共查询到20条相似文献，搜索用时 15 毫秒
1.
Automated threshold selection methods for extreme wave analysis 总被引：2，自引：0，他引：2
The study of the extreme values of a variable such as wave height is very important in flood risk assessment and coastal design. Often values above a sufficiently large threshold can be modelled using the Generalized Pareto Distribution, the parameters of which are estimated using maximum likelihood. There are several popular empirical techniques for choosing a suitable threshold, but these require the subjective interpretation of plots by the user.In this paper we present a pragmatic automated, simple and computationally inexpensive threshold selection method based on the distribution of the difference of parameter estimates when the threshold is changed, and apply it to a published rainfall and a new wave height data set. We assess the effect of the uncertainty associated with our threshold selection technique on return level estimation by using the bootstrap procedure. We illustrate the effectiveness of our methodology by a simulation study and compare it with the approach used in the JOINSEA software. In addition, we present an extension that allows the threshold selected to depend on the value of a covariate such as the cosine of wave direction. 相似文献
2.
Melisa Menéndez Fernando J. Méndez Cristina Izaguirre Alberto Luceño Inigo J. Losada 《Coastal Engineering》2009
A time-dependent generalized extreme value (GEV) model for monthly significant wave heights maxima is developed. The model is applied to several 3-hour time series from the Spanish buoy network. Monthly maxima show a clear non-stationary behavior within a year, suggesting that the location, scale and shape parameters of the GEV distribution can be parameterized using harmonic functions. To avoid a possible over-parameterization, an automatic selection model, based on the Akaike Information Criterion, is carried out. Results show that the non-stationary behavior of monthly maxima significant wave height is adequately modeled, drastically increasing the significance of the parameters involved and reducing the uncertainty in the return level estimation. The model provides new information to analyze the seasonal behavior of wave height extremes affecting different natural coastal processes. 相似文献
3.
A non-traditional fuzzy quantification method is presented in the modeling of an extreme significant wave height. First, a set of parametric models are selected to fit time series data for the significant wave height and the extrapolation for extremes are obtained based on high quantile estimations. The quality of these results is compared and discussed. Then, the proposed fuzzy model, which combines Poisson process and generalized Pareto distribution(GPD) model, is applied to characterizing the wave extremes in the time series data. The estimations for a long-term return value are considered as time-varying as a threshold is regarded as non-stationary. The estimated intervals coupled with the fuzzy theory are then introduced to construct the probability bounds for the return values. This nontraditional model is analyzed in comparison with the traditional model in the degree of conservatism for the long-term estimate. The impact on the fuzzy bounds of extreme estimations from the non stationary effect in the proposed model is also investigated. 相似文献
4.
The generalised Pareto distribution (GPD) is often used to model the distribution of storm peak wave heights exceeding a high threshold, from which return values can be calculated. There are large differences in the performance of various parameter and quantile estimators for the GPD. Commonly used estimation methods such as maximum likelihood or probability weighted moments are not optimal, especially for smaller sample sizes. The performance of several estimators for the GPD is compared by the Monte Carlo simulation and the implications for estimating return values of significant wave height are discussed. Of the estimators compared, the likelihood-moment (LM) estimator has close to the lowest bias and variance over a wide range of sample sizes and GPD shape parameters. The LM estimator always exists, is simple to compute and has a low sensitivity to choice of threshold. It is recommended that the LM estimator is used for calculating return values of significant wave height when the sample size is less than 500. For sample sizes above 500 the NEW estimator of Zhang and Stephens (2009) can give accurate results for low computational cost. 相似文献
5.
波高的长期极值统计分布 总被引：1，自引：0，他引：1
通过对国内外常用的４种极值波高分布模式的拟合与比较,得到了以下结论：（１）由于地区差异,港口工程技术规范给出的一单一模式并非具有普遍性,对同一工程应该采用多种理论分布进行计算比较,从中选择最佳模式。（２）应用麦奎尔特法拟合Ｗｅｉｂｕｌｌ分布实现了对未知参数的一举寻优,解的收敛速度快,结果稳定且精度高。同时对其它几种分布实现了资料的微机化处理;（３）本文算例用４种极值分布对不同重视值波高进行了比较, 相似文献
6.
The peaks over threshold（POT） methods are used for the univariate and multivariate extreme value analyses of the wave and wind records collected from a hydrometric station in the South China Sea. A new multivariate POT method： Multivariate GPD（MGPD） model is proposed, which can be built easily according to developed parametric models and is a natural distribution of multivariate POT methods. A joint threshold selection approach is used in the MGPD model well. Finally, sensitivity analyses are carried out to calculate the return values of the base shear, and two declustering schemes are compared in this study. 相似文献
7.
Long term wave climate of both extreme wave and operational wave height is essential for planning and designing coastal structures.
Since the field wave data for the waters around Korean peninsula is not enough to provide reliable wave statistics, the wave
climate information has been generated by means of long-term wave hindcasting using available meteorological data. Basic data
base of hindcasted wave parameters such as significant wave height, peak period and direction has been established continuously
for the period of 25 years starting from 1979 and for major 106 typhoons for the past 53 years since 1951 for each grid point
of the North East Asia Regional Seas with grid size of 18 km. Wind field reanalyzed by European Center for Midrange Weather
Forecasts (ECMWF) was used for the simulation of waves for the extratropical storms, while wind field calculated by typhoon
wind model with typhoon parameters carefully analyzed using most of the available data was used for the simulation of typhoon
waves. Design wave heights for the return period of 10, 20, 30, 50 and 100 years for 16 directions at each grid point have
been estimated by means of extreme wave analysis using the wave simulation data. As in conventional methodsi of design criteria
estimation, it is assumed that the climate is stationary and the statistics and extreme analysis using the long-term hindcasting
data are used in the statistical prediction for the future. The method of extreme statistical analysis in handling the extreme
events like typhoon Maemi in 2003 was evaluated for more stable results of design wave height estimation for the return periods
of 30–50 years for the cost effective construction of coastal structures. 相似文献
8.
重现期波高是港口海岸及海洋工程设计中不可回避的一个重要设计参数,尤其对深水海港、海上平台、海底油气管道、沿海核电站等重大涉海工程设计具有巨大的经济价值和深远的社会效益。但是,现有重现期波高推算缺乏统一的计算方法,导致计算结果相差悬殊。研究重现期波高的统一化计算方法,分析重现期波高计算中存在的各种不确定因素,提出减少这些不确定因素的新方法,建立误差小、应用方便、方法统一的重现期波高计算方法。基于澳大利亚悉尼站的长期连续观测波浪数据,研究发现:广义帕累托函数(generalized Pareto distribution III,GPD-III)和威布尔(Weibull)是重现期波高计算的最佳候选极值分布函数,新推导的函数形状参数计算公式较好提高重现期波高的计算精度,极值波高数据的分析方法和样本大小是影响重现期波高计算精确度的两个重要因素,短期波浪资料和年极值法可能高估重现期波高值。逐个风暴的极值波高数据分析法及最佳候选极值分布函数GPD-III和Weibull建议应用于涉海工程设计的重现期波高推算。 相似文献
9.
This paper concerns the calculation of wave height exceedance probabilities for nonlinear irregular waves in transitional water depths, and a Transformed Rayleigh method is first proposed for carrying out the calculation. In the proposed Transformed Rayleigh method, the transformation model is chosen to be a monotonic exponential function, calibrated such that the first three moments of the transformed model match the moments of the true process. The proposed new method has been applied for calculating the wave height exceedance probabilities of a sea state with the surface elevation data measured at the Poseidon platform. It is demonstrated in this case that the proposed new method can offer better predictions than those by using the conventional Rayleigh wave height distribution model. The proposed new method has been further applied for calculating the total horizontal loads on a generic jacket, and its accuracy has once again been substantiated. The research findings gained from this study demonstrate that the proposed Transformed Rayleigh model can be utilized as a promising alternative to the well-established nonlinear wave height distribution models. 相似文献
10.
This paper concerns the calculation of wave height exceedance probabilities for nonlinear irregular waves in transitional water depths, and a Transformed Rayleigh method is first proposed for carrying out the calculation. In the proposed Transformed Rayleigh method, the transformation model is chosen to be a monotonic exponential function, calibrated such that the first three moments of the transformed model match the moments of the true process. The proposed new method has been applied for calculating the wave height exceedance probabilities of a sea state with the surface elevation data measured at the Poseidon platform. It is demonstrated in this case that the proposed new method can offer better predictions than those by using the conventional Rayleigh wave height distribution model. The proposed new method has been further applied for calculating the total horizontal loads on a generic jacket, and its accuracy has once again been substantiated. The research findings gained from this study demonstrate that the proposed Transformed Rayleigh model can be utilized as a promising alternative to the well-established nonlinear wave height distribution models. 相似文献
11.
基于Gumbel-Hougaard copula、Kendall和生存Kendall函数对比分析波高和周期联合分布的4种重现水平。以位于北卡罗来纳州Duck的美国陆军工程师团FRF (Field Research Facility)实验场观测的波高与周期样本为例, 计算二者联合分布的“或”重现期、“且”重现期、Kendall重现期和生存Kendall重现期及其联合设计值。主要结论如下: 对比设定重现期, 相对于“或”联合重现期, Kendall重现期可更准确地反映波高周期联合分布的风险率; 相对于“且”联合重现期, 生存Kendall重现期可更准确地反映波高周期同时超值情况下的风险率。按目前有关规范设计要求的单变量波高设计值基本达到设计标准, 按两变量“或”重现期和波高周期两变量同频率设计值推算的设计值偏高, 以最大可能概率推算的两变量的Kendall重现期和生存Kendall重现期设计值可为海岸海洋工程安全与风险管理提供新的选择。 相似文献
12.
采用非对称Archimedean Copula函数与Kendall分布函数分析极端波况下的波高、周期和风速三变量联合概率分布与风险率及其设计分位数,为海岸海洋工程设计和风险评估提供参考依据。以粤东汕尾海域的实测风浪数据为例,使用非对称Gumbel-Hougaard Copula函数计算三变量风浪联合分布的"或"重现期、"且"重现期和二次重现期及其最可能的风浪设计值。主要结论如下:对比不同设计风浪重现期显示,"或"重现期的风险率偏高,"且"重现期的风险率偏低,二次重现期更准确地反映了特定设计频率情况下三变量风浪的风险率;按目前有关规范设计要求的单变量风浪要素设计值已经达到安全标准,按三变量"或"重现期和三变量同频率设计值推算的风浪设计值偏高,以最大可能概率推算的三变量风浪要素的二次重现期设计值可为相关工程安全与风险管理提供新的选择。 相似文献
13.
The significant wave representation method is the simplest method for computing the transformation of significant wave height across-shore. However, many engineers are reluctant to use this method because many researchers have pointed out that the method possibly contains a large estimation error. Nevertheless, Rattanapitikon et al. [Rattanapitikon, W., Karunchintadit, R., Shibayama, T., 2003. Irregular wave height transformation using representative wave approach. Coastal Engineering Journal, JSCE 45(3), 489–510.] showed that the wave representation method could be used to compute the transformation of root mean square wave heights. It may also be possible to use it for computing the significant wave height transformation. Therefore, this study was carried out to examine the possibility of simulating significant wave height transformation across-shore by using the significant wave representation method. Laboratory data from small- and large-scale wave flumes were used to calibrate and examine the models. Six regular wave models were applied directly to irregular waves by using the significant wave height and spectral peak period. The examination showed that three regular wave models (with new coefficients) could be used to compute the significant wave height transformation with very good accuracy. On the strength of both accuracy and simplicity of the three models, a suitable model is recommended for computing the significant wave height transformation. The suitable model was also modified for better predictions. The modified model (with different coefficients) can be used to compute either regular wave height or significant wave height transformation across-shore. 相似文献
14.
使用美国北卡罗来纳州的 FRF 1985—2016 年的极值波高及其持续时间数据，采用最优的 Gumbel-Hougaard copula函数和 Kendall 分布函数构建极值波高和相应历时不同组合的联合概率分布模式，分析各个组合的遭遇概率、“或”重现期、“且”重现期和 Kendall 重现期，以出现最大可能概率的方法推算各组合联合设计值。结果表明：Kendall 重现期所对应的累积频率更准确地代表了特定设计频率下的风险率；重现期分别为 5 年、10 年、20 年、50 年、100 年、200 年推算的 Kendall重现期设计值介于“或”重现期和“且”重现期设计值之间，小于相应的边缘分布设计值；基于 Kendall 重现期的极值波高及其持续时间不同重现期组合推算的结果可为海洋工程构筑物设计与风险管理提供新的选择与参考。 相似文献
15.
The extreme significant wave heights and the corresponding wave periods were predicted for return periods of 12, 25, 50, 100 and 200 yr for 19 different locations in Kuwaiti territorial waters. Though the total coast length of Kuwait is only about 500 km including all islands and the total area of the Kuwaiti territorial water is about 7611 km2, the extreme significant wave height vary from 1.86 to 4.02 m for 100 yr return period, among these 19 locations. In general Weibull distribution is found to fit the data well compared to the Gumbel distribution. The input wave data for the present work is obtained by hind casting waves using a WAM model. Wave data is hindcasted for a total period of 12 yr, starting from 1 January 1993 to 31 December 2004. From the joint probability of wave height and wave period, a simple polynomial relationship is obtained between the significant wave height and mean period for all the 19 locations. It is found that the wave period for wave heights of 100 yr return period cannot exceed 6.5 s. A large number of coastal projects are in progress and many new projects are planned for the near future in the Kuwaiti territorial waters. The results of the present study will be highly useful for optimal design of these projects. 相似文献
16.
基于随机集合的非传统型有效波极值模型 总被引：1，自引：0，他引：1
The analysis and design of offshore structures necessitates the consideration of wave loads. Realistic modeling of wave loads is particularly important to ensure reliable performance of these structures. Among the available methods for the modeling of the extreme significant wave height on a statistical basis, the peak over threshold method has attracted most attention. This method employs Poisson process to character- ize time-varying properties in the parameters of an extreme value distribution. In this paper, the peak over threshold method is reviewed and extended to account for subjectivity in the modeling. The freedom in selecting the threshold and the time span to separate extremes from the original time series data is incorpo- rated as imprecision in the model. This leads to an extension from random variables to random sets in the probabilistic model for the extreme significant wave height. The extended model is also applied to different periods of the sampled data to evaluate the significance of the climatic conditions on the uncertainties of the parameters. 相似文献
17.
推算波浪多年一遇波高的新方法 总被引：5，自引：0，他引：5
采用卫星遥感推算多年一遇波高的新方法，对中国近海多年一遇波高进行推算研究。运用卫星遥感散射计得到的风资料推算了整个渤海区域波浪多年一遇的波高分布。通过与有实测资料4个点推算的结果比较表明：卫星资料和实测计算的误差随着重现期的增大而减小，最大误差百年和50年一遇波高为20cm；而百年和50年一遇波高正是工程中最为关心的，说明运用卫星遥感散射计风资料推算渤海多年一遇波高可行且结果合理。本研究方法为进一步运用和完善卫星遥感资料推算中国近海多年一波高场提供了一条新途径。 相似文献
18.
Wave and wind characteristics based on the cyclones, in the vicinity of the Nagapattinam coastline (east coast of India) were estimated. In all, 11 cyclones have crossed near the study region during 1960–1996. For the four severe cyclones, the isobaric charts were collected at three hourly intervals from the India Meteorological Department. The storm variables such as central pressure, radius of maximum wind, speed of forward motion and direction of storm movement were extracted and the method based on standard Hydromet pressure profile, were used for the hindcast of storm wind fields. For all the cyclones the maximum significant wave height within the storm and its associated spectral peak period was estimated using the Young’s model considering the moving wind field and the results are compared with the hurricane wave prediction techniques provided in the shore protection manual published by the US Army Corps of Engineers in 1984. The study shows that the estimated wind speed and the data reported by ships were comparable. Empirical expressions relating wind speed, wave height and wave period to storm parameters were derived. The design wave height for different return periods was obtained by fitting a two-parameter Weibull distribution to the estimated significant wave heights. The design wave height was 9.39 m for 1 in 100 year return period for a direct hit of cyclone. 相似文献
19.
采用Gumbel Logistic模型对江苏及邻近海域深水极值波浪与增水进行了联合概率分析。首先对联合概率模型参数进行拟合,得到联合超越概率与经验联合超越概率比较图。在此基础上开展有效波高和增水年极值序列联合概率分析,比较了三种经验有效波高与增水重现期组合事件的联合概率,结果表明在选定的13个代表点位处,有效波高在二者的联合概率分布中处于主导地位,采用100年一遇有效波高与10年一遇增水组合事件作为100年一遇联合事件偏保守;而50年一遇有效波高与50年一遇增水以及10年一遇有效波高与100年一遇增水组合事件的联合概率则随着点位的移动而高于或低于100年一遇的水平。 相似文献
20.
By analysing the scatter diagrams of characteristic the wave height H and the period T on the basis of instrumental data from various ocean wave stations, we found that the conditional expectation and standard deviation of wave period for a given wave height can be better predicted by using the equations of normal linear regression rather than by those based on the log- normal law. The latter was implied in Ochi' s bivariate log-normal model(Ochi. 1978) for the long-term joint distribution of H and T. With the expectation and standard deviation predicted by the normal linear regression equations and applying proper types of distribution, we have obtained the conditional distribution of T for given H. Then combining this conditional P(T / H) with long-term marginal distribution of the wave height P(H) we establish a new parameterized model for the long-term joint distribution P(H,T). As an example of the application of the new model we give a method for estimating wave period associated with an extreme w 相似文献