Continuous broadband digital interferometry of lightning using a generalized cross-correlation algorithm
Continuous broadband digital interferometry of lightning using a generalized cross-correlation algorithm
复制标题
DOI：
10.1002/2013jd020217
复制
发表时间：
2014-03-27
影响因子：
4.4
通讯作者：
Stanley, M. A.
中科院分区：
文献类型：
--
作者：
Stock, M. G.;Akita, M.;Stanley, M. A.
由大坂大学开发的VHF宽带数字干涉仪已经得到改进，允许在闪电的整个持续时间内连续采样，并利用广义互相关技术来确定闪电源方向。在三个正交定位的天线接收到的20-80 MHz信号的时间序列波形在多秒间隔上连续数字化，而不是短持续时间触发的序列。由于测量的相干性，辐射源位于周围的接收器和环境噪声水平，提供了一个量子飞跃的能力，研究闪电放电过程。当使用互相关进行后处理时，测量值提供小于1度的角度不确定性和优于1 μ s的时间分辨率。已经开发了特殊的技术来区分实际的闪电源和噪声事件，其结果是，对于典型的闪电闪光，定位了大约50，000 - 80，000个辐射源。在这项研究中，一个经典的双层云内闪光的二维干涉仪观测，并结合三维闪电映射阵列观测产生一个准3-D的闪电活动与干涉仪的时间分辨率的地图。作为一个例子的科学效用的意见，结果提出了3-D的发展速度的负领导人与云内K-领导人。
The VHF Broadband Digital Interferometer developed by Osaka University has been improved to allow continuous sampling over the entire duration of a lightning flash and to utilize a generalized cross-correlation technique for determining the lightning source directions. Time series waveforms of 20-80 MHz signals received at three orthogonally located antennas are continuously digitized over multisecond intervals, as opposed to sequences of short-duration triggers. Because of the coherent nature of the measurements, radiation sources are located down into the ambient receiver and environmental noise levels, providing a quantum leap in the ability to study lightning discharge processes. When postprocessed using cross correlation, the measurements provide angular uncertainties less than 1 degrees and time resolution better than 1 mu s. Special techniques have been developed to distinguish between actual lightning sources and noise events, with the result being that on the order of 50,000-80,000 radiation sources are located for a typical lightning flash. In this study, two-dimensional interferometer observations of a classic bilevel intracloud flash are presented and combined with three-dimensional Lightning Mapping Array observations to produce a quasi 3-D map of lightning activity with the time resolution of the interferometer. As an example of the scientific utility of the observations, results are presented for the 3-D progression speed of negative leaders associated with intracloud K-leaders.