Comprehensive observation of leader characteristics using TVLS

In order to examine lightning leader processes, a single-station-based lightning observation system termed TVLS (Thunder and VHF lightning Locating System) is introduced and used for lightning leader observation. This system adopts advantages of VHF (30-300MHz) broadband interferometer and thunder imaging technique, which could provide the temporal and quasi-3D spatial evolution of lightning discharges, as well as broadband EM radiation and electric field change waveforms. Ten leaders from two negative natural cloud-to-ground (CG) flashes are analyzed. Based on the evolution characteristic of leader speed, electric field changes, VHF spectra, et al, three stepped leaders, five dart leaders and two dart-stepped leaders are identified. All dart leaders presented exhibit part or whole irregular (or termed “erratic”) impulsive electric field change (E-change) characteristic, which occur in coincidence with VHF radiation burst. A transition point exists in the dart-stepped leader process, and divides the dart-stepped leader into dart phase and stepped phase. The behavior of these two phases resemble dart and stepped leader respectively except for the higher speed and more regular E-change pulse wave shapes in stepped phase than typical stepped leaders.