Semidiurnal Perturbations to Storm Surges on the U.S. Eastern Seaboard

美国东海岸风暴潮的半日扰动

• 批准号: 1332718
• 负责人: Arnoldo Valle-Levinson
• 金额: $ 39.94万
• 依托单位: University of Florida
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2013
• 资助国家: 美国
• 起止时间: 2013-08-15 至 2018-07-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1332718&HistoricalAwards=false
• 关键词: Semidiurnal; Perturbations; Storm; Surges; U.S.

Semidiurnal perturbations modified the non-tidal surges of hurricanes Sandy (2012) and Irene (2011) which affected the entire U.S. eastern seaboard. In the South Atlantic Bight, the amplitude of the perturbations reached up to 50-60% of the total surge amplitude. In general, semidiurnal perturbations become evident when predicted water levels are subtracted from observed water levels. A response of such tide-surge interaction is to modify the timing of tidal low and high water, which is expected to be different from nearly progressive to nearly standing tides. This project seeks to advance understanding of the processes that trigger semidiurnal perturbations on storm surges and that determine the size of the perturbations. Atmospheric forcing can disturb the surge through direct surface stress and by inducing additional bottom stress and tidal stress. The relative contribution of each stress needs improved understanding. Specific objectives of this investigation are to determine a) whether semidiurnal perturbations appear under other tropical storms and under extratropical storms, b) the relative size of the dynamic agents associated with the perturbations, and c) the atmospheric and tidal forcing thresholds that produce them. Specific objectives will be addressed with observations from tidal and meteorological stations along the U.S. eastern coast, and with realistic and process-oriented numerical simulations.Intellectual Merit: In recent decades, coastal areas worldwide have been affected by storms that cause severe flooding, damage to buildings, and beach erosion. Storm-tide interactions can produce the highest storm-related levels at times not linked to high tide but still at semidiurnal periodicities. It is therefore necessary to understand the behavior of semidiurnal perturbations triggered by storms in order to improve forecasts and warning systems of storm surges. This project will try to answer several key questions: Do semidiurnal perturbations occur in every storm that moves along the eastern US? Do semidiurnal perturbations also occur during nor'easters? What are the dynamics associated with these perturbations? Are there atmospheric forcing thresholds below which these perturbations vanish? Do perturbations depend on the tidal amplitude? Does the peak in semidiurnal perturbations develop consistently in one phase of the tidal cycle? Clearly, there is a need to understand appropriate conditions for triggering semidiurnal perturbations on the surge. Findings generated from the study will help understand the causes for the appearance of high frequency (periods smaller than the inertial period) perturbations, semidiurnal residuals, which modify storm surges.Broader Impacts: This project will study a phenomenon that can affect the entire U.S. eastern seaboard. Because semidiurnal perturbations can reach amplitudes of up to 50-60% of the total surge signal in the South Atlantic Bight, it is imperative to include tide-surge interactions. These interactions will also affect the timing of maximum surge, relative to high tide. Probability density functions related to arrival of storm surges will thus be affected by semidiurnal residuals. Better understanding of these perturbations will help to refine storm surge predictions and risk analysis for the entire eastern U.S. seaboard. The project will support one graduate student, one undergraduate, through semester-long research experiences, and one high school student through summer internships. The high school student will be recruited among minority groups among high schools in Gainesville, Florida. Results derived from this project will be presented to K-12 audiences and will be incorporated in classes taught by the PIs at the University of Florida. The involvement of both PIs enhances the participation of underrepresented groups in science.

半日扰动改变了影响整个美国东海岸的飓风“桑迪”（2012 年）和“艾琳”（2011 年）的非潮汐浪涌。在南大西洋湾，扰动幅度达到总浪涌幅度的50-60%。一般来说，当从观测水位减去预测水位时，半日扰动变得明显。这种潮涌相互作用的响应是改变潮汐低潮和高潮的时间，预计这与近渐进潮和近静止潮不同。该项目旨在加深对触发风暴潮半日扰动并确定扰动大小的过程的理解。大气强迫可以通过直接的表面应力和诱发额外的底部应力和潮汐应力来干扰涌浪。每种压力的相对贡献需要加深理解。 这项调查的具体目标是确定a）其他热带风暴和温带风暴下是否出现半日扰动，b）与扰动相关的动力因素的相对大小，以及c）产生扰动的大气和潮汐强迫阈值。具体目标将通过美国东海岸潮汐和气象站的观测以及现实和面向过程的数值模拟来实现。 智力价值：近几十年来，世界各地的沿海地区受到风暴的影响，造成严重的洪水、建筑物损坏和海滩侵蚀。风暴潮相互作用有时会产生与高潮无关的最高风暴相关水平，但仍以半日为周期。因此，有必要了解风暴引发的半日扰动行为，以改进风暴潮的预报和预警系统。该项目将尝试回答几个关键问题：沿着美国东部移动的每次风暴是否都会发生半日扰动？东北复活节期间也会发生半日扰动吗？与这些扰动相关的动态是什么？是否存在大气强迫阈值，低于该阈值这些扰动就会消失？扰动取决于潮汐幅度吗？半日扰动的峰值是否在潮汐周期的一个阶段一致发展？显然，需要了解触发浪涌半日扰动的适当条件。研究结果将有助于理解高频（小于惯性周期的周期）扰动、半日残差出现的原因，这些扰动会改变风暴潮。更广泛的影响：该项目将研究一种可能影响整个美国东海岸的现象。由于半日扰动的幅度可高达南大西洋湾总潮汐信号的 50-60%，因此必须考虑潮汐与潮汐的相互作用。这些相互作用也会影响相对于高潮的最大浪涌的时间。因此，与风暴潮到来相关的概率密度函数将受到半日残差的影响。更好地了解这些扰动将有助于完善整个美国东部沿海地区的风暴潮预测和风险分析。该项目将支持一名研究生、一名本科生进行为期一个学期的研究经历，以及一名高中生的暑期实习。这名高中生将在佛罗里达州盖恩斯维尔的高中少数群体中招募。该项目的结果将呈现给 K-12 受众，并将纳入佛罗里达大学 PI 教授的课程中。两位 PI 的参与增强了代表性不足的群体对科学的参与。