Lightning Phenomena in the Alpine Region of Austria

Publikation: StudienabschlussarbeitDissertation

Abstract

Cloud-to-ground (CG) lightning phenomena in the Alpine region of Austria and associated analyzes of recorded data represent the research focus of the present thesis. First, on-site measurements of CG flashes were performed to generate a ground truth data set. A high speed Video camera (recording speed of 2000 frames per second) and an electric Field Recording System (VFRS) was used for this purpose. The VFRS measurements have been conducted at 21 different measurement locations. 531 CG flashes including 1639 CG strokes have been recorded on 51 days during warm season thunderstorms in the years 2015, 2017 and 2018. The recorded ground truth VFRS data were correlated with Lightning Location System (LLS) data of the Austrian Lightning Detection and Information System (ALDIS) to complement the data set. This data set was used to analyze characteristic parameters of the recorded flashes and to calculate annual and total performance parameters of the LLS. The results of the analyses are then compared with former findings from the literature.

Flashes in the Alpine region of Austria show a particularly high amount of negative single stroke flashes compared to other regions in the world. Mean multiplicity values determined with the VFRS data are comparable to the previous results for measurements in the Austrian Alps but the values are situated at the lower end compared to previous studies for other countries. Analyses for negative first return stroke peak current estimations by the LLS show a significant difference compared to the used values in standards, derived from direct current measurements. The hypothesis that larger return stroke peak currents of subsequent strokes then the first stroke of LLS grouped flashes are resulting from first strokes to a new ground strike point cannot be confirmed. The analysis of LLS performance parameters for negative flashes revealed a median location accuracy value of 100 m and LLS flash detection efficiency
(DE) values constantly higher than 96 % have been detected for all three investigated years. DE percentages for strokes show a higher variance over the three years. Analyses of the positive flash data revealed a rather low single stroke flash percentage compared to previous analyses for Austria but the percentage is situated within the range of previously published values for other countries whereas LLS median return stroke peak current show a comparatively high value. Mean multiplicity as well as DE values for positive flashes show similar results than for previous studies. A rare stepwise analysis of VFRS data of direct lightning strikes to wind turbines and a railway transmission line correlated with system operator data completes this work.
Originalspracheenglisch
QualifikationDoktor der Technik
Gradverleihende Hochschule
Betreuer/-in / Berater/-in
  • Pack, Stephan, Betreuer
Datum der Bewilligung20 Nov 2019
PublikationsstatusVeröffentlicht - 2019

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