Challenges in Understanding Tornadogenesis and Related Phenomena

后侧下沉气流(RFD)、龙卷风气旋(TC)和龙卷风是与超级单体雷暴有关的一些最独特的动力和运动学现象。自从使用移动平台的各种多普勒雷达技术和最近的极化雷达技术问世以来，龙卷风以及较少出现的RFDS和龙卷风气旋得到了严格的研究。此外，文献中还介绍了在很小的网格间距(25到125米)下使用先进的微物理和高阶数值的数值模式模拟的一些研究。然而，关于热带气旋和热带气旋的起源和演变，以及在热带气旋和龙卷风的生命周期中可能起到的作用，人们揭示得很少。这项研究的主要目的是：a)研究控制热带气旋起源和时空演变的动力和热力学过程。b)研究控制热带气旋起源和时空演变的动力和热力学过程。C)在此基础上，开发一个概念模式，阐明中气旋、龙卷风和龙卷风之间的动力学差异，如果这些差异存在的话。希望通过使用龙卷风实验涡旋和VORTEX2中验证的旋转原点的观测数据，以及使用Straka大气模式的数值模拟信息，可以获得关于RFDS的演变、它们与TCS的生命周期的联系以及TCS与龙卷风的关系的新知识。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的RFD之间的水平涡度。反过来，RFD似乎部分是超级单体特有的小尺度降水结构的结果：钩状回波和/或一个狭窄的下降反射率核心。在一些超级单体中，在主要垂直气流之间产生的初始水平涡线在上升气流中向上拉起，导致拱形涡线和与之相关的低层反旋转涡线在后侧阵风锋汇合区出现。在某些条件下，这一过程似乎受负浮力的控制，龙卷风可能发生在反旋转涡旋对的气旋成员附近。这项研究工作利用了最先进的观测、观测分析工具套件和云模型，有望有助于阐明RFDS、TC成因和龙卷风发生之间的物理和动力学关系。广泛的影响：该项目在公共安全领域具有相当大的价值，特别是WSR-88D雷达即将进行两次升级。这些雷达的第一次升级将包括方位向过采样到1/2度，以及消除当前的径向反射率平滑。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偏振雷达能力。通过利用具有双极化分集能力的多普勒雷达诊断后侧降水深度和水流星结构，可以直接将对RFD浮力和龙卷风气旋成因的新认识用于龙卷风警报过程。最终，业务气象学家很可能能够更好地区分潜在的龙卷风超级单体和非龙卷风超级单体。其中一位首席绩效指标一直积极通过研讨会将新知识直接传授给国家气象局和其他预测组织。此外，所有合作的私人投资机构都参加会议，并邀请研讨会交流新的知识。这些类型的外联工作计划继续下去。联合PI正在考虑建立一个以K-12为导向的网站，该网站描述了与龙卷风有关的各种形式的恶劣天气。资金将支持俄亥俄州立大学的一名教员、两名高级研究科学家(其中一名是女性)和两名女性博士生从事涡旋、VORTEX2和其他观测分析以及数值模拟结果的解释工作。

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.