Synchronized observations of cloud‐to‐ground lightning using VHF broadband interferometer and acoustic arrays

Abstract

A single‐station‐based lightning discharge channel reconstruction system by combining a two‐dimensional (2D) VHF broadband interferometer and a three‐dimensional (3D) acoustic lighting mapping system has been developed and used for lightning observations. Two cloud‐to‐ground (CG) flashes with highly branched leaders recorded by the system are analyzed and presented in this paper. VHF radiation could well delineate the development of simultaneous leader branches, while acoustic emissions mainly located on the main channel which was traversed by return stroke (RS) process. Localizations by VHF and acoustic emissions agree well with each other. The mapping results confirm that audible acoustic emission of lightning discharge is mainly associated with high current process like RS. Leaders could generate detectable acoustic signals, with amplitude at least an order weaker than ensuing RS, but they are hard to identify except in closer ranges than the main channel. As a significant phenomenon, this paper provides the first 3D locations associated with sources of tearing sounds, which are inferred to be generated by downward negative leaders when they approach ground. The synchronized observation enable VHF interferometer locate lightning development in spatially quasi 3D, and three stepped leaders, five dart leaders and two dart‐stepped leaders are identified, with the 3D velocity (1.3–3.9) × 105 m/s, (1.0–2.9) × 107 m/s and from (1.0–1.3) × 107 m/s to (2.4–2.6) × 106 m/s, respectively. In addition, the application of this approach in improving the accuracy of thunder ranging is discussed.