2021

Schwalt L., S. Pack, W. Schulz, G. Pistotnik:
Percentage of single-stroke flashes related to different thunderstorm types

Electric Power Systems Research, Vol. 194, 2021

This study shows an analysis of data from measurements of natural cloud-to-ground lightning performed in Austria between 2009 and 2018. The measurement system consists of a high-speed Video and electric Field Recording System (VFRS). Over the whole period, 735 negative cloud-to-ground flashes were recorded at 33 different locations on 61 individual days. The measurement locations are scattered across the Austrian territory in Alpine and pre-Alpine terrain. Data from the Austrian Lightning Location System (LLS), ALDIS, are correlated with the collected VFRS ground truth data to complete the dataset. These datasets are used to analyze possible reasons for the detected variation of single-stroke flashes in Austria. The percentage of single-stroke flashes among all negative flashes is higher in this study (27 %) than in previous studies from different countries (12 to 24 %). A classification of thunderstorms does not show any dependency of the single-stroke flash occurrence on different thunderstorm types (based on radar data) or underlying meteorological characteristics (based on vertical wind shear computed from weather stations and radiosondes). In contrast, a possible dependency of the occurrence of single-stroke flashes on underlying terrain (Alpine versus pre-Alpine) is noted.

No PDF Download

Download Link

Kolmašová I., O. Santolík, P. Kašpar , M. Popek, A. Pizzuti, P. Spurný, J. Borovička, J. Mlynarczyk, J. Manninen, E. L. Macotela, P. Zacharov, R. Lán, L. Uhlíř, G. Diendorfer, A. Bennett, M. Füllekrug, R. Slošiar:

First Observations of Elves and Their Causative Very Strong Lightning Discharges in an Unusual Small-Scale Continental Spring-Time Thunderstorm

Journal of Geophysical Research: Atmospheres, DOI: 10.1029/2020JD032825, 2021

We show for the first time that elves can be produced by an unusual small-scale continental spring-time thunderstorm. The storm occurred in Central Europe, covered a very small area of ∼50 × ∼30 km and lasted only for ∼4 h on April 2, 2017. The fraction of intense positive cloud-toground lightning strokes was unusually high, reaching 55%, with a mean peak current of 64 kA. The peak currents of return strokes (RS) associated with elves exceeded ∼300 kA. Elves and their causative RS have been observed with different optical and electromagnetic recordings. Signatures of ionospheric disturbances indicating the presence of elves were found in measurements of displacement currents, ionospheric reflections of sferics and man-made narrow-band transmissions. All these electromagnetic observations coincide with four optical detections of elves and strongly suggest the occurrence of two more elves later in the decaying phase of the storm. Surprisingly, the same electromagnetic measurements indicate that other strong strokes did not produce any elves. Our simulation results show that the formation of an elve is not only determined by the high-peak current of their causative strokes but that it is also controlled by the conductivity of the lightning channels and velocity of the current wavefront. We hypothesize that because of a lower conductivity of RS lightning channels and/or slower current waves only very strong strokes with peak currents above ∼300 kA might have been capable to produce observable elves during this thunderstorm.

No PDF Download

Download Link

OVE uses cookies to provide you with the best possible service. By using our website, you consent to the use of cookies. Read more about cookies here.