Collaborative Research: Concentrating Vorticity Near the Ground: Investigation of Supercell Rear-Flank Precipitation, Vorticity Generation, and Transport Processes

合作研究：近地面集中涡度：超级单体后侧降水、涡度产生和传输过程的研究

• 批准号: 0338661
• 负责人: Paul Markowski
• 金额: $ 22.18万
• 依托单位: Pennsylvania State Univ University Park
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2004
• 资助国家: 美国
• 起止时间: 2004-03-15 至 2008-02-29
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0338661&HistoricalAwards=false
• 关键词: Collaborative; Research; Concentrating; Vorticity; Near

Recent research has indicated the possibility of a critical role of the supercell rear flank downdraft (RFD) in the tornadogenesis process. A multi-sensor analysis of the Dimmitt tornadic storm observed during the Verification of Origins of Rotation in Tornadoes Experiment (VORTEX) has revealed vorticity patterns and evolution consistent with processes first described theoretically by prior researchers. Further, the observed patterns were very similar to those in most of the supercell case studies in the literature. In particular, the prior research of the Principal Investigators supported the conceptual model that vorticity is generated baroclinically as air passes through the RFD from rear to front. This baroclinically generated quasi-horizontal vorticity develops in rings about the buoyancy minimum present at the RFD owing to precipitation loading and/or melting/evaporation of hydrometeors. As the rings pass forward through the RFD, their leading sides are tilted upward in the gradient of vertical velocity present just ahead of the RFD, giving them an arch-like configuration. They are subsequently strongly stretched in the low-level updraft, leading to an intensification of a counter-rotating vortex pair (shown, but not elaborated upon, in most historical case studies). In the Dimmitt storm, the cyclonic member of the counter-rotating vortex pair (connected by arches of vortex lines) was augmented by intense low-level tilting of streamwise inflow vorticity. This member subsequently intensified into a tornado through stretching in the low-level updraft.In this research, the Principal Investigators seek to advance the understanding of supercell RFD processes. They will concentrate on the following topics: How is the development of the near-ground, counter-rotating vortex pair governed by downdraft strength, buoyancy, and the ambient shear profile? It is hypothesized that certain shear profiles lead to augmentation of one or both vortices, and/or partial or complete cancellation of one or both.What factors allow for the development of neutral or positively-buoyant (near the ground) RFDs? It is hypothesized that the rate of inflow of potentially cold air aloft into the rear flank, and the distributions and types of hydrometeors, play dominant roles.What factors govern the likelihood of baroclinically generated RFD vorticity being concentrated into a tornadic vortex? Recently, it has been demonstrated that a measurable jump in tornado warning skill by the National Weather Service can be attributed to new scientific knowledge coming from the VORTEX experiment. Prior research findings of these Principal Investigators have been cited in real-time forecast products. The likely societal impact of this research is a continued measurable improvement in tornado forecasts and warnings, leading to continued reductions in losses of property, health, and lives. Further, the Principal Investigators will continue to emphasize direct outreach to the public (web site, public lectures, television documentaries, email queries) as well as to forecasters.

最近的研究表明，超级电池后侧侧面气流（RFD）在龙卷风发生过程中起着关键作用。 对龙卷风实验中旋转起源的验证期间观察到的DIMMITT龙卷风风暴（Vortex）的多传感器分析揭示了涡度模式和与​​先前研究人员在理论上首先描述的过程一致的涡度模式和进化。 此外，观察到的模式与文献中大多数超级案例研究中的模式非常相似。 特别是，先前的主要研究人员的研究支持了概念模型，即当空气从后方到前方通过RFD，涡度是在压力线上产生的。 由于降水量加载和/或融化/或融化/蒸发水合物，这种用于浮力最小值的环上产生的准线性产生的涡度涡度。 当戒指穿过RFD时，它们的领先侧面在RFD前方的垂直速度梯度上向上倾斜，从而使它们具有类似拱形的配置。 随后，它们在低级上升气流中强烈伸展，从而导致反向旋转对的加剧（在大多数历史案例研究中，显示但没有详细说明）。 在Dimmitt Storm中，通过强烈的低级流向流入涡度的低水平倾斜来增强反旋转涡流对的旋风成员（通过涡流线的拱形连接）。 随后，该成员通过在低级上升气流中拉伸到龙卷风。在这项研究中，首席研究人员试图提高对超级电池RFD过程的理解。 他们将专注于以下主题：如何由下降强度，浮力和环境剪切曲线控制的近地，反向旋转对的发展？ 假设某些剪切曲线会导致一个或两个涡流的增强，以及/或部分或完全取消一个或两者。哪些因素允许发展中性或积极成型（接近地面）RFD？ 假设，潜在的冷空气在后侧的流入率，以及氢通量的分布和类型，扮演着主要的角色。哪些因素控制着压力机会产生的RFD涡度的可能性，将RFD涡度集中在龙卷风涡旋中？ 最近，已经证明，国家气象局的龙卷风警告技巧可衡量的可衡量，这可以归因于Vortex实验的新科学知识。 这些主要研究人员的事先研究发现已被实时预测产品引用。 这项研究的社会影响可能是龙卷风预测和警告的持续可衡量改善，导致财产，健康和生活的损失持续减少。 此外，首席调查人员将继续强调直接向公众（网站，公共演讲，电视纪录片，电子邮件查询）以及预报员的直接推广。