SGER: Transient Shelf Response to the Hurricane Wilma's Impact

SGER：对飓风威尔玛影响的短暂陆架响应

• 批准号: 0617130
• 负责人: Alexander Yankovsky
• 金额: $ 7.96万
• 依托单位: Nova Southeastern University
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2006
• 资助国家: 美国
• 起止时间: 2006-03-01 至 2006-10-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0617130&HistoricalAwards=false
• 关键词: SGER; Transient; Shelf; Response; Hurricane

The frequency and severity of hurricane activity has risen sharply over the last few years. Several major hurricanes hit the US Southeast coast in the 2004 and 2005 seasons, with the impacts from Katrina and Wilma being among the costliest in the US history. Typically, the storm surge predictions are focused on local dynamics associated with the wind-induced onshore drift and the wave action. However, the evolution of storm surge also includes an alongshore propagation of the coastally trapped wave (CTW) pulse. Linear theories predict that in such a case the strongest response occurs downstream (in the sense of Kelvin wave propagation) and later in time relative to the location and moment of the landfall. This notion is consistent with the events in New Orleans, when the protective levies were overwhelmed a few hours after the Hurricane Katrina's landfall some distance upstream, on the Mississippi coast.Unique and detailed observations of sea level and barometric pressure along the Southwest Florida coast collected during Hurricane Wilma's landfall in October 2005 will be analyzed to delineate the coastally trapped wave (CTW) pulse propagation, dispersion and decay as it leaves the forcing region and moves downstream (northward). While the observational array was not designed to capture the complex hydrodynamics of the storm surge, it occupied an optimal position for observing the hurricane-generated CTW pulse.. These data will also be used for tuning-up the primitive equation model in order to conduct a process-oriented study of the hurricane's impact on the wide and shallow shelf. The data set consists of weeklong time series of storm surge (S) and barometric pressure (B) measured by the USGS Florida Integrated Science Center at approximately 30 locations. The survey area spanned more than 100 km alongshore with the instruments deployed both on the coastline and in the inlets/estuaries. These data will be augmented with the existing NOAA wind and sea level measurements. The atmospheric pressure data will be used in order to determine a temporal and spatial evolution of the wind forcing: the available time series of wind will be extrapolated by applying the structure of atmospheric pressure variations. Detailed barometric pressure measurements will be also applied to accurately adjust the sea level data and thus to detect the CTW pulse evolution along the coastline. The CTW pulse amplitude will be determined by using data from the exposed coastline only, while the phase will be estimated based both on data from the coastline and from the inlets. The latter will be adjusted in time by allowing the signal propagation from the mouth inland at a speed of a long gravity wave. The observations will be reproduced in the model by applying the observed forcing and tuning the bottom stress and horizontal eddy "viscosity" coefficients in order to obtain a realistic propagation speed and amplitude of the storm surge. The shelf topography will be uniform alongshore, except for the upstream boundary, where the shelf width will diminish abruptly, thus mimicking the southern tip of Florida. The role of dispersion, friction and nonlinearity will be systematically studied by conducting realistic model runs with the observed wind forcing and complimentary model runs with the same initial disturbance (induced by the hurricane) but traveling as a free wave pulse with much reduced friction, and also as a pulse of the same spatial-temporal structure but with a smaller amplitude (allowing linear dispersion). In subsequent model experiments, the coastline feature will also be placed downstream, representing the conditions of Hurricane Katrina (i.e., protruding Mississippi delta). Broader Impacts: The results of data analysis and numerical experiments will reveal the importance of dispersion, nonlinearity, frictional decay and topographic variations in the alongshore evolution of storm surge driven by a hurricane landfall. The results will also improve our understanding and predictability of hurricane-induced flooding with a focus on vulnerability of the downstream areas.

过去几年，飓风活动的频率和严重程度急剧上升。 2004 年和 2005 年季节，美国东南海岸遭受了数次重大飓风袭击，其中卡特里娜飓风和威尔玛飓风的影响是美国历史上损失最惨重的飓风之一。通常，风暴潮预测侧重于与风引起的陆上漂移和波浪作用相关的局部动态。然而，风暴潮的演变还包括沿海陷波（CTW）脉冲的沿岸传播。线性理论预测，在这种情况下，最强的响应发生在下游（在开尔文波传播的意义上），并且相对于登陆的位置和时刻而言，时间较晚。这一概念与新奥尔良发生的事件一致，当时卡特里娜飓风在密西西比海岸上游一段距离登陆后几个小时，防护税就被淹没了。将对 2005 年 10 月飓风威尔玛登陆期间沿佛罗里达州西南部海岸收集的海平面和气压的独特而详细的观测结果进行分析，以描绘沿海陷波 (CTW) 脉冲 当它离开强迫区域并向下游（向北）移动时，会传播、分散和衰变。虽然观测阵列的设计目的不是捕捉风暴潮的复杂流体动力学，但它占据了观测飓风产生的CTW脉冲的最佳位置。这些数据还将用于调整原始方程模型，以便对飓风对宽浅陆架的影响进行面向过程的研究。该数据集由 USGS 佛罗里达综合科学中心在大约 30 个地点测量的为期一周的风暴潮 (S) 和气压 (B) 时间序列组成。调查区域绵延100多公里，仪器部署在海岸线和入海口/河口。这些数据将通过现有的 NOAA 风和海平面测量得到增强。将使用大气压力数据来确定风力强迫的时间和空间演变：将通过应用大气压力变化的结构来推断可用的风时间序列。详细的气压测量还将用于精确调整海平面数据，从而检测沿海岸线的 CTW 脉冲演变。 CTW 脉冲幅度将仅通过使用来自暴露海岸线的数据来确定，而相位将根据来自海岸线和入口的数据来估计。后者将通过允许信号以长重力波的速度从河口向内陆传播来进行及时调整。通过应用观测到的强迫并调整底部应力和水平涡流“粘度”系数，观测结果将在模型中重现，以获得风暴潮的实际传播速度和幅度。除了上游边界外，沿岸的陆架地形将是均匀的，上游边界除外，陆架宽度将突然减小，从而模仿佛罗里达州的南端。将系统地研究色散、摩擦和非线性的作用，方法是使用观测到的风力进行实际模型运行，并进行具有相同初始扰动（由飓风引起）但作为摩擦力大大降低的自由波脉冲行进的互补模型运行，以及作为具有相同时空结构但幅度较小（允许线性色散）的脉冲行进。在后续的模型实验中，海岸线要素也将放置在下游，代表卡特里娜飓风的情况（即突出的密西西比三角洲）。更广泛的影响：数据分析和数值实验的结果将揭示分散性、非线性、摩擦衰减和地形变化在飓风登陆驱动的风暴潮沿岸演变中的重要性。研究结果还将提高我们对飓风引发的洪水的理解和可预测性，重点关注下游地区的脆弱性。