A method to calculate design tide levels on the basis of numerical model of tidal current and its application

In order to determine the design tide levels in the areas without measured tide level data, especially in the areas where it is difficult to measure tidal levels, a calculation method based on a numerical model of tidal current is proposed. The essentials of the method are described, and its application is illustrated with an example. The results of the application show that the design tide levels calculated by the method are close to those determined by long-time measured tide level data, and its calculation precision is high, so it is feasible to use the method to determine the design tide levels in the areas.

Evolutive Trend of Water Level in the Ebrie Lagoon by Reconstitution of the Tide Gauge Time Series in Front of the Abidjan Coastline (Côte d’Ivoire)

The latest Intergovernmental Panel on Climate Change (IPCC) report shows that sea-level rise, which has been accelerated since the 19th century resulting to the global warming, threatens coastal areas with high population growth. A Global Sea Level Observing System (GLOSS) assessment highlighted the lack of data in Africa, and in Côte d’Ivoire in particular. In order to estimate the evolutionary trend of sea level along the Ivorian coast, and to draw up preventive plans to protect properties and populations, we digitized 65 years of historical tidegrams recorded in the Ebrie Lagoon, using the “Surfer” and “Nunieau” software, then processed them using “T-Tide” and “U-Tide” software. The average levels were calculated using the Demerliac filter from complete daily (day and night) recordings for providing a usable database of 31 years of hourly lagoon data from 1979 to 2015. Our results show that a mean water level in lagoon is 1.04 m. The evolutionary trend in sea level, estimated in the lagoon via the Vridi canal, during the rainy season is the most significant at 2.93 mm/year. This is followed by the dry season, with a trend of 2.89 mm/year. The flood season trend is 2.78 mm/year. This suggests that marine water inflows dominate continental inflows. Our results highlight the vulnerability of Côte d’Ivoire’s coasts to the risk of marine submersion.

Validation of Sea Level Data in the East Asian Marginal Seas: Comparison between TOPEX/POSEIDON Altimeter and In-Situ Tide Gauges

In an effort to assess the reliability of satellite altimeter systems, the authors conduct a comparative analysis of sea level data that were collected from the TOPEX/POSEIDON (T/P) altimeter and 10 tide gauges (TG) near the satellite passing ground tracks. The analysis is made using datasets collected from marginal sea regions surrounding the Korean Peninsula at T/P cycles of 2 to 230, which correspond to October 1992 to December 1998. Proper treatment of tidal errors is a very critical step in data processing because the study area has very strong tide. When the T/P data are processed, the procedures of Park and Gamberoni (1995) are adapted to reduce errors associated with the tide. When the T/P data are processed in this way, the alias periods of M2, S2, and K1 constituents are found to be 62.1, 58.7, and 173 days repectively. The compatibility of the T/P and TG datasets are examined at various filtering periods. The results indicate that the low-frequency signals of the T/P data can be interpreted more safely with longer filtering periods (such as up to the maximum selected value of 200 days). When RMS errors for the 200-day low-pass filter period are compared with all 10 tidal stations, the values span the range of 2.8 to 6.7 cm. The results of a correlation analysis for this filtering period also show a strong agreement between the T/P and TG datasets across all stations investigated (e.g.,p- values consistently less than 0.001). Hence according to the analysis, the conclusion is made that the analysis of surface sea level using satellite altimeter data can be made safely with reasonably extended filtering periods such as 200 days.

Short-term and imminent anomalies of earthquake of load and unload response ratio of the well level to earth tides

In this paper, through the nonlinear response of rock strain and stress, we have analized the physical mechanism of loading and unloading response ratio of the well level to the earth tides,the respouse of an aquifer of confined well to bulk strain tide and showed two methods of the calculation of loading and unloading response ratio of the well level to the earth tides. We took the example of the Yu 01 well, which is near the epicenter of Heze M S 5.9 earthquake, calculated the response rate and loading and unloading response ratio of two kinds of the earth tides of it. The response rate and response ratio before the earthquake had the variation of increase.

Influence of Tide Models on the Use of Altimetry Data to Research Sea Level Anomaly

A tide model (named DN1.0), which contains 12 principal constituents over China seas and the Northwest Pacific is estimated by along-track harmonic analysis with TOPEX/Poseidon altimetry data taken from 1993 to 2002. CSR3.0, FES95.2 and DN1.0 are used respectively to detide the data for the time series of sea level anomaly (SLA) in the Yellow Sea, East China Sea, South China Sea and Northwest Pacific. The SLA curves and the power spectral density show that the major components that exist in SLA in China seas arise from the error of the tide models.

INFLUENCE OF SEA LEVEL RISE ON SHANGHAI ASTRONOMICAL TIDE AND STORM SURGE AND ESTIMATION OF PROBABLE WATER LEVEL

A nonlinear two-dimension dynamic model of storm surge (SS) and astronomical tide(AT) was used to investigate the effects of SS and AT on expected sea level rise (SLR) at principalcoastal stations in the Shanghai region and to estimate numerically the probable maximum water lerel for2010 - 2050. Evidence suggests tha SLR causes reduction of SS; that its influence on SS depends on theintensity and path of a tropical cyclone and the station locality; tha the SLR’s effects on AT vary periodi-cally, with the peried being the same as tha of the AT’s: and that as the SLR increment grows, its impactincreases; below mean sea level (MSL) the effect is positive at rising tide and negative at ebb tide, andvice versa for the effect above MSL. Study of the probable maximum water level (by assuming SLR, SSalong favorable tropical cyclone’s path, its possible maximum intensity and effectivee spring AT at a rangeof set paths of Cyclones 5612, 8114, 9417) showed that the probable maximum water level is 740, 745,and 751 cm in the years 2010, 2030, and 2050, respetively, over the target region.

Determination of the Absolute Rate of Sea Level by Using GPS Reference Station and Tide Gauge Data

The absolute rate of mean sea level of Xiamen area is derived from the data of Xiamen tide gauge station and Xiamen GPS fiducial station of crustal movement observation network of China(CMONC). The height variation is discussed deeply in this paper. It is shown that height has periodic variations. So the rate of vertical land movement can not be precisely obtained only from several GPS campaigns. It is pointed out that the vertical crustal movement of tide gauge station should be monitored by using long-term continuous GPS observations.

Numerical modelling of the sea level under the actions of the tide and strong wind in the Bohai Sea

In this paper, the numerical modelling of the tidal level and current in the Bohai Sea was carried out with ADI method, by taking the sum of four main tidal components M2,S2K2,O1 as the open boundary condition. The calculated values were consistent with the predicted ones (the observed values in the case of calm) in the Tidal Table. On the basis of the modelling of the tide, the sea level and current fields under the effects of strong wind were simulated. The calculated results were also quite satisfactory.

中国沿海地区热带气旋危险性分析

基于1980—2016年的西北太平洋热带气旋尺度资料,采用2种方法分析了热带气旋灾害的危险性。第一种方法根据热带气旋的风圈半径,用GIS生成了每个气旋的影响范围,对于登陆中国沿海的227个热带气旋,用叠加法得到了其影响范围与频次。第二种方法侧重热带气旋引发的风暴潮灾害,用潮位模型估算了热带气旋登陆时的潮位数据,提出了H3指标,该指标用潮位、风速和中心气压3个因子计算潮位点的风暴潮危险性,并根据H3指标得到了海岸线的危险性综合指标。分析结果表明,福建、广东两省受热带气旋的影响最为严重。37 a间,福建省有80%的面积(约9.8万km^(2))受热带气旋影响的频次超过20次;广东省则有70%的面积(约12.6万km2)受热带气旋影响的频次超过20次。受风暴潮危害大的海岸线主要位于广东、广西、福建、浙江四省,危险性指标在30以上的有广东的湛江市、茂名市、江门市、阳江市和珠海市;广西的北海市、防城港市和钦州市;福建的福州市以及浙江的台州市和温州市。

水位升降和潮汐水位作用下围堰的安全稳定性

为了分析水位升降和潮汐水位作用下滨海区域围堰的安全稳定性,基于厦门市集美岛车站工程实例,应用Plaxis有限元程序的非饱和土渗流理论,采用有限元强度折减法,进行不同水位升降速度及潮汐水位循环作用下围堰的稳定性分析,通过围堰的安全系数变化曲线分析水位变化对围堰稳定性影响的机理。结果表明:围堰安全系数在水位升高时减小,水位上升速度越快,围堰安全系数减小速率越大;水位下降时存在临界水位降速,临界水位降速为1.0 m·d^(-1),当水位下降速度超过临界水位降速时,围堰安全系数先减小后增大,当水位下降速度小于临界水位降速时,围堰安全系数逐渐增大;围堰安全系数在落潮时增大,在涨潮时减小,潮汐振幅越大,围堰安全系数增值越大,随着循环次数的增加,相邻两次循环间围堰安全系数增量逐渐减小并趋于稳定。

渤、黄海天文潮—风暴潮相互作用及其对极值水位的贡献

基于Delft3D模型建立了中国渤、黄海风暴潮数值模型,选取1979—2020年影响该海域的93场风暴过程(包括台风、寒潮和温带气旋),模拟了所产生的风暴增水和风暴潮总水位。采用泊松—皮尔逊复合极值分布理论,推算了渤、黄海对应不同重现期的极值水位;通过数值试验,对天文潮—风暴潮非线性相互作用对极值水位的贡献进行了量化分析。研究结果表明,渤海的莱州湾、渤海湾,以及黄海的江华湾、西朝鲜湾风暴增水最大,其中江华湾北侧和渤海湾西南侧的百年一遇风暴增水可达4 m;天文潮—风暴潮非线性相互作用在潮差较大、水深较浅的河口、湾顶区域更为显著,与耦合模型结果相比,非线性作用使极值水位值偏小,天文潮、风暴潮增水的线性叠加可显著高估极值水位,高估的幅值可达0.5~0.8 m。考虑重现期极值水位是海岸灾害防护工程的关键设计参数之一,对海岸构筑物的安全和建造成本影响极大,应重视天文潮—风暴潮非线性相互作用对重现期水位的影响。

顾及时差特征的LSTM模型余水位短期预报

目前余水位预报都是采用单站方式,仅基于余水位的自相关性。针对较大范围的沿岸验潮站余水位预报,进一步结合余水位的空间强相关性和站间余水位的时差信息,以“预测站-辅助站”验潮站组的形式,由历史同步余水位数据训练多变量LSTM(long short-term memory)长短期记忆网络模型,实现预测站的余水位预报。渤海沿岸四个长期验潮站的实例分析表明:所提的预报方法因增加利用了时域上的时差信息,预报精度优于三类单站方法,并显著增大了预报时长。方法可用于解决大范围航海动态水位保障中的余水位预报问题。

利用SG平滑滤波优化GNSS-R潮位反演

利用全球导航卫星系统反射(GNSS-R)信号进行潮位反演时,需要对多路径频率进行估计.常规反演方法仅对主频率估计,因此存在数据利用率低、反演结果时间分辨率不足的问题.为解决该问题,本文利用Savitzky-Golay(SG)平滑滤波优化GNSS-R潮位反演.首先,利用Lomb-Scargle周期图(LSP)法提取信号功率的前4个频率f_(1)~f_(4),并反演它们对应的潮位值;然后,利用SG平滑滤波方法提取最佳反演结果;最后,以法国BRST站和MAYG站30 d的数据验证算法的有效性.通过与LSP法和窗口LSP(WINLSP)法进行对比,结果表明:相比LSP法,滤波后BRST站和MAYG站的日均反演值数量分别提升34.3%和19.6%,反演值的最大时间间隔分别减少43.2%和29.4%,RMSE值变化不大;相比WINLSP法,滤波后BRST站和MAYG站的日均反演值数量分别提升24.2%和45.9%,反演值最大时间间隔分别减少25.4%和28.6%,RMSE值均减少了7 cm.总体而言,该方法能够在保证精度的前提下提高反演结果的数量,同时提高了数据的利用率和潮位反演的时间分辨率.

一种GNSS-MR海平面高度反演模型研究

针对大地测量型GNSS接收机获取的信噪比(Signal to Noise Ratio,SNR)观测值存在趋势项分离不佳和信号叠加干涉的问题,融合自适应噪声完备集合鲁棒局部均值分解方法对原始SNR信号进行分解,有效分离SNR观测值中的趋势项并提取相应的潮位信号,以布设在美国华盛顿州星期五海港岸边的SC02测站为例,利用实测数据反演潮位变化并与传统的低阶多项式拟合方法进行对比分析。结果表明,融合CERLMDAN方法的反演结果的均方根误差(Root Mean Square Error,RMSE)、相关系数分别为0.56 m和0.97,相比于传统方法的反演精度提升了33.7%。

基于虚拟潮位站技术的云潮位服务研究与应用

针对疏浚工程施工对高质量、智能化实时水位信息服务的需求,设计并实现了可服务于疏浚工程施工活动的北斗实时水位信息服务云平台系统。系统采用了后端、计算存储中心和前端三层结构,使用北斗通信链路将三层结构连接起来,系统可根据施工船舶的实时动态位置,应用区域高精度潮汐模型和区域高精度余水位模型,虚拟一个目标船舶专用的虚拟水位站,并根据该虚拟水位站的预报水位和余水位计算实时水位数据,通过北斗通信链路将实时水位数据传输至施工船舶。系统有效提升了实时水位信息服务的精度、可靠性和智能化水平,可为疏浚工程项目提供稳定可靠的实时水位数据服务。

长江感潮河段径流对潮波变形和传播的影响研究

受径、潮流相互作用,长江感潮河段潮波从河口向上游传播过程中沿程变形过程复杂。基于长江感潮河段实测高、低潮位,潮时资料以及大通站日均流量数据,采用数理统计、Hermit插值和小波分析方法,分析了长江感潮河段潮汐特征值和潮波传播特征值随流量的变化关系。结果表明:高、低潮位及平均水位随流量增大而增大,并且越往下游对流量的敏感度越低;江阴以上河段潮差随流量增大而先减小后增大;径流对分潮振幅的影响在江阴以上河段较明显,半日潮和全日潮振幅随流量增大先减小后增大,1/4日分潮振幅随流量增大而减小,其中半日潮振幅变化幅度最大;平均水位坡度在芜湖-马鞍山段随流量增大而先增大后减小,在马鞍山以下河段与流量呈正相关;潮波振幅衰减率随流量增大而先增大后减小,越靠近入海口,流量阈值越大。研究成果有助于深入认识河口径潮相互作用机制,亦可为河口治理提供参考。

LNG接收站港池水深扫测技术

液化天然气作为清洁能源,在能源行业正在迅猛发展。而LNG码头区域由于受到潮流等因素掀起的海底泥沙的影响,导致水下回淤严重,直接威胁到LNG接卸船通航的安全。本文以粤东LNG为例,系统阐述了港池水深扫测技术,并根据调查结果提出合理化建议,推动LNG产业高质量发展。

临海工程项目防洪水位研究

临海工程项目的防洪安全受洪水及海潮影响,为确定盘锦某精细化工及原料工程项目的风险源及防洪(潮)水位,需要综合分析现状及规划工况条件下辽河、大辽河及辽东湾海潮对工程项目的影响,并采用适当的洪水及潮流数学模型分别进行计算。经分析,确定采用MIKE FLOOD一二维耦合溃堤数学模型,分析大辽河洪水对工程项目的影响;采用MIKE21 FM二维潮流数学模型,分析辽东湾海潮对工程项目的影响。计算结果表明,现状工况条件下工程区主要风险源来自海潮,规划工况条件下工程区主要风险源来自大辽河洪水,工程建设需要综合考虑洪水及海潮的影响。文中采用的计算方法和结论可为类似工程项目的防洪(潮)水位确定及报告编制提供依据。

强潮河口进港航道水深保证率分析——以上虞液体化工码头为例

钱塘江河口潮强流急,河床大冲大淤,主流摆动频繁,航线不固定,难以采用常规方法分析确定进港航道通航水深保证率。以上虞液体化工码头工程为例,利用长系列水文地形实测资料,分析工程河段水文、河床演变特征及航道条件,据此计算进港航道通航水深保证率,提出码头通航所需条件及优化建议。

Stochastic Model for Estimating Extreme Water Level in Port and Coastal Engineering Design

Extreme water level is an important consideration when designing coastal protection structures. However, frequency analysis recommended by standard codes only considers the annual maximum water level, whereas water levels should actually be regarded as a combination of astronomical tide and storm surge. The two impacting factors are both random variables, and this paper discusses their dependency structures and proposes a new joint probability method to determine extreme design water levels. The lognormal, Gumbel, Weibull, Pearson type 3, traditional maximum entropy, and modified maximum entropy distributions are applied to fit univariate data of astronomical tides and storm surges separately, and the bivariate normal, Gumbel-Hougaard, Frank and Clayton copulas are then utilized to construct their joint probability distributions. To ensure that the new design method is suitable for use with typhoon data, the annual occurrence frequency of typhoon processes is considered and corresponding bivariate compound probability distributions are proposed. Based on maximum water level data obtained from Hengmen hydrological station in the Pearl River Basin, China, these probability models are applied to obtain designs for extreme water levels using the largest sum of the astronomical tide and storm surge obtained under fixed joint return periods. These design values provide an improved approach for determining the necessary height of coastal and offshore structures.