Climatological, Composite, and Case Study Analyses Linking Rossby Wave Breaking to Potential Vorticity Streamer and Cutoff Cyclone Formation in the Subtropical North Atlantic Basin

极端天气事件虽然发生的概率很低，但会对社会经济产生非常严重的不利影响。这项资助研究的目的是调查影响美国、中美洲和西加勒比部分地区的各种极端天气事件的气候学、季节性及其与背景流的相互作用。要调查的候选极端天气事件包括在一年中较冷的一半期间产生洪水的暴雨，以及在一年中较暖的一半期间可能带来洪水、破坏性风和破坏性风暴潮的热带扰动。这些候选的极端天气事件通常与对流层上层的扰动（即切断气旋）同时发生。在高纬度地区形成的切断式气旋可以将寒冷的空气倾倒到亚热带地区，引发最初的寒潮和随后的大暴雨。在低纬度地区形成的切断气旋可以使温暖潮湿的热带空气到达中纬度地区，助长热带气旋登陆和/或异常强降雨。这项研究的一个新颖方面是，它的目标是与切断气旋有关的热带和中纬度环流的相互作用。这些切断气旋可以控制美国、中美洲和加勒比海西部极端天气事件的时间、发生和地点。这个研究项目的另一个创新之处在于，历史上的极端天气事件被孤立地研究了。这种历史方法排除了检测多个地理上分离但动态关联的极端天气事件发生的可能性，这些极端天气事件可能几乎同时发生在世界不同地区。极端天气事件发生的一个可靠因素是，北半球存在一种波浪状的、高振幅的、大规模的气流模式，这种模式可以分解成一系列的气旋。一个关键的科学问题是确定可能导致切断旋风形成的流动破裂的物理原因。该研究项目将使用最先进的全球网格数据集来确定与切断气旋相关的极端天气事件的频率。气候、综合和案例研究分析将从这些网格数据集构建，以帮助量化控制这些极端天气事件的位置和发生的物理过程。该研究的广泛影响是实质性的，包括(1)对该领域下一代科学家的教育，(2)与NOAA国家飓风中心的科学家互动的机会，以促进研究向业务的转移，以及(3)通过外联和培训活动教育中美洲和加勒比地区的气象学家，以确保他们了解有利于极端天气事件发生的天气模式。

Extreme weather events, although having a low probability of occurrence, can exert very high adverse socioeconomic impacts. The goal of the funded research is to investigate the climatology, seasonality, and their interactions with background flows of a variety of extreme weather events that impact parts of the United States, Central America, and the Western Caribbean. Candidate extreme weather events to be investigated include heavy, flood-producing rainstorms during the cooler half of the year and tropical disturbances that can bring flooding rains, damaging winds, and devastating storm surges during the warmer half of the year. These candidate extreme weather events often occur in conjunction with upper tropospheric disturbances known as cutoff cyclones. Cutoff cyclones that form in higher latitudes can dump chilly air into the subtropics, fueling cold waves initially and big rainstorms subsequently. Cutoff cyclones that form in lower latitudes can enable warm, moist tropical air to reach midlatitudes, fueling tropical cyclone landfalls and/or exceptionally heavy rainfalls. A novel aspect of the research is that it is targeted at the interaction of tropical and midlatitude circulations associated with cutoff cyclones. These cutoff cyclones can govern the timing, occurrence, and location of extreme weather events in the United States, Central America, and western Caribbean. Another innovation of this research project is that historically extreme weather events have been studied in isolation. This historical approach precludes the possibility of detecting the occurrence of multiple geographically separated but dynamically linked extreme weather events that may be occurring near simultaneously in different parts of the world. A sure-fire recipe for the occurrence of extreme weather events is the existence of a wavy, high-amplitude, large-scale flow pattern across the Northern Hemisphere that can break down into a series of cutoff cyclones. A critical science issue is determining the physical causes of flow breakdown that can lead to cutoff cyclone formation. The research project will use state-of-the-art global gridded datasets to identify the frequency of extreme weather events associated with cutoff cyclones. Climatological, composite, and case study analyses will be constructed from these gridded datasets to help quantify the physical processes governing the location and occurrence of these extreme weather events.The broader impacts of the research are substantial, including (1) the education of the next generation of scientists in the field, (2) opportunities to interact with scientists at NOAA's National Hurricane Center to facilitate the transfer of research to operations, and (3) educating meteorologists from Central America and the Caribbean through outreach and training activities to ensure they are current on weather patterns conducive to the occurrence of extreme weather events in their regions.