Evaluation of the performance characteristics of the European Lightning Detection Network EUCLID in the Alps region for upward negative flashes using direct measurements at the instrumented Säntis Tower

Abstract

In this paper, we present a performance analysis of the European Cooperation for Lightning Detection (EUCLID) lightning detection network using data obtained on lightning currents measured at the Säntis Tower (located in northeastern of Switzerland) from June 2010 to December 2013. In the considered period of analysis, a total number of 269 upward negative flashes were recorded at the Säntis Tower. The performance of the EUCLID lightning detection network is evaluated in terms of detection efficiency, location accuracy, and peak current estimates for upward flashes. Excluding flashes containing only an initial continuous current with no superimposed pulses exceeding 2 kA, the flash detection efficiency for upward flashes is estimated to be 97%. The recorded flashes contained a total of 2795 pulses (including return strokes and International Conference on Communications pulses characterized by risetimes lower than 8 μs and peaks greater than 2 kA). The overall pulse detection efficiency was found to be 73%. For pulses with peak values higher than 5 kA, the pulse detection efficiency was found to be about 83%. Peak current estimates provided by the EUCLID network were found to be significantly larger than their directly measured counterparts. This overestimation might be attributed to the enhancement of the radiated electromagnetic fields associated with the presence of the tower and the mountain. The median of the absolute distance error, defined as the median distance between the Säntis Tower location and the EUCLID's stroke locations, was found to be 186 m, the majority of large location errors being associated with measured current peaks lower than 10 kA. The analysis revealed also that the location accuracy of the EUCLID network improved significantly in 2013 as a result of an upgrade in the location algorithms to take into account propagation effects.

On Lightning Electromagnetic Field Propagation Along an Irregular Terrain

“…On the other hand, the assumption of a flat ground resulted in a significant underestimation of the peak electric field. The obtained results were found to be consistent with the recent study on the performance analysis of the EUCLID presented in [31], in which, it was shown that the peak current estimates provided by the EUCLID network were about 1.8 times higher than those from direct measurements. This overestimation can be attributed to the enhancement of the radiated electromagnetic fields associated with the presence of the irregular, mountainous terrain around the Säntis Tower.…”

“…On the other hand, the assumption of a flat ground results in a significant underestimation of the peak electric field. It is interesting to note that the obtained results are consistent with a recent study on the performance analysis of the European lightning detection network (EUCLID) presented in [31], in which it was shown that the peak current estimates provided by the EUCLID network were about 1.8 times higher than those from Fig 11), and the ground with a tall mountain (see red profile in Fig. 11).…”

Analysis of lightning outliers in the EUCLID network

“…1. The network has been tested continuously over the years against ground-truth data from direct lightning current measurements at the Gaisberg tower in Austria , Peißenberg tower in Germany (Heidler and Schulz, 2016) and Säntis tower in Switzerland (Romero et al, 2011;Azadifar et al, 2016) from E-field measurements and video recordings in Austria, France and Belgium . The latest comprehensive performance analysis of the EUCLID network based on those measurements revealed that the flash and stroke DE for negative CG discharges in different regions of the EU-CLID network are greater than 93 and 84 %, respectively, while for positive events those are greater than 87 and 84 %, respectively .…”

“…Those observations provide valuable information on the DE, location accuracy and in some cases even the peak current estimates retrieved from an LLS. This is done for instance by examining direct lightning strikes to instrumented towers (Diendorfer et al, 2000a, b;Pavanello et al, 2009;Romero et al, 2011;Schulz et al, 2012Schulz et al, , 2013Cramer and Cummins, 2014;Azadifar et al, 2016) through the use of rocket-triggered lightning (Jerauld et al, 2005;Nag et al, 2011;Mallick et al, 2014a, b, c) and/or by recording lightning strikes with highspeed video and E-field (electric field) measurements in open field (Biagi et al, 2007;Poelman et al, 2013a;Schulz et al, 2016). Although they are the best methods for retrieving robust information of a networks' performance, they are quite labor intensive when used to acquire a large enough dataset for a statistically reliable output.…”

Simultaneous records of current and 380-km distant electric field of a bipolar lightning flash

“…Among reasons that could explain this difference are: -The return stroke speed for positive strokes is, in general, smaller than that for negative strokes [24]- [26]; -The enhancement of the electric field due to the presence of the tower and the mountain [27]- [31] might be more significant for negative pulses, which are characterized by faster risetimes, than for positive pulses.…”