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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.

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.

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.

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 | 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.

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