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Pau, France

Poelman D.R.,Royal Meteorological Institute of Belgium | Honore F.,Meteo - France | Anderson G.,UK Met Office | Pedeboy S.,Meteorage
Journal of Atmospheric and Oceanic Technology

Increasing possibilities for using lightning data-for instance, in monitoring and tracking applications-necessitate proper spatial and temporal mapping of lightning events. It is therefore of importance to assess the capabilities and limitations of a ground-based lightning network of interest to locate electromagnetic signals emitted by lightning discharges. In this paper, data covering two storm seasons, between May and September 2011 and 2012, are used to compare the spatial and temporal lightning observations of three different lightning location systems over an area covering the Benelux and France. The lightning datasets from a regional network employing Surveillance et Alerte Foudre par Interférométrie Radioélectrique (SAFIR) sensors operated by the Royal Meteorological Institute of Belgium (RMIB), a subcontinental network operated by Météorage (MTRG), and the Met Office's long-range Arrival Time Difference network (ATDnet) are considered. It is found that the median location difference among corresponding strokes and flashes between ATDnet and MTRGis 1.9 and 2.8 km, respectively, and increases by a factor of;3 when comparing ATDnet and/or MTRG to SAFIR. The absolute mean time difference between shared events fluctuates between approximately 25 and 100 ms. Furthermore, lightning data are correlated in terms of relative detection efficiency, quantifying the number of detections that coincide between two different networks. The highest relative values are found among ATDnet and MTRG. In addition, a lower limit of;25% of ATDnet's flashes are of type inter/intracloud. Finally, it is demonstrated that all three networks are competent in mapping the electrical activity in thunderstorms. © 2013 American Meteorological Society. Source

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

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

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. Source

Pedeboy S.,Meteorage
2015 International Symposium on Lightning Protection, XIII SIPDA 2015

The location accuracy is one of the important parameters characterizing the performance of a lightning location system. It is also one of the most difficult to determine as the actual location of the discharge being located must be accurately known to achieve a reliable assessment of the real error. Among all the measurement techniques which can be used to collect such ground truth data, none can cover large area preventing the estimation of the location accuracy at a regional or national scale. Trying to get around this limitation, Météorage has developed a method based on lightning ground strike point data collected by the French national lightning locating system computing the separation distances of return strokes identified as using the same attachment point on the ground. As a result, statistics on the relative location accuracy over the last 10 years of operation at the national scale are produced. In order to determine whether this data could be a proxy for the absolute location accuracy they are compared against systematic errors estimated in the vicinity of high elevation towers well known to attract or trigger lightning. If the study shows some discrepancies between relative and absolute errors at the beginning of the period, mainly due to technological upgrades in the system, it turns out both parameters fit nicely since 2010. This tending to demonstrate the relative errors estimated based on the ground strike point can be used as a good proxy for the absolute location errors estimate. © 2015 IEEE. Source

Soula S.,CNRS Laboratory for Aerology | Defer E.,French National Center for Scientific Research | Fullekrug M.,University of Bath | Van Der Velde O.,Polytechnic University of Catalonia | And 9 more authors.
Journal of Geophysical Research: Atmospheres

During the night of 22-23 October 2012, together with the Hydrology cycle in the Mediterranean eXperiment (HyMeX) Special Observation Period 1 campaign, optical observations of sprite events were performed above a leading stratiform Mesoscale Convective System in southeastern France. The total lightning activity of the storm was monitored in three dimensions with the HyMeX Lightning Mapping Array. Broadband Extremely Low Frequency/Very Low Frequency records and radar observations allowed characterizing the flashes and the regions of the cloud where they propagated. Twelve sprite events occurred over the stratiform region, during the last third of the lightning activity period, and well after the coldest satellite-based cloud top temperature (-62°C) and the maximum total lightning flash rate (11 min-1). The sprite-producing positive cloud-to-ground (SP + CG) strokes exhibit peak current from 14 to 247 kA, Charge Moment Changes (CMC) from 625 to 3086 C km, and Impulsive CMC (iCMC) between 242 and 1525 C km. The +CG flashes that do not trigger sprites are initiated outside the main convective core, have much lower CMC values, and in average, shorter durations, lower peak currents, and shorter distances of propagation. The CMC appears to be the best sprite predictor. The delay between the parent stroke and the sprite allows classifying the events as short delayed (<20 ms) and long delayed (>20 ms). All long-delayed sprites, i.e., most of the time carrot sprites, are produced by SP + CG strokes with low iCMC values. All SP + CG flashes initiate close to the convective core and generate leaders in opposite directions. Negative leaders finally propagate toward lower altitudes, within the stratiform region that coincides with the projected location of the sprite elements. © 2015. American Geophysical Union. All Rights Reserved. Source

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