Landward limit of wind setup on beaches

Open coast storm surge water levels consist of a wind shear forcing component generally referred to as wind setup; a wave setup component caused by wind-induced waves transferring momentum to the water column; an atmospheric pressure head component due to the atmospheric pressure deficit over the spatial extent of the storm system; a Coriolis-forced component due to effects of the rotation of the earth acting on the wind-driven alongshore current at the coast; and, if astronomical tides are present, an astronomical tide component. Astronomical tide is considered to be predictable and, therefore, not a meteorological driven component of storm surge although there may be interaction between the tide and meteorological driven water levels. Typically the most important component of storm surge on the US East Coast and Gulf of Mexico shorelines is the wind setup component. The importance of inland flooding due to the wind setup component of storm surge is considered herein with special reference to the effect of subaerial slope on inland flooding where three different linear slopes are considered and storm surge is calculated for the region above still water level, using an analytic solution. The present study findings show that the inland storm surge from the wind setup component can be of considerable importance and lead to significantly higher storm surges than found for storm surge at the still water level intersection of the beach/land. It is shown that mild slopes can lead to very high water levels at the land–water interface (i.e. above the still water level intersection of the beach).     

Numerical Investigation of High Tide Level Due to A Super Typhoon in A Coastal Region

A numerical model of the coupling between astronomical tide and storm surge based on Mike 21 is applied to the coastal regions of Zhejiang Province.The model is used to simulate high tide levels combined with storm surge during 5 typhoons,including two super typhoons,that landed in the Province.In the model,the atmospheric forcing fields are calculated with parametric wind and pressure models.The computational results,with average computed errors of 13 cm for the high astronomical tide levels and 20 cm for the high storm-tide levels,show that the model yields good simulations.Typhoon No.5612,the most intense to land in China since 1949,is taken as the typical super typhoon for the design of 5 typhoon routes,each landing at a different location along the coast.The possible extreme storm-tide levels along the coast are calculated by the model under the conditions of the 5 designed typhoon routes when they coincide with the spring tide.Results are compared with the high storm-tide levels due to the increase of the central atmospheric pressure at the base of a typical super typhoon,the change of tidal type,and the behavior of a Saomai-type typhoon.The results have practical significance for forecasting and minimization of damage during super typhoons.     

河北省沿海风暴潮特征及成因分析

以秦皇岛、京唐港、曹妃甸、黄骅4个验潮站的实测潮位和逐时风的数据为基础,以2013年河北省政府发布的风暴潮四色警戒潮位值为标准,统计了2008-2017年10 a河北省沿海的风暴潮过程,从警报级别、区域分布、时间分布、天气系统、经济损失5个方面分析河北省沿海风暴潮特征,并从地形、天文潮与天气系统配合、海平面上升、全球变暖引发的气候异常4个方面分析了影响河北省沿海风暴潮的成因,分析得出:受天气系统的影响,7-10月是河北省风暴潮高发时段,且由于河北省岸线分布特点,沧州市沿海受到风暴潮影响的次数最多,唐山和秦皇岛次之,沧州和唐山地区的风暴潮过程多由东北向大风引起,而秦皇岛地区的风暴潮过程多由东南向风引起。     

风暴潮三维数值计算模式的研究及在渤海湾的应用

以实验室二维温带风暴潮数值模型为基础,综合考虑海洋潮波动力与风应力联合作用,建立温带风暴潮三维数值计算模型.模型从推导三维风暴潮基本控制方程出发,并应用交替方向隐格式(ADI)方法对方程进行离散求解.对于浅水动边界,模型采取局部深槽、缩小水域的活动边界处理方法.利用拟三维数值计算方法,并提出了非平面水深等分模式和平面等水深分布模式,应用这两种计算模式分别对渤海湾2009年5月8～10日发生的风暴潮过程进行了数值模拟.将风暴潮位计算结果和增水位计算结果与塘沽验潮站的实际观测数值进行对比验证,结果显示受风应力与潮波联合作用的风暴潮位和增水位与实测数据吻合良好;通过比较得到了平面等水深分布模式的计算成果要比非平面水深等分模式的计算成果更接近观测资料的结论,为风暴潮预报提供了理论依据.     

典型海湾风暴潮特征数值模拟与研究

铁山港海湾是一个遭受风暴潮灾害影响较为严重的半封闭型海湾,基于有限元海洋数学模型ADCIRC (Advanced Circulation Model)研究了1409号"威马逊"台风期间铁山港海湾的风暴潮特征及非线性作用。结果表明:当考虑天文潮与风暴潮之间的相互作用时,风暴潮水位的计算结果更加准确,只考虑纯台风影响时,计算结果会低估风暴潮增水值,高估减水值,对预报结果造成较大的误差。海湾内部的增水要远大于湾外,但是减水值则相差不大。通过对天文潮和风暴潮非线性作用的影响因子进行分析,风应力的浅水效应可以忽略,但底摩擦项和对流项影响较大。在海湾内部对流项占主导地位,与天文潮的耦合作用也较强;而在湾外,底摩擦项占优势,耦合作用在海湾内外都较强。天文潮与风暴潮相互作用产生的非线性水位在湾顶处最大可达0.94 m,出现在风暴潮最大减水时刻,风暴潮增水发生后有所减弱,非线性水位表现出从湾外向湾内递增的规律。     

Effect of Sea Level Variation on Calculation of Design Water Level

The long-term variation and seasonal variation of sea level have a notable effect on the calculation of engineering water level. Such an effect is first analyzed in this paper. The maximal amplitude of inter-annual anomaly of monthly mean sea level along the China coast is larger than 60 cm. Both the storm surge disaster and cold wave disaster are seasonal disasters in various regions, so the water level corresponding to the 1% of the cumulative frequency in the cumulative frequency curve of hourly water level data for different seasons in various sea areas is different from design water level, for example, the difference between them reaches maximum in June, July and August for northern sea area, and maximum in September, October and November for Southern China Sea. The hourly water level data of 19 gauge stations along the China coast are analyzed. Firstly, the annual mean sea level for every station is obtained; secondly, linear chan ging rates of annual mean sea level are obtained with the stochasti     

东南沿海台风风暴潮增水过程中非线性机制和地形的作用研究:以1509号台风"灿鸿"为例

本文基于FVCOM（Finite Volume Community Ocean Model）构建了一个覆盖中国渤海、黄海和东海的数值模型,采用NCEP-CFSR风场数据对1509号台风“灿鸿”产生的风暴潮进行模拟,与实测水位数据的对比表明该模型可靠、模拟结果合理。基于此模型,本文对非线性作用和地形在风暴潮增水过程中的作用进行了研究。首先,重点分析了增水过程中潮汐与风暴潮的非线性作用,结果表明：高潮时非线性作用使增水值降低;低潮时非线性作用使增水值升高。另外,开边界处分别只添加M₂、S₂和K₁分潮,分析天文潮的潮高和周期对非线性作用的影响,结果表明：潮高越高,非线性作用越明显;半日潮的非线性作用较全日潮更明显;并且,增水极值附近出现的半日周期的波动也与非线性作用有关。其次,除了非线性作用,地形对风暴潮的增水也有一定影响,本文改变地形的实验结果表明：坡度越大,增水极值越小。琉球群岛的存在使得东南沿海出现风暴潮增水的面积减小,但使得风暴潮增水的高值区域扩大。     

浪潮耦合的舟山渔港台风暴潮数值模拟

建立能精确模拟舟山渔港台风暴潮过程的浪潮耦合模型,对渔港防灾减灾具有重要意义。基于Delft3D中的FLOW和WAVE模块,在二重嵌套网格下建立风暴潮和波浪的耦合模型。以9711号台风Winnie为背景,验证耦合模型的可靠性,结果显示,风速、天文潮潮位、风暴潮潮位和有效波高的计算值与实测值吻合良好。利用风暴潮模型与耦合模型分别计算了舟山海域的风暴潮,分析了波浪对风暴潮潮位的抬升影响,定海和镇海站最大波浪增水分别为23 cm和34 cm,耦合模型的模拟精度要高于风暴潮模型。通过模拟9711号台风期间舟山渔港的风暴潮过程,分析了风暴潮的时空分布特征,并给出了浪潮耦合作用对于风暴潮时空分布的影响。     

江苏近海风暴潮增水数值模拟研究

为研究江苏近海海域风暴潮的特性以及为该海域风暴潮增水变化机理及后报做铺垫,本文基于FVCOM(Finite Volume Coast and Ocean Model)海洋模式和Jelesnianski圆形台风风场模型,建立了江苏近海风暴潮数值模型,并对江苏近海的天文潮以及1109号台风和1210号台风引起的风暴潮进行模拟。结合验潮站水位观测,研究了连云港站和吕泗站的天文潮和风暴潮增水过程。我们将风暴潮与天文潮非线性作用下的风暴潮增水和纯风暴潮增水过程进行对比,讨论了天文潮与1109号和1210号台风风暴潮之间的非线性作用引起的增水特征。结果均表明,在天文潮高潮时,天文潮和风暴潮之间的非线性作用可以抑制增水,在天文潮低潮时,天文潮和风暴潮之间的非线性作用有利于增水。除了气象因子以及天文潮和风暴潮之间的非线性作用外,该海区的地理环境也对台风风暴潮增水产生影响。因此对江苏近海的海岸线变化和浅滩地形变化进行敏感性试验,结果表明,本文所设计的海岸线变化对该海域的风暴潮增水影响较小,江苏沿海岸线的向外推移使得江苏海域风暴潮的增水略微上涨,而本文所设计的地形的变化对风暴潮增水影响较大。     

广东沿海台风风暴潮可视化预报系统

广东省地处南海北部,风暴潮灾害严重。为快速准确做好风暴潮预报并将预报结果应用于防灾减灾中,根据南海预报中心多年来在风暴潮数值预报、经验统计方法预报和潮汐预报的实践,研制了可视化软件。此软件可显示广东省28个沿海主要港口的逐时风暴增水与天文潮位的综合潮位曲线与数值,以动态或静态显示广东沿海海面的增水等值线图,成为业务化预报软件。多年的风暴潮数值预报的实践证明,国家海洋环境预报中心王喜年等在八·五攻关项目中推广应用的台风风暴潮模式,在广东沿岸的风暴潮数值预报中效果较好,可视化预报软件采用这一模式是合适的。     

1003号台风“灿都”风暴潮特征分析与模拟

根据粤西沿海4个海洋站潮位资料分析、讨论了“灿都”台风风暴潮特征:利用改进的Jelesnianski风场,并采用耦合天文潮模拟与非耦合天文潮两种方案,对1003号台风“灿都”进行模拟、分析,模拟结果显示:在改进的杰氏风场驱动下,两种预报结果误差都比较小,但耦合天文潮预报结果优于非耦合天文潮预报结果.     

浙江沿海超强台风作用下风暴潮增水数值分析

基于河口海岸水动力二维数值模型,建立风暴潮与天文潮耦合作用的数值模式,通过三次强台风和二次超强台风引起的风暴潮增水模拟和分析,证实该模式可用于浙江沿海增水预测.以1949年以来登陆我国大陆沿海最强的"5612"号台风作为典型的超强台风,利用本模式计算分析了超强台风在浙北至浙南5个不同地点登陆遭遇大潮时可能出现的风暴潮增水过程和最大增水,该结果对于海岸工程的防护具有实际的意义.     

典型海湾风暴潮增水特征与机理研究

以三门湾为例,基于经验模态分解方法 (EMD)将原始风暴潮增水过程进行分解,并对各个子模态进行能量谱分析,研究每种波动对应的生成机制。结果表明:半封闭海湾内的风暴潮增水较为严重,造成三门湾内强增水的台风为三门湾南侧的西北向登陆台风。EMD分解结果显示三门湾内的风暴潮增水包含6 h,12 h,20 h左右的波动,其中6 h左右的波动来源于海湾共振,共振的频率是由海湾的形状、水深等固有性质所决定的。12 h的波动是由于天文潮与风暴潮耦合作用导致,20 h左右的波动是由于台风移动过程中外海波动的传入。结果表明EMD方法为风暴潮波动增水特征的精细认知提供了一种新的思路和方法,可以加深对海湾内风暴潮波动增水特征的研究。     

A numerical study on the impact of tidal waves on the storm surge in the north of Liaodong Bay

A storm surge is an abnormal sharp rise or fall in the seawater level produced by the strong wind and low pressure field of an approaching storm system.A storm tide is a water level rise or fall caused by the combined effect of the storm surge and an astronomical tide.The storm surge depends on many factors,such as the tracks of typhoon movement,the intensity of typhoon,the topography of sea area,the amplitude of tidal wave,the period during which the storm surge couples with the tidal wave.When coupling with different parts of a tidal wave,the storm surges caused by a typhoon vary widely.The variation of the storm surges is studied.An once-in-a-century storm surge was caused by Typhoon 7203 at Huludao Port in the north of the Liaodong Bay from July 26th to 27th,1972.The maximum storm surge is about 1.90 m.The wind field and pressure field used in numerical simulations in the research were derived from the historical data of the Typhoon 7203 from July 23rd to 28th,1972.DHI Mike21 is used as the software tools.The whole Bohai Sea is defined as the computational domain.The numerical simulation models are forced with sea levels at water boundaries,that is the tide along the Bohai Straits from July 18th to 29th（2012）.The tide wave and the storm tides caused by the wind field and pressure field mentioned above are calculated in the numerical simulations.The coupling processes of storm surges and tidal waves are simulated in the following way.The first simulation start date and time are 00：00 July 18th,2012; the second simulation start date and time are 03：00 July 18th,2012.There is a three-hour lag between the start date and time of the simulation and that of the former one,the last simulation start date and time are 00：00 July 25th,2012.All the simulations have a same duration of 5 days,which is same as the time length of typhoon data.With the first day and the second day simulation output,which is affected by the initial field,being ignored,only the 3rd to 5th day simulation results are used to study the rules of the storm surges in the north of the Liaodong Bay.In total,57 cases are calculated and analyzed,including the coupling effects between the storm surge and a tidal wave during different tidal durations and on different tidal levels.Based on the results of the 57 numerical examples,the following conclusions are obtained：For the same location,the maximum storm surges are determined by the primary vibration（the storm tide keeps rising quickly） duration and tidal duration.If the primary vibration duration is a part of the flood tidal duration,the maximum storm surge is lower（1.01,1.05 and 1.37 m at the Huludao Port,the Daling Estuary and the Liaohe Estuary respectively）.If the primary vibration duration is a part of the ebb tidal duration,the maximum storm surge is higher（1.92,2.05 and 2.80 m at the Huludao Port,the Daling Estuary and the Liaohe Estuary respectively）.In the mean time,the sea level restrains the growth of storm surges.The hour of the highest storm tide has a margin of error of plus or minus 80 min,comparing the high water hour of the astronomical tide,in the north of the Liaodong Bay.     

台风移行速度与登陆角度对风暴潮的影响:一个理想模型数值实验

The effects of hurricane forward speed(V) and approach angle(θ) on storm surge are important and a systematic investigation covering possible and continuous ranges of these parameters has not been done before. Here we present such a study with a numerical experiment using the Finite Volume Community Ocean Model(FVCOM).The hurricane track is simplified as a straight line, such that V and θ fully define the motion of the hurricane. The maximum surge is contributed by both free waves and a forced storm surge wave moving with the hurricane.Among the free waves, Kelvin-type waves can only propagate in the down-coast direction. Simulations show that those waves can only have a significant positive storm surge when the hurricane velocity has a down-coast component. The optimal values of V and θ that maximize the storm surge in an idealized semi-circular ocean basin are functions of the bathymetry. For a constant bathymetry, the maximum surge occurs when the hurricane approaches the coast from the normal direction when the free wave generation is minimal; for a stepped bathymetry, the maximum surge occurs at a certain acute approach angle which maximizes the duration of persistent wind forcing; a step-like bathymetry with a sloped shelf is similar to the stepped bathymetry, with the added possibility of landfall resonance when the free and forced waves are moving at about the same velocity. For other cases, the storm surge is smaller, given other parameters(hurricane size, maximum wind speed, etc.)unchanged.     

福建沿海浪潮耦合漫堤风险评估:以台风天兔为例

漫堤是天文潮、风暴潮与海浪等物理要素作用于海堤后海水翻越海堤的物理过程。本文利用天文潮-风暴潮-台风浪耦合模式(ADCIRC+SWAN)、基于非结构三角形网格和高分辨率地理数据(海堤位置和高程、岸线和水深等)构建福建沿海精细化漫堤风险等级评估系统。该系统在近岸网格分辨率最高达50m,可精确刻画福建沿海复杂地形。利用模拟的水位与海浪参数,采用波浪爬高公式计算得到各海堤堤前波浪爬高。按照总水位与波浪爬高之和与海堤高程的对比,将漫堤风险分为五个等级。对2013年的超强台风天兔过程进行后报检验。结果显示,该系统计算的漫堤情况与灾后调查的漫堤实况基本一致,结果准确,说明本研究中采用的漫堤风险评估标准和方法是可行的。在此基础上,设计了4种不同的台风强度等级,对福建沿海206条海堤进行了漫堤风险等级评估,探究台风强度对漫堤风险的影响。结果表明:波浪爬高对漫堤风险的影响高于单纯的风暴潮增水;风暴潮增水随台风强度的增强增量较小,对于漫堤的风险影响较小;福建沿海波浪爬高普遍较高,随着台风强度的增强,波浪爬高会显著增加漫堤的风险等级,且应重视台风浪对海堤造成的冲击所导致的溃堤灾害。本研究可为沿海防灾减灾提供...     

“威马逊”台风暴潮增水及水动力响应数值模拟

基于河口海岸水动力三维数值计算模型,建立浙江沿海天文潮与风暴潮耦合预报模式。利用该模式,对经过浙江沿海海域的台风"威马逊"进行数值计算,风暴潮增水计算结果与实测值符合较好,误差基本在±20 cm以内。计算增水值与传统的调和分析法所得的增水结果相比,也较为一致。进一步对局部水动力响应的研究发现,风暴潮期间,局部地区从底到表各层水流流速均急剧增大或减小,其值达到了与天文潮流同等的数量级。当水流流向与风向相同或相近时,流速增大,相反时,则流速减小。且台风期间,各层水流流向也随风向发生改变,流态变得更加复杂。     

福建沿海风暴潮特征的分析

通过普查1960-2001年正面登陆我国东南沿海的台风,分析了福建沿海风暴潮的特征及其可能原因。台湾海峡特殊地形对福建沿海风暴潮的时空分布有明显影响,登陆岸段不同,台湾海峡对风暴潮的影响作用也不同,导致福建沿海风暴潮出现明显不同的分布和变化特征。当台风位于台湾海峡时,其大风区位置利范围不同,会影响福建沿海各地风暴增水的幅度。台风横穿台湾海峡时,易使福建沿海台风大风区中心岸段出现双增水峰现象,第一个增水峰出现在台风离开台湾岛进入台湾海峡后,第二个增水峰出现在台风登陆福建沿海前后。台风横穿台湾海峡有时会引起台湾海峡北部出现奇异增水现象,风暴潮与天文潮之间的相互作用可能是其重要原因。奇异增水峰往往出现在天文潮低潮附近,此时实际潮位并不高。     

河北沿海1909号台风风暴潮过程和分析

为促进对台风风暴潮灾害的预报预警,减少灾害带来的损失,文章综合分析2019年第9号台风“利奇马”对河北沿海引发的严重台风风暴潮灾害过程。研究结果表明：台风“利奇马”是2019年以来登陆我国的最强台风和1949年以来登陆浙江的第三强台风,给河北沿海造成长时间和高强度的风暴增水过程;水体远距离输运、东北大风、天文高潮和增水相结合,使河北沿海出现3次超过蓝色警戒潮位的高潮位,其中1次超过红色警戒潮位,这在20年来是首次;其中,强烈而持久的东北风是造成增水的主要原因。     

Quantifying the potential impact of land cover changes due to sea-level rise on storm surge on lower Texas coast bays

In this study we investigated the impacts of potential changes of land cover due to sea-level rise (SLR) on storm surge (i.e., the rise of water above normal sea level, namely mean-sea level and the astronomical tide, caused by hurricane winds and pressure) response inside bays on the lower Texas coast. We applied a hydrodynamic and wave model (ADCIRC + SWAN) forced by hurricane wind and pressure fields to quantify the importance of SLR-induced land cover changes, considering its impacts by changing bottom friction and the transfer of wind momentum to the water column, on the peak surge inside coastal bays. The SLR increments considered, 0.5 m to 2.0 m, significantly impacted the surge response inside the bays. The contribution of land cover changes due to SLR to the surge response, on average, ranged from a mean surge increase of 2% (SLR of 0.5 m) to 15% (SLR of 2.0 m), in addition to the SLR increments. The increase in surge response strongly depended on storm condition, with larger increases for more intense storms, and geographical location. Although land cover changes had little impact on the surge increase for SLR increments lower than 1.0 m, intense storms resulted in surge increase of up to 10% even for SLR below 1.0 m, but in most cases, the geometry changes were the major factor impacting the surge response due to SLR. We also found a strong relationship between changes in bottom friction and the surge response intensification; demonstrating the importance of considering land cover changes in coastal regions that are highly susceptible to SLR when planning for climate change.