Challenges in Understanding Tornadogenesis and Related Phenomena

了解龙卷风发生及相关现象的挑战

• 批准号: 1036237
• 负责人: Jerry Straka
• 金额: $ 74.98万
• 依托单位: University of Oklahoma Norman Campus
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2011
• 资助国家: 美国
• 起止时间: 2011-04-01 至 2017-03-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1036237&HistoricalAwards=false
• 关键词: Challenges; Understanding; Tornadogenesis; Related; Phenomena

Rear flank downdrafts (RFD), tornado cyclones (TC), and tornadoes are some of the most distinctive dynamic and kinematic phenomena associated with supercell thunderstorms. Tornadoes, and less frequently RFDs and tornado cyclones, have been rigorously studied since the advent of various Doppler, and more recently polarimetric, radar technologies employing mobile platforms. In addition, a few studies using numerical model simulations with advanced microphysics and high-order numerics at very small grid spacings (25 to 125 m) have been presented in the literature. However, little has been revealed about the origins and evolution of the RFD and TC, and the possible role the RFD plays in the life cycle of the TC and tornado. The main objectives of this research are:a) To examine the dynamic forces and thermodynamic processes governing the origins, and temporal and spatial evolution of the RFD.b) To examine the dynamic forces and thermodynamic processes governing the origins, and temporal and spatial evolution of the TC. c) Based on this examination, develop a conceptual model that elucidates the dynamical differences between mesocyclones, tornado cyclones, and tornadoes, if these differences exist.It is hoped that new knowledge might be gained regarding the evolution of RFDs, their association with the life cycles of TCs, and in what ways TCs are related to tornadoes, by using observational data from the Verifications of the Origins of Rotation in Tornadoes Experiments VORTEX and VORTEX2, as well as numerically modeled information using the Straka Atmospheric Model.Intellectual Merit: Supercell RFDs, the genesis of TCs, and tornadoes are the result of a complex series of nonlinear processes. Evidence suggests that the vorticity in a tornado originates as horizontal vorticity between the supercell updraft and an associated RFD. The RFD, in turn, appears to be partially the result of small-scale precipitation structures unique to supercells: the hook echo and/or a narrow descending reflectivity core. In some supercells, the initially horizontal vortex lines generated between the major vertical drafts are drawn upward in the updraft, which leads to arched vortex lines and associated low-level counter-rotating vortices in the rear flank gust front convergence zone. Under certain conditions, this process appears to be governed by the degree of negative buoyancy in the RFD, and tornadogenesis can occur in the vicinity of the cyclonic member of the counter-rotating vortex pair. This research work, which utilizes state-of-the-art observations, observational analysis tool suites and cloud models, will hopefully help elucidate the physical and dynamical relationships between RFDs, TC genesis, and tornadogenesis.Broader Impacts: The project has considerable value in the area of public safety, especially with two upgrades forthcoming to the WSR-88D radars. The first of these radar upgrades will include over sampling to 1/2 deg in azimuth and removal of the current radial smoothing of reflectivity. The second upgrade will be the introduction of dual polarimetric radar capabilities across the nation sometime during late 2010. New understanding of RFD buoyancy and tornado cyclone genesis can be used directly in the tornado warning process by diagnosing rear-flank precipitation depth and hydrometeor structure using Doppler radars with dual-polarization diversity capability. Eventually, it is likely that operational meteorologists will be able to make much better distinctions between potentially tornadic and non-tornadic supercells. One of the lead PIs has been active in transferring new knowledge directly to NWS and other forecasting organizations via seminars. Also, all of the co-PIs participate in conferences, and invited seminars to communicate new knowledge. These types of outreach work are planned to continue. The co-PIs are contemplating a K-12 oriented website, which describes various forms of severe weather associated with tornadoes. Funding will support a faculty member at OU, two senior research scientists (one of which is female), and two female Ph.D. students to work on interpretation of VORTEX, VORTEX2 and other observational analyses as well as numerical simulation results.

后翼下沉气流（RFD）、龙卷风气旋（TC）和龙卷风是与超级单体雷暴相关的一些最独特的动力学和运动学现象。自从各种多普勒雷达技术出现以来，以及最近采用移动的平台的偏振雷达技术，人们对龙卷风以及频率较低的RFD和龙卷风气旋进行了严格的研究。 此外，一些研究使用数值模型模拟与先进的微物理和高阶数值在非常小的网格间距（25至125米）已在文献中。 然而，很少有人透露的起源和演变的RFD和TC，以及可能的作用RFD中扮演的TC和龙卷风的生命周期。 本研究的主要目的是：（1）探讨控制热带气旋形成及其时空演变的动力和热力过程;（B）探讨控制热带气旋形成及其时空演变的动力和热力过程。 c）在此研究的基础上，建立一个概念模型，阐明中气旋、龙卷风气旋和龙卷风之间的动力学差异，如果这些差异存在的话。希望可以获得关于RFD的演变、它们与TC生命周期的联系以及TC与龙卷风的关系的新知识，利用验证龙卷风实验VORTEX和VORTEX 2中旋转起源的观测数据，以及利用斯特拉卡大气模型数值模拟的信息。超级单体RFD、TC的形成和龙卷风是一系列复杂的非线性过程的结果。 有证据表明，龙卷风中的涡度起源于超级单体上升气流和相关RFD之间的水平涡度。 RFD，反过来，似乎是部分的结果，小规模的降水结构独特的超级单体：钩回波和/或一个狭窄的下降反射率的核心。 在某些超级单体中，在主要垂直气流之间产生的最初水平涡线在上升气流中被向上拉，这导致在后翼阵风锋辐合区产生拱形涡线和相关的低空反向旋转涡。 在某些条件下，这一过程似乎是由在RFD的负浮力的程度，和龙卷风的发生可以发生在附近的反旋转涡对的气旋成员。 这项研究工作，它利用国家的最先进的观测，观测分析工具套件和云模型，将有希望帮助阐明RFDs，TC成因和tornadogenesic.Broader影响之间的物理和动力学关系：该项目在公共安全领域具有相当大的价值，特别是两个升级即将WSR-88 D雷达。 这些雷达升级中的第一个将包括在方位角上过采样到1/2度，并去除当前反射率的径向平滑。 第二次升级将是在2010年底的某个时候在全国范围内引入双极化雷达能力。 通过使用具有双极化分集能力的多普勒雷达诊断后翼降水深度和水凝物结构，对RFD浮力和龙卷风气旋成因的新认识可以直接用于龙卷风预警过程。 最终，业务气象学家可能能够更好地区分潜在的龙卷风和非龙卷风超级单体。 其中一个主要的项目执行人一直积极通过研讨会向国家气象局和其他预报组织直接传授新知识。 此外，所有共同PI都参加会议，并邀请研讨会交流新知识。 计划继续开展这类外联工作。 联合PI正在考虑建立一个面向K-12的网站，该网站描述了与龙卷风相关的各种形式的恶劣天气。 资金将用于支持一名教员，两名高级研究科学家（其中一名是女性）和两名女博士。学生们将致力于解释VORTEX，VORTEX 2和其他观测分析以及数值模拟结果。