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1.
Increasing wave heights and extreme value projections: The wave climate of the U.S. Pacific Northwest 总被引：1，自引：0，他引：1
Deep-water wave buoy data offshore from the U.S. Pacific Northwest (Oregon and Washington) document that the annual averages of deep-water significant wave heights (SWHs) have increased at a rate of approximately 0.015 m/yr since the mid-1970s, while averages of the five highest SWHs per year have increased at the appreciably greater rate of 0.071 m/yr. Histograms of the hourly-measured SWHs more fully document this shift toward higher values over the decades, demonstrating that both the relatively low waves of the summer and the highest SWHs generated by winter storms have increased. Wave heights associated with higher percentiles in the SWH cumulative distribution function are shown to be increasing at progressively faster rates than those associated with lower percentiles. This property is demonstrated to be a direct result of the probability distributions for annual wave climates having lognormal- or Weibull-like forms in that a moderate increase in the mean SWH produces significantly greater increases in the tail of the distribution. Both the linear regressions of increasing annual averages and the evolving probability distribution of the SWH climate, demonstrating the non-stationarity of the Pacific Northwest wave climate, translate into substantial increases in extreme value projections, important in coastal engineering design and in quantifying coastal hazards. Buoy data have been analyzed to assess this response in the wave climate by employing various time-dependent extreme value models that directly compute the progressive increases in the 25- to 100-year projections. The results depend somewhat on the assumptions made in the statistical procedures, on the numbers of storm-generated SWHs included, and on the threshold value for inclusion in the analyses, but the results are consistent with the linear regressions of annual averages and the observed shifts in the histograms. 相似文献
2.
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
3.
In this study, future changes in regional extreme wave heights around the Korean Peninsula are projected by using the results of an atmosphere general circulation model and a third-generation wave model. The direct use of the model output at each grid point is not appropriate even though high resolution of 20 km is used for the models. Therefore, the model output is grouped into six regions around the Korean Peninsula. The grouping approach is reasonable in assessing climate change effects with alleviated model uncertainty. The extreme wave heights are simulated for two climate periods of 1979–2003 (present climate) and 2075–2099 (future climate). The model results are validated by comparing the simulated wave heights for the present climate with observed and hindcasted wave data. The extreme wave heights for the future climate are then projected for different seasons and in different regions. The 50-year return wave height in summer is projected to increase in most regions, especially in the high-latitude Yellow Sea and the East Sea, while the wave height in winter is projected to decrease in all the regions, especially in the East Sea. 相似文献
4.
气候变化背景下,海平面上升叠加台风—风暴潮、天文大潮等产生的海岸极值水位事件趋多增强,对我国滨海城市社会经济可持发展构成了严重威胁。为认识未来我国滨海城市海岸极值水位危害性（强度和频率）的变化,本文首先采用第五次国际耦合模式比较计划（CMIP5）数据,分析了不同气候情景下（RCP2.6, 4.5, 8.5,简称为RCPs）下,未来不同年代（2030年、2050年和2100年）我国滨海城市沿岸海平面变化幅度;其次,基于沿海验潮站的历史观测资料和文献数据,分析了未来热带气旋强度变化对海岸极值水位的影响;最后,利用皮尔逊Ⅲ型（P-Ⅲ）水文概率曲线方法,预估了不同气候（RCPs）情景下未来不同年代（2030年、2050年和2100年）我国9个滨海城市海岸极值水位重现期的变化。结果表明：（1）在不同气候情景下,我国滨海城市沿海平均海平面均呈现上升趋势,其中,到21世纪末,长三角地区沿海海平面上升幅度最大,上升速度比全国平均高出约30%;（2）热带气旋的强度与台风—风暴潮的增水幅度存在正相关关系。预计到21世纪末,热带气旋的整体强度很可能将增强,热带气旋引发的台风—风暴潮的增水幅度较当前很可能有明显提高。（3）未来我国滨海城市沿海极值水位将有显著增高的趋势,当前极值水位的重现期将明显缩短。到21世纪末,我国滨海城市当前百年一遇的极值水位,重现期几乎都将缩短至20年一遇以下,其中,大连、青岛、上海和厦门等城市海岸极值水位重现期很可能缩短为（或低于）1年一遇。本文虽在一定程度上反映了不同气候情景下海岸洪水危害性的变化,但对于未来热带气旋的变化及其影响的研究尚有待进一步深入。 相似文献
5.
《African Journal of Marine Science》2013,35(4):407-421
This article investigates spatio-temporal trends for different return periods of extreme significant wave height (SWH) in the Gulf of Guinea (GG), northeastern tropical Atlantic Ocean, based on a 37-year (1980–2016) wave hindcast. High-resolution reanalysis windfield datasets were used to force the spectral wave model WAVEWATCH III. The wave hindcast information was validated using data gathered from the US National Data Buoy Center. The model performance was adequate. In a spatial analysis, the trends were less than 0.3 m decade?1 in all parts of the GG, and were increasingly positive westwards, extending to the far western part of the GG; trends below 0.01 m decade?1 dominated in the eastern part and some areas of the northern part of the gulf. Temporal analysis showed that the trends were negative in all cases. Spatio-temporal trends in the return periods for the 99th-percentile wave height were generally weak. Also, trends in the yearly, seasonal and monthly means of extreme SWH all generally increased from east to west in the GG. Furthermore, temporal trend analysis showed that extreme SWH exhibited an increasing trend of 0.0041 m y–1 throughout the 37-year period; by season, it exhibited a declining trend of ?0.0005 m y–1 in winter, and an increasing trend of 0.0048 m y?1 in summer. The observed increasing positive trend of extreme SWH westward in the GG, however, suggests an increasing storminess towards the western part of the gulf, with potential implications for coastal flooding and erosion, and consequences for coastal structures. 相似文献
7.
本文基于第3代海浪模式WAVEWATCH Ⅲ (WW3）模拟的1996–2015年海浪后报数据，分析了南海北部有效波高及其极值的时空变化特征，并采用Pearson-Ⅲ和Gumbel两种极值分布方法对该区极值波高重现期进行了估算。结果表明，南海北部有效波高的季节变化和空间分布与季风风场基本一致，呈现秋冬高春夏低，并自吕宋海峡西侧向西南降低的特征，与ERA5再分析数据结果高度相似。有效波高极值（简称极值波高）的时空分布特征受时间分辨率强烈影响，采用极值数据的分辨率越高（如逐小时），所展现的台风型波浪特征越显著。扣除季节变化信号后的有效波高和年极值波高均体现出较强的线性增高趋势，近20年升高的比例分别为7.7%和31.6%，值得警惕和关注。该区多年一遇极值波高存在若干个大值区，且与台风的路径、强度有直接联系，表明台风是引发该区域极端大浪的最主要机制。对比Pearson-Ⅲ和Gumbel极值分布估算结果发现：若极值波高较低，频率随极值波高升高缓慢降低，此时两种极值分布的估算都比较准确，差异极小，可忽略不计；但当研究时间范围内，某年极值波高远超其他年份时，Pearson-Ⅲ极值分布估算结果明显高... 相似文献
8.
Global sea surface wind field data derived from NCEP reanalysis were used in driving a SWAN wave model to reconstruct historical wave records from 1948 to 2008. The reconstructed wave data were compared and verified by the observation of the data buoys of the Central Weather Bureau and the Water Resources Agency, Taiwan, and the National Data Buoy Center/National Oceanic and Atmospheric Administration, United States. Over the past six decades, the wave climate in Taiwan waters has undergone considerable changes. The annual mean significant wave heights have reduced an average of 0.31 cm/year. Winter wave heights have gradually dropped 0.86 cm/year, which are related to the weakening of winter monsoons. Regarding the inter-annual wave climate variation, the influence of El Niño/southern oscillation was substantial; the wave heights increased in La Niña years and decreased in El Niño years. In the past 60 years, extreme wave events have been concentrated in two periods: 1967–1974 and 2000–2008. More severe extreme wave events occurred in the latter compared with the former, and all were induced by typhoons. A clear trend, in which the summer (winter) extreme wave events have increased (decreased) gradually, has been identified. The 1980s was the transition period. After the transition period, the annual occurrence of extreme wave events caused by typhoons exceeded those caused by an intense outbreak of winter cold surges, although the total number of the annual extreme wave events has not changed substantially. 相似文献
9.
This paper is aimed at the whole Bohai Sea,as the complement and improvement of wave characteristics and extreme parameters.Wave fields were simulated in the Bohai Sea by using wave model SWAN from 1985 to 2004.The input data based on the hindcast of high-resolution wind fields from RAMS and water level fields from POM,which have been tested and verified well.Comparisons of significant wave heights between simulation and station observations show a good agreement in general.By statistical analysis,the wave characteristics such as significant wave heights, dominant wave directions and their seasonal variations are discussed.In addition,main wave extreme parameters and directional extreme values particularly for 100-year return period are investigated. 相似文献
10.
1988-2002年黄海和渤海风浪后报 总被引：2，自引：1，他引：1
本文对黄海和渤海风浪开展长期后报实验,时间范围覆盖1988至2002年,并分析相应的区域波候特征。首先,模式输出的月平均有效波高和卫星数据比对一致。其次,我们讨论了气候态月平均有效波高和平均波周期的时空分布特征。有效波高和平均波周期的气候态空间分布都呈现出西北-东南、或由近岸向深水区增加的趋势,这种空间的分布特征和局地的风强迫和水深密切相关。同时,海浪参数的季节变化也较显著。进一步,我们统计分析了风场和有效波高的极值,给出并揭示了黄海和渤海多年一遇有效波高的空间结构,并讨论了有效波高极值和风强迫极值之间的联系。 相似文献
11.
Recent developments in extreme values modelling have been used to develop a framework for determining the coastal erosion hazard on sandy coastlines. This framework quantitatively reproduced the extreme beach erosion volumes obtained from field measurements at Narrabeen Beach, Australia. This encouraging finding was achieved using Kriebel and Dean's [Kriebel, D.L. and Dean, R.G., 1993. Convolution method for time-dependent beach profile response. Journal of Waterway, Port, Coastal and Ocean Engineering, 119(2): 204–226.] simple beach erosion and accretion model. The method includes allowances for joint probability between all basic erosion variates including; wave height, period and direction, event duration, tidal anomalies and event spacing. A new formulation for the dependency between wave height and period has been developed. It includes the physical wave steepness limitation. Event grouping, where significantly more erosion can occur from two closely spaced storms is handled by temporally simulating the synthetic wave climate and the resulting beach erosion and accretion. 相似文献
12.
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
13.
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
14.
Accurately estimating the mean and extreme wave statistics and better understanding their directional and seasonal variations are of great importance in the planning and designing of ocean and coastal engineering works. Due to the lack of long-term wave measurement data, the analysis of extreme waves is often based on the numerical wave hind-casting results. In this study, the wave climate in the East China Seas (including the Bohai Sea, the Yellow Sea and the East China Sea) for the past 35 years (1979–2013) is hind-casted using a third generation wave model – WAMC4 (Cycle 4 version of WAM model). Two sets of reanalysis wind data from NCEP (National Centers for Environmental Prediction, USA) and ECMWF (European Centre for Medium-range Weather Forecasts) are used to drive the wave model to generate the long-term wave climate. The hind-casted waves are then analysed to study the mean and extreme wave statistics in the study area. The results show that the mean wave heights decrease from south to north and from sea to land in general. The extreme wave heights with return periods of 50 and 100 years in the summer and autumn seasons are significantly higher than those in the other two seasons, mainly due to the effect of typhoon events. The mean wave heights in the winter season have the highest values, mainly due to the effect of winter monsoon winds. The comparison of extreme wave statistics from both wind fields with the field measurements at several nearshore wave observation stations shows that the extreme waves generated by the ECMWF winds are better than those generated by the NCEP winds. The comparison also shows the extreme waves in deep waters are better reproduced than those in shallow waters, which is partly attributed to the limitations of the wave model used. The results presented in this paper provide useful insight into the wave climate in the area of the East China Seas, as well as the effect of wind data resolution on the simulation of long-term waves. 相似文献
15.
海平面上升、强台风和风暴潮对厦门海域极值水位的影响及危险性预估 总被引：1，自引：0，他引：1
气候变化背景下海平面上升、强台风和风暴潮对我国东南沿海地区的洪涝灾害影响日益严重,为应对气候变化的影响,本文以位于我国东南沿海的厦门地区为例,应用多种海洋大气观测资料和数理统计及模拟方法,分析了历史上9914号和1614号两次台风对厦门海域极端海面高度(极值水位)的影响,预估了未来海平面上升情景下厦门海域极值水位的变化及其危险性。结果表明:(1) 9914号台风期间,天文大潮、风暴增水和强降水的同时出现造成了厦门沿海地区超警戒极值水位(732 cm)的出现;(2) 风(向岸强风)、雨(强降水)、浪(巨浪)、潮(高潮位)、流(急流)等多致灾因子的共同作用是厦门沿海地区发生严重灾情的重要原因;(3) 在温室气体中等和高排放(RCP4.5和RCP8.5)情景下,到2050年(2100年),当前百年一遇的极值水位将分别变为30年(2年)一遇(RCP4.5)和25年(低于1年)一遇(RCP8.5)的频繁极端事件。这表明未来厦门沿海极值水位的危险性将显著上升,应采取充分的适应措施降低洪涝灾害风险。 相似文献
16.
全球气候变化背景下,海平面上升是一个潜在的重大风险,为防范气候灾害,应对极端气象海洋事件,需客观、定量地对未来极端海平面变化进行科学预测。为此,基于Copula函数和动态极值分析理论,综合考虑平均海平面变化(包括垂直陆地运动和基准的局地变化)与潮、涌、浪等其他气候变化的增水对极端海平面高度的影响,采用DREAM方法改进Bayes推断对动态极值模型的参数空间估计问题,提出一种新的模型对未来极端海平面高度变化进行预测,旨在改进传统模型存在的不确定性问题,并运用该模型对气候变化背景下厦门地区未来35年的海平面变化情景进行了模型应用和实验模拟。 相似文献
17.
The impact of climate change on design wind speeds corresponding to different return periods at two selected offshore locations in India has been assessed. Extreme daily wind speeds corresponding to various return periods were derived based on the observations made by wave rider buoys during the period 1998–2005. Thereafter, the future climate over the next century was simulated at these locations using the input from the climate model: GCM-CGCM3 corresponding to the A2 scenario. The underlying downscaling model was developed with the help of artificial neural networks and using observed wind as output. The local wind speeds corresponding to these projected wind data were generated for the next century and return period wind speeds were extracted by the distribution fitting. Comparison of design wind speeds derived with and without consideration of future climate showed that the magnitude of the long term wind speed would certainly and significantly increases if the effect of global climate change is incorporated in the analysis. For the two locations considered, the increase in the 100-year wind was found to be varying from 44% to 74%. 相似文献
18.
Characterising the dependence between extremes of wave spectral parameters such as significant wave height (HS) and spectral peak period (TP) is important in understanding extreme ocean environments and in the design and assessment of marine structures. For example, it is known that mean values of wave periods tend to increase with increasing storm intensity. Here we seek to characterise joint dependence in a straightforward manner, accessible to the ocean engineering community, using a statistically sound approach.Many methods of multivariate extreme value analyses are based on models which assume implicitly that in some joint tail region each parameter is either independent of or asymptotically dependent on other parameters; yet in reality the dependence structure in general is neither of these. The underpinning assumption of multivariate regular variation restricts these methods to estimation of joint regions in which all parameters are extreme; but regions where only a subset of parameters are extreme can be equally important for design. The conditional approach of Heffernan and Tawn (2004), similar in spirit to that of Haver (1985) but with better theoretical foundation, overcomes these difficulties.We use the conditional approach to characterise the dependence structure of HS and TP. The key elements of the procedure are: (1) marginal modelling for all parameters, (2) transformation of data to a common standard Gumbel marginal form, (3) modelling dependence between data for extremes of pairs of parameters using a form of regression, (4) simulation of long return periods to estimate joint extremes. We demonstrate the approach in application to measured and hindcast data from the Northern North Sea, the Gulf of Mexico and the North West Shelf of Australia. We also illustrate the use of data re-sampling techniques such as bootstrapping to estimate the uncertainty in marginal and dependence models and accommodate this uncertainty in extreme quantile estimation.We discuss the current approach in the context of other approaches to multivariate extreme value estimation popular in the ocean engineering community. 相似文献
19.
The study focuses on investigating significant wave height, including both mean and extreme values, in the North Atlantic in winter during the period from 1979 to 2010. We perform a 32-year wind wave hindcast for the North Atlantic using a spectral ocean wave model (WaveWatch III) and a high-resolution nonhydrostatic atmospheric model (WRF-ARW), which provides the wind forcing function. Analysis of the 32-year hindcast of wave characteristics in the North Atlantic reveals stronger mean and extreme waves simulated with high resolution modeling systems and identifies significant downward trends in the mean significant wave height in the subpolar North Atlantic. Such trends were not found in the wave characteristics from ERA-Interim reanalysis. At the same time, the 32-year hindcast did not confirm the statistically significance of strong positive trends in the central Atlantic diagnosed by ERA-Interim reanalysis; differences between the reanalysis and hindcast are discussed. 相似文献
20.
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