Single-Station-Based Lightning Mapping System With Electromagnetic and Thunder Signals

摘要

A single-station-based lighting mapping system comprising a microphone array, which detects electromagnetic (EM) and thunder signals, has recently been developed and deployed for lightning observations. Using one microphone array consisting of 19 electret microphones installed on a 3-D steel frame, this system receives and processes the EM and thunder signals to determine the location of lightning thunder sources. We implement a new broadband direction-of-arrival estimation technique, namely, the maximum power beamforming algorithm and derive the 3-D location results based on the time difference between the acoustic signal and the EM signal. In this paper, four cloud-to-ground flashes with different branch channels recorded by the system are analyzed and presented in which the located thunder sources of two lightning flashes are compared with the photograph of the high-speed camera. The details of the system implementation along with the successful reconstruction of the lightning channel in 2-D and 3-D space are discussed. The results indicate that the location system could effectively map the lightning thunder sources, and the result is highly consistent with the high-speed video camera images. Moreover, the acoustic mapping system is capable of locating the main channel produced by the return stroke process; it also depicts the branching channels. It is shown that the system is capable of distinguish different branches of the same lightning; it also obtains different lightning channels occurring almost simultaneously.