Extratropical Transition and Recurvature of Tropical Cyclones in a Changing Climate

气候变化中热带气旋的温带转变和回归

• 批准号: 1546743
• 负责人: Gary Lackmann
• 金额: $ 50.93万
• 依托单位: North Carolina State University
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2016
• 资助国家: 美国
• 起止时间: 2016-03-01 至 2022-02-28
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1546743&HistoricalAwards=false
• 关键词: Extratropical; Transition; Recurvature; Tropical; Cyclones

When tropical cyclones move poleward, they can produce adverse societal impacts, especially when they make landfall. While many tropical cyclones weaken as they move out of the tropics, a subset of these systems actually intensifies, and may increase in size. A recent example is Hurricane Sandy, which affected the Mid-Atlantic and Northeastern US in the fall of 2012. In recent years, there has been intensive study of how climate change would affect the frequency and intensity of tropical cyclones. However, only limited research has examined how climate change affects the important category of tropical cyclones that move out of the tropics. One expected result of climate change is warming air at upper levels in the tropics; prior research demonstrates that this upper warming limits the strengthening of tropical cyclones that would otherwise occur. However, tropical cyclones that move out of the tropics may escape this mitigating influence. Therefore, one goal of this study is to test the hypothesis that tropical cyclones exiting the tropics will show a greater intensity increase with warming than would storms that remain in the tropics. Another goal is to determine if and how warming changes the fraction of tropical cyclones that undergo the re-intensification process mentioned above. Finally, this project will also analyze changes in the locations and seasons in which tropical cyclones form. All of these goals will be accomplished using methods that are similar to what has been done in studying how tropical cyclones that remain in the tropics respond to climate change, but with a study area that extends well outside of the tropics. Highly sophisticated computer models, of the type used in weather prediction, will be used in combination with larger-scale changes obtained from climate models. Then, comparing "present day" to "future" simulations, with all else equal, allows determination of changes in the strength and frequency of tropical cyclones moving poleward into mid-latitude locations.This project addresses gaps in understanding of how climate change would influence the intensity and frequency of the subset of tropical cyclones that move out of the tropics, affecting higher-latitude locations. This category of tropical cyclones is extremely important, because it is precisely these systems, as they exit the tropics, which exert the strongest influence on the major population centers in mid-latitude locations such as the US. Given their importance, it is perhaps surprising that the response of these systems to climate change has not received more research attention to date. The project will also determine if geographical and/or seasonal changes in tropical cyclone activity will change with the climate. Owing to the highly technical nature of this project, the graduate students who work on it will gain valuable skills in scientific computing, data analysis and visualization, and in science communication. Graduate research assistants working on this project will be invited to assist in supervising undergraduate researchers, thereby gaining experience in leadership and mentoring.

当热带气旋向极地移动时，它们会产生不利的社会影响，特别是当它们登陆时。虽然许多热带气旋在离开热带地区时会减弱，但这些系统中的一个子集实际上会加强，并且可能会增加规模。最近的一个例子是飓风桑迪，它在2012年秋季影响了美国大西洋中部和东北部。近年来，人们对气候变化如何影响热带气旋的频率和强度进行了深入研究。然而，只有有限的研究探讨了气候变化如何影响热带气旋的重要类别。气候变化的一个预期结果是热带地区高层空气变暖;先前的研究表明，这种变暖上限限制了热带气旋的加强，否则就会发生。然而，离开热带地区的热带气旋可能会逃脱这种缓解影响。因此，这项研究的一个目标是检验一个假设，即离开热带的热带气旋将显示出比留在热带的风暴更大的强度增加。另一个目标是确定变暖是否以及如何改变经历上述再强化过程的热带气旋的比例。最后，本项目还将分析热带气旋形成地点和季节的变化。所有这些目标都将使用类似于研究热带气旋如何应对气候变化的方法来实现，但研究区域远远超出了热带地区。用于天气预报的高度复杂的计算机模型将与从气候模型获得的更大规模的变化结合使用。然后，在其他条件相同的情况下，比较“现在”和“未来”的模拟结果，就可以确定向极地移动进入中纬度地区的热带气旋的强度和频率的变化。该项目旨在解决人们在理解气候变化如何影响离开热带地区、影响高纬度地区的热带气旋子集的强度和频率方面存在的差距。这类热带气旋非常重要，因为正是这些系统在离开热带时，对美国等中纬度地区的主要人口中心产生了最大的影响。考虑到它们的重要性，也许令人惊讶的是，这些系统对气候变化的反应迄今没有得到更多的研究关注。该项目还将确定热带气旋活动的地理和/或季节变化是否会随气候变化而变化。由于该项目的高度技术性，从事该项目的研究生将获得科学计算，数据分析和可视化以及科学传播方面的宝贵技能。将邀请从事该项目的研究生研究助理协助监督本科生研究人员，从而获得领导和指导方面的经验。