Optical Observations of 99 Upward Flashes in Johannesburg, South Africa

Abstract

Upward flashes are one of the most increasing topics of study in the lightning science community, due to the increase of tall structures, such as tall wind turbines and tall buildings. During the period from January 2017 to January 2020, a total of 99 upward flashes were observed in Johannesburg, South Africa. This paper presents the analysis of prior activity observed by high- speed cameras as well as the polarity of the leader and other leader characteristics. The data from lightning location network associated with the cases is also presented in this paper. The cases showed an initial continuous current duration of 417.3ms, and during this continuous current the presence of 1,000 ICC pulses was observed. Another characteristic observed was that 41 % of the cases had subsequent return strokes and that the average duration of the subsequent return strokes was 22ms, and only 10% were longer than 40ms (as per definition of long continuing current).