Formation and Structure of Wall Clouds Observed During VORTEX2

这项研究的重点是与超级单体雷暴相关的壁云的形成和结构，这些雷暴是在验证龙卷风实验II（VORTEX 2）中旋转起源期间观察到的。 这项研究将通过分析超级单体钩状区域的摄影测量分析照片和高清视频来完成，这些照片和视频也同时被移动的多普勒雷达扫描。 下面的目标将通过整合超级单体钩状区域的高分辨率单和双多普勒分析的视觉数据来实现。 地面速度跟踪显示技术将用于获得风暴的轴对称风场，具有良好的可视数据和仅用一部雷达的覆盖范围。 探测、移动的中尺度网和地面站的数据也将被纳入，以记录环境和超级单体钩区的热力学特征。第一个目标是了解负责壁云形成的过程。目前对壁云形成的理解是基于25年前发表的理想化数值模拟和目视观测。 将检验三个假设。 第一种是超级单体阵风锋后面的低层空气被吸入上升气流，并在比主云底低的高度饱和。 第二，壁云是由绝热冷却形成的，绝热冷却与壁云中可能存在的环流产生的压力不足有关。 第三，壁云的形成是由于附着在主云底的低空飞毛腿上升。第二个目标是记录龙卷风和非龙卷风壁云内的降水（反射率）、涡度、垂直运动、扰动压力、角动量和水平风场的三维结构。这项分析将首次记录龙卷风和非龙卷风壁云之间的差异和/或相似之处。它也将有助于定义的规模和强度的壁云相对于上升气流，低层中气旋，低降水，经典和高降水的超级单体在VORTEX 2采样钩区域内的降水分布之间的关系。最后，它将有可能比较壁云的视觉特征与多普勒雷达数据的运动学结构。智力优点：与超级单体雷暴相关的壁云已经在许多观测研究中得到了直观的记录。 它通常被认为与低层上升气流有关，并且经常是龙卷风发生的位置。 令人惊讶的是，迄今为止还没有观测研究系统地研究了壁云的形成，结构和演变相对于低层上升气流，中气旋和降水分布的钩区。 因此，实现上述目标将增强我们对超级单体雷暴的低层视觉结构和演变的基本了解。更广泛的影响：预计这项研究的结果将纳入国家气象局Skywarn风暴观测员培训中。 天文警报观测员对在恶劣天气情况下准确发布视觉天气信息至关重要。该项目将使一些本科生接触到研究过程，并将加强林登州立学院的研究基础设施（也用于教学）。研究成果将被纳入许多本科课程。

This research focuses on the formation and structure of wall clouds associated with supercell thunderstorms that were observed during the Verification of the Origins of Rotation in Tornadoes Experiment II (VORTEX2). The study will be accomplished through analysis of photogrammetrically analyzed photos and high-definition video of the hook region of supercells that were also concurrently being scanned by mobile Doppler radars. The objectives below will be met by integrating the visual data with high-resolution single and dual-Doppler analyses of the supercell hook region. The Ground Based Velocity Track Display (GBVTD) technique will be used to obtain axisymmetric wind fields for storms with good visual data and coverage with only one radar. Sounding, mobile mesonet, and surface station data will also be incorporated to document the thermodynamic characteristics of the environment and supercell hook region.The first objective is to understand the processes responsible for wall cloud formation.Current understanding of wall cloud formation is based on idealized numerical simulations published more than 25 years ago and visual observations. Three hypotheses will be tested. The first is that lower èe air behind the supercell gust front is ingested into the updraft and saturates at a lower altitude than the primary cloud base. Second, the wall cloud is formed by the adiabatic cooling associated with the pressure deficit created by circulation that may be present in the wall cloud. Third, wall cloud formation is due to rising low-level scud that attaches to the primary cloud base.The second objective is to document the three-dimensional structure of the precipitation (reflectivity), vorticity, vertical motion, perturbation pressure, angular momentum, and horizontal wind fields within tornadic and non tornadic wall clouds. This analysis will, for the first time, document the differences and/or similarities between tornadic and nontornadic wall clouds. It will also help to define the relationship between the scale and intensity of the wall cloud relative to the updraft, low-level mesocyclone, and precipitation distribution within the hook region for lower precipitation, classic, and high precipitation supercells sampled during VORTEX2. Finally, it will be possible to compare the visual characteristics of the wall cloud with the kinematic structure derived from the Doppler radar data.Intellectual Merit: The wall cloud associated with supercell thunderstorms has been visually documented in many observational studies. It is generally accepted to be associated with the low-level updraft and is often the location of tornadogenesis. Amazingly, no observational study to date has systematically examined wall cloud formation, structure, and evolution relative to the low-level updraft, mesocyclone, and precipitation distribution within the hook region. Hence, realizing the above stated objectives would enhance our fundamental understanding of the low-level visual structure and evolution of supercell thunderstorms.Broader Impacts: It is anticipated that results from this research will be incorporated into the National Weather Service Skywarn storm spotter training. Skywarn spotters are vital to the accurate dissemination of visual weather information during severe weather situations. The project will expose a number of undergraduate students to the research process and will enhance the research infrastructure (also used in teaching) at Lyndon State College. Research results will be incorporated into many of the undergraduate classes.