Tidal current observation in the southern Yellow Sea in the summers of 2001 and 2003

Direct current observations in the Yellow Sea interior are very scarce due to intense fishing and trawling activities. Most previous studies on tides in the area were based on coastal measurements or satellite altimeter sea levels and have not been rigorously compared with direct measurements. In this paper, tidal currents are studied with current profiles from three bottom-moored Sontek Acoustic Doppler Profilers （ADPs） deployed in the southern Yellow Sea in summer of 2001 and 2003. The measured current series were dominated by tidal currents. Maximum velocities are between 40-80 cm/s at the mooring stations. M2 current is the most dominant primary tidal constituent, while MS4 and M4 are the most significant shallow water tides with much smaller amplitudes than the primary tides.     

Tidal Effects on the Bottom Thermal Front of North Yellow Sea Cold Water Mass near Zhangzi Island in Summer 2009

Three seabed-mounted TD/CTD chains and two upward-looking acoustic Doppler current profilers(ADCPs) in the southwest of Zhangzi Island are used and a simultaneous cruise observation in the northern North Yellow Sea(NYS) is conducted to study temperature variation in the bottom thermal front zone of the NYS Cold Water Mass(NYSCWM) during the summer of 2009. In the flood-ebb tidal cycles, the bottom temperature decreases(increases) during flood(ebb) tides, which are dominated by the tidal-current induced horizontal advection. The ebb tide-induced temperature increase is larger than the flood tide-induced temperature decrease due to seasonal warming. In the spring-neap tidal cycles, the temperature and the vertical temperature structure show notable fortnightly variation from 16 July to 25 August. The bottom temperature increases from neap to spring tides and decreases from spring to neap. The Richardson number demonstrates strengthened vertical mixing during spring tides but enhanced stratification during neap tides. The spring-neap variation in vertical shear caused by tidal current is the dominant factor that induces the fortnightly variation in vertical mixing and thus bottom temperature.     

2013年芦山7.0级地震前重力固体潮参数时空变化研究

以2013年芦山7.0级地震为例,探讨重力固体潮参数的时空分布特征与地震孕育的关系。收集分析芦山震区附近17个台站震前2 a的连续重力观测数据,采用VAV调和分析方法分析计算日波和半日波潮汐参数,主要研究半日波M 2波潮汐因子随时间变化的趋势及空间分布情况。结果表明,芦山地震前M 2波潮汐因子趋势变化空间分布大体呈现上升与下降趋势的四象限分布,芦山地震处于四象限中心部位,可能是由震前存在的“闭锁剪力”引起的区域介质变形或密度扰动所致。     

Assessment of the Tidal Current Energy Resources and the Hydrodynamic Impacts of Energy Extraction at the PuHu Channel in Zhoushan Archipelago,China

An unstructured model FVCOM(The Unstructured Grid Finite Volume Community Ocean Model) with sink momentum term was applied to simulate the tidal current field in Zhoushan Archipelago, China, with focus on the region named PuHu Channel between Putuo Island and Hulu Island. The model was calibrated with several measurements in the channel, and the model performance was validated. An examination of the spatial and temporal distributions of tidal energy resources based on the numerical simulation revealed that the greatest power density of tidal energy during spring tide is 3.6 kW m-2 at the northern area of the channel. Two parameters were introduced to characterize the generation duration of the tidal array that causes the temporal variation of tidal current energy. The annual average available energy in the channel was found to be approximately 2.6 MW. The annual generating hours at rated power was found to be 1800 h when the installed capacity of tidal array is approximately 12 MW. A site for the tidal array with 25 turbines was selected, and the layout of the array was configured based on the EMEC specifications. Hydrodynamic influence due to the deployment of the tidal array was simulated by the modified FVCOM model. The simulation showed that the tidal level did not significantly change because of the operation of the tidal array. The velocity reduction covered a 2 km~2 area of the downstream the tidal array, with a maximum velocity reduction of 8 cm s-1 at mid-flood tide, whereas the streamwise velocity on both sides of the farm increased slightly.     

中国台湾地区海洋负荷潮汐对重力、位移、倾斜和应变固体潮观测的影响

利用最新的由卫星测高数据解算获得的Csr4.0全球海潮模型，中国近海海潮资料和标准地球模型负荷格林函数，采用积分格林函数方法研究了台湾地区10个台站的重力，位移，倾斜和应变固体潮观测中的海潮负荷效应。给出了4个主要潮波（O1，K1，M2，S2）的负荷振幅和相位，研究了负荷应变花分布特征，构制了台北站的负荷时变特征，数值结果说明，台湾地区各台站受海潮影响十分明显，因此在实施重力，位移，倾斜和应变固体潮观测中心必须考虑海潮负荷效应。     

Tidal effects on diel variations of picoplankton and viruses in the Changjiang estuary

Spatial distributions and seasonal variations of picoplankton (i.e. Synechococcus spp., Prochlorococcus spp., picoeukaryotes and heterotrophic bacteria) and viruses in the Changjiang estuary have been reported in the past. However, short-term variations (e.g. at a tidal timescale) of these organisms and their regulating factors remain unclear. We determined the time-series of fluctuations of picoplankton and viruses with tide simultaneously in flow cytometry in the Changjiang estuary during a cruise in June 2006, in which a tidal model based rectangle equation was applied. The results indicate that high cell abundances of picoplankton and viruses occurred during flood tide and low cell abundances during ebb tide. The period of the surface cell abundance variations was about 13 h, suggesting the surface cell abundances in the Changjiang estuary were largely regulated by tide. However, cell abundances in middle and bottom waters varied in different periods due to influences of tidal induced physical forces such as resuspension and stratification. Therefore, tidal action is an important factor for the diel variations of picoplankton and viruses in the Changjiang estuary.     

Nonlinear interactions among internal tidal waves in the northeastern South China Sea

We used a set of 75-day long ADCP data from the northeastern South China Sea (SCS) to investigate nonlinear interactions among freely propagating internal tidal waves. The kinetic energy spectra displayed significant peaks at some higher tidal frequencies, such as O₁M₂ (O₁+M₂), and M₄ (M₂+M₂), where O₁ is the lunar diurnal internal tide, M₂ is the lunar semidiurnal internal tide, and M₄ is the first higher harmonic frequency of M₂. These higher tidal harmonic frequency peaks, as well as the fundamental tidal harmonic peaks, show a σ ^−2.3 spectral falloff rate with frequency. In addition, we explored the possible generation mechanism of higher tidal harmonics. Analysis on the rotary and bicoherence spectra suggests that strong forced non-resonant interaction induced by nonlinear advections was the dominant physical mechanism that induced these higher tidal harmonics. Moreover, the energetic, freely propagating semidiurnal (M₂) internal tidal wave played the most crucial role in these interactions. These results indicate that strong nonlinear forced non-resonant interactions among internal tides can be one of the processes responsible for the redistribution of energy in the internal wave spectrum.     

A numerical study on water diversion ratio of the Changjiang (Yangtze) estuary in dry season

We studied the flood, ebb and tidal averaged along (net) water diversion ratio (WDR) during dry season in the Changjiang (Yangtze) estuary, China, along with the effects of northerly wind, river discharge, tide and their interactions on WDR using the improved version of three-dimensional numerical model ECOM. Using data for annual mean wind speed and river discharge during January, we determined that the flood, ebb, net WDR values in the North Branch of the estuary were 3.48%, 1.68%, −4.06% during spring tide, and 4.82%, 2.34%, −2.79% during neap tide, respectively. Negative net WDR values denote the transport of water from the North Branch into the South Branch. Using the same data, the corresponding ratios were 50.09%, 50.92%, 54.97%, and 52.33%, 50.15%, 43.86% in the North Channel and 38.56%, 44.78%, 103.96%, and 36.92%, 43.17%, 60.97% in the North Passage, respectively. When northerly wind speed increased, landward Ekman transport was enhanced in the North Branch, increasing the flood WDR, while the ebb WDR declined and the net WDR exhibited a significant decrease. Similarly, in the North Channel, the flood WDR is increased, the ebb WDR reduced, and the net WDR showed a marked decrease. In the North Passage, the flood WDR also increased while the ebb and net WDR declined. As the river discharge increased, the flood and ebb WDR of the North Branch increased slightly and the net WDR increased markedly. In the North Channel the flood and ebb WDR changed very slightly, while the net WDR declined during spring tides and increased during neap tides. The WDR in the North Passage changed slightly during flood and ebb tides while the net WDR showed a marked increase. The WDR values of different bifurcations and the responses to northerly wind, river discharge, and tide are discussed in comparison with variations in river topography, horizontal wind-induced circulation, and tidal-induced residual current.     

Global ocean tides from Geosat altimetry by Quasi-Harmonic analysis

ＩＮＴＲＯＤＵＣＴＩＯＮＯｃｅａｎｔｉｄｅｓｐｌａｙａｖｅｒｙｉｍｐｏｒｔａｎｔｒｏｌｅｉｎｔｈｅｄｙｎａｍｉｃｓｏｆｔｈｅＥａｒｔｈａｎｄｈａｖｅａｔｔｒａｃｔｅｄｍａｎｙｐｅｏｐｌｅ’ｓａｔｔｅｎｔｉｏｎｓｉｎｃｅａｎｃｉｅｎｔｔｉｍｅｓ.Ｂｅｆｏｒｅｔｈｅｌａｔｅ 1 970ｓ,ｔｉｄｅｓｗｅｒｅｍｅａｓｕｒｅｄｍａｉｎｌｙｂｙｃｏａｓｔａｌｇａｕｇｅｓ .Ｄｉｒｅｃｔｍｅａｓｕｒｅｍｅｎｔｓａｓｗｅｌｌａｓｎｕｍｅｒｉｃａｌｓｉｍｕｌａｔｉｏｎｓ,ｃａｎｐｒｏｖｉｄｅｆａｉｒｌｙａｃｃｕｒａｔｅｕ…     

Observation of currents in the southern Yellow Sea in the summers of 2001 and 2003

Long term current observations in the southern Yellow Sea are very scarce because of the intense fishing and trawling activities. Most of the previous studies on tides and circulation were not rigorously validated with direct current measurements. In this study, tidal and sub-tidal currents were examined using current profiles from three bottom-moored Sontek Acoustic Doppler Profilers （ADPs） deployed in the southern Yellow Sea in the summers of 2001 and 2003. The measured current time series were dominated by tidal currents. The maximum velocities were between 40-80 cm s^-1 at the mooring stations. The M2 current was the dominant primary tidal constituent, while the MS4 and M4 components produced the most significant shallow water tidal currents with much weaker amplitudes. The measured mean sub-tidal velocities were less than 5 cmsl. The mean flows in the lower layer implied that an anti-cyclonic circulation pattern might exist in the deeper central Yellow Sea. However, the previously expected cyclonic circulation pattern in the upper layer was not clearly shown by the observations.     

A two-dimensional numerical model of the tidal motions in the Bohai sea

The motions of diurnal, semidiurnal, and shallow-water tides and tidal current in the Bohai Sea are computed using a finite-difference method based on two-dimensional tidal wave equations. Good agreement of the computed results with the observed data is achieved for diurnal and semidiurnal tides. The general pattern of the computed quarterdiurnal tide conforms to the observed pattern, but the computed amplitudes are on the high side. This is attributed to the ineligibility of the friction terms in the two-dimensional governing equations to dissipate the energy of high frequency tidal waves. It is found that the existing semidiurnal cotidal charts have considerable differences in Laizhou Bay. The difference is likely caused by the movement of the coastline of the Yellow River Delta. The present result coincides with the recent empirical cotidal chart. The computation shows a new current-amphidromic point for both semidiurnal and durnal tidal currents. The diurnal current has two current-amphidromic points in the Bohai Sea with co-phase lines progressing clockwise round these points. The semi-diurnal current has also two current-amphidromic points with co-phase lines progressing counterclockwise. The distributions of tide-induced residual elevation and currents are illustrated, and the tidal energy fluxes are computed. Institute of Marine Scientific and Technological Information, State Oceanic Administration Contribution No. 1125, Institute of Oceanology, Academia Sinica, Qingdao, China.     

An investigation of the properties of low-frequency internal waves in the northeastern China Seas

A simple and practical method for separating low-frequency internal waves from low-frequency barotropic waves was employed to analyze the observation data. Analysis of some data gathered in the northestern China Seas revealed strong semidiurnal internal tides and near-inertial internal waves at the stations in the East China Sea and near-inertial waves but no semidiurnal internal tides at the station in the centre of the Yellow Sea. The geographic properties of low-frequency internal waves in the region are discussed primarily on the basis of the mechanism of internal tide generation on the continental shelfbreak, and the mechanisms of local generation and global generation. Project supported by the National Natural Science Foundation of China.     

固体潮潮汐因子的空间分布特征与机理

基于Ｏ１波与Ｋ１波和Ｍ２波潮汐因子的比值，介绍了我国南北地震带及华北等地区９个重力台站（１０套重力仪）、１０个静水位井、１１个倾斜及线应变台站潮汐因子的空间分布特征。与莫氏地球模型对比，重力线应变和水位潮汐中，Ｏ１波与Ｋ１波潮汐因子的比值均显示了液态地核的振荡效应。倾斜固体潮中，潮汐因子（特别是ＮＳ向）受局部构造环境影响畸变严重     

Factorial analysis of annual erosion-accretion cycles of tidal flats in the front area of the southern Changjiang river delta

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Influence of sea level rise on Shanghai astronomical tide and storm surge and estimation of probable water level

reODUCTIONSthtrendanditsinfluencehaveattiactedInanresearchersinrecentyears.He(l994)exPloredthePOssibleeffectofSLRonZhuiang(Pear)fuverdeltaSSbyusingarelativelysimPletecboqUeofcollatingfutUreSthincrementswithrecenily-measuredtidalcharaCteristicvalues.Pengetal.(l994)usedasindlaraPProachtoinvestigatetheSthinf[uenceonTianinSS.SthhasqUitepronouncedimPatontheinteractionbetweenSSandATinshallowwater-SSandATgenesisaxegrealyinfluencedbylocalwaterdepthandtOpography-TocoPewiththenonlinearr…     

深圳湾潮流动力特征研究

应用短期资料的潮流准调和分析方法,对深圳湾4测站两周日海流观测获得的表、中、底层海流资料进行分析,计算了4测站O_1、K_1、M_2、S_2、M_4、MS_4 6个主要分潮的潮流调和常数,并给出各测站在各层的潮流椭圆要素。计算结果表明:深圳湾主要为不规则半日潮流海区,浅水分潮流在总海流中的影响较大;站位1、2和4主要分潮流的北分量大于东分量,而站位3主要分潮流的北分量小于东分量。观测期间余流的流向主要呈北和东北向;最小余流速度出现在站位3;余流流速表层最大,中层次之,底层最小。整个海区潮流的可能最大流速表层在76～102cm/s之间;中层在80～106cm/s之间;底层在56～88cm/s之间。整个海区潮流表现出往复流的性质。     

Estimates of global M 2 internal tide energy fluxes using TOPEX/POSEIDON altimeter data

TOPEX/POSEIDON altimeter data from October 1992 to June 2002 are used to calculate the global barotropic M ₂ tidal currents using long-term tidal harmonic analysis. The tides calculated agree well with ADCP data obtained from the South China Sea (SCS). The maximum tide velocities along the semi-major axis and semi-minor axis can be computed from the tidal ellipse. The global distribution of M ₂ internal tide vertical energy flux from the sea bottom is calculated based on a linear internal wave generation model. The global vertical energy flux of M ₂ internal tide is 0.96 TW, with 0.36 TW in the Pacific, 0.31 TW in the Atlantic and 0.29 TW in the Indian Ocean, obtained in this study. The total horizontal energy flux of M ₂ internal tide radiating into the open ocean from the lateral boundaries is 0.13 TW, with 0.06 TW in the Pacific, 0.04TW in the Atlantic, and 0.03 TW in the Indian Ocean. The result shows that the principal lunar semi-diurnal tide M ₂ provides enough energy to maintain the large-scale thermohaline circulation of the ocean. Supported by the National Basic Research Program of China (973 Program, No. 2005CB422303), the International Cooperation Program (No. 2004DFB02700), and the National Natural Science Foundation of China (No. 40552002). The TOPEX/POSEIDON data are provided by Physical Oceanography Distributed Active Archive Center (PO DACC)     

陆态网络腾冲台连续重力观测质量分析

对陆态网络腾冲台2012-07-01~2013-06-30连续重力观测资料进行处理,获得该台站观测精度及噪声水平。结果表明,腾冲台1~100s噪声水平在9×10^-8ms^-2左右,100s~100min噪声水平在0.3×10^-8ms^-2左右,白噪声水平为0.509×10^-8ms^-2,对O₁波、M₂波等主要潮波振幅因子测量精度达到SG-053超导重力仪的观测量级,其中M₂波振幅因子测量精度最高（为0.000 18）。腾冲台可为川滇地区强震和腾冲火山活动监测、震前重力变化及相关研究提供高精度、可靠的连续重力观测资料。     

RESEARCH ON RED TIDE OCCURRENCES USING ENCLOSED EXPERIMENTAL ECOSYSTEM IN WEST XIAMEN HARBOR, CHINA RELATIONSHIP BETWEEN NUTRIENTS AND RED TIDE OCCURRENCE

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Factorial analysis of annual erosion-accretion cycles of tidal flats in the front area of the southern Changjiang river delta

Based on surveyed data from seven coastal sections and the collected data of wind, sea level, tide, nearshore suspended sediment concentration and river flux from adjacent stations, this paper deals with regressive correlation between monthly average flat elevation and monthly average figures of the influential factors. All sections except one which is located within the river mouth showed negative correlation between flat elevation and sea level and between flat elevation and tidal range, with correlation coefficients being −0.53 – −0.91 (−0.77 on the average) in the former condition and −0.56 – −0.97 (−0.80 on the average) under the latter. Each of the sections with available suspended sediment concentration (SSC) data shows a positive correlation between flat elevation and SSC, with correlative coefficients being 0.35 – 0.97 (0.66 on the average). Only two sections (one in the Changjiang River Estuary and the other in the Hangzhou Bay) which are similar to beaches in sediment grain-size and slope gradient showed a negative correlation between flat elevation and onshore wind frequency and between flat elevation and average wind velocity, with correlative coefficients being respectively −0.57 and −0.69 (−0.63 on the average) in the former situation and −0.61 and −0.75 (−0.68 on the average) in the latter. Other sections did not show uniform relationship between flat elevation and wind conditions. Due to local marine factors the nearshore SSC in the studied area is negatively correlated with the Changjiang River sediment flux (r=−0.78), which results in false negative correlation between flat elevation and river sediment flux. The paper also gives sediment dynamic and morphodynamic explanation for the above correlations. Sea level rise results in the spread of breaker zone from subtidal area to intertidal area and then increases the intertidal water energy. The larger the tidal range, the stronger the tide currents and the easier for the flat to be eroded. The higher the SSC of flood water, the easier for the sediment to deposit down. Because of correlations among the influential factors, it is difficult to give the prime one which dominates the erosion and accretion processes in tidal flats.