2012 Volume 132 Issue 6 Pages 560-567
The characteristics of upward leaders were observed at a 200m chimney in the coastal area of the Sea of Japan from 1989 to 2008 for clarification of the initiation processes of upward lightning using a high-speed video camera and the ALPS(Automatic Lightning Progressing feature observation System). In the observation, we obtained images showing the inception processes of both positive and negative upward leaders with the corresponding current waveforms. Positive upward leaders propagate continuously and negative upward leaders propagate intermittently. We evaluated the line charge densities of the upward leaders, which were found to be much larger than those used in the lightning shielding model for the lightning protection design.