Diagnose and Understand the Mechanisms behind Warm Season Extreme Weather over Central and Intermountain United States

持续干旱、热浪、火灾等极端天气是引发自然灾害的主要原因。 近几十年来，它对生命、公共卫生、经济和环境的影响迅速升级。 例如，2018年加州的野火，由密集的火灾天气引发，已造成超过1261亿至1929亿美元的经济损失。然而，我们并不完全了解其根本原因。 例如，以下问题仍然困扰着科学界。 为什么在相似的大气流动模式下，极端事件有时会发生，而在其他时间不会发生？ 为什么暖季极端干旱和炎热的日子有时会一起发生，而不是在其他时候？ 为什么一些极端天气类型，如美国西部最大的野火期间的火灾天气，与20世纪80年代和90年代的天气相比，自2000年以来的天气环流似乎变得不那么容易解释？ 该项目将应用最先进的统计分析来捕捉导致极端事件的天气风模式的多样性和复杂性。 更重要的是，云、降水和气溶胶在加剧极端天气中的作用将被研究。 此外，还将采用综合办法，系统地描述极端干旱和潮湿时期、炎热天气、火灾天气和洪水背后的大气物理和动态过程以及地表反馈。 多方面的综合办法将澄清大气动力学和物理过程在确定极端天气和多种极端天气类型同时发生方面的相对作用。 这种方法可能导致从事件为基础的和天气环流为重点的方法，占主导地位的文献在这一研究领域的范式转变，并显着推进我们对极端天气的理解，特别是对于那些不能充分解释的天气环流异常。 该项目将培训一名女博士生、本科暑期研究实习生和一名博士后研究员，并将其研究成果纳入一门大型高年级本科理科课程。 这些活动将有助于国家科学基金会的教育使命和未来的劳动力的物理和动力气象学。 通过媒体进行的公众宣传将使PI能够将该项目关于极端天气的最新研究成果转化为对社会有意义甚至可采取行动的信息。 该项目由NSF物理和动力气象学和气候以及大规模动力学项目共同资助。该奖项反映了NSF的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。

Extreme weather, such as persistent dry spells, heatwaves, fire weather, is a major cause of natural disasters. Its impacts on lives, public health, economy, and environment have been escalating rapidly in recent decades. For example, the wildfires in 2018 over California, induced by intensive fire weather, have caused over $126.1-192.9 billion economic loss. Yet, we do not fully understand its underlying causes. For example, the following questions are still perplexing the scientific community. Why do extreme events occur sometimes, but not at other times under similar atmospheric flow patterns? Why do warm season extreme dry spells and hot days occur together sometimes, but not at other times? Why do some extreme weather types, such as fire weather during the largest wildfires in western United State, appear to become less explainable by the synoptic circulation since 2000 compared to those from the time in the 1980s’ and 90s’? This project will apply state-of-the-art statistical analyses to capture the variety and complexity of the synoptic wind patterns responsible for the extreme events. More importantly, the roles of clouds, precipitation, and aerosols relative to atmospheric dynamic process in intensifying extreme weather will be investigated. Furthermore, an integrated approach will be applied to systematically characterize the atmospheric physical and dynamic processes and land surface feedbacks behind extreme dry and wet spells, hot days, fire weather and floods. The multifaceted and integrated approach will clarify the relative roles of the atmospheric dynamics and physical processes in determining extreme weather and concurrence of multiple extreme weather types. Such an approach could lead to a paradigm shift from event-based and synoptic-circulation-focused approaches that have dominated the literature in this research area, and significantly advance our understanding of extreme weather, especially for that which cannot be sufficiently explained by synoptic circulation anomalies. The project will train a woman PhD student, undergraduate summer research interns, and a postdoctoral researcher, and incorporate its research results into a large upper-division undergraduate science course. These activities will contribute to the NSF educational mission and future workforce of physical and dynamic meteorology. The proposed public outreach through media will enable the PI to translate the latest research result about extreme weather from this project to meaningful or even actionable information for society. The project was co-funded by NSF Physical and Dynamic Meteorology and Climate and Large-scale Dynamics programs.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.