Digital High-Speed Spectroscopic Lightning Studies

一个能够每秒5400帧时间分辨率的数码相机将配备由研究人员先前建造的衍射光栅，以记录雷暴下自然发生的闪电的光发射。光谱数据将在380-850纳米范围内从闪电通道的整个可见部分获得，包括闪电元素，可能包括回击，阶梯和飞镖领导者，M-冲程和“持续电流”事件。（被认为是造成对结构和设备的不成比例的闪电损坏的原因）在10米和微秒的空间和时间分辨率下，分别这些数据将进行分析，以提供测量通道温度，电子密度和其他热力学信息。观测活动将在气候学春季雷暴最大期间在位于俄克拉荷马州诺曼的国家气象中心的一个主要地点进行，并在淡季期间在主要研究者位于得克萨斯州南部的家乡机构（得克萨斯农工大学）进行。俄克拉荷马州的站点有广泛的支持性气象设施和特殊测量，包括由另一个由国家科学基金会支持的位于俄克拉荷马州大学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。这两个站点都包含在国家闪电探测网络（NLDN）以及更专业的闪电测绘阵列（LMA）设备中。这些辅助系统将共同提供有关闪电通道位置、几何形状和传播的上下文4D信息（可见和云内），以及极性，估计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提高对光谱学的理解上-在精细的空间和时间分辨率，这将导致自然闪电的物理学更好的理解自然照明的衍生属性。关于闪电对关键大气化学过程的贡献，也有可能获得更多的见解。这项工作的更广泛的影响将包括大学研究生和本科生的培训，K-12教育机构的推广，以及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.