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渤海寒潮风暴潮增水风险的数值研究

Numerical Study on Risk of Storm Surge Induced by Cold-air Outbreak in the Bohai Sea

【作者】 赵鹏

【导师】 江文胜;

【作者基本信息】 中国海洋大学 , 物理海洋学, 2010, 博士

【摘要】 风暴潮灾害居各类海洋灾害之首,世界上绝大多数因强天气系统引起的特大海岸灾害都是由风暴潮造成的。在我国,风暴潮灾害几乎遍及我国沿海,从南到北均有发生。在纬度比较低的东南沿海地区,风暴潮灾害主要发生于夏秋季节,多由在西北太平洋上生成的台风或热带气旋引起;而在像渤海这样纬度比较高的海域,其受到台风或热带气旋影响的机率较低,但在秋冬过渡或冬春过渡季节极易受到寒潮的影响在其沿岸造成持续而不急剧的风暴潮增水(为方便研究,本文将此类风暴潮称为寒潮风暴潮)。本文通过分析影响我国渤海地区的寒潮的特征要素,从中归纳提取出三个有利于计算风暴潮增水的要素,在对这些要素进行敏感性分析之后,按照寒潮的四个主要路径将影响渤海地区的寒潮划分为四大类,并且在每一路径下分别考虑五个不同强度的寒潮情景,合理地构造了20个寒潮情景以刻画影响渤海地区寒潮的真实情况。在此基础上使用FVCOM模式对渤海中由寒潮引发的风暴潮进行了数值模拟,发现寒潮风暴潮主要对渤海的西南沿岸造成危害,其中受灾最严重的区域为渤海湾顶部,其次为莱州湾顶部区域。由不同路径下寒潮所引发的风暴潮的特点亦各不相同,其中北路和西北路寒潮同时在渤海湾和莱州湾地区引起增水,且北路寒潮造成的风暴潮灾害最严重;东北路寒潮易在渤海湾造成显著增水;而西路寒潮仅在莱州湾地区形成较严重的增水。在讨论了渤海风暴潮增水极值的分布情况之后,本文对渤海沿岸受风暴潮影响比较严重的三个地区的风暴潮增水风险进行了分析。为具体研究寒潮风暴潮在受灾地区造成的漫滩风险,本文选取受学者关注较多的塘沽地区和黄河三角洲地区做示范性研究,并将这两个地区的漫滩灾害根据诱发风暴潮的寒潮情景强度的不同划分为五个级别。为了克服极值水位和增水风险的概率分布两者的缺点,更直观合理的表现出风暴潮灾害沿渤海沿岸的分布情况,本文引入风暴潮水位超过某一预定警戒值的时间来描述其风险大小,通过构造新的增水风险计算方案,用简单直观的方式表现出渤海沿岸的风暴潮风险分布情况。然而风暴潮不仅取决于诱其发生的气象条件,还会受到局地海岸线及地形变化、气候变化导致的海平面上升、地下水等诸多因素的影响。为研究近年来渤海中黄河三角洲地区和曹妃甸地区的岸线变化对风暴潮的影响,本文着眼于这两处区域在1976年、2010年及2030年三个时期的岸线形状,并对这三个时期渤海的寒潮风暴潮情况进行了模拟。通过对不同时期渤海中的天文潮水位、寒潮风暴潮的增水极值和风暴潮增水风险进行计算、模拟与分析后发现:当渤海岸线仅在本文所考虑的区域发生变化时,在渤海湾中的天文潮水位、寒潮风暴潮增水极值和风暴潮增水风险都呈下降趋势,因此其风暴潮的总体风险亦应呈下降趋势:而在莱州湾地区天文潮水位、增水极值及风暴潮增水风险(此处为新方案的结论)均呈增加趋势,故该区域的风暴潮总体风险亦呈增加趋势。

【Abstract】 Storm surge can be ranked as the most serious disaster among the marine disasters.Most of the serious disasters that occurred along the coastal zone are associated with storm surges induced by extreme weather systems.In China, almost all the coastal zones are susceptible to storm surges. In the coastal zone of the south-east part of China, storm surges are usually induced by typhoons or tropical cyclones that generate over the northwestern Pacific, but in the Bohai Sea, which is located in the high latitude and seldom affected by typhoons and tropical cyclones, storm surges caused by cold-air outbreaks in winter usually lead to a sustained significant sea level rising along the south-western coastal zone.By analyzing the characteristics of cold-air outbreaks, three typical characteristics are summarized to calculate the storm surge.After the sensitivity experiment with these characteristics, the cold-air outbreaks are divided into four categories according to the major track by which they attack China, and in each category there are one control scenario and four more extended scenarios. Therefore,the cold-air outbreaks over the Bohai Sea are described by these 20 scenarios.Base on these cold-air scenarios, storm surges induced by cold-air outbreaks in the Bohai Sea are modeled by FVCOM.It is find that the tops of the Bohai Bay and the Laizhou Bay are most seriously affected by the storm surges in the Bohai Sea.The characteristics of storm surges change with the tracks of cold-air outbreaks.The cold-air outbreaks from the NW and N track could place both the Bohai Bay and the Laizhou Bay at risk, the cold-air outbreaks from NE track usually lead significant water level rising to the top of Bohai Bay, but the ones from W track can only affect the Laizhou Bay. After the discussion of the water level rising induced by cold-air outbreaks, the risk of storm surge in Tanggu, Huanghua and Yangjiaogou is analyzed.As the most concerned areas, the risk of inundation in Tanggu and the Yellow River Delta is investigated respectively according to the strength of the cold-air outbreaks. In order to estimate the risk along the coast more reasonably, the time period that the water level exceeds a given threshold is involved.Based on the function considering the surge elevation, the probability of the storm surge scenarios and the time period mentioned above, the risk along the coast of the Bohai Sea is estimated, and the distribution of risk of storm surge along the Bohai Sea can be presented easily and clearly by this method.Strom surges are not only determined by the atmospheric forcing, but also influenced by many other factors, such as the coastal geometry and bathymetry, sea level rising caused by climate change and underground water. As the coastline of the Bohai Sea has changed evidently in the Caofeidian area and Yellow River Delta these years, storm surges in the Bohai Sea may have some new characteristics due to the local changing of the geometry. To find out these new characteristics, the influence of the changes in coastal geometry on storm surges is primarily investigated by numerical methods by involving the coastline of the Bohai Sea during 1976,2010 and 2030.By comparing the amplitude of astronomic tide, the distribution of maximum surge elevation and the risk of the storm surge during different periods, the main changes made by the variation of the coastline in Caofeidian and the Yellow River Delta can be found in the Bohai Bay and the Laizhou Bay. In the Bohai Bay, the amplitude of astronomic tide, the distribution of maximum surge elevation and the risk of the storm surge are all found decreasing with the changing of coastline, however, in the Laizhou Bay, all these terms are enhanced by the changing Yellow River Delta.

【关键词】 渤海寒潮风暴潮风险漫滩
【Key words】 the Bohai Seacold-air outbreaksstorm surgeriskinundation
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