Fullekrug M.,University of Bath |
Liu Z.,University of Bath |
Koh K.,University of Bath |
Mezentsev A.,University of Bergen |
And 5 more authors.
Geophysical Research Letters | Year: 2016
Mini arrays are commonly used for infrasonic and seismic studies. Here we report for the first time the detection and mapping of distant lightning discharges in the sky with a mini array. The array has a baseline to wavelength ratio ∼4.2·10−2 to record very low frequency electromagnetic waves from 2 to 18 kHz. It is found that the mini array detects ∼69 lightning pulses per second from cloud-to-ground and in-cloud discharges, even though the parent thunderstorms are ∼900–1100 km away and a rigorous selection criterion based on the quality of the wavefront across the array is used. In particular, lightning pulses that exhibit a clockwise phase progression are found at larger elevation angles in the sky as the result of a birefringent subionospheric wave propagation attributed to ordinary and extraordinary waves. These results imply that long range lightning detection networks might benefit from an exploration of the wave propagation conditions with mini arrays. ©2016. The Authors.
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 | Year: 2015
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.
Defer E.,French National Center for Scientific Research |
Pinty J.-P.,French National Center for Scientific Research |
Coquillat S.,French National Center for Scientific Research |
Martin J.-M.,French National Center for Scientific Research |
And 25 more authors.
Atmospheric Measurement Techniques | Year: 2015
The PEACH project (Projet en Electricité Atmosphérique pour la Campagne HyMeX - the Atmospheric Electricity Project of the HyMeX Program) is the atmospheric electricity component of the Hydrology cycle in the Mediterranean Experiment (HyMeX) experiment and is dedicated to the observation of both lightning activity and electrical state of continental and maritime thunderstorms in the area of the Mediterranean Sea. During the HyMeX SOP1 (Special Observation Period) from 5 September to 6 November 2012, four European operational lightning locating systems (ATDnet, EUCLID, LINET, ZEUS) and the HyMeX lightning mapping array network (HyLMA) were used to locate and characterize the lightning activity over the northwestern Mediterranean at flash, storm and regional scales. Additional research instruments like slow antennas, video cameras, microbarometer and microphone arrays were also operated. All these observations in conjunction with operational/research ground-based and airborne radars, rain gauges and in situ microphysical records are aimed at characterizing and understanding electrically active and highly precipitating events over southeastern France that often lead to severe flash floods. Simulations performed with cloud resolving models like Meso-NH and Weather Research and Forecasting are used to interpret the results and to investigate further the links between dynamics, microphysics, electrification and lightning occurrence. Herein we present an overview of the PEACH project and its different instruments. Examples are discussed to illustrate the comprehensive and unique lightning data set, from radio frequency to acoustics, collected during the SOP1 for lightning phenomenology understanding, instrumentation validation, storm characterization and modeling. © Author(s) 2015.
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.
Poelman D.R.,Royal Meteorological Institute of Belgium |
Honore F.,Meteo - France |
Anderson G.,UK Met Office |
Journal of Atmospheric and Oceanic Technology | Year: 2013
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.
2015 International Symposium on Lightning Protection, XIII SIPDA 2015 | Year: 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.
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 , . 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.
2012 31st International Conference on Lightning Protection, ICLP 2012 | Year: 2012
Most of lightning statistics used by the lightning protection community are derived from lightning locating systems. Such systems collect flash data over large regions and during long period of time. In their life, those systems are likely to undergo several major changes as the state of the art in remote sensing techniques improves leading to some impacts on the data. In addition the flash data measured by lightning locating systems underestimate the actual lightning risk since it accounts only for one ground contact per flash that is well known nowadays not correct. Then the different evolutions in observing systems and underestimation introduced by flash data must be addressed and compensated in order to give a more accurate and relevant information for lightning risk assessment. The French national lightning locating system operated by Meteorage, has collected more than 20 years of lightning data all over the country. This system is no exception since from its inception several major changes, in either technology or system settings, have significantly modified the lightning detection performances affecting the homogeneity of the data and the relevancy of the GFD statistics. The work presented in this paper is based on this long duration French dataset. It attempts to define a method which comes around the inhomogeneity introduced by lightning detection performance evolutions and suggests the use of the flash ground contacts multiplicity instead of flash data only. To achieve this goal the cumulative peak current distribution method developed by the CIGRE task force C404 is used to determine the compensation factors to correct the statistics for detection efficiency effect. In addition, it is suggested the use of ground contacts data instead of flash data for lightning risk statistics. This parameter is derived from the lightning data collected in France on 2011 with a program developed by Meteorage based on a clustering algorithm so called 'k-means'. The method suffers from some necessary assumptions depending on the Meteorage's LLS history and operational background, but the final new ground contacts density parameter derived from the longest observation period available in France looks more realistic and reliable. This work is a first attempt that must be extended in the future to compute high spatial resolution statistics supporting new applications for lightning risk assessment. © 2012 IEEE.