Measurement results of lightning current at Nikaho in winter from 2013 to 2017

Measurement of the lightning current waveforms have been carried out at Nikaho. In this study, we analyzed the current waveforms of 221 flashes obtained from 2013 to 2017, and 157 flashes were associated with negative lightning. In 99 cases the ICC was observed satisfactorily. We classified the current waveforms for a negative lightning into the 3 types based on the existence of return strokes and superimposing pulses with amplitude of higher than 2kA. The percentage of the current waveforms with the return stroke (RS) was 16.2%. As a result, the charge transfer of the current waveform that the ICC not followed by any RS but with one or more ICC pulses with amplitude of higher than 2kA was the largest. ICC with the large current peak value was observed frequently in this type. Possible reason is the weather condition. The charge transfer associated with the TWP (Typical winter air pressure pattern thunderstorm) is smaller than that associated with the others such as frontal or cyclonic thunderstorm. In this study, the same trend can be seen in all 3 types of current waveform.