Fundamental Photographic Observations of Triggered Lightning

本研究的目的是获取和分析1997年夏天在佛罗里达州布兰丁营地获得的高时间分辨率触发闪电的照片记录。所获得的数据将用于研究1)通道形成过程，2)回程行程和镖头直径随时间的发展，以及3)通道微尺度扭曲的演变。这些实验将产生独特的数据集，这些数据集从根本上来说是新的，对于测试新出现的闪电放电不同阶段的模型至关重要。拟议的录音将在两个不同的地点进行。一个较远的地点（约1公里）将被用来提供沿云底以下大部分通道传播的发光闪电分量的整体记录。一个“近摄影站点”（80米外）也被提议用于记录放电过程中闪电通道演变的新细节。所获得的全部摄影记录将与参加这项运动的其他研究人员同时获得的其他数据集相关联并加以补充。远距离记录将使用近紫外照相系统记录闪电通道的形成过程；这提供了放电初始阶段的优越渲染。近地点的实验将提供相同雷击的闪电通道横截面的高时间分辨率图像，这些记录是从只有8毫米范围的垂直部分获得的。这些近距离记录将产生对发光通道直径小至6毫米的直接测量，时间分辨率为0.9毫秒。一旦获得10-20个回射图像，将尝试从通道段高空对向下传播的导元或导元阶跃的截面进行成像，因为导元发光直径以前没有直接检查过。相同视场的取景照片（4000帧/秒）将记录微尺度（~2厘米）上通道的运动和几何变化。预计在支助的第一个夏季，可以在一次外地运动中获得实地观察结果。该项目的剩余部分将用于分析摄影数据本身，并将这些结果用于与其他研究人员的合作分析。

Idone/Abstract The objective of this research is the acquisition and analysis of highly time-resolved photographic records of triggered lightning flashes to be obtained during the summer of 1997 at Camp Blanding, Florida. The data acquired will allow study of 1) the channel creation process, 2) the development of the return stroke and dart-leader diameter with time, and 3) the evolution of channel microscale tortuosity. These experiments will yield unique data sets that are fundamentally new and that could be critical in the testing of newly emerging models of different phases of the lightning discharge. The recordings proposed would be made from two separate sites. A distant site (~ 1 km away) would be used to provide an overall record of the luminous lightning components propagating along most of the channel below cloud base. A "near photographic site (80 m away) is also proposed to record new details of the evolution of lightning channels during the course of the discharge. The totality of photographic records obtained would correlate with and complement other data sets to be acquired simultaneously by other researchers participating in this campaign. The distant-site recordings would document the creation of the lightning channel by the initial leader process using a near-UV photographic system; this provides a superior rendering of the initial phase of the discharge. The near-site experiments would provide highly time-resolved imagery of the cross-sections of lightning channels for the same strokes, these records being attained from a vertical section only 8 mm in extent. These close-up recordings would yield a direct measurement of the luminous channel diameter as small as 6mm with a time resolution of 0.9 ms. Once 10-20 return stroke images are obtained, attempts would be made to image the cross-sections of downward propagating dart-leaders or dart-stepped leaders from a channel section aloft as the dart-leader luminous diameter has not been examined directly before. Framing photographs (4000 fr/sec) of the same field of view would document the movement and geometric variation of the channels on the microscale (~2 cm). It is anticipated that the field observations could be acquired in a single field campaign during the first summer of support. The remainder of the project would be devoted to analysis of the photographic data in its own right along with use of these results in collaborative analyses with other researchers.