Ground strike point properties derived from observations of the European Lightning Location System EUCLID

In order to evaluate the lightning risk to a particular structure, it is common practice to follow the guidelines set out in IEC 62305-2, i.e., the reference standard for lightning risk calculation. Amongst the various components that influence the total risk, the flash density is a key parameter. However, flashes have on average more than one ground termination point. This study seeks to ascertain whether existing ground strike point (GSP) algorithms estimate correctly the actual observed number of GSPs per flash based on observations made by high-speed cameras. In addition, lightning data as observed by the European Cooperation for Lightning Detection (EUCLID) network are used in combination with a particular GSP algorithm to retrieve the temporal behavior of GSPs in two topographically different regions in Europe, i.e., Austria and Belgium, over a ten-year period from 2012 to 2021. We find that although most GSP algorithms over-or underestimate to some extent the number of GSPs per flash, this number is fairly close to the observed value as derived from the ground-truth observations. Furthermore, it is found that the average number of GSPs per flash is highest during the summer months. Finally, a diurnal trend is visible where the number of GSPs per flash is lowest between 12 and 18 UTC (Universal Time Coordinated).