一种改进的卫星高度计绝对定标方法:以中国黄海海上试验为例

An improved absolute calibration technology based on indirect measurements was developed through two probative experiments, the performance of which was evaluated by applying the approach to in situ sea surface height(SSH) at the Tianheng Island(tidal gauge) and the satellite nadir(GPS buoy). Using Geoid/MSS(mean sea surface) data, which accounted for a constant offset between nadir and onshore tidal gauge water levels, and TMD(tidal model driver), which canceled out the time-varying offsets, nadir SSH(sea surface height) could be indirectly acquired at an onshore tidal gauge instead of from direct offshore observation. The approach extrapolated the onshore SSH out to the offshore nadir with an accuracy of(1.88±0.20) cm and a standard deviation of 3.3 cm, which suggested that the approach presented was feasible in absolute altimeter calibration/validation(Cal/Val), and the approach enormously facilitated the obtaining SSH from the offshore nadir.     

半封闭海区潮波运动问题的构建

利用海底粘滞性条件,首先导出了海底摩擦与海面坡度之间的简单关系式,在此基础上导出了水平流通量与海面坡度的关系式。然后利用连续性方程进一步得到了海面升高即潮位所满足的二阶椭圆型方程,进而导出了以潮位形式给出的半封闭海区岸壁不可穿透条件。最终在给定半封闭海区开边界水位分布的条件下构建了完整的关于潮位分布函数的微分方程边值问题。初步讨论表明,海底摩擦矢量与水平流通量矢量并不在相反的方向上。     

基于长期观测的辽东湾口东部海域水动力特征研究

辽东湾口东部海域是辽东湾与渤海中部进行物质和能量交换的主要通道之一。本文利用坐底式海床基平台获取的近8个月的水动力连续观测资料,通过谱分析和调和分析方法对该海域的潮汐、潮流特征进行分析,并讨论了余流及底层温度的季节变化规律。研究结果表明:该海域潮汐属于不规则半日潮,平均潮差为0.95 m,最大可能潮差为2.27 m。潮流属于不规则半日潮流,M₂分潮流为其优势分潮流。主要分潮流运动形式为往复流,最大流速方向为西南-东北向。余流的季节性特征较为明显:秋季,余流流速在中层达到最大,流向以西南向为主;冬季,余流流速垂向变化较小,并呈西南偏西向流动;春季,流速随深度增加而减小,流向从表层至底层呈现逆时针旋转的特征。受底层潮流、水平温度梯度及海面温度日变化的影响,底层温度表现出短期的高频变化特征:秋季,短期振荡以半日周期信号为主;冬季,全日周期信号较为显著;春季,短期振荡的现象较弱。     

Tidal Current Measurements Using VHF Radar and ADCP in the Normand Breton Gulf: Comparison of Observations and Numerical Model

Performance and operational feasibility of very high-frequency (VHF) Doppler radar have been demonstrated in a region dominated by strong tidal currents. An analysis of remote measurements of sea surface currents acquired by Courants de Surface MEsureacutes par Radar (COSMER)-pulsed Doppler radar during Evaluation et Preacutevision de l'Environnement Littoral (EPEL) experiment (supported by the French Navy) is presented in this paper. The VHF COSMER radar was deployed to provide continuous sea surface current measurements within an area of about 25 km times 25 km in the Normand Breton Gulf, France. This paper presents VHF measurement comparisons with observations such as acoustic Doppler current profiler (ADCP), as well as comparisons with numerical model TELEMAC 2-D. Results of tidal waves extraction, using harmonic analysis and residual currents, are shown in this paper. We also present a case where radar method is limited, due to the presence of additional peaks in the Doppler spectrum     

On the fundamental dynamics of barotropic circulation in shallow seas

It is suggested that the shallow sea circulation should be related to the Lagrangian residual circulation but not to the conventional Eulerjan mean circulation, and further, the first order Lagrangian residual circulation-the mass-transport velocity field is used to define the steady circulation as the lowest order shallow sea circulation.The set of equation governing the shallow sea circulation is reformulated, which shows that there are no the so-called “tidal surface source” and the “tidal stress”. A vorticity equation for the stream function of horizontal transports is derived, which is easily solved by the conventional numerical methods.An intertidal convection-diffusion equation governing the concentration of conservative and passive tracer is derived. Differing from the conventional equation, the equation derived in the present paper reveals the Lagrangian convection and has no need to introduce the artificial hypothesis for the so-called “tidal dispersion”.The theory presented here is base     

TOPEX/POSEIDON高度计浅海潮汐混淆的初步分析

根据对卫星轨道特征和观测结果的分析,对TOPEX/POSEIDON(简称T/P)星载高度计在我国近海的潮致混淆现象进行了初步研究.分析表明,在浅海区T/P高度计的观测结果存在很强的潮致高频混淆.NASA分发的地球物理记录中所提供的潮汐订正值虽适用于大洋,但不能有效地除去浅海潮汐.虽然如此,T/P潮致混淆的主要频段的周期小于90d,因而可以通过滤波方法提取周期较长的海面高度季节信号,从而用于季节环流(如南海季风环流)的研究.采用FFT/IFFT方法滤波试验的结果显示,T/P的海面高度观测结果有很高的精度,滤波处理后的海面高度距平变化和地面潮位观测结果一致性良好,上、下行轨道交叉处相邻测点间的标准偏差在3cm左右,可满足南海环流研究的需要.     

Tidal Effects on Determining a Point at the Bottom of the Sea by Combining GPS and Sonar Observations

This paper discusses tidal effects on an observation scheme to determine a point at the bottom of the sea by combining GPS and Sonar observations. For the purpose, three kinds of Earth tides are introduced (i.e., the crust tide, the equipotential surface point (ocean depth) tide, and the geoid tide). The corresponding mathematical expressions are derived to demonstrate the tidal effects on GPS and Sonar observations. The relations between the Earth tides are also discussed. Theoretical results imply a very interesting conclusion, namely that, for a local area, the static position of a point at the bottom of sea can be obtained by the dynamic observations without any tidal correction. Actually, the tidal effects cancel each other in the mentioned observation scheme. It therefore indicates that the observation scheme is free of tidal effects. Furthermore, we learned that the divergence caused by any error source on ocean surface is canceled and does not affect the final results. Therefore, to determine the position of a point at the bottom of sea, we need not consider any tidal effects.     

Tidal Effects on Determining a Point at the Bottom of the Sea by Combining GPS and Sonar Observations

This paper discusses tidal effects on an observation scheme to determine a point at the bottom of the sea by combining GPS and Sonar observations. For the purpose, three kinds of Earth tides are introduced (i.e., the crust tide, the equipotential surface point (ocean depth) tide, and the geoid tide). The corresponding mathematical expressions are derived to demonstrate the tidal effects on GPS and Sonar observations. The relations between the Earth tides are also discussed. Theoretical results imply a very interesting conclusion, namely that, for a local area, the static position of a point at the bottom of sea can be obtained by the dynamic observations without any tidal correction. Actually, the tidal effects cancel each other in the mentioned observation scheme. It therefore indicates that the observation scheme is free of tidal effects. Furthermore, we learned that the divergence caused by any error source on ocean surface is canceled and does not affect the final results. Therefore, to determine the position of a point at the bottom of sea, we need not consider any tidal effects.     

黄海潮波系统下的GOCI反演及OSU模式海表流场数据适用性研究

黄海呈现独有的地形条件,且该海域的潮波运动独具特征。本文利用静止海洋水色成像仪（Geostationary Ocean Color Imager, GOCI）遥感反演和俄勒冈州立大学（Oregon State University,OSU）潮流模式分别获取了黄海海域的海表流场,基于该海域独特的潮波系统提出并识别潮波干涉区,进而对GOCI反演的流场做潮流提取,并对两种潮流数据作分区可用性评价,通过实测的漂流浮标数据验证评估。结果表明：利用GOCI反演和OSU潮流模式获取的海表流场具有一定程度的可靠性,GOCI反演的海表流场的流速平均相对大小误差值为0.77,OSU潮流模式获取的海表流场流速平均相对大小误差值为0.49;在靠近潮波干涉区的黄海中部海域,GOCI潮流数据与实测数据在方向上的一致性要优于OSU潮流数据,两者平均角度误差值分别为48.45°和63.10°;在远离潮波干涉区的黄海近岸海域,OSU潮流数据与实测数据在速度大小和方向上的一致性要优于GOCI潮流数据。     

Estimation of 3-D current fields near the Rhine outflow from HF radar surface current data

HF radar systems are designed to measure spatially variable sea surface currents. A methodology was developed to complement these data with information about the current variability over the water column in a stratified shallow sea. Current profiles were estimated using a diagnostic model driven by surface current measurements from an HF radar system and by sea surface slopes derived from tide gauge data. The structure of the model has a physical basis but its parameters were derived from an analysis of in-situ current profile measurements. Application of the model to HF radar data from the SCAWVEX Rhine outflow experiment showed fair agreement with in-situ current data. As applications, estimation and tidal analysis of current fields are demonstrated.     

Modeling the tidal ice drift and ice-induced changes in tidal dynamics on the Siberian continental shelf

The tidal ice drift is treated as an element of the three-dimensional tidal dynamics in a sea covered by ice. This dynamics is described by the QUODDY-4 finite-element model, and the tidal ice drift is described by a continuous viscous-elastic approximation. We present the results of modeling not only the tidal ice drift (M ₂ wave) (its velocity, direction, and tidal variations in the concentration and pressure of ice compression) but also ice-induced changes in tidal dynamics and the residual tidal ice drift. The modeling results indicate that the maximum velocity of tidal ice drift, which is determined by a combination of various factors responsible for ice evolution and primarily by the horizontal gradient of the level and local tidal velocity, can be higher or lower than the velocity of the surface tidal current in the ice-free sea. This depends on the sign of deviations of tidal sea level elevations in the sea covered by ice from their values in the ice-free sea. In addition, it has been found that ice cover has a stronger effect on the energetics of tides than on their dynamics: the area-mean relative deviations constitute 1.5% for the density of the total tidal energy, 61.5% for the dissipation, 0.1% for the amplitudes of tidal sea level elevations, and 0.9% for the amplitudes of maximum barotropic tidal velocity. In this sense, the conclusion that the role of sea ice is insignificant in the formation of tides can be justified only partially. The main results of this paper are as follows: (1) the development of a module for tidal ice drift, (2) the inclusion of this module into the three-dimensional finite-element hydrothermodynamic model QUODDY-4 to extend its capabilities, and (3) the reproduction (on the basis of the modified model) of qualitative features of the practically important tidal ice drift and ice-induced changes in the tidal dynamics of marginal seas on the Siberian continental shelf.     

天津海域潮流嵌套模型

采用ADI法建立了天津海域的潮流模型,得出了该海域M_2分潮同潮时线和等振幅线以及潮流椭圆的分布,对天津市行政管理范围的局部海域建立了变空间步长的嵌套模型,提高了该研究海域的分辨率,得到了满意的结果。     

Vertical Distributions of Larvae of the Clam <Emphasis Type="Italic">Ruditapes philippinarum</Emphasis> and the Striped Horse Mussel <Emphasis Type="Italic">Musculista senhousia</Emphasis> in Eastern Ariake Bay,Southern Japan

We have examined the vertical distributions of planktonic bivalve larvae, particularly the clam Ruditapes philippinarum and the mussel Musculista senhousia which are common and abundant on tidal flats of eastern Ariake Bay, southern Japan. Submersible pumping gear was used to take samples at 2 stations every 2 hours during the spring tide over a whole tidal cycle and/or through daytime and nighttime. Water samples were pumped up from 3 to 5 depths from the surface to sea bottom. Regardless of tidal cycles, D-shaped larvae were concentrated near the surface, while umbo larvae were found at the surface to intermediate depths. On average, these larval densities were significantly higher at the station close to the shore than the offshore station, with no significant difference between daytime and nighttime and between flood and ebb tides at each station. The velocity and direction of water movement at both stations revealed remarkable difference between the surface and bottom waters. The larvae at the surface may quickly disperse and be transported elsewhere, while those in water close to the sea bottom may tend to be retained.     

The effect of ocean tides on a climate model simulation

We implemented an explicit forcing of the complete lunisolar tides into an ocean model which is part of a coupled atmosphere–hydrology–ocean–sea ice model. An ensemble of experiments with this climate model shows that the model is significantly affected by the induced tidal mixing and nonlinear interactions of tides with low frequency motion. The largest changes occur in the North Atlantic where the ocean current system gets changed on large scales. In particular, the pathway of the North Atlantic Current is modified resulting in improved sea surface temperature fields compared to the non-tidal run. These modifications are accompanied by a more realistic simulation of the convection in the Labrador Sea. The modification of sea surface temperature in the North Atlantic region leads to heat flux changes of up to 50 W/m². The climate simulations indicate that an improvement of the North Atlantic Current has implications for the simulation of the Western European Climate, with amplified temperature trends between 1950 and 2000, which are closer to the observed trends.     

Three dimensional modal model of wind induced flow in a sea region

The solution of the linear three dimensional hydrodynamic equations describing wind induced flow in a sea region is developed using the Galerkin method through the vertical. A basis set of B-splines is shown to have some computational advantages over a set of eigenfunctions (vertical modes). However, a basis set of modes leads to a system of essentially uncoupled equations and current profiles can be interpreted in terms of vertical modes.The influence of wind induced surface turbulence and turbulence at depth due to tidal motion upon current profiles in both deep (260 m) and shallow (35 m) sea regions is examined. The variation in the angle between surface current and surface wind for different viscosity profiles, and the effect of bottom friction upon it is considered.The magnitude and direction of the surface current is significantly influenced by surface eddy viscosity. However, viscosity at depth due to tidal motion also has an important effect upon the surface current.The time evolution of current structure following the sudden onset of a wind is examined using the modal model. Calculations show that the rate of damping of the internal modes is inversely proportional to the square of the depth. Consequently wind induced current structure takes longer to reach a steady state in a deep sea region than a shallow area.The influence of sea surface elevation gradients in determining the direction of surface current is also considered.     

杭州湾南岸潮滩的~(210)Pb分布及其沉积学意义

杭州湾南岸潮滩的~(210)Pb垂向分布具有随深度波动的特征。湖滩颗粒物在吸附模拟系统中的~(210)Pb分配系数,主要受颗粒物含量的影响。本文从潮滩沉积~(210)Pb初始比度在低于平衡点一侧波动的机理,以及被沉积间断所分隔的有效封闭段的存在出发,提出选择常态沉积层的高~(210)Pb比度窗口,建立以CIC模式估计潮滩沉积速率的方法。     

Tidal modification and its effect on sluice-gate outflow after completion of the Saemangeum dike,South Korea

This study examined tidal modification and change in tidal currents caused by the construction of the Saemangeum dike, based on field observations and a numerical model. The Saemangeum dike was completed in April 2006, enclosing an estuarine area along the mid-western coast of South Korea. After closure of the dike, the tidal range outside the dike decreased slightly but significantly, while the inside tidal range decreased drastically. The numerical model results show that the dike construction has influenced tidal energy propagation and the tidal system in the Yellow Sea. The tidal current speed near the dike decreased abruptly following closure of the dike, except in front of the sluice gates. Since completion of the dike, outflow water discharged from the sluice gates has longer residence times due to the weakened tidal current; the change in the tidal current field has also caused greater northward expansion of outflow water. The sluice gates release fresher water, which spreads over the sea surface mainly by inertial momentum near the gate; this water is then gradually mixed with sea water farther from the gate. The less saline, possibly more contaminated outflow impacts the marine environment near the Saemangeum dike. Controlling the discharge and gate-opening timing can partially mitigate these impacts on the marine environment.     

环日本岛沿岸海平面长期变化特征与机制的研究

利用环日本岛沿岸38个验潮站连续36 a的实测水位资料,分析了环日本岛沿岸平均海平面的长期变化特征,结果表明平均海平面的异常变化在1984年前后发生较大转折,近20多年来主要呈现持续上升趋势,部分站位在1997年前后也有较明显的下降趋势,表明海平面的长期变化中存在较长周期的波动情况。通过对所有验潮站的日平均海平面序列进行平均,发现与西北太平洋SST异常变化呈正相关,相关系数为0.908;与太平洋年代际变化(PDO)指数呈负相关,相关系数为-0.6;与西北太平洋风旋度场的异常变化呈正相关,相关系数为0.402。结果表明环日本岛沿岸平均海平面的长期变化受到海水热膨胀效应、太平洋年代际变化以及风应力引起的海水堆积和流失等因素的影响。同时,发现从2000年开始西北太平洋的SST开始下降,而平均海平面仍然在持续上升,其上升原因还需作进一步研究与探讨。     

高频地波雷达观测的苏北辐射沙洲南部海域夏季表层海流特征

本文利用高频地波雷达获得的江苏如东海域大范围长期海流观测资料对苏北辐射沙洲南部烂沙洋海域夏季表层海流特征进行了分析。分析结果表明:研究海域表层海流靠近近岸一侧为往复流,流向总体上呈西北-东南向,靠近外海一侧为旋转流;海域潮流动力较为强劲,夏季表层海流实测最大流速达1.47 m/s,涨潮平均流速介于0.44~0.55 m/s,落潮平均流速介于0.38~0.52 m/s,海域西北部区域涨落潮平均流速明显大于其他区域;表层潮流为正规半日潮流,M₂分潮为最主要分潮,其潮流椭圆长轴范围为0.57~0.71 m/s,远大于其他分潮,其次为S₂分潮;该海域夏季表层余流呈现近岸大离岸小的分布趋势,余流流向基本指向近岸方向,从离岸到近岸余流流向呈现逆时针偏转。     

黄河水下三角洲前沿深度基准面及潮位变化分析研究

黄河三角洲前沿的陆地由于受地面沉降的影响,使地面高程不断发生变化.在水深测量中,深度基准面是根据陆地水准点高程确定的,陆地水准点高程的变化影响深度基准面的确定,从而影响水深测量的准确性.又由于黄河海港附近有一无潮点,其附近的潮汐性质变化大,在黄河三角洲前沿大范围水深测量中,根据测区潮位变化设立足够的验潮站及统一各个验潮站的水尺零点到同一个深度基准面上,是保证水深测量结果可靠的关键.通过黄河三角洲前沿陆地高程的变化和验潮获得的资料,介绍了黄河三角洲前沿深度基准面的变化和潮位变化情况.