An overview of the lightning and atmospheric electricity observations collected in Southern France during the HYdrological cycle in Mediterranean EXperiment (HyMeX), Special Observation Period 1

Defer, Éric; Pinty, Jean‐Pierre; Coquillat, Sylvain; Martín, Javier Martín; Prieur, Serge; Soula, Serge; Richard, Évelyne; Rison, W.; Krehbiel, P. R.; Thomas, R. J.; Rodeheffer, D.; Vergeiner, Christian; Malaterre, F.; Pédeboy, S.; Schulz, Wolfgang; Farges, Thomas; Gallin, Louis-Jonardan; Ortéga, Pascal; Ribaud, Jean-François; Anderson, Graeme; Betz, Hans Dieter; Meneux, B.; Kotroni, Vassiliki; Lagouvardos, K.; Roos, Shannon de; Ducrocq, Véronique; Roussot, Odile; Labatut, Laurent; Molinié, Gilles

doi:10.5194/amtd-7-8013-2014

Cited by 12 publications

(19 citation statements)

References 71 publications

(70 reference statements)

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“…In order to explore the electrical activity during thunderstorms, an experimental setup was deployed in Southern France during September to October 2012 providing an extensive database of acoustic and EM measurements as part of the HYdrological cycle in the Mediterranean EXperiment Special Operation Period 1 (SOP1) campaign (Defer et al, ). The Commissariat à l'Énergie Atomique et aux Énergies Alternatives acoustic station was deployed within the coverage of a Lightning Mapping Array (HyLMA) research network (Rison et al, ; Thomas et al, ).…”

Section: Methodsmentioning

confidence: 99%

Acoustical Measurement of Natural Lightning Flashes: Reconstructions and Statistical Analysis of Energy Spectra

et al. 2018

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Twenty-seven natural flashes of three thunderstorms which occurred during October 2012 in Southern France are acoustically reconstructed and analyzed in the [0.1 − 180]-Hz frequency bandwidth and the [0.3−20]-km distance range. A 50-m triangular array of four recalibrated microphones sampled at 500 Hz has been used for the recording. A novel method of separation of return strokes from intracloud discharges within the acoustical signal is detailed and systematically applied. It shows the possibility to separate nearby cloud-to-ground (CG) events or nearby and distant CGs of the same flash. The separation method yields a total of 36 return stroke signals and spectra, along with some intracloud signals. The combination of reconstruction, separation, and frequency analysis provides new insights on the origin of thunder infrasound, showing unambiguously that thunder infrasound originate dominantly from return strokes. Apart from the higher amplitude of CGs, no clear difference between intracloud and CG spectra is observed. No sharp frequency peaks can be put into evidence. The spectral variability with distance is highlighted, especially for the total acoustic energy and the center frequency and bandwidth. A link between acoustic energy and impulse charge moment change is also found, though only by a small number of data.The description of these two mechanisms explaining the infrasonic and audible acoustic content of thunder has been summarized by Few (1995). Regarding the audible content, the sudden core heating (25,000-30,000 K) just after the electric discharge produces a chain of strong shock waves along the lightning channel. The time dependence of pressure within the lightning channel was estimated by Orville (1968a) from the first measured time resolved optical spectra (Orville, 1968b), with peak overpressure exceeding 80 kPa. Based on a radiation thermodynamical model, Hill (1971) could simulate such values, with even higher shock amplitudes for shorter times (see his Figure 5). The different steps to switch from strong shock waves to weak shock waves and finally to acoustic waves are developed by Few (1969). Theory for self similar strong shock wave was proposed by Taylor (1950) for point sources and Lin (1954) for line sources and then numerically extended to transition and weak shock regimes by Brode (1955) for spherically symmetric shocks. The cylindrical symmetry was described by Plooster (1970). An empirical match between strong and weak shock theories has been applied to lightning by Jones et al. (1968) assuming a rectilinear channel. However, lightning channel tortuosity has been observed optically by Hill (1968), who proposed a mean value of 16 ∘ deflection of one segment to the next. Synthesizing these previous studies, Few et al. (1967) andFew (1969) assumed that the transition between strong and weak shocks takes place approximately in the same range of distances as the transition between cylindrical and spherical divergence. This distance is called relaxation radius. Indeed,

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Section: Methodsmentioning

confidence: 99%

Acoustical Measurement of Natural Lightning Flashes: Reconstructions and Statistical Analysis of Energy Spectra

et al. 2018

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“…We have used the data recorded by (1) the HyMeX (Hydrology cycle in the Mediterranean Experiment) LMA operated during HyMeX Special Observation Period 1 (Sept to Nov 2012) 32 and (2) the SAETTA (Suivi de l’Activité Electrique Tridimensionnelle Totale de l’Atmosphère) network operated in Corsica since June 2014. The HyLMA (HyMeX Lightning Mapping Array) was composed of 12 stations.…”

Section: Methodsmentioning

confidence: 99%

Lightning initiation: Strong pulses of VHF radiation accompany preliminary breakdown

Kolmašová

Santolı́k

Defer

et al. 2018

Sci Rep

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We analyze lightning initiation process using magnetic field waveforms of preliminary breakdown (PB) pulses observed at time scales of a few tens of microseconds by a broad-band receiver. We compare these pulses with sources of narrow-band very high frequency (VHF) radiation at 60–66 MHz recorded by two separate Lightning Mapping Arrays (LMAs). We find that almost none of the observed PB pulses correspond to geo-located VHF radiation sources, in agreement with previous results and with the hypothesis that processes generating VHF radiation and PB pulses are only weakly related. However, our detailed analysis discovers that individual peaks of strong VHF radiation seen by separate LMA stations correspond surprisingly well to the PB pulses. This result shows that electromagnetic radiation generated during fast stepwise extension of developing lightning channels is spread over a large interval of frequencies. We also show that intense VHF radiation abruptly starts with the first PB pulse and that it is then continuously present during the entire PB phase of developing discharges.

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“…Concerning microphysics parametrization, the WRF Single‐Moment 6‐Class Scheme (WSM6: Hong and Lim, ) has been adopted. This scheme takes into account ice species processes, whose relevance in this case study is confirmed by the intense lightning activity recorded during the day (not shown here) as well as by Day Microphysics red‐green‐blue (RGB) Meteosat Second Generation (MSG) data (panel in the left bottom corner of Figure ), which suggests the presence of solid species of hydrometeors (Defer et al ., ). The Day Microphysics RGB is based on the work of Lensky and Rosenfeld () and Merino et al .…”

Section: The Wrf Model Setting and The Validation Of The Cloud‐resolvmentioning

confidence: 97%

Triggering and evolution of a deep convective system in the Mediterranean Sea: modelling and observations at a very fine scale

Fiori

Ferraris

Molini

et al. 2017

Quart J Royal Meteoro Soc

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Gaining a deeper physical understanding of the high-impact weather events which repeatedly affected the Western Mediterranean Basin in recent years on the coastal areas of easternSpain, southern France and northern Italy is strongly motivated by the social request to reduce the casualties and the economical impacts due to these highly localized and hardly predictable phenomena.In October 2014, an extreme event hit Genoa city centre, less than 3 years after a very similar event, which occurred in November 2011.Taking advantage of the availability of both observational data and modelling results at the micro-α meteorological scale, this article provides insights about the triggering mechanism and the subsequent spatio-temporal evolution of the Genoa 2014 back-building Mesoscale Convective System. The major finding is the effect of a virtual mountain created over the Ligurian Sea by the convergence of a cold and dry jet outflowing from the Po valley and a warm and moist low-level southeasterly jet within the planetary boundary layer.

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An overview of the lightning and atmospheric electricity observations collected in Southern France during the HYdrological cycle in Mediterranean EXperiment (HyMeX), Special Observation Period 1

Cited by 12 publications

References 71 publications

Acoustical Measurement of Natural Lightning Flashes: Reconstructions and Statistical Analysis of Energy Spectra

Acoustical Measurement of Natural Lightning Flashes: Reconstructions and Statistical Analysis of Energy Spectra

Lightning initiation: Strong pulses of VHF radiation accompany preliminary breakdown

Triggering and evolution of a deep convective system in the Mediterranean Sea: modelling and observations at a very fine scale

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