but the observation and research results show that the surface current deflexion angle is smaller than 45° in the Arctic and high latitude areas while larger than 45° in the low latitude areas.In order to explain these phenomena,a series of idealized numerical experiments are designed to investigate the influence of vertical viscosity coefficients with different vertical distribution characteristics on the classical and steady Ekman spiral structure.Results show that when the vertical viscosity coefficient decreases with water depth,the surface current deflexion angle is larger than 45°,whereas the angle is smaller than 45° when the vertical viscosity coefficient increases with water depth.So the different observed surface current deflexion angles in low latitude sea areas and the Arctic regions should be attributed to the different vertical distribution characteristics of vertical viscosity coefficients in the upper ocean.The flatness of the Ekman spiral is not equal to one and does not show regular behaviors for the numerical experiments with different distribution of vertical viscosity.However,the magnitudes and directions of volume transport of Ekman spirals are almost the same as the results of classical Ekman theory,i.e.,vertical viscosity coefficient distributions have no effect on the magnitudes and directions of volume transport.
