Collaborative Research: Cloud Top Discharges and their Parent Storms

雷暴是一种高度带电的现象，闪电是由云中的电荷分离形成的。雷暴不仅会产生云对地和云对云的闪电，而且雷暴还会从云的顶部产生向上的放电。这些被称为云顶排放物，根据它们的大小和外观有许多不同的名称，如精灵、小精灵和喷气机。虽然这些排放已经被拍摄下来，但很少有科学研究质量的数据可用于这些事件，并且各种问题仍未得到解答。该合同将涉及两种新仪器的开发和一项多年的观测工作，以提供有关云顶放电的最全面的数据。该项目与社会的相关性在于，向上放电是NOx的强烈生产者，可以影响平流层臭氧化学。该奖项还包括向格鲁吉亚的农村学校提供有关电学和磁学主题的科学教育。该项目的总体目标是研究云顶放电（CTDs）的电性，如精灵、侏儒、精灵、启动器、喷气机和巨型喷气机，以及雷暴是如何产生这些独特事件的。由于先前的观测限制，对这些CTDs的观测很少。在这个项目中，研究小组将开发和部署一种新的地面光谱成像系统，该系统由两台蓝敏高速相机组成。蓝色方面很重要，因为ctd的特征是以蓝色为主，但蓝色和紫外线（UV）光被低层大气严重散射，而且大多数先前的光学成像仪对蓝色/紫外线不敏感。新系统将部署在德克萨斯州，并结合来自甚低频(VLF)/低频（LF）无线电接收器、闪电映射阵列（lma）和传统气象数据的额外观测信息，回答有关CTD电学和形态特性以及CTD雷暴电荷结构特征的关键问题。具体的研究问题包括：ctd的先导体和拖缆动力学是什么，例如先导体的热温度和拖缆的电子能量的演变？•先导到拖缆过渡区域的定量特征是什么？•云上产生的lma如何测量甚高频（VHF） ？什么参数决定CTD的终端高度？•母风暴电荷结构是什么？形成它们的气象过程是什么？•云顶混合和散度、雷暴电荷结构和事件形成之间的关系是什么？•不同的CTDs的风暴结构有什么不同？该奖项反映了美国国家科学基金会的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。

Thunderstorms are highly-electrified phenomena where lightning is formed from the separation of electrical charge within the cloud. Not only do thunderstorms produce cloud-to-ground and cloud-to-cloud lightning, but thunderstorms also can produce upward-pointed electrical discharges from the tops of the clouds. These are known as cloud top discharges and have many different names based on their size and appearance, such as sprites, pixies, and jets. While these discharges have been photographed, there are very few scientific research-quality data available for these events, and a variety of questions remain unanswered. This award will involve the development of two new instruments and a multi-year observational effort to provide the most comprehensive data on cloud top discharges available. The relevance of this project to society is that upward electrical discharges are strong producers of NOx which can affect stratospheric ozone chemistry. This award also includes outreach to rural schools in Georgia to provide science education on the topics of electricity and magnetism. The overall objective of this project is to investigate the electrical nature of cloud top discharges (CTDs) such as sprites, gnomes, pixies, starters, jets and gigantic jets and how thunderstorms produce these unique events. Observations of these CTDs are rare due to prior observational constraints. In this project, the research team will develop and deploy a new ground-based spectroscopic imaging system consisting of two blue-sensitive high-speed cameras. The blue aspect is important because CTDs are characterized by their predominantly blue color, but blue and ultraviolet (UV) light is heavily scattered by the lower atmosphere and most prior optical imagers were not sensitive to blue/UV light. The new system will be deployed in Texas and combined with additional observational information from Very Low Frequency (VLF)/Low Frequency (LF) radio receivers, Lightning Mapping Arrays (LMAs), and traditional meteorological data to answer key questions about the electrical and morphological properties of CTDs and the characterization of CTD thunderstorm charge structures. Specific research questions include:• What are the leader and streamer dynamics of CTDs, such as evolution of thermal temperature for leaders and electron energy for streamers?• What are quantitative characteristics of the leader-to-streamer transition region? • How is the very high frequency (VHF) measured by LMAs produced above the cloud? • What parameters dictate the terminal altitude of a CTD?• What are the parent storm charge structures and what meteorological processes form them?• What is the relationship between cloud top mixing and divergence, the thunderstorm charge structure, and event formation?• How does the storm structure vary for different CTDs?This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.