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.

后侧侧面气流（RFD），龙卷风旋风（TC）和龙卷风是与超级细胞雷暴有关的一些最独特的动态和运动学现象。自多多普勒出现以及最近使用移动平台的雷达雷达技术出现以来，龙卷风，RFD和龙卷风旋风的频率较低。 此外，文献中介绍了一些使用高级微型物理学和高级数字的数值模型模拟（25至125 m）的研究。 但是，关于RFD和TC的起源和演变以及RFD在TC和TORNADO生命周期中的可能作用几乎没有揭示。 这项研究的主要目的是：a）检查控制起源的动态力和热力学过程，以及rfd.b的时间和空间演化，以检查控制原始的动态力和热力学过程，以及TC的时间和空间进化。 c）基于这项检查，开发了一个概念模型，该模型阐明了中环酮，龙卷风旋风和龙卷风之间的动态差异，如果存在这些差异，希望可以通过与TCS的生命相关的tcs cosition to tonsifition of tcs of tcs of tcs of tcs of tcs of tcs的发展，从而获得了新知识。在龙卷风中，实验涡流和涡流2以及使用Straka大气模型进行了数值建模的信息。IntlectualFure：SuperCell RFD，TCS的起源和龙卷风是复杂的一系列非线性过程的结果。 有证据表明，龙卷风中的涡度起源于超级电池上升气流和相关RFD之间的水平涡度。 反过来，RFD似乎是超级降水结构的部分结果：钩子回声和/或狭窄的下降反射率核心。 在某些超级电池中，在上升气流中向上绘制了最初生成的水平涡流线，这导致了拱形涡流线和相关的低级反旋转涡流，并在后侧面阵风前融合区域中。 在某些条件下，该过程似乎受RFD中负浮力的程度支配，并且在反旋转涡流对的旋风成员附近可能发生tornadegenese。 这项利用最先进的观察，观察分析工具套件和云模型的研究工作将有望阐明RFD，TC Genenes和Tornadogenesis之间的物理和动态关系。Broader的影响：该项目在公共安全领域具有相当大的价值，尤其是两个升级到即将到来的WSR-88D radars的两个升级。 这些雷达升级中的第一个将包括对方位角的采样至1/2度，并去除当前反射率的径向平滑。 第二次升级将是2010年底某个时候在全国范围内引入双偏光雷达功能。通过诊断具有双层化多极化能力的多普勒雷达的龙卷风警告过程，可以直接在龙卷风警告过程中直接了解RFD浮力和龙卷风旋风的创世纪的新了解。 最终，运营气象学家很可能能够在潜在的龙卷风和非龙卷风中做出更好的区别。 PIS之一一直积极通过研讨会将新知识直接转移到NWS和其他预测组织。 此外，所有共同主题都参加会议，并邀请研讨会传达新知识。 这些类型的外展工作计划继续进行。 Co-Pis正在考虑一个面向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。 资金将支持OU的一名教职员工，两名高级研究科学家（其中一位是女性）和两位女性博士学位。学生努力解释涡流，涡流2和其他观察性分析以及数值模拟结果。