非结构网格三维斜压模型研究人类活动对海南岛清澜潮汐汊道水动力影响

清澜潮汐汊道为海南岛东部一个典型的泻湖-潮汐汊道-沙坝系统,由于其优越的自然条件而成为开发的重点区域。近几年的人类活动主要包括:口门西侧的围填工程,航道的疏浚和八门湾泻湖内的围塘工程。采用SELFE模型,结合观测资料,研究了不同人类活动对潮汐汊道的潮波、潮通量与涨落潮历时、河口重力环流、盐水入侵和河口羽流的影响。结果表明不同的人类活动其对动力的影响不同,口门西侧围填工程减小了潮汐汊道的潮差,对潮通量和盐水入侵影响很小;航道疏浚则加大了潮差和潮通量,加强了河口环流和盐水入侵;泻湖内围塘工程使潮差有所增大,但减小了潮通量,对盐水入侵的影响不显著。口门西侧围填工程改变了河口羽流的路径,而航道疏浚则使河口羽流更加向海扩散。     

近40a象山港潮汐汊道岸线的时空变化特征及其与人类活动的关系

利用多时期遥感数据,以8 a为时间步长,提取了1974~2014年间各时期象山港潮汐汊道海岸线空间位置、长度以及曲折度信息,同时对人类活动强度进行定量化评价,并探讨了人类活动强度变化和岸线变化的关系.结果表明:(1)40 a来,随着人类活动加剧,象山港潮汐汊道自然岸线长度不断缩减,人工岸线长度不断增加,并逐渐趋于稳定变化;(2)在不同方式人类活动影响下,象山港局部岸段形态发生剧烈变化,使得象山港潮汐汊道岸线曲折度不断变小;(3)人类活动强度在1974~1998年阶段增加快速,1998年以后增强速度有所变缓,同时,人类活动影响区域逐渐变大,几乎遍及整个港湾海岸;(4)人类活动强度与整体岸线的长度和曲折度呈现显著负相关性,随着人类活动强度的增大,岸线长度和曲折度逐渐减小.     

潮汐对东海陆架边缘处水交换的影响

为探讨潮汐对东海陆架边缘处水交换通量的影响,本文基于ROMS海洋数值模式,对渤海、黄海、东海的潮汐、环流进行了模拟研究。研究结果显示,在水平方向上,潮汐效应主要影响我国台湾岛东北及日本九州西南的水交换,其中在台湾岛东北区域,潮汐效应通过增加黑潮分支流(KBC)的向岸及离岸速度来加强黑潮水的跨陆架交换。潮汐效应对200 m等深线处跨等深线流速的影响量值约为3～5 cm/s。从垂直方向上来看,潮汐效应能够影响到深度200m处水层的深层交换。进一步研究其作用机制,发现潮汐效应主要通过平流输送项来影响水体交换,而其对水体的水平及垂直扩散项的影响较小。     

基于EFDC模型的盐度数值模拟研究

在地形变化剧烈的海域, 由于?坐标在垂向离散出现了较大的压强梯度力误差, 导致盐度模拟误差较大。本文在EFDC(Environmental Fluid Dynamics Code)模型的基础上, 以美国莫比尔湾(Mobile Bay)为例, 比较了在水深变化剧烈的区域?坐标和LCL ?坐标下盐度数值模拟结果的差异。研究结果表明, 采用LCL ?坐标能使得压强梯度力所产生的截断误差降到最低; 在LCL ?坐标下, 模拟的趋势和模拟数值都能够真实地反应实际的物理情况, 为今后解决此类问题提供了一种新方法。     

珠江磨刀门河口潮汐动力变化对人类活动的响应

磨刀门河口是珠江流域西江的主干入海口, 20世纪80年代以来受到网河区无序采砂和磨刀门整治工程的双重影响, 潮汐动力必然发生相应的调整。本文基于多年的水文资料, 结合统计分析、调和分析和数值模拟的方法, 对近五十年以来磨刀门河口的潮汐动力变化过程及其对人类活动的响应进行研究。结果表明, 20世纪80年代以前, 磨刀门河口总体上呈现出高、低潮位缓慢上升、潮差逐渐减小的趋势, 潮汐动力变化呈现出径流优势型入海口门水道向海延展的自然演变趋势; 20世纪80年代以来, 网河区无序采砂使水位下降、诱使潮汐动力增强, 磨刀门整治工程使水位上升、潮汐动力减弱, 由于河口不同段受到人类活动以及外海潮汐多年变化和海平面上升的干扰程度不同, 其潮汐动力变化呈现出不同特征。近口段受网河区无序采砂影响较大, 水位下降, 潮汐动力增强; 河口段受两种人类活动的双重影响, 水位上升, 在整治工程期间(1983—1993)潮汐动力减弱, 在整治工程后(1993—2003)受网河区无序采砂的影响潮汐动力增强; 口外海滨段受外海潮汐多年变化和全球海平面上升以及整治工程的共同作用, 水位上升, 潮汐动力减弱     

台风对杭州湾水交换影响的定量研究

基于ADCIRC(Advanced Circulation Model for Shelves,Coasts,and Estuaries)模式建立了杭州湾台风风暴潮流二维数值模型,结合粒子追踪模型,分别研究了天文潮和台风过程作用下杭州湾的水交换情况,定量分析了台风对杭州湾水交换的影响;统计7场典型路径的台风,结果表明:台风影响比较剧烈时,与天文潮的单独作用相比,湾内、外参与交换的水体范围分别可增加约1.6倍和7倍,湾内流出的水体影响范围可以增加31%;湾内水交换速度可提高1.7倍。研究还发现不同路径的台风对杭州湾内外水体交换的影响有所不同。     

人类活动对碳循环的影响

在地球系统中,海洋、大气和陆地以及其中的生命与非生命部分都存在着相互联系。人类正在以各种方式根本性地改变着地球的各种系统和循环。一个崭新的地质时代“人类世”不期而至。碳循环是一个极其复杂的地球化学循环过程,包括碳元素在各个储库的贮存和在不同储库之间的流通。不同时间尺度的碳的自然循环都保持着动态平衡状态。人类活动触动了这种平衡机制,成为当前全球碳循环变化的主要驱动因子。     

潮汐影响下的海岸带地下河口水交换及其生物地球化学效应

海岸带地下河口中的生物地球化学过程是一种重要的陆海相互作用驱动力,对于海洋中的物质收支至关重要。以青岛金沙滩为典型研究区域,借助电阻率成像、同位素示踪等技术手段对潮汐影响下的地下河口的生物地球化学特征进行刻画,发现地下水体的电阻率、盐度、pH、镭氡同位素及营养盐含量等各种理化参数的周日变化均表现出明显的潮汐规律,但较同步潮汐信号滞后2~4 h。研究结果表明,在涨落潮过程中,海水在地下河口发生倒灌排放,并显著地改变了含水层的生物地球化学背景场。     

Prediction of water levels in a tidal inlet

It is a very important and difficult problem to operate gates at the inlets of tidal lakes to control water quality and quantity, simultaneously. The main purpose of gate operation at the inlets of tidal lakes are flood control and irrigation. That is to say, the gate operation must sufficiently satisfy two purposes. As the first step to optimize the effect of gate control, the water levels downstream of the gate are predicted by a combined model between regression theory and control theory. The prediction model consists of two parts. The regression equation is used to predict the water levels downstream of the gate by the sea levels in the first part. The causality in this part is physically evident. The Kalman filtering algorithm is employed to identify parameters which construct the state equation in the second part. The prediction is made by joining the two parts.By applying this process to the prediction of water levels on the downstream side of the gate at the inlet of Lake Kahokugata, Kanazawa, Japan, it becomes possible to predict the fluctuations of the water levels under arbitrary gate operations before one or two hours. As the state equation in the Kalman filtering algorithm, first- and second-order Markov models are adopted for the prediction. The result of the latter is better than that of the former.     

The concept of tidal exchange and the tidal exchange ratio

The principal character of the tidal exchange process is neither diffusion nor advection, but a third category of transport, “Massenaustausch”, which appears in the space/time averaged transport. The exchange process can be divided into four fluxes: the flux of standing eddies, the flux of tidal exchange, the flux of tidal eddies and the flux of local eddies. The results of observations at the entrance channel of Kumihama-Bay show a typical example of transport dominated by tidal exchange. The tidal exchange ratio defined by Parkeret al. (1972) applies to the process of exchange between the outflowing watermass and the surrounding watermass outside of the bay mouth, but this should also be considered as being coupled with the ratio for the process of exchange between the inflowing watermass and the surrounding watermass inside of the bay mouth. These two exchange ratios can be combined into a single exchange ratio which describes the exchange process between the outer watermass and the bay water.     

TIDICS—Control of tidal residual circulation and tidal exchange in a channel-basin system

A self-excited oscillation of tidal flow occurs in a tidal channel-basin system with a narrow and high speed inflowing tidal jet. The mechanism of this oscillation was examined through hydraulic experiments. Results show that the oscillation is caused by alternation in the strength of asymmetric residual circulation caused by a biased supply of vorticity by asymmetric tidal vortex pairs, and that the mechanism of alternation also depends on negative feed-back between the residual circulation and the vorticity supply.The unstable state of the flow suggested the possibility of controlling the tidal current and tidal exchange in the channel-basin system and this was confirmed experimentally. Under fixed tidal conditions and with fixed basin dimensions, the tidal residual circulation was controlled to form two strong clockwise and anticlockwise circulations or a single circulation by changing the shape of the bay entrance.     

Long-term ferry-ADCP observations of tidal currents in the Marsdiep inlet

A unique, five-year long data set of ferry-mounted ADCP measurements in the Marsdiep inlet, the Netherlands, obtained between 1998 and 2003, is presented. A least-squares harmonic analysis was applied to the water transport, (depth-averaged) currents, and water level to study the contribution of the tides. With 144 tidal constituents, maximally 98% of the variance in the water transport and streamwise currents is explained by the tides, whereas for the stream-normal currents this is maximally 50%. The most important constituent is the semi-diurnal M₂ constituent, which is modulated by the second-largest S₂ constituent (about 27% of M₂). Compound and overtides, such as 2MS₂, 2MN₂, M₄, and M₆, are important in the inlet. Due to interaction of M₂ with its quarter-diurnal overtide M₄, the tidal asymmetry in the southern two thirds of the inlet is flood dominant. The amplitudes of all non-astronomic constituents are largest during spring tides, strongly distorting the water level and velocity curves. The M₂ water transport is 40° ahead in phase compared to the M₂ water level, reflecting the progressive character of the tidal wave in the inlet. The currents are strongly rectilinear and they are sheared vertically and horizontally, with the highest currents at the surface above the deepest part of the inlet. During spring tides, near-surface currents can be as large as 1.8 m s^− 1. Due to the relative importance of inertia compared to friction, the M₂ currents near the centre (surface) lag maximal 20° (3°) in phase with the currents near the sides (bottom). The tidal-mean currents are directed into the basin in the shallower channel to the south and out of the basin in the deeper channel to the north.     

Spatial variations of tidal water level and their impact on the exposure patterns of tidal land on the central Jiangsu coast

The exposed area of intertidal zone varies with tidal water level changes. If intercomparisons of satellite images are adopted as a method to determine geomorphological changes of the intertidal zone in response to accretion or erosion processes, then the e?ect of water level variations must be evaluated. In this study, two Landsat TM images overpassing the central Jiangsu coastal waters on 2 January and 7 March 2002, respectively, were treated by the changing detection analysis using Image Di?erencing and Post-classiˉcation Comparison. The simultaneous tide level data from four tide gauge stations along the coast were used for displaying the spatial variations of water levels and determining the elevations of waterlines. The results show that the spatial variations of water levels are highly signiˉcant in the central Jiangsu coastal waters. The huge di?erences of tidal land exposure patterns between the two imaging times are related mainly to the spatial variations of tidal water levels, which are controlled by the di?erences in tidal phases for di?erent imaging times and the spatial variations of water level over the study area at each imaging time. Under complex tidal conditions, e.g., those of the central Jiangsu coastal waters, the tide-surge model should be used to eliminate e?ectively the e?ects of water level variations on remote sensing interpretation of geomorphological changes in the intertidal zone.     

用活有孔虫分布指示三亚汊道外港潮流格局

由因子分析得知,海南岛三亚湾汊道外港海底分布有四个主因子活有孔虫群,它们分别代表海湾内水体、湖冲出半盐水水体、湾外内陆架水体及内陆架与海湾水相混的过渡水体.这些水体在潮汐作用下的运动、相互混合,可由各水体的有孔虫指示.由每个主因子因子得分最高的三个属种百分含量之和等值线图所指示的外港潮流循环格局,与海洋学研究所得的结果相当一致.利用有孔虫指示潮汐汊道潮流格局尚属首次尝试,这方法对海岸开发分析泥沙运动、污染物排放等有实践意义.     

The impact of tidal waves on impurity diffusion

A mathematical model is presented for the diffusion of a local impurity patch in the presence of waves in a homogeneous fluid. A semi-empirical equation for the turbulent diffusion of a passive substance is solved numerically, with the initial and boundary conditions imposed. Temporal evolution of the patch is studied in a tidal wave field. Relations have been derived linking the patch parameters with tidal characteristics.Translated by Mikhail M. Trufanov.     

Cohesive sediment transport in the 3D-hydrodynamic-baroclinic circulation model,: study case for idealized tidal inlet

This work provides a general hydrodynamic circulation model that can be used to understand density driven flows, which may arise in the case of suspension of fine-grained materials. The research is expected to provide a better understanding of the characteristics of spatial and temporal variability of current, which is associated with the period of ebb and flood tidal cycles.The model development includes extending the existing three-dimensional (3D) ADCIRC model with (1) baroclinic forcing term and (2) transport module of suspended and soluble materials. The transport module covers the erosion, material suspension and deposition processes for cohesive type sediment. In the case of an idealized tidal inlet in stratified water, the inclusion of baroclinic term can demonstrate the prevailing longshore sediment transport. It is shown that the model has application to the transport of the cohesive sediments from the mouth of the Mississippi River along the north shore of the Gulf of Mexico towards and along the Texas coast.     

The impact of ocean data assimilation on seasonal predictions based on the National Climate Center climate system model

An ensemble optimal interpolation (EnOI) data assimilation method is applied in the BCC_CSM1.1 to investigate the impact of ocean data assimilations on seasonal forecasts in an idealized twin experiment framework. Pseudo-observations of sea surface temperature (SST), sea surface height (SSH), sea surface salinity (SSS), temperature and salinity (T/S) profiles were first generated in a free model run. Then, a series of sensitivity tests initialized with predefined bias were conducted for a one-year period; this involved a free run (CTR) and seven assimilation runs. These tests allowed us to check the analysis field accuracy against the “truth”. As expected, data assimilation improved all investigated quantities; the joint assimilation of all variables gave more improved results than assimilating them separately. One-year predictions initialized from the seven runs and CTR were then conducted and compared. The forecasts initialized from joint assimilation of surface data produced comparable SST root mean square errors to that from assimilation of T/S profiles, but the assimilation of T/S profiles is crucial to reduce subsurface deficiencies. The ocean surface currents in the tropics were better predicted when initial conditions produced by assimilating T/S profiles, while surface data assimilation became more important at higher latitudes, particularly near the western boundary currents. The predictions of ocean heat content and mixed layer depth are significantly improved initialized from the joint assimilation of all the variables. Finally, a central Pacific El Ni?o was well predicted from the joint assimilation of surface data, indicating the importance of joint assimilation of SST, SSH, and SSS for ENSO predictions.