Improving our Understanding of Tornadic Storms using VORTEX2 Observations and Idealized Simulations

这项研究的目的是提高我们对超级单体雷暴内发生的过程的理解，这些过程控制着表面旋转的发展，可能的强化，以及此后使用最先进的观测结果的环流演变。 超级单体风暴中层旋转的产生是众所周知的，但是，关于低层旋转的发展以及随后旋转增强为龙卷风强度，还有一些悬而未决的问题。本研究的主要目的是--研究超级单体中的低层环流如何受风暴环境和外流浮力的控制--研究环境不均匀性和风暴相互作用如何影响低层旋转的发展和演变-确定地面摩擦如何影响近地面垂直涡度的发展-探索小尺度外流“浪涌”的起源以及超级单体后侧的下降降水轴及其对低层旋转发展和演变的影响。尽管科学家们很好地掌握了风暴环境中的垂直风切变和不稳定性如何促进上升气流旋转，但他们仍然缺乏对风暴环境的其他方面的透彻了解，包括环境异质性，影响超级单体风暴中低层旋转的发展和维持。关于风暴的相互作用、突然的降水脉冲和外流潮如何影响低层旋转，人们所知更少。 此外，科学家们现在才刚刚触及表面摩擦如何可能是发展龙卷风的一个重要角动量来源（而不是简单地通过增强通过其他方式产生的近地表角动量会聚来在龙卷风形成中发挥“间接”作用）。更广泛的影响：更好地了解龙卷风的起源，维持和消亡将对我们预测和警告这些恶劣天气事件并减少伤亡的能力产生广泛的影响。 国家气象局（NWS）警报发布从县到更灵活的多边形的迁移现在提供了一个机会，以调整警报的大小（和，隐含的，警报的持续时间）的龙卷风的预期寿命。 这项研究可能有助于改善预报员预测龙卷风可能持续多久的指导。 除了在会议上向学术界通报调查结果外，两个项目执行主任还通过研讨会直接参与向核武器国家转让新知识。 两个PI还积极参与广泛的外联活动，包括向国会自然灾害核心小组介绍情况，向国家科学院大气科学和气候委员会介绍情况，担任龙卷风IMAX电影的科学顾问，开发K-12教育材料，向非科学家团体（例如，小学、风暴观测员等），和发展博物馆展品。

This research is targeted to improve our understanding of the processes occurring within supercell thunderstorms that control the development of rotation at the surface, its possible intensification, and the evolution of the circulations thereafter using state-of-the-art observations from the Second Verification of the Origins of Rotation in Tornadoes Experiment (VORTEX2) and a hierarchy of numerical models. The generation of midlevel rotation in supercell storms is well understood, but there are a number of outstanding questions pertaining to the development of rotation at low levels and the subsequent intensification of that rotation to tornado strength.The main objectives of this research are- To examine how low-level circulation in supercells is controlled by the storm environment and buoyancy of the outflow- To investigate how environmental heterogeneity and storm interactions influence the development and evolution of low-level rotation- To determine how surface friction affects the development of near-surface vertical vorticity- To explore the origins of small-scale outflow "surges" and descending precipitation shafts on the supercell's rear flank and their influence on the development and evolution of low-level rotationIntellectual Merit:Despite having a good grasp of how vertical wind shear and instability in a storm's environment promote updraft rotation, scientists still lack a thorough understanding of how many other aspects of a storm's environment, including environmental heterogeneity, influence the development and maintenance of low-level rotation in supercell storms. Even less is known about how storm interactions, sudden precipitation impulses, and outflow surges affect low-level rotation. Moreover, scientists are just now scratching the surface on how surface friction might be an important source of angular momentum for developing tornadoes (as opposed to simply playing an "indirect" role in tornadogenesis by enhancing near-surface convergence of angular momentum that arises through other means).Broader Impacts:A greater understanding of tornado genesis, maintenance, and demise will have a broad impact on our ability to predict and warn of these severe weather events and to reduce casualties. The migration of National Weather Service (NWS) warning issuance from counties to more flexible polygons now affords the opportunity to tailor the size of the warning (and, implicitly, the duration of the warning) to the expected longevity of the tornado. This research may help improve the guidance that can be used by forecasters to anticipate how long a tornado might last. In addition to communicating findings to the academic community at conferences, both PIs have been directly involved with the transfer of new knowledge to the NWS via seminars. Both PIs also have been active in a wide range of outreach activities, including briefing the Congressional Natural Hazards Caucus, briefing the National Academies Board on Atmospheric Sciences and Climate, serving as science advisers for an IMAX film on tornadoes, developing K-12 educational materials, giving talks to nonscientist groups (e.g., elementary schools, storm spotters, etc.), and developing museum exhibits.