FINE SILT PARTICLE PATHLINE OF DREDGING SEDIMENT IN THE YANGTZE RIVER DEEPWATER NAVIGATION CHANNEL BASED ON EFDC MODEL

Based on the Environmental Fluid Dynamics Code(EFDC),a three-dimensional baroclinic model for lower reaches of the Yangtze River,Yangtze River Estuary,Hangzhou Bay and the adjacent sea areas was established with the sigma-coordinate in the vertical direction and the orthogonal curvilinear coordinates in the horizontal direction.The fine silt particle tracers were injected during different tides with the calibrated three-dimensional numerical model in the Yangtze River Estuary to simulate the migration track...     

EFDC模型在长江口及相邻海域三维水流模拟中的开发应用

基于公开代码的EFDC(Environmental Fluid Dynamics Computer Code)模型,建立了范围包括长江下游段、长江口、杭州湾及邻近海域的三维水流数值模型。用Deflt3D附带软件得到了长江口海域正交曲线网格剖分,更好地实现了网格与地形边界的拟合;并在模拟浅滩动力过程中,设置最小水深条件限制,成功地消除了复杂浅滩地形情况下原模式运行出现负水深的局限。利用10个潮位站的实测潮位以及9个流速测站的水流流速资料对模型参数进行了验证和率定。模拟结果能够与实测值较好地吻合,各站模拟计算潮位值相对误差小于10%,。率定、改造后的模型不仅能够较好地模拟反映长江口海域三维潮汐及水流运动,而且还能对潮流运动特征进行分析。该模型可用于长江口海域相关问题的进一步研究。     

海平面上升对长江江阴以下河段风暴潮增水的影响

随全球气候变暖,海平面呈加速上升态势。长江口地处西北太平洋风暴盆地的西北缘,地势低洼,被评估为风暴潮灾害影响下的脆弱区。为研究海平面上升后长江江阴以下河段风暴潮位的变化,建立了精细化长江口天文潮-风暴潮耦合数学模型。该模型模拟分析了海平面上升后,在9711号“芸妮”和1509号“灿鸿”这两种典型台风作用下,长江口近岸天文潮和风暴增水的响应规律。研究结果表明:预计未来100年,海平面抬升70 cm后,长江口平均潮位上升50～80 cm。长江口江阴以下河段及近岸区域增水极值略微下降。增水极值自上游江阴到下游牛皮礁先增后减,增水极值沿程最大值的具体位置与台风路径、台风强度密切相关。研究可为中长期长江口沿岸城镇防洪排涝提供一定的理论依据。     

THE EFFECTS OF RADIATION STRESS ON WAVE HEIGHTS AND SEA LEVEL IN THE INTERACTION OF COUPLED WAVE-TIDE-SURGE IN THE COASTAL AREA

1 .　ＩＮＴＲＯＤＵＣＴＩＯＮＷｉｎｄｇｅｎｅｒａｔｅｓｂｏｔｈｗａｖｅｓａｎｄｓｔｏｒｍｓｕｒｇｅｓ,ｓｏｔｈｅｉｒ ｇｅｎｅｒａｔｉｏｎｉｓｃｌｏｓｅｌｙｒｅｌａｔｅｄ .Ｆｕｒｔｈｅｒ ｍｏｒｅ ,ｓｔｒｏｎｇｌｙｎｏｎｌｉｎｅａｒｉｎｔｅｒａｃｔｉｏｎｓｂｅｔｗｅｅｎｔｉｄｅｓａｎｄｓｔｏｒｍｓｕｒｇｅｓｅｘｉｓｔｉｎｓｈａｌｌｏｗｗａｔｅｒ .Ｔｈｅｉｎｔｅｒａｃｔｉｏｎｓｂｅｔｗｅｅｎｗａｖｅａｎｄｔｉｄｅ ｓｕｒｇｅｍｏｔｉｏｎ ,ｂｅｔｗｅｅｎｗａｖｅａｎｄｔｈｅｍｅａｎｆｌｏｗｏｒｗａｔｅ…     

长江口深水航道海域悬浮泥沙光谱特性研究

 长江口深水航道治理和维护的核心问题为泥沙问题。对长江口深水航道 7 个浮标所在海域进行了不同浓度含沙水体的反射光谱测量,并且结合“长江口深水航道水文、泥沙、波浪自动遥测系统”遥测数据和野外现场取样数据,对其光谱特性进行了分析,发现这些海域悬浮泥沙的敏感波段在 730 ～ 930 nm 之间,并且 731 nm 附近的一阶微分与悬浮泥沙浓度相关性较好。在对其光谱特性进行分析的基础上,分别建立了悬浮泥沙光谱反射率、光谱反射率均值和反射率一阶微分的指数反演模型和二次反演模型,结果显示 900 nm 波长的指数模型可以较准确地定量反演出悬浮泥沙浓度。     

INTERANNUAL VARIABILITY OF KUROSHIO CURRENT AND ITS EFFECT ON THE NEARSHORE BRANCH IN JAPAN/EAST SEA

Based on the Hybrid Coordinate Ocean Model (HYCOM), this article presents simulations of the three-dimensional dynamic and thermal structure of the North Pacific Ocean (NPO) in the time domain from January 1991 to December 2000. The baroclinic current field and its interannual variability in Northwest Pacific Ocean (NWPO), especially, the Kuroshio Current (KC) and the Japan/East Sea (JES) are analyzed and discussed. The results show that the HYCOM covers a complete dynamic and thermo process with adequate representations of the eddy fields and variability in main spatial and temporal scales. The model is used to simulate the strong interanual variability of the KC, which may affect the strength of the eastern bifurcation of the Tsushima Warm Current (TSWC), named the Nearshore Branch (NB) in the JES. When the KC is strong and its axis is close to the Japan Island, the TSWC and its bifurcations in the JES would intensify accordingly. Our results confirm once again the hypothesis of Yang et al. that the KC determines the annual mean NB in the JES via the “island integral constraint”. This article further extends this hypothesis to study the KC role in the NB on a time dependent scale.     

THE INTRUSION AND INFLUENCES OF INTRASEASONAL LONG ROSSBY WAVES IN THE EAST CHINA SEA

The analysis of sea level data from tide stations and ocean general circulation model (OGCM) shows that the intraseasonal long Rossby wave results in the intraseasonal variations of Kuroshio axis and transport in the upper reaches of the Kuroshio in the East China Sea (ECS). Due to the transport modulation induced by Ryukyu Islands, the intraseasonal variation is very weak in the lower reaches of the Kuroshio in the ECS. A two-layer model reveals the relation among Kuroshio frontal unstable wave with topography,transport and the axis position of the Kuroshio, from which we can infer that the intrusion of intraseasonal long Rosshy wave may stimulate the Kuroshio frontal unstable wave in the upper reaches of the Kuroshio in the ECS. The altimeter data also shows that the sea level anomaly resulting from intraseasonal long Rossby wave could pass the channel between Taiwan and Ryukyu Islands and propagate northeastward in accord with the Kuroshio frontal unstable wave. However, the sea level anomalies passingIslands are relative weak and Kuroshio variation.through the gaps of Ryukyu have negligible effects on the Kuroshio variation.     

长江口及近海区沉积物重金属与底质环境评价

为了评价长江口及毗邻海域重金属环境污染情况,用评价区49个站位的实测资料对表层沉积物重金属含量与分布变化情况进行了分析。结果表明：调查海域中,沉积物中锌的含量最高,其次为铜、铅,而汞的含量最低,且铜和锌具有明显的线性相关关系;重金属含量分布呈南高北低（特别是调查区东北部）、近岸高远岸低的特征,高值区不仅出现在长江口水质浑浊水域,也出现在杭州湾湾口海域,杭州湾可能已经成为长江口海域重金属元素的另一重要的沉积“汇”。长江口及邻近海域表层沉积物中重金属元素含量整体上呈逐步降低的趋势,2005年沉积物各项指标均符合国家《海洋沉积物质量》一类标准,原因可能是三峡工程蓄水和近年来流域及河口的治理。     

ANALYTICAL SOLUTION OF GROUNDWATER FLUCTUATIONS IN ESTUARINE AQUIFER

1.INTRODUCTIONTide-induced head fluctuations are a naturalphenomenon in a coastal aquifer[1-3].For an un-confined aquifer,groundwater level changes corre-sponding to the tidal waves.As the tidal propagateinland,their amplitude is attenuated and phase-shifts occur.A typical damping distance for tidalwater table fluctuation in an unconfined aquifer isseveral hundred meters whereas the tidal influenceon a confined aquifer can extended landward byseveral thousand meters[2,4].According to thef…     

Response of nearshore circulation outside Yangtze Estuary to El Nio events

With consideration of the comprehensive effects of runoff from the Yangtze River, East China Sea background circulation, and tidal currents,a regional circulation model, including the Yangtze Estuary, Hangzhou Bay, and adjacent sea areas was established. The 2002/2003 El Ni~no event was chosen for study of the anomalies of circulation outside the Yangtze Estuary. The coastal and ocean current systems of the East China Sea and the current structure outside the Yangtze Estuary were accurately described. The results of vertical circulation analysis basically coincide with those of horizontal circulation analysis, showing that the circulation outside the Yangtze Estuary is mainly affected by the Taiwan warm current, runoff from the Yangtze Estuary, and the tide-induced residual current. The El Ni~no event weakens Yangtze Estuary circulation to a certain degree, and the impacts are more significant in summer than in winter. During the 2002/2003 El Ni~no event, the flux of the Taiwan warm current decreases, and the northward component of the Taiwan warm current decreases by half in February 2003 compared to the previous year. However, its path is relatively stable.     

AN APPROACH TO SEPARATING THE CURRENT VELOCITY IN ESTUARINE AND COASTAL WATERS

In the near-shore waters, the actual flow is mainly induced by tide, wind and salinity, and the river water runoff should also be included as a component in the estuary waters. The interactions among these major components are very complicated. Many approaches were proposed to study isolated tide and wind-driven currents or run-off based on the measured velocity, with all its components taken as a whole. In this article, firstly, based on the actual hydrodynamic characteristics of estuarine and coastal waters, an approach is proposed to separate the measured velocity by considering the theoretical current velocity profiles and using the least squares method. The vertical structures of tidal, wind-driven currents, density current and runoff can be obtained as well as their proportions in the measured velocity. Then, this approach is applied to the analysis of velocity data obtained in the North Branch of Yangtze River estuary and of laboratory test data. The results are found to be satisfactory. Finally, this approach is used to separate the measured velocity in the South Branch of Yangtze River estuary, to determine not only the bed friction velocity and roughness height, but also the surface wind stress, and to estimate the wind velocity data above the water surface. The results show that this method is simple in principle, practical in use, and reasonable in obtained results. So it can be used to effectively analyze the field data.     

SEASONAL REVERSE OF SEA SURFACE SLOPE IN THE NORTHERN YELLOW SEA AND ITS DYNAMIC RELATION WITH MONSOON EFFECTS

Based on the monthly average sea level data from the tide gauge measurement (1999-2001), the seasonal variability of the sea level in the Northern and Middle Yellow Sea is studied to reveal that the sea surface height at all the tide gauges becomes higher in summer than that in winter. In addition, the sea surface height of the Northern Yellow Sea is higher than the one of the Middle Yellow Sea with a slope downward from the north to the south in summer, while it is lower with a reversed slope in winter. The seasonal reverse of the sea surface slope can be attributed to the monsoon effects i.e. the annual reverse of the monsoon direction and the annual variation of the monsoon rainfall. A set of equations are established in light of the dynamic principles to expound how the monsoon forcing and the sea surface slope generate a summer outflow and a winter inflow in the Yellow Sea.     

长江口水源地取水口盐度对径潮动力的响应

上海市饮用水的80%来自长江口三大水源地——陈行水库、青草沙水库和东风西沙水库。枯季盐水入侵一直是长江口水源地安全面临的最大威胁。作为河口区域的主要动力, 有必要进一步研究径流和潮汐对长江口水源地盐水入侵的影响。通过建立长江口平面二维潮流盐度数学模型, 对长江口盐水入侵进行模拟, 分析了水源地取水口盐度过程与潮位过程的关系, 探讨了北支盐水倒灌对水源地的影响。研究结果表明:三大水源地因位置不同, 盐度过程线特征也不相同。水源地取水口盐度过程线与潮位过程线的关系可作为受北支倒灌盐水和正面入侵盐水影响程度的重要依据。北支盐水倒灌发生时, 东风西沙水库、陈行水库、青草沙水库水源地分别在大潮、中潮及小潮时受倒灌盐水影响最为严重。随着径流增大, 水源地受盐水入侵影响的时间会提前, 但是盐度则随径流的增大而减弱。     

新沭河—蔷薇河洪水调度模型研究

根据连云港地区河流分布及洪水特点，合理确定该地区的防洪调度原则，建立了考虑降雨汇流过程与潮汐顶托作用下的洪水演进模型，与实测资料比较证实了本模型的可靠性，可为该地区防洪调度提供依据。     

长江流域水量模型初步研究

基于MIKEBASIN平台，将长江流域划分为91个子流域，采用NAM模型来模拟各分区径流过程，再将各分区NAM模型连接成为整体，构建了长江流域水量模型，并完成了模型系统中面雨量计算、参数批量修改、水库调度等关键功能的二次开发。模拟结果表明，模拟径流过程与实测过程基本一致。鉴于部分子流域面积过大，取、排水用户未纳入模型等原因，导致模拟年径流有所偏大，以汉江流域为试点进行了模型细化研究，显著提高了模拟精度，表明长江流域水量模型模拟精度尚有进一步提高的空间。     

THE RELATIONSHIP BETWEEN THE TAIWAN WARM CURRENT AND TSUSHIMA WARM CURRENT

The Taiwan Warm Current (TWC) and the Tsushima Warm Current (TSWC) flow northward over the shelf in the East China Sea (ECS), which some previous studies regard as a Taiwan-Tsushima Warm Current (TTWC) System. But the roles of the TWC and TSWC in the formation of the TTWC system have not been clarified. This article will show that the TSWC is more important in the TTWC system. Using a three-dimensional baroclinic model, we conducted several numerical experiments to reveal the dynamic relationship between the TWC and TSWC. The results show that the TWC has little effect on the TSWC, while the TSWC has a significant effect on the TWC. A source-sink driven mechanism along isobaths may be used to explain this phenomenon. The perennial northward flow through the Tsushima Strait pumps the response over the northern shelf in the ECS that gives rise to the TWC. Although the TSWC is located at the "downstream" region, it could induce about 0.5 Sv to TWC in annual mean values.     

长江口河段近期演变特点与整治研究建议

长江口河段历史上大规模的并岸并洲形成了目前两岸和崇明岛分隔南、北支的宏观边界,同时进一步塑造了近河口段宽窄相间的江心洲分汊河型和河口段"三级分汊、四口入海"的喇叭型河口。阐述了长江口近河口段和河口段2种不同的河型与河床地貌概况,分析了长江口河段近期演变特点和存在的问题,在此基础上提出了应加强河道观测与分析研究工作,尽早实施九龙港节点整治工程,深入研究南港河势控制关系等整治研究建议。     

长江口污水超标排放对水质影响的数值模拟研究

为分析长江口污水超标排放对水质的影响,建立了包括溶解氧(DO)、生化需氧量(BOD)、氨氮(NH_3-N)和磷酸盐(PO_4~(3-)-P)等水质指标的长江口杭州湾水动力水质数学模型,并对长江口污水超标排放过程进行了模拟。计算结果表明:长江口的水动力条件有利于污染物的稀释扩散,对短期超标排放(如24 h)的污水,可以在短时间内稀释并使海域水环境恢复至正常水平;对于长期超标排放,污染物质的累积作用将会对整个海域水质产生不利影响,使水质下降。     

DYNAMIC CORRECTION OF ROUGHNESS IN THE HYDRODYNAMIC MODEL

Based on the hydrodynamic model and the Xinanjiang model, the river stage forecasting model has been proposed. But its performance is not satisfactory as applied to estuary areas. River roughness is a sensitive parameter in the hydrodynamic model, and its value is related to some substantial uncertainties in the tidal river. According to roughness tests, a new method of roughness dynamic correction was developed to improve the performance of the stage model. The method was focused on the usage of observed data for the studied section, and its parameters were analyzed. Nested with the dynamic correction of roughness, the stage model was applied to the tidal reach of the Caoe River. The results demonstrate that the roughness dynamic correction can improve the simulation accuracy of the stage model, and especially has the capacity of reducing the errors at peak stages.     

THE STUDY OF THE YELLOW SEA WARM CURRENT AND ITS SEASONAL VARIABILITY

The Yellow Sea Warm Current (YSWC) penetrates northward along the Yellow Sea Trough, and brings warm and saline water towards the Bohai Sea. The YSWC becomes much less intrusive in summer and is limited mostly in the southern trough, contrasting with a deep winter penetration well into the trough. The seasonal variability of the YSWC has prompted a debate regarding which controls the YSWC and its seasonal variability. In this article, the annual mean and seasonal variability of the YSWC was examined by using a 3-D ocean model together with several experiments. The results show that in the annual mean the YSWC is a compensating current firstly for the southward Korea Coastal Current (KCC), which is mainly caused by the Kuroshio Current (KC). The local wind-stress forcing plays an important but secondary role. However, the local monsoonal forcing plays a prominent role in modulating the seasonal variability. A deep northwestward intrusion of the YSWC in winter, for instance, is mainly due to a robustly developed China Coastal Current (CCC) which draws water along the Yellow Sea trough to feed a southward flow all the way from the Bohai Sea to the Taiwan Strait.