应用电子计算机整编潮水位资料

潮水位资料的整编,是将人工观测或自记仪器记录的高、低潮水位及对应出现时间的原始数据,进行分析检查和综合加工,提供便于使用的系统潮水位资料。现行的人工整编方法,是根据测验的潮水位资料,通过计算得出对应潮水位的高低潮间隙、涨落潮潮差和历时,从中统计出月年高高潮、低高潮;高低潮、低低潮;高潮间隙、低潮间隙;涨潮潮差、历时,落潮潮差、历时的特征值(见图1)。     

利用T/P海面高度数据校验验潮站地面升降的初步研究

利用TOPEX/Poseidon卫星1993—2001年的海面测高资料提取了上海和江苏临近海域这9年间的绝对海面变化信息，并与该区域6个验潮站的同时段潮位记录数据进行了对比分析。研究结果表明根据T/P海面高度数据提取的月均海面变化曲线与同海区验潮站测得的同期海面变化过程具有相当好的一致性和同步性，但是根据潮位序列得出的9年平均海面上升速率值均大于根据卫星资料得出的上升速率值。由于卫星测高数据是严格建立在地心坐标基础上的，因此二者的差异在很大程度上应与验潮站所在地点的地面沉降有关。值得注意的是经过地面沉降校正的上海吴淞验潮站数据得出的9年平均海面上升速率值仅比卫星测高结果大0. 43 mm/a，而江苏省射阳河口至三条巷之间5个未经地面沉降校正的验潮站得出海面上升速率与卫星测高结果之间的差值在0.95～3.01 cm/a之间，并呈向北递增趋势。这一对比结果反映该岸段近期的地面沉降速率可能有自南向北增大的趋势，其量值有可能达到年厘米量级。     

基于联合分布的珠江口设计潮位过程线方法研究

针对同倍比方法与同频率方法推求设计潮位过程线中的局限性,采用4种边际分布函数对珠江口年最高潮位与年最大潮差序列进行拟合的基础上,选取4种不同的二维Archimedean Copula函数建立珠江口年最高潮位与年最大潮差的联合分布,并分析了高潮位重现期与潮位过程同现重现期的线性关系。结果表明:高潮位与潮差的同现重现期总是大于相应边际分布的重现期,并且随着边际分布重现期的增大,同现重现期增幅也越大,说明较高重现期的高潮位与潮差同时发生的可能性很小;基于高潮位重现期与潮位过程同现重现期的线性关系,采用基于联合分布的方法推求珠江口潮位过程线,推求结果较同频率法更为合理。     

长江南京潮水位站近百年高潮位变化特征及成因分析

为研究南京站多年来年最高潮位的变化特征,根据水文变异综合诊断方法,分析检验了长江南京站近百年高潮潮位变化的整体趋势;利用db N系列小波变换分析了年高潮潮位变化的局部趋势;利用复数Morlet小波分析了年最高潮位的周期变化规律。分析结果表明,南京站年最高潮位序列总体上无明显趋势变化,局部变化趋势明显;年最高潮位存在5a、11a、42a和63a时间尺度四个主要变化周期。分析结果为认识南京站年最高潮位变化、做好水安全工作以及水资源的开发利用提供相关依据。     

径潮共同作用对径流型河口盐水上溯的影响

为进一步认识径流型河口枯季盐水上溯距离变化的影响因素及其作用机制,将实际河口简化并在不同径流量下分别用等潮差正弦潮和主要分潮驱动,进行盐水三维数值模拟试验。结果表明:随着径流和潮汐两大基本作用的相对强度不同,平衡态下盐水形态和位置自动调整并最终达到盐输运平衡,径流量小于3 000 m3/s且潮差小于2 m时,最大上溯距离随潮差的变化规律在不同径流量下存在明显差别;大小潮半月周期内盐水呈现非平衡态,非强混合时潮周期盐水上溯最大距离围绕平衡态随潮差呈顺时针绳套关系变化。径流导致的密度环流作用和潮汐的混合作用交织,两者相互影响并协同发展,两种作用相对强度的不同是导致径流型河口盐水上溯距离变化显著的主导因素。     

滨海城市雨潮遭遇联合分布模拟与设计

滨海城市河流常常遭受暴雨和潮汐顶托双重影响导致洪涝灾害,需要重视雨潮遭遇联合分布模拟与设计。以深圳市西乡河为例,采用年最大值法（AM）和超定量序列法（POT）两种选样方法,基于Copula方法模拟24 h暴雨遭遇日高潮位的联合分布特征,对比雨潮遭遇传统重现期和二次重现期差异,根据同频法和权函数法反推计算雨潮设计组合值。结果表明:雨潮边缘分布最优模型均为广义正态分布（GNO）,不同选样方法雨量分布模型参数差异明显。雨潮之间呈现较弱的正相依性,Archimedean Copulas均能较好地模拟雨潮遭遇联合分布特征,最优模型为Gumbel-Hougaard Copula。同频法反推雨潮设计组合值,二次重现期雨量和潮位均大于传统联合重现期,POT选样的潮位大于AM。权函数法选出的雨潮设计组合值,偏重于较高的潮位,雨量设计值较小。当明确了选样方法、联合分布模型和重现期类型,给定联合重现期的雨潮设计组合值是个此消彼长的过程,若选择较大的雨量设计值,则潮位值变小,反之亦然。从防洪潮设计安全角度考虑,POT选样方法及二次重现期设计更为安全。     

长江口咸潮入侵扩散响应函数及初步应用

咸潮入侵是入海径流和潮汐共同作用的盐度扩散过程。以量能累积与阻抗交互作用过程为理论基础,采用逻辑推理和数学分析推导了入海流量、潮差和咸潮入侵面积三者扩散响应的函数关系和曲线型态,并利用长江口近50年枯季入海流量、潮差和咸潮入侵面积进行了实证分析。结果表明,在一定入海流量条件下潮差与咸潮入侵面积关系具有S型曲线特征,入海流量与咸潮入侵最大面积关系也具有S型曲线特征,共同构成一个三维咸潮入侵扩散响应函数;长江口近50年的实测数据实证了上述三维关系特征,据此构建了双曲正切的S型长江口咸潮入侵扩散响应函数,并阐述了参数定值与量化方法;以此函数为基础,分析确定了长江口入海流量大于10 000 m3/s时可抵御大规模咸潮入侵,同时计算了2001-2012年咸潮入侵损失。     

中国近海潮汐变化对外海海平面上升的响应

针对外海海平面上升对中国沿海潮波系统和潮汐水位可能带来的影响,通过西北太平洋潮波数学模型对边界海平面上升后潮波变化进行了数值模拟。研究发现边界海平面上升后,在无潮点附近东侧迟角增加,西侧迟角减小;无潮点北侧振幅增加,南侧振幅减小;辽东湾、渤海湾顶、辽东半岛东海域、海州湾至鲁南沿海、苏北沿海、台湾海峡至浙东沿海和南海平均潮差增加,海平面上升0.90 m后潮差最大增幅达0.40 m;长江口、杭州湾至对马海峡、朝鲜西海岸和莱州湾海域潮差减小。随着海平面上升量值的增加,渤海、台湾海峡潮差变化速率相对稳定,黄海、东海和南海站位变化速率有所变动;平均高水位的变化趋势与潮差一致;潮差增加的区域,高水位抬升幅度超过边界海平面上升幅度。海平面上升引起的高水位超幅变化,增加了沿海地区对风暴潮和其他灾害防护的风险。     

设计潮位过程线及其推求

针对现行推求设计潮位过程线方法中存在的不合理现象,在分析研究各潮汐要素之间的关系的基础上,提出根据高潮位(或低潮位)与潮差同频率控制放大的方法推求设计潮位过程线。结果表明,用该方法推算得到的设计潮位过程线比较符合实际,能较好地满足工程设计的防洪防潮标准,达到工程预期的效果。     

河口湾水动力环境对滩涂利用的累积响应——以珠江口伶仃洋为例

为揭示河口湾水动力环境对滩涂利用的累积响应过程,以珠江口伶仃洋河口湾为例,基于潮波数学模型和潮流数学模型,研究了1981年以来湾内进出潮量、分潮振幅和潮流流速的累积变化。结果表明:相对于1981年,2018年岸线条件下伶仃洋湾口断面涨落潮量累积减少4.9%~6.0%、内伶仃断面涨落潮量累积减少9.0%~12.8%、深圳湾断面涨落潮量累积减少17.8%、南沙断面涨落潮量累积减少5.0%~6.3%;伶仃洋M₂分潮振幅呈增加趋势,振幅增幅由南向北增加,潮波由南向北变形进一步加剧;伶仃洋最大可能潮差变化与M₂分潮振幅变化趋势一致,潮汐性质没有发生变化;伶仃洋潮流流速总体减小,西岸流速减幅高于东岸,湾顶附近流速略有增加。     

长江河口崇明东滩周期性淹水区域水流的基本特征

潮间带周期性淹水区域水深、流速的变化过程是潮滩水动力过程的基本组成部分,也是潮流与泥沙相互作用的基础。通过2002年4月至2003年1月4个季节的野外实测,获得了平静天气条件下,崇明东滩滩面潮流水深、流速与流向的变化过程数据。结果表明,崇明东滩盐沼和邻近光滩处涨潮历时均小于落潮历时,水深过程变化呈现出“陡涨缓落”的特点。光滩与盐沼交界处光滩一侧流速过程呈“双峰型”特征,涨落潮均出现流速峰值;盐沼（植物生长期）流速过程具有“单峰型”特点,仅在涨潮初出现峰值。研究区潮流不对称性明显,主要表现为涨潮优势,且由光滩向盐沼上部不断增强,潮沼植物和地形变化是加强盐沼区涨潮优势的主要原因。流速变化过程的差异和潮流不对称性使盐沼区域发生稳定的泥沙淤积,盐沼前缘光滩则会出现较频繁的冲淤变化,平静天气条件下,它们是控制崇明东滩泥沙输移和潮滩动力地貌过程的动力基础。     

大凌河口水动力数值模拟分析

采用大凌河实测长系列河道径流及水下地形等数据, 通过建立水动力数值模型, 综合考虑潮流和河道径流的影响, 对大凌河口的潮流进行模拟, 探讨大凌河口及辽东湾北部海域水动力过程的主要特征. 结果表明: 大凌河口附近海域的海流以潮流为主, 具有明显的往复性质. 潮流总的运动趋势是, 涨潮主流向为北东, 落潮主流向为南西. 大潮流速大于小潮流速, 涨潮流历时与落潮流历时几乎相当. 最大涨潮流速约为0.52 m/s, 最大落潮流速约为0.4 m/s, 潮流涨落平均潮流强度的分布大体和该海域等深线相适应.     

Tidal rectification on drying estuarine sandbanks

Drying estuarine sandbanks experience only that part of the tidal cycle around high water. In a partially progressive tidal wave, this means that the duration of the flood over the sandbank will be greater than that of the ebb: a process of tidal rectification. In this paper, we propose the hypothesis that this leads to flood-directed tidal residual currents over drying sandbanks. The hypothesis is tested by observation and a 2-D hydrodynamical model in the Conwy estuary, a vertically well-mixed macrotidal estuary in North Wales. The observations include tide gauge data, tidal cycle boat surveys, and fixed current meter data. The data show weak flood-directed residual currents over a drying sandbank and much stronger ebb-directed residuals in the channels along the sides of the sandbank. The model reproduces the observations in the vicinity of the sandbank and shows that the tidal rectification mechanism produces a general pattern of residual circulation in the estuary, with flood-directed flow in the drying areas and ebb-directed flow in the channels. The flood residuals are most marked near the estuary mouth where the tidal wave is most progressive in nature. The main application of this mechanism is believed to be in the transport of bedload sediment. The flood-directed residuals will tend to move the tops of the sandbanks upstream.     

Tidal dynamics and low-frequency exchanges in the Aransas Pass,Texas

Current, water level and wind data collected from a study site at the Aransas Pass, Texas, during a 45-day period in mid 1977 are used to describe tidal motions and low-frequency, meteorologically-forced exchanges between the inner shelf and a series of intracoastal bays. Analysis of individual tidal constituents indicates a mixed but principally diurnal tide. Tidal constituents move through the Pass as nearly progressive waves. Asymmetry in the co-oscillating tidal motions is explained as a result of unequal frictional forces acting on flood and ebb currents in the Pass. Tidal excursions computed from the tidal harmonic constants and from cumulative net displacements suggest that tidal-period exchanges are not effective in flushing the bays even under tropic tidal conditions. Nontidal water levels are related to the cross-shelf component of the coastal windstress at statistically significant levels. This suggests that low-frequency local meteorological forcing, as a set-up or set-down of coastal water levels, plays a valuable role in assisting tidally-driven exchanges.     

Tidal flushing of an estuarine embayment subject to recurrent dinoflagellate blooms

A rhodamine dye tracer study was conducted over eight tidal cycles to investigate mixing and tidal exchange processes in Perch Pond, a Cape Cod embayment subject to recurrent blooms of the toxic dinoflagellate, Gonyaulax tamarensis. Dye injected at the inlet to Perch Pond during flood tide became well-mixed within the pond in one day and was removed at an effective first order rate of 0.36 d^?1, equivalent to a 70% utilization of the maximum possible tidal exchange. This relatively high flushing efficiency can be attributed to a density-driven circulation within the pond, consisting of a subsurface inflow of high salinity dense water on the flood tide followed by removal of lighter surface layers through the shallow inlet during ebb tide. The formation of a frontal convergence near the inlet on flood tide is consistent with the observed distribution of G. tamarensis cysts and shelifish toxicity. It is also clear that phytoplankton like G. tamarensis, whose maximum growth rates approximate the rate of tidal flushing, can only bloom within the embayment by avoiding the outflowing surface waters. Mixing within the pond is probably less efficient and population losses greater during dry periods when the pond salinity is higher and the stratification weaker.     

Tidal Changes and Coastal Hazards: Past,Present and Future

A review is presented of the nature of tidal changes and their importance in the context of coastal hazards. This is done in order to illustrate the way in which tides do and may impact on the coast as a hazard and highlight the need for research to be carried out in this context. Three main aspects of tides are significant in this respect – these are: (1) tidal heights, including tidal range and the asymmetry or otherwise of the flood/ebb cycle; (2) tidal currents, the speed and direction of which affect sediment movement, sources and sinks; and (3) tidal mixing of fresh water with water of varying levels of salinity and differing temperatures. A variety of tools, from geological data to modelling, and tide gauges to satellites, may be used to assess tidal changes. Tides form the basis on which all other coastal processes operate and are therefore important with regard to the physical, chemical and biological hazards in the coastal zone. There is an urgent need to study tidal changes – both their nature and causes – in order to ensure successful coastal management.     

Tidal nitrogen exchanges across a freshwater wetland succession gradient in the upper Cooper River,South Carolina

Tidal freshwater sections of the Cooper River Estuary (South Carolina) include extensive wetlands, which were formerly impounded for rice culture during the 1,700s and 1,800s. Most of these former rice fields are now open to tidal exchange and have developed into productive wetlands that vary in bottom topography, tidal hydrography and vegetation dominants. The purpose of this project was to quantify nitrogen (N) transport via tidal exchange between the main estuarine channel and representative wetland types and to relate exchange patterns to the succession of vegetation dominants. We examined N concentration and mass exchange at the main tidal inlets for the three representative wetland types (submerged aquatic vegetation [SAV], floating leaf vegetation, and intertidal emergent marsh) over 18-21 tidal cycles (July 1998–August 2000). Nitrate + nitrite concentrations were significantly lower during ebb flow at all study sites, suggesting potential patterns of uptake by all wetland types. The magnitude of nitrate decline during ebb flow was negatively correlated with oxygen concentration, reflecting the potential importance of denitrification and nitrate reduction within hypoxic wetland waters and sediments. The net tidal exchange of nitrate + nitrite was particularly consistent for the intertidal emergent marsh, where flow-weighted ebb concentrations were usually 18–40% lower than during flood tides. Seasonal patterns for the emergent marsh indicated higher rates of nitrate + nitrite uptake during the spring and summer (> 400 μmol N m^-2 tide^-1) with an annual mean uptake of 248 ± 162 μmol m^–2 tide^–1. The emergent marsh also removed ammonium through most of the year (207 ± 109 μmol m^–2 tide^–1), and exported dissolved organic nitrogen (DON) in the fall (1,690 ± 793 μmol m^–2 tide^–1), suggesting an approximate annual balance between the dissolved inorganic N uptake and DON export. The other wetland types (SAV and floating leaf vegetation) were less consistent in magnitude and direction of N exchange. Since the emergent marsh site had the highest bottom elevation and the highest relative cover of intertidal habitat, these results suggest that the nature of N exchange between the estuarine waters and bordering wetlands is affected by wetland morphometry, tidal hydrography, and corresponding vegetation dominants. With the recent diversion of river discharge, water levels in the upper Cooper estuary have dropped more than 10 cm, leading to a succession of wetland communities from subtidal habitats toward more intertidal habitats. Results of this study suggest that current trends of wetland succession in the upper Cooper River may result in higher rates of system-wide inorganic N removal and DON inputs by the growing distributions of intertidal emergent marshes.     

Flow,stress and sediment resuspension in a shallow tidal channel

In October of 2004, a 3-d observational program to measure flow and sediment resuspension within a coastal intertidal salt marsh was conducted in the North Inlet/Winyah Bay National Estuarine Research Reserve located near Georgetown, South Carolina. Current and acoustic backscatter profiles were obtained from a moored acoustic Doppler current profiler (ADCP) deployed in a shallow tidal channel during the spring phase of the tidal cycle under high discharge conditions. The channel serves as a conduit between Winyah Bay, a large brackish estuary, and North Inlet, a saline intertidal coastal salt marsh with little freshwater input. Salinity measurements indicate that the water column is vertically well mixed during flood, but becomes vertically stratified during early ebb. The stratification results from brackish (15 psu) Winyah Bay water entering North Inlet via the tidal channel, suggesting an exchange mechanism that permits North Inlet to receive a fraction of the poor water quality and high discharge flow from upland rivers. Although maximum flood currents exceed maximum ebb currents by 0.2 m s⁻¹, suspended sediment concentrations are highest during the latter ebb phase and persist for a longer fraction of the ebb cycle. Even though the channel is flood-dominated, the higher concentrations occurring over a longer fraction of the ebb phase indicate net particulate transport from Winyah Bay to North Inlet during spring tide accompanied by high discharge. Our evidence suggests that the higher concentrations during ebb result from increased bed friction caused by flow asymmetries and variations in water depth in which the highest stresses occur near the end of ebb near low water despite stronger maximum currents during flood.     

海南岛洋浦湾沉积作用研究

本文对海南岛洋浦湾海域的洋浦湾、新英湾、洋浦深槽及拦门沙浅滩的沉积环境和沉积特征做了描述、讨论，对河流、海岸侵蚀和珊瑚礁生物的３种沉积物来源及数量做了分析计算，得出其总量为９×１０⁴ｍ^３／ａ。根据钻孔柱状样的¹⁴Ｃ及²¹⁰Ｐｂ分析，得出８０００ａＢ．Ｐ．以来沉积速率为０．１～０．２ｃｍ／ａ，近百年来沉积速率为１～２ｃｍ／ａ。