Digital High-Speed Spectroscopic Lightning Studies

一台分辨率为5400帧/秒的数码相机将配备由研究人员预先建造的衍射栅，以记录雷暴下自然发生的闪电的光学发射。光谱数据将在380-850 nm范围内获得，从包含闪电元素的整个可见部分开始，闪电元素可能包括回击、阶跃和省道先导、M-冲程和“持续电流”事件(据信对建筑物和设备造成不成比例的闪电损坏)，空间和时间分辨率分别为10‘S米和微秒。这些数据将被分析，以提供通道温度、电子密度和其他热力学信息的测量。观测活动将在气候学春季雷雨最大时期在俄克拉何马州诺曼市国家天气中心的主要地点进行，在淡季在主要调查员的家乡机构(德克萨斯州农工大学)进行。俄克拉荷马州的现场有广泛的气象辅助设施和特殊测量，包括由俄克拉何马大学的另一位美国国家科学基金会支持的研究人员记录的闪电通道的精细分辨率(纳秒级)光学成像。这两个地点都被国家闪电探测网络(NLDN)以及更专业的闪电测绘阵列(LMA)设备所覆盖。总之，这些辅助系统将提供有关闪电通道位置、几何形状和传播(可见和在云中)的上下文4D信息，以及到达地面的闪电通道的极性、估计的峰值电流和闪光多重性(即回击次数)。这项研究的智力价值集中在更好地理解在精细空间和时间分辨率下观察的自然闪电的光谱派生属性，这将导致对自然闪电物理的更好理解。关于闪电对关键大气化学过程的贡献，也有可能有更多的见解。这项工作的更广泛影响将包括培训大学研究生和本科生，扩大到K-12教育机构，以及加强参与照明研究的多所大学和政府机构之间的合作。

A digital camera capable of 5400 frame-per-second time resolution will be equipped with diffraction gratings previously built by the investigator to document optical emissions from naturally occurring lightning flashes beneath thunderstorms. Spectral data will be obtained in the 380-850 nm range from the entire visible portion of lightning channels encompassing flash elements that may include return strokes, stepped and dart leaders, M-strokes, and episodes of "continuing current" (thought to be responsible for a disproportionate amount of lightning damage to structures and equipment) at spatial and temporal resolutions of 10's of meters and microseconds, respectively. These data will be analyzed to provide measures of channel temperature, electron density, and other thermodynamic information. Observing activities will be conducted during the climatological springtime thunderstorm maximum at a primary site located at the National Weather Center in Norman, Oklahoma, and during the off-season at the principal investigator's home institution (Texas A&M University) in southern Texas. Extensive supporting meteorological facilities and special measurements are available at the Oklahoma site, and include finely resolved (nanosecond-scale) optical imaging of lightning channels recorded by another NSF-supported investigator based at the University of Oklahoma. Both sites are encompassed by the National Lightning Detection Network (NLDN) as well as more specialized lightning mapping array (LMA) equipment. Together, these ancillary systems will provide contextual 4D information on lightning channel location, geometry and propagation (both visible and in-cloud), as well as the polarity, estimated peak current and flash multiplicity (i.e. number of return strokes) for lightning channels reaching the ground.The intellectual merit of this research centers upon improved understanding of the spectroscopically-derived properties of natural lighting viewed at fine spatial and temporal resolution, which will lead to improved understanding of the physics of natural lightning. Additional insights are also possible concerning lightning's contribution to key atmospheric chemical processes. Broader impacts of this work will include training of university graduate and undergraduate students, outreach to K-12 educational institutions, and increased collaboration between multiple university and government facilities involved in lighting research.