The effect of ground altitude on lightning striking distance based on a bi-directional leader model

The effect of ground altitude on lightning striking distance has been investigated based on a bi-directional leader model. The model, which is a development of that proposed originally by Mazur and Ruhnke in 1998, enables the calculation of leader channel parameters, such as leader charge density, leader current, leader potential, and lightning striking distance to flat ground. In the model, the lightning striking distance is directly related to the critical electric field in the negative streamer zone in front of the leader tip and to the leader potential. The former may vary with the ground altitude above sea level and the latter may also be affected by it. Based on this thought and on the bi-directional leader model, the effect of regional ground altitude on lightning striking distance was investigated. The result shows that the striking distance increases significantly as the ground altitude increases. This is because the critical electric field necessary for sustaining the negative streamer zone decreases as the ground altitude increases. The result is useful to both physical and engineering application.