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Simon T.,University of Innsbruck | Umlauf N.,University of Innsbruck | Zeileis A.,University of Innsbruck | Mayr G.J.,University of Innsbruck | And 2 more authors.
Natural Hazards and Earth System Sciences | Year: 2017

This study develops methods for estimating lightning climatologies on the dayĝ'1ĝ€kmĝ'2 scale for regions with complex terrain and applies them to summertime observations (2010–2015) of the lightning location system ALDIS in the Austrian state of Carinthia in the Eastern Alps.

Generalized additive models (GAMs) are used to model both the probability of occurrence and the intensity of lightning. Additive effects are set up for altitude, day of the year (season) and geographical location (longitude/latitude). The performance of the models is verified by 6-fold cross-validation.

The altitude effect of the occurrence model suggests higher probabilities of lightning for locations on higher elevations. The seasonal effect peaks in mid-July. The spatial effect models several local features, but there is a pronounced minimum in the north-west and a clear maximum in the eastern part of Carinthia. The estimated effects of the intensity model reveal similar features, though they are not equal. The main difference is that the spatial effect varies more strongly than the analogous effect of the occurrence model.

A major asset of the introduced method is that the resulting climatological information varies smoothly over space, time and altitude. Thus, the climatology is capable of serving as a useful tool in quantitative applications, i.e. risk assessment and weather prediction.


Poelman D.R.,Royal Meteorological Institute of Belgium | Schulz W.,OVE ALDIS | Diendorfer G.,OVE ALDIS | Bernardi M.,SiRF
2014 International Conference on Lightning Protection, ICLP 2014 | Year: 2014

Cloud-to-ground (CG) lightning data from the European Cooperation for Lightning Detection (EUCLID) network over the period 2006-2012 are explored. Mean CG flash densities vary over the European continent, with the highest density of about 7 km-2yr-1 found at the triple point between Austria, Italy and Slovenia. The majority of lightning activity takes place between May and September, accounting for 85% of the total observed CG activity. Furthermore, the thunderstorm season reaches its highest activity in July, while the diurnal cycle peaks around 1500 UTC. A difference between CG flashes over land and sea becomes apparent when looking at the peak current estimates. It is found that flashes with higher peak currents occur in greater numbers over sea than over land. © 2014 IEEE.


Poelman D.R.,Royal Meteorological Institute of Belgium | Schulz W.,OVE ALDIS | Vergeiner C.,University of Graz
Journal of Atmospheric and Oceanic Technology | Year: 2013

This study reports results from electric field measurements coupled to high-speed camera observations of cloud-to-ground lightning to test the performance of lightning location networks in terms of its detection efficiency and location accuracy. The measurements were carried out in August 2011 in Belgium, during which 57 negative cloud-to-ground flashes, with a total of 210 strokes, were recorded. One of these flashes was followed by a continuing current of over 1 s-one of the longest ever observed in natural negative cloud-toground lightning. Lightning data gathered from the lightning detection network operated by the Royal Meteorological Institute of Belgium [consisting of a network employing solely Surveillance et Alerte Foudre par Interféromé trie Radioé lectrique (SAFIR) sensors and a network combining SAFIR and LS sensors], the European Cooperation for Lightning Detection (EUCLID), Vaisala's Global Lightning Detection network GLD360, and the Met Office's long-range Arrival Time Difference network (ATDnet) are evaluated against this ground-truth dataset. It is found that all networks are capable of detecting over 90% of the observed flashes, but a larger spread is observed at the level of the individual strokes. The median location accuracy varies between 0.6 and 1 km, except for the SAFIR network, locating the ground contacts with 6.1-km median accuracy. The same holds for the reported peak currents, where a good correlation is found among the networks that provide peak current estimates, apart from the SAFIR network being off by a factor of 3. © 2013 American Meteorological Society.


Pichler H.,OVE ALDIS | Diendorfer G.,OVE ALDIS | Mair M.,Vienna University of Technology
IEEJ Transactions on Electrical and Electronic Engineering | Year: 2010

Simultaneous measurements of lightning current and associated radiated electromagnetic field are of fundamental interest for various applications in lightning research. These data can be used for the evaluation of return stroke (RS) models or to investigate the so-called tower effect when lightning hits an elevated object. In this paper, we show the results of simultaneous measurements of current pulses from lightning strikes on the instrumented Gaisberg tower (Austria) and the correlated vertical E-field components at a distance of 78.8 and 108.7 km, respectively. We have analyzed some main lightning current parameters (peak current Ip, 30-90% rise time TI-30-90, and full width at half maximum TI-FWHM) and the time-correlated field waveform parameters (Ep, 30-90% rise time TE-30-90, TE-FWHM, and the peak-to-zero time TE-PTZ). With a geometric mean of TI-FWHM = 19 μs and Ip = 9.6 kA (N = 73) of the RS current pulses used in this study, those strokes are very similar to the strokes in triggered lightning in Florida and Alabama [1]. With a TE-PTZ of about 10 μs, the zero-crossing time of the radiated E-fields from the tower strokes are significantly shorter than the typical values of 30 - 40 μs (e.g. [2]). Correlation between the current and field parameters TI-FWHM versus TE-FWHM and TE-PTZ, respectively, is low (R2 = 0.29 and 0.14). We assume that the relatively short lightning channel in the case of the RSs in object-triggered upward flashes is the main reason for the observed short zero-crossing time. © 2010 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc.


Poelman D.R.,Royal Meteorological Institute of Belgium | Schulz W.,OVE ALDIS | Diendorfer G.,OVE ALDIS | Bernardi M.,Centro Elettrotecnico Sperimentale Italiano
Natural Hazards and Earth System Sciences | Year: 2016

Cloud-to-ground (CG) lightning data from the European Cooperation for Lightning Detection (EUCLID) network over the period 2006-2014 are explored. Mean CG flash densities vary over the European continent, with the highest density of about 6 km-2 yr-1 found at the intersection of the borders between Austria, Italy and Slovenia. The majority of lightning activity takes place between May and September, accounting for 85% of the total observed CG activity. Furthermore, the thunderstorm season reaches its highest activity in July, while the diurnal cycle peaks around 15:00 UTC. A difference between CG flashes over land and sea becomes apparent when looking at the peak current estimates. It is found that flashes with higher peak currents occur in greater proportion over sea than over land. © Author(s) 2016.


Schulz W.,OVE ALDIS | Diendorfer G.,OVE ALDIS | Pedeboy S.,Meteorage | Roel Poelman D.,Royal Meteorological Institute of Belgium
Natural Hazards and Earth System Sciences | Year: 2016

In this paper we present a performance analysis of the European lightning location system EUCLID for cloud-to ground flashes/strokes in terms of location accuracy (LA), detection efficiency (DE) and peak current estimation. The performance analysis is based on ground truth data from direct lightning current measurements at the Gaisberg Tower (GBT) and data from E-field and video recordings. The E-field and video recordings were collected in three different regions in Europe, namely in Austria, Belgium and France. The analysis shows a significant improvement of the LA of the EUCLID network over the past 7 years. Currently, the median LA is in the range of 100m in the center of the network and better than 500m within the majority of the network. The observed DE in Austria and Belgium is similar, yet a slightly lower DE is determined in a particular region in France, due to malfunctioning of a relevant lightning location sensor during the time of observation. The overall accuracy of the lightning location system (LLS) peak current estimation for subsequent strokes is reasonable keeping in mind that the LLS-estimated peak currents are determined from the radiated electromagnetic fields, assuming a constant return stroke speed. The results presented in this paper can be used to estimate the performance of the EUCLID network related to cloud-to-ground flashes/strokes for regions with similar sensor baselines and sensor technology. © Author(s) 2016.


Schumann C.,National Institute for Space Research | Saba M.M.F.,National Institute for Space Research | da Silva R.B.G.,National Institute for Space Research | Schulz W.,OVE ALDIS
Journal of Atmospheric and Solar-Terrestrial Physics | Year: 2013

Positive flashes correspond to approximately only 10% of the total number of flashes produced by a thunderstorm. However, strokes with high peak currents and long continuing currents are usually present in positive flashes. Therefore, positive flashes are responsible for more intense damage than the negative ones. Positive flashes often are preceded by significant and long duration intracloud (IC) discharge activity. We observe in detail the electric field variations produced by 80 cloud-to-ground lightning flashes in 9 different storms in S. Paulo, Brazil during the summers of 2009-2011. Intracloud discharges preceding the positive cloud-to-ground flashes and some characteristics of the electric field changes produced by the return stroke that occurred at ranges of 3-80. km from the site of the electric field measurements were analyzed. All flashes presented breakdown pulses prior to the return stroke. The mean time interval between the preliminary breakdown pulse (PBP) and return stroke was 157. ms. The pulse train duration have a mean value of 3.1. ms. Only 6 out of 80 cases analyzed did not present pulse trains but only one single bipolar breakdown pulse before the return stroke. In 95% of cases the initial breakdown pulse presented the same initial polarity of the succeeding return stroke. Time interval between pulses in a pulse train had a mean value of 280. μs. The mean values of pulse width is 25.2. μs. The mean values of zero-to-peak risetimes and of the 10-90% risetimes for 72 return strokes electric field waveforms are 9.5 and 5.7. μs respectively. The AM value of peak amplitudes of the positive return strokes fields normalized to 100. km is 17.0. V/m. © 2012 Elsevier Ltd.


Birkl J.,Dehn Sohne GmbH Co.KG. | Bohm T.,Dehn Sohne GmbH Co.KG. | Schulzhenko E.,Dehn Sohne GmbH Co.KG. | Zahlmann P.,Dehn Sohne GmbH Co.KG. | And 2 more authors.
2011 International Symposium on Lightning Protection, XI SIPDA 2011 | Year: 2011

Comparison measurements with a mobile lightning current detection system and measuring station used for scientific purposes were carried out. The mobile system including sensors, data acquisition and transmission are described. The lightning current parameters recorded during comparative measurements are analyzed. The results are in line with the lightning current statistics. Mainly upward initiated flashes were measured. © 2011 IEEE.


Nag A.,Vaisala | Murphy M.J.,Vaisala | Schulz W.,OVE ALDIS | Cummins K.L.,University of Arizona
2014 International Conference on Lightning Protection, ICLP 2014 | Year: 2014

Ground-based or satellite-based lightning locating systems are the most common way to geolocate lightning. Depending upon the frequency range of operation, such systems can also report a variety of characteristics associated with lightning events (channel formation processes, leader pulses, cloud-to-ground return strokes, M-components, ICC pulses, and cloud lightning pulses). In this paper, we summarize the various methods to geolocate lightning, both ground-based and satellite-based, and discuss the characteristics of lightning data available from various sources. The performance characteristics of lightning locating systems are determined by their ability to geolocate lightning events accurately and report various features such as lightning type and peak current. We examine the various methods used to validate the performance characteristics of different types of lightning locating systems. © 2014 IEEE.


Schulz W.,OVE ALDIS | Pedeboy S.,Meteorage | Saba M.M.F.,National Institute for Space Research
2014 International Conference on Lightning Protection, ICLP 2014 | Year: 2014

During the last years the ground strike points of a flash got more attention because it was realized that risk estimation should not be performed with flash densities but with ground strike point densities. In countries with a lightning location system (LLS) the ground flash densities are normally derived from the LLS data. Recently an effort has been made to derive also ground strike points and ground strike point densities from LLS data [1], [2]. Detection efficiencies (DE) for flashes are well understood and often used to correct the ground flash densities. In this paper we show that also ground strike point densities determined with a LLS exhibit a DE. We further present a theoretical estimation of this DE, which we validate with real data from video and E-field measurements. © 2014 IEEE.

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