The Dynamics and Energetics of Small-Scale Atmospheric Vortices

小尺度大气涡旋的动力学和能量学

• 批准号: 9727150
• 负责人: Douglas Lilly
• 金额: $ 23.61万
• 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: 1998
• 资助国家: 美国
• 起止时间: 1998-07-01 至 2001-12-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=9727150&HistoricalAwards=false
• 关键词: Dynamics; Energetics; Small; Scale; Atmospheric

9727150 Lilly The boundary layer vortex, which includes the relatively well-known dust devil, generally takes the form of a benign columnar atmospheric vortex. It is less well understood than its more dramatic cousin, the tornado, but recent evidence suggests that it may be more common than originally thought and may be important as a controlling factor of boundary layer structure and interactions. An investigation is proposed of the dynamics of the initiation and maintenance of boundary layer vortices, in particular, the dust devil vortex. This research will be primarily a theoretical and numerical simulation study, but may include limited acquisition and analysis of observational data, especially from mobile Doppler radar. As with their larger scale relatives, the principal scientific question regarding dust devils is their source of rotation. A single answer probably doesn't exist. An ambient source of vertical vorticity may be found, in some cases, as an environmental feature, or it may be generated locally. In the absence of horizontal shear, the vertical vorticity in a dust devil might form from tilting of horizontal vorticity, either that of the mean shear in the surface layer or again by local generation. In absence of other environmental sources, pre-existing convective cells and their mutual interactions have been evidenced as sources of both vertical and horizontal vorticity. The study will consider all these possibilities, but the primary focus is on the last, due partly to its mostly unexplained appearance in several laboratory experiments and field projects. By inhibiting dissipation and diffusion, highly helical dust devils may transport near-surface air higher into the atmosphere than can non-rotating thermals. Thus they may be important or even dominant in establishing the height of the mixed layer, controlling or modifying heat, momentum and particulate transports. These energetic and transport properties of rotating ther mals will also be considered in this study. The objectives of the proposed research are summarized as the following: 1. To seek and compare mechanisms by which convective thermals acquire rotation and become quasi-vertical columnar vortices in either the presence or absence of horizontal or vertical wind shear; 2. To examine the energetics associated with the maintenance of such vortices; 3. To evaluate and compare the vertical transports of heat, momentum and particulates by rotating and non-rotating boundary layer thermals From this study, some necessary conditions for the formation and maintenance of boundary layer vortices will be determined. Results may shed some light on the formation mechanisms of tornadoes. Knowledge gained of the role that boundary layer vortices play in transports of heat, momentum, chemicals and particulates may have impact on /pollution studies, hazardous waste management, and the prediction of initiation of deep convection. ***

9727150礼来的边界层涡流，其中包括相对众所周知的尘埃，通常采用良性柱状大气涡流的形式。 它比龙卷风更具戏剧性的表弟所理解，但最近的证据表明，它可能比原始思想更为普遍，并且可能是边界层结构和相互作用的控制因素。 提出了对边界层涡流启动和维护的动力学的研究，尤其是尘埃魔鬼涡流。 这项研究将主要是一项理论和数值模拟研究，但可能包括对观察数据的获取和分析，尤其是移动多普勒雷达。 与他们较大的亲戚一样，关于尘埃魔鬼的主要科学问题是它们的旋转来源。 一个答案可能不存在。 在某些情况下，可以在某些情况下发现垂直涡度的环境来源，或者可以在本地生成。 在没有水平剪切的情况下，尘埃魔鬼中的垂直涡度可能是由于水平涡度的倾斜而形成的，即表面层中的平均剪切或局部发电的平均剪切。 在没有其他环境来源的情况下，已经证明对流细胞及其相互作用已被证明是垂直和水平涡度的来源。 该研究将考虑所有这些可能性，但主要重点是最后一个，部分是由于其在几个实验室实验和现场项目中大部分无法解释的外观。 通过抑制耗散和扩散，高度螺旋灰尘的魔鬼可以将近地面空气传输到大气中，而不是非旋转热的热量。因此，它们可能在建立混合层的高度，控制或修改热量，动量和颗粒物转运方面很重要甚至主导。 在本研究中，还将考虑这些旋转旋转的能量和运输特性。 拟议研究的目标总结为以下内容：1。寻求和比较对流热旋转并在存在或不存在水平或垂直风剪的情况下旋转并成为准垂直柱状涡流的机制； 2。检查与这种涡旋的维持相关的能量； 3。为了通过旋转和非旋转边界层热量来评估和比较热量，动量和微粒的垂直运输，将确定边界层涡流的形成和维持的一些必要条件。 结果可能会阐明龙卷风的形成机理。 知识获得了边界层涡流在热，动量，化学物质和微粒传输中发挥作用的作用，可能会影响 /污染研究，危险废物管理以及对对流的启动的预测。 ***