Current Observation Results of Upward Negative Flashes Initiated from Tokyo Skytree during 2012 to 2016

Abstract

Lightning observation has been carried out at Tokyo Skytree, which is a 634-m high freestanding broadcasting tower located in a flat terrain at 1m ASL. 25 downward and 37 upward flashes were observed at the tower during 2012 to 2016. This paper focuses on upward negative flashes initiated from the top of the tower. Of the 37 confirmed upward flashes, 35 current waveforms were recorded by Rogowski coils installed at 497-m height of the tower. One out of 35 upward flashes was a positive flash initiated by a negative upward leader, 7 out of 35 flashes were bipolar flashes initiated by positive upward leaders, and the rest were negative flashes initiated by positive upward leaders. The authors evaluated the lightning current parameters of subsequent strokes and initial continuous currents (ICC) of the upward negative flashes.