Digital High-Speed Spectroscopic Lightning Studies

一台每秒分辨率为5400帧的数码相机将配备衍射光栅，该衍射光栅是由研究人员先前建造的，用于记录雷暴下自然发生的闪电的光学发射。光谱数据将在380- 850nm范围内从闪电通道的整个可见部分获得，包括闪光元素，可能包括回击，阶梯和镖头，m -冲程和“持续电流”片段（被认为是造成建筑物和设备不比例的闪电损坏的原因），分别以10米和微秒的空间和时间分辨率获得。这些数据将进行分析，以提供通道温度、电子密度和其他热力学信息的测量。观测活动将在位于俄克拉何马州诺曼的国家气象中心的一个主要地点进行，并在德克萨斯州南部的主要研究者的家庭机构（德克萨斯农工大学）的淡季进行。在俄克拉何马站点有广泛的支持气象设施和特殊测量，包括由另一位在俄克拉何马大学的nsf支持的研究者记录的精细分辨率（纳秒级）的闪电通道光学成像。这两个站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）设备所包围。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（可见和云内）的上下文4D信息，以及到达地面的闪电通道的极性、估计峰值电流和闪光多重度（即回击次数）。这项研究的智力价值在于提高了对自然光线在精细空间和时间分辨率下的光谱衍生特性的理解，这将有助于提高对自然闪电物理学的理解。关于闪电对关键大气化学过程的贡献，也可能有更多的见解。这项工作的更广泛影响将包括大学研究生和本科生的培训，扩展到K-12教育机构，以及增加多个大学和政府机构之间在照明研究方面的合作。

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.