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Acta Oceanologica Sinica 2020年第7期39卷 165-174页

作者： anzhou cao Zheng Guo Ocean College Zhejiang UniversityZhoushan 316021China Marine Science and Technology College Zhejiang Ocean UniversityZhoushan 316021China

Recent studies have revealed that the predominant tidal constituents have seasonal variations at some ***,how to accurately obtain these variations remains a problem for the traditional harmonic analysis(HA)due to the tradeoff between length of time window and resolution of ***,a method named as"two-step HA"is developed in this study,which consists of both long-and short-time-window *** a series of ideal experiments,practical application at two tidal gauges and comparison with the traditional HA,the feasibility and accuracy of the two-step HA are verified:The two-step HA performs better than the traditional HA in estimating monthly amplitudes and phases for the predominant constituents,whether they have seasonal variability or *** addition to capturing variations of the predominant constituents at tidal gauges,the two-step HA would be useful in investigation of the coherence and incoherence of internal tides.

关键词： tides harmonic analysis seasonal variation tidal gauges

Tide-Induced Mixing in the Bottom Boundary Layer in the Western East China Sea

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Journal of Ocean University of China 2023年第1期22卷 1-8页

作者： GUO Zheng cao anzhou WANG Jianfeng Marine Science and Technology College Zhejiang Ocean UniversityZhoushan 316022China Ocean College Zhejiang UniversityZhoushan 316021China Institute of Oceanology Chinese Academy of SciencesQingdao 266071China Center for Ocean Mega-Science Chinese Academy of SciencesQingdao 266071China

The East China Sea(ECS)boasts a vast continental shelf,where strong tidal motions play an important role in the substance transport and energy *** this study,the tide-induced mixing in the bottom boundary layer in the western ECS is analyzed based on records measured by moored acoustic Doppler current profilers from June to October *** show that the M_(2) tide is strong and shows a barotropic feature,whereas the O_(1) tide is much *** on the M_(2) tidal currents,the eddy viscosity in the bottom Ekman boundary layer is estimated with three *** estimated eddy viscosity values vary within 10^(-4)–10^(-2)m^(2) s^(−1),reaching a maximum at approximately 5 m height from the bottom and decreasing exponentially with the height at all three ***,the shear production of turbulent kinetic energy is calculated to quantify the mixing induced by different tidal *** results show that the shear production of the M_(2) tide is much stronger than that of the O_(1) tide and shows a bottom intensified feature.

关键词： tides East China Sea bottom boundary layer mixing eddy viscosity

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Three-dimensional numerical simulation of M_2 internal tides in the Luzon Strait

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Acta Oceanologica Sinica 2015年第11期34卷 55-62页

作者： LI Bingtian cao anzhou LV Xianqing Key Laboratory of Physical Oceanography Ocean University of China Ministry of Education

A three-dimensional isopycnic-coordinate internal tidal model is employed to investigate the generation, propagation, vertical structure and energy conversion ofM2 internal tides in the Luzon Strait （LS） with mooring observations. Simulated results, especially the tidal current amplitudes, agree well with observations, demonstrating the reasonability and accuracy of the model. Results indicate that M2 internal tides mainly propagate into three directions horizontally, i.e., eastward towards the western Pacific Ocean, westward towards the Dongsha Island and southwestward towards the South China Sea Basin. In the horizontal direction, tidal current amplitudes decrease as distance increases away from the LS; in the vertical direction, they show an obvious decreasing tendency with depth. Between the double ridges of the LS, a clockwise gyre of M2 baroclinic energy flux appears, which is caused by reflections of M2 internal tides at supercritical topographies, and resonance of M2 internal tides happens along 19.5° and 21.5°N due to the heights and separation distance of the double ridges. The total energy conversion in the LS is about 14.20 GW.

关键词： internal tide numerical simulation Luzon Strait

Effects of tide-surge interactions on storm surges along the coast of the Bohai Sea, Yellow Sea, and East China Sea

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Science China Earth Sciences 2016年第6期59卷 1308-1316页

作者： XU JunLi ZHANG YuHong cao anzhou LIU Qiang LV XianQing Key Laboratory of Physical Oceanography (Ocean University of China) Ministry of Education Ocean University of China College of Engineering Ocean University of China

A two-dimensional coupled tide-surge model was used to investigate the effects of tide-surge interactions on storm surges along the coast of the Bohai Sea, Yellow Sea, and East China Sea. In order to estimate the impacts of tide-surge interactions on storm surge elevations, Typhoon 7203 was assumed to arrive at 12 different times, with all other conditions remaining constant. This allowed simulation of tide and total water levels for 12 separate cases. Numerical simulation results for Yingkou, Huludao, Shijiusuo, and Lianyungang tidal stations were analyzed. Model results showed wide variations in storm surge elevations across the 12 cases. The largest difference between 12 extreme storm surge elevation values was of up to 58 cm and occurred at Yingkou tidal station. The results indicate that the effects of tide-surge interactions on storm surge elevations are very significant. It is therefore essential that these are taken into account when predicting storm surge elevations.

关键词： Storm surges Astronomical tides Tide-surge interactions Typhoon 7203 Coupled tide-surge model

Gravity-capillary waves modulated by linear shear flow in arbitrary water depth

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Chinese Physics B 2020年第12期29卷 346-355页

作者： Shaofeng Li Jinbao Song anzhou cao Ocean College Zhejiang UniversityZhoushan 316000China

Considering that the fluid is inviscid and incompressible and the flow is irrotational in a fixed frame of reference and using the multiple scale analysis method, we derive a nonlinear Schrodinger equation(NLSE) describing the evolution dynamics of gravity-capillary wavetrains in arbitrary constant depth. The gravity-capillary waves(GCWs) are influenced by a linear shear flow(LSF) which consists of a uniform flow and a shear flow with constant vorticity. The modulational instability(MI) of GCWs with the LSF is analyzed using the NLSE. The MI is effectively modified by the LSF. In infinite depth, there are four asymptotes which are the boundaries between MI and modulational stability(MS) in the instability diagram. In addition, the dimensionless free surface elevation as a function of time for different dimensionless water depth,surface tension, uniform flow and vorticity is exhibited. It is found that the decay of free surface elevation and the steepness of free surface amplitude change over time, which are greatly affected by the water depth, surface tension, uniform flow and vorticity.

关键词： gravity-capillary waves nonlinear Schrodinger equation linear shear flow modulational instability

Seasonal variation and modal content of internal tides in the northern South China Sea

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Journal of Oceanology and Limnology 2018年第3期36卷 651-662页

作者： GUO Zheng cao anzhou LU Xianqing Physical Oceanography Laboratory/CIMST Ocean University of ChinaQingdao 266100China Qingdao National Laboratory for Marine Science and Technology Qingdao 266100China Ocean College Zhejiang UniversityZhoushan 316021China

A nine-month mooring record was used to investigate seasonal variation and modal content of internal tides(ITs) on the continental slope in the northern South China Sea(SCS). Diurnal tides at this site show clear seasonal change with higher energy in winter than in spring and autumn, whereas semidiurnal tides show the opposite seasonal pattern. The consistency of ITs with barotropic tides within the Luzon Strait, which is the generation region of the ITs, implies that the seasonal variation of ITs depends on their astronomical forcing, even after extended propagation across the SCS basin. Diurnal tides also differ from semidiurnal tides in relation to modal content; they display signals of high modes while semidiurnal tides are dominated by low modes. Reflection of the diurnal tides on the continental slope serves as a reasonable explanation for their high modes. Both diurnal and semidiurnal tides are composed of a larger proportion of coherent components that have a regular 14-day spring-neap cycle. The coherent components are dominated by low modes and they show obvious seasonal variation, while the incoherent components are composed mainly of higher modes and they display intermittent characteristics.

关键词： internal tide(IT) South China Sea(SCS) seasonal variation modal content

Observations of near-inertial waves induced by parametric subharmonic instability

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Journal of Oceanology and Limnology 2018年第3期36卷 641-650页

作者： LI Bingtian cao anzhou LU Xianqing Physical Oceanography Laboratory/CIMST Ocean University of China and Qingdao National Laboratory for Marine Science and TechnologyQingdao 266200China Ocean College Zhejiang UniversityMinistry of EducationZhoushan 316021China

Near-inertial waves(NIWs), which can be generated by wind or the parametric subharmonic instability(PSI) of internal tides, are common in the South China Sea(SCS). Moored current observations from the northern SCS have revealed that the PSI of semidiurnal(D_2) internal tides is another source of NIWs. The objective of this study was to examine the energy variance in the PSI of D_2 tides. The PSI of D_2 internal tides generated NIWs and waves with frequencies around the difference frequency of D_2 and f. The observed NIWs induced by PSI could be distinguished clearly from those elicited by typhoon Krosa. Shortly after Krosa entered the SCS, NIWs began to intensify on the surface and they propagated downward over subsequent days. The near-inertial currents were damped quickly and they became relatively weak before the waves were reinforced beneath the mixed layer when wind stress was relatively weak. Rotation spectra indicated an energy peak at exactly the difference frequency D_2–f of the NIWs and D_2, indicating nonlinear wave-wave interaction among D_2, f, and D_2–f. Depth-time maps of band-pass fi ltered velocities of D_2 –f showed the waves amplifi ed when the NIWs were reinforced, and they intensifi ed at depths with strong D_2 tides. The energies of the NIWs and D_2 –f had high correlation with the D_2 tides. The PSI transferred energy of low-mode D_2 internal tides to high-mode NIWs and D_2–f waves. For the entire observational period, PSI reinforcement was observed only when mesoscale eddies emerged and when D_2 was in spring tide, revealing a close connection between mesoscale eddies and NIWs. Mesoscale eddies could increase the energy in the f-band by enhancing the PSI of D_2 internal tides. Thus, this represents another mechanism linking the energy of mesoscale eddies to that of NIWs.

关键词： near inertial waves(NIWs) parametric subharmonic instability(PSI) South China Sea(SCS)

A nonlinear Schrodinger equation for gravity waves slowly modulated by linear shear flow

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Chinese Physics B 2019年第12期28卷 215-222页

作者： Shaofeng Li Juan Chen anzhou cao Jinbao Song Ocean College Zhejiang UniversityZhoushan 316000China

Assume that a fluid is inviscid, incompressible, and irrotational. A nonlinear Schr?dinger equation(NLSE) describing the evolution of gravity waves in finite water depth is derived using the multiple-scale analysis method. The gravity waves are influenced by a linear shear flow, which is composed of a uniform flow and a shear flow with constant vorticity. The modulational instability(MI) of the NLSE is analyzed, and the region of the MI for gravity waves(the necessary condition for existence of freak waves) is identified. In this work, the uniform background flows along or against wave propagation are referred to as down-flow and up-flow, respectively. Uniform up-flow enhances the MI, whereas uniform down-flow reduces it. Positive vorticity enhances the MI, while negative vorticity reduces it. Hence, the influence of positive(negative)vorticity on MI can be balanced out by that of uniform down(up) flow. Furthermore, the Peregrine breather solution of the NLSE is applied to freak waves. Uniform up-flow increases the steepness of the free surface elevation, while uniform down-flow decreases it. Positive vorticity increases the steepness of the free surface elevation, whereas negative vorticity decreases it.

关键词： nonlinear Schrodinger equation gravity waves linear shear flow modulational instability

Estimation of the Reflection of Internal Tides on a Slope

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Journal of Ocean University of China 2020年第3期19卷 489-496页

作者： WANG Shuya cao anzhou CHEN Xu LI Qiang SONG Jinbao MENG Jing Key Laboratory of Physical Oceanography Qingdao Collaborative Innovation Center of Marine Science and Technology(CIMST)Ocean University of Chinaand Qingdao National Laboratory for Marine Science and TechnologyQingdao 266100China Ocean College Zhejiang UniversityZhoushan 316021China Graduate School at Shenzhen Tsinghua UniversityShenzhen 518055China College of Oceanic and Atmospheric Sciences Ocean University of ChinaQingdao 266100China

Reflection occurs when internal tides impact on a steep continental slope. Separating reflected internal tide signals from incident ones is crucial to develop the parameterization of internal tide-driven turbulent mixing on the continental slopes. In this study, the performances of three different methods for estimating internal tide reflections are examined by using two different cases. The Hilbert transform-based method is found to be more suitable than two other methods for both cases considered in this study. The two other methods are effective for westward-propagating mode-1 internal tides impacting a slope, but inappropriate in the case where internal tides radiate from a Gaussian ridge impact the slope because of their inaccurate estimation of incident internal tides in the latter case. Such inaccurate estimation further influences the extraction of reflected signals and calculation of the reflected and cross term of energy fluxes. In addition, it should be noted that, due to the use of filtering, the method based on Hilbert transform may result in slight bias when assessing the incident and reflected signals near topographic features.

关键词： internal tide reflection continental slope Hilbert transform energy flux filtering

Observational study of super typhoon Meranti (2016) using satellite, surface drifter, Argo float and reanalysis data

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Acta Oceanologica Sinica 2021年第1期40卷 70-84页

作者： Hui Chen Shuang Li Hailun He Jinbao Song Zheng Ling anzhou cao Zhongshui Zou Wenli Qiao Ocean College Zhejiang UniversityZhoushan 316021China State Key Laboratory of Satellite Ocean Environment Dynamics Second Institute of OceanographyMinistry of Natural ResourcesHangzhou 310012China Key Laboratory of Coastal Resources and Environment in Continental and Deep Sea of Department of Education of Guangdong ProvinceGuangdong Ocean UniversityZhanjiang 524088China

The present work describes the basic features of super typhoon Meranti(2016)by multiple data *** mainly focus on the upper ocean response to Meranti using multiplatform satellites,in situ surface drifter and Argo floats,and compare the results with the widely used idealized wind vortex model and reanalysis *** pre-existing meso-scale eddy provided a favor underlying surface boundary condition and also modulated the upper ocean response to *** show that the maximum sea surface cooling was 2.0℃after *** satellite surface wind failed to capture the core structure of Meranti as the idealized wind vortex model *** to the observation of sea surface drifters,the near-inertial currents were significantly enhanced during the passage of *** temperature and salinity profiles from Argo floats revealed both the mixed-layer extension and subsurface upwelling induced by *** comparison results show that the sea surface temperature and surface wind in the reanalysis datasets differs from those in remote sensing *** surface cooling is similar in both satellite and in situ observation,and sea surface salinity response has a lower correlation with the precipitation rate.

关键词： super typhoon satellite data sea surface temperature surface wind