Analysis of a Fatality Case Caused by “a Bolt from the Blue”

Investigation and analysis of a lethal event caused by a lightning discharge in Conghua, Guangzhou, in 2017, is presented in this paper. The lightning strike first hit a tree with a height of 13m, and then hit the head of a person near the tree, causing death. The data from the Low Frequency Electric Field Detection Array, Guangdong Lightning Location System, and a nearby radar station, were analyzed. The event was identified as a lightning death incident caused by “a bolt from the blue”. The accident discharge was found to be the first return stroke (RS) with a current peak of -30.9kA, which belonged to a cloud-toground lightning flash with seven RSs. The flash initiated at a height of about 13km. At a height of 2.8km, the horizontal distance from the lightning disaster point to the edge of precipitation (18dBZ) was about 3.6km, and to the edge of the convective core (30dBZ) was about 6km. At a height of 7km, the horizontal distance of the initiation point to the edge of precipitation (18dBZ) was about 0.3km, with the distance to the edge of the convective core (30dBZ) being about 3.5km. According to the equivalent circuit model of the lightning strike, we calculated the air breakdown voltage of the side flash and step voltage on the ground. The results indicated that the event process involved the flash hitting the tree, the current flowing to the “jump point”, and then the side stroke to the victim. Crucially, the victim was exposed by a step voltage of 78.3kV, while a witness, who was 10 m from the lightning strike point, was only exposed to 0.783kV.