A five-year study of lightning activity using a CGR3 flash counter in Gaborone, Botswana

Summary

We have used a CGR3 lightning flash counter to gather lightning type and occurrence data over five complete years in Gaborone, Botswana. The results show that the mean ground flash density is 4.6 km⁻² yr⁻¹. Of these, 4.9% of ground flashes lower a net positive charge. The overall ratio of intracloud flashes to ground flashes is 1.9, the value being slightly higher during the nights than the daytime. A typical lightning season lasts from September to May, the activity reaching a peak between November and January. There is virtually no lightning at all during the dry winter months of June, July and August. The number of flashes per storm shows a marked decrease as the season progresses. In the diurnal cycle, the peak lightning activity occurs at around 19 h, which is somewhat late when compared with most other locations. However, together with observations in the Central United States, it seems to suggest that the peak activity occurs later in the day at mid-continental locations.