Narrow Bipolar Events (NBEs) are brief intracloud (IC) discharge processes that generate powerful radiation in the HF and VHF radio bands. NBEs typically occur in isolation, but they have also been identified as initial events in IC lightning flashes. Their incidence is statistically correlated with the strength of convection. NBEs can exhibit both polarities and usually occur in the upper regions of the thundercloud. We present, for the first time, properties of NBEs detected in the Mediterranean region. The dataset comprises 37 events recorded by broadband magnetic loops located at two sites in France. The events were identified using the list of NBEs from 2022 provided by the Earth Network. The frequency range of our broadband sensors enabled us to obtain detailed shapes of NBE pulses. We calculated rise times, full width at half maximum times, and zero-crossing times of NBE pulses to facilitate comparisons with observations of NBEs in other parts of the world. The majority of NBE pulses observed in the Mediterranean region were isolated events occurring above the land and displaying a simple bipolar waveform with an overshoot peak of the opposite polarity. For two events, we supplemented our observation with the data from the SAETTA (Suivi de l’Activité Electrique Tridimensionnelle Totale de l’Atmosphère) lightning mapping array. Additionally, we estimated the altitude of the NBE events and placed our observations in the meteorological contexts to determine why NBE occurrences in the Mediterranean region have been overlooked until now.

About 45 lightning flashes occur per second all around the Earth with a predominant distribution over the continents and along the inter-tropical band. While different types of Transient Luminous Events (TLEs) induced by lightning flashes can be produced above the thunderstorms, Terrestrial Gamma Ray Flashes (TGFs) are bursts of high-energy photons originating from the Earth’s atmosphere in association with thunderstorm activity with a great majority of TGFs occurring in the inter-tropical region. In addition to those radiation bursts, another type of high-energy emission, so-called gamma ray glows, has been observed inside thunderstorms corresponding to significant enhancements of background radiation that last for more than a few seconds. All these connected phenomena remain to be documented both remotely and on an in-situ manner. Balloon-borne missions offer the required in-situ close-range high-altitude measurements of the ambient electrostatic field, conductivity, TGF radiation and lightning occurrence for a better understanding and modeling of these complex phenomena and of their effects on the Earth atmosphere and the global atmospheric electrical circuit.The STRATELEC (STRatéole-2 ATmospheric ELECtricity) project (Defer et al., 2022), funded by CNES, aims at deploying within the Stratéole-2 framework (Hertzog and Plougonven, 2020) new atmospheric electricity instrumentation on several stratospheric balloons to:Document the electrical state of the atmosphere and the production of high-energy radiation through in-situ and remote sensing measurements to reach better understanding and better modeling capabilities of the processes occurring during thunderstorms, Identify state-of-the-art and emerging technologies to populate the STRATELEC instrumentation package with new sensors in the perspective of their operation on stratospheric balloons, high altitude aircraft and even low-level drones to eventually propose new balloon and/or space mission concepts, Contribute to additional scientific returns on any space mission dedicated to lightning detection (e.g. MTG-LI, GOES-GLM) and more generally to the study of the convection in the Tropics and of electrodynamic couplings in the terrestrial atmosphere-ionosphere-magnetosphere system. First, we will remind the scientific objectives of the STRATELEC project. Then we will provide an update on the different scientific and technical activities, including the development and the testing of STRATELEC instruments, but also the data analysis méthodology. Finally, we will discuss the way forward for the upcoming and final Stratéole-2 campaign (winter 2026-2027), as well as some initial thoughts on future balloon campaigns. Hertzog A., and R. Plougonven (2020), Stratéole-2 : des ballons longue durée pour étudier la tropopause tropicale, La Météorologie - n° 108 - février 2020.Defer, E., et al. (2022), An Overview of the STRATELEC (STRatéole-2 ATmospheric ELECtricity) Project, 25th ESA Symposium on European Rocket and Balloon Programmes and Related Research, 1-5 May 2022, Biarritz, France.

We investigate properties of the electromagnetic activity following the first lightning return stroke (RS), using concurrent observations from the SLAVIA (Shielded Loop Antenna with a Versatile Integrated Amplifier) sensor, the SAETTA (Suivi de l'Activité Electrique Tridimensionnelle Totale de l'Atmosphère) Lightning Mapping Array (LMA) and the METEORAGE LF (low-frequency) network in the Corsica region. From the data collected between September and December 2015, we selected 66 negative cloud-to-ground (−CG) and 26 positive cloud-to-ground (+CG) lightning flashes in the north-western Mediterranean region. In the SAETTA data, we observe a decrease in the very high frequency (VHF) radiation rate and the VHF power, as recorded within a typical 80 µs time window at the LMA stations, immediately after the RS pulse in 59 −CG flashes. Contrastingly, we show that all examined +CG flashes exhibit a rapid increase in the VHF radiation rate and the VHF power immediately after the RS. We suggest a possible explanation of this phenomenon by considering the step-like propagation of a negative part of the bidirectional leader starting at the top end of the positive lightning channel inside the thundercloud, emitting electromagnetic radiation across a broad frequency spectrum.

Thunderclouds and lightning produce high-energy radiation over a wide range of time scales. Terrestrial gamma-ray flashes (TGFs) are brief emissions lasting ~100 µs, consisting of photons with energies ranging from 20 keV to 40 MeV. Simultaneous ground-based measurements of electromagnetic fields and gamma-ray emissions have found TGFs to be associated with the evolutionary phases of both intracloud and cloud-to-ground lightning discharges.Gamma-ray glows, on the other hand, last from a few seconds to several tens of minutes, typically coincide with the passage of thunderclouds, and are sometimes abruptly terminated by nearby lightning. Photons emitted during gamma-ray glows share the same energy spectrum as TGFs but are less intense. It was recently discovered that thundercloud regions can glow for hours and that gamma glows are more dynamic phenomena than originally thought.Both types of gamma-ray emissions are believed to be generated via bremsstrahlung by energetic runaway electrons accelerated in the strong electric fields within thunderclouds. However, the connection between TGFs and gamma-ray glows remains not fully understood.Until now, the only simultaneous gamma ray and radio wave measurements were conducted onboard an airplane during the ALOFT campaign. The TARANIS mission, which was intended to carry a unique set of electromagnetic, particle, gamma ray, and optical instruments, was unfortunately lost due to the failure of the Vega launcher in 2020.The STRATELEC balloon project (part of the French-US STRATEOLE-2 project of long-duration balloon flights at the tropical tropopause), with precise synchronization of broadband electric field measurements and a gamma-ray detector, will provide a unique opportunity to correlate individual photon detections with electromagnetic pulses emitted by various lightning processes. These coordinated measurements could help answer the following questions:a) At which stage of the evolution of lightning discharges are TGFs produced? b) Which types of intracloud discharges produce detectable high-energy radiation? c) What are the differences in the electromagnetic signatures of lightning processes associated with TGFs and gamma glows? d) What are the temporal variations in electromagnetic emissions associated with gamma glows? e) Are flickering TGFs truly radio silent? In this presentation, we introduce the FPGA-based radio receiver RIP (Radio Instrument Package), developed for the STRATELEC balloon project. The receiver is designed to capture and analyze the electromagnetic signatures of various lightning phenomena associated with gamma-ray production, including leader pulses, initial breakdown pulses, compact intracloud discharges, and dart-stepped leader pulses. The anticipated launch is late 2026.

We investigate the electromagnetic activity following the first return stroke (RS), using data from the SLAVIA (Shielded Loop Antenna with a Versatile Integrated Amplifier) sensor and the lightning mapping array SAETTA (Suivi de l'Activite Electrique Tridimensionnelle Totale de l'Atmosphere). From data collected between September and December 2015 in the north-western Mediterranean region, we selected 69 negative cloud-to-ground (-CG) and 29 positive cloud-to-ground (+CG) flashes. Within SAETTA data, we observe a reduction in counts and power of VHF radiation sources immediately after the RS pulse in 62 -CG flashes. Contrastingly, all examined +CG flashes exhibit a rapid increase in the counts and power of VHF radiation sources immediately after the RS. We offer a hypothesis of a step-like propagation of a negative leader starting at the top end of the lightning channel inside the thundercloud, emitting electromagnetic radiation across a broad frequency spectrum.

The objective of this study is to prepare the assimilation of the Meteosat Third Generation Lightning Imager (MTG-LI) observations in the regional numerical weather prediction model AROME-France using a 3D-EnVar data assimilation algorithm. As opposed to the current operational configuration of AROME-France data assimilation system, the hydrometeor specific contents are added in the control variable and are thus updated during the assimilation process. Consequently, a lightning observation operator based on the specific contents of snow and graupel is used. As the first MTG satellite was launched in December 2022, the real MTG-LI observations are not available yet, and proxy spaceborne lightning observations generated from ground-based lightning detection network are used. We assess the forecast skills of experiments assimilating lightning in a close to operational configuration by comparing the results to a reference experiment that does not assimilate lightning. In the studied cases, the frequency bias and fraction skill score are improved for brightness temperatures forecasts lower than 280 K up to 4 h after the assimilation, implying a better description of the general cloud cover. The convective cores, identified by brightness temperatures lower than 220 K, are better captured in the first forecast hour but this improvement is not maintained through time and quickly fades.

Abstract Lightning characteristics of Corsican storms with different charge structures are investigated in this study. Observations of an LMA network are used to document the total lightning activity. Complementary lightning observations of the lightning detection network Météorage are also used. A clustering algorithm is used to build a database of electrical cells from June to October 2018. A method is also applied to infer the vertical charge structure, as dominant dipoles, per 10‐min period for each electrical cell. As an example, one cell recorded in July 2018 is discussed. The cell database is then presented as well as the main electrical properties according to the dominant charge structures. For instance, the higher in altitude the dominant dipole, the higher the flash rate. Overall, dominant negative dipole are observed for 25% of the 10‐min periods and can be separated into two categories: (a) low altitude negative dipole class dominated by negative cloud‐to‐ground (CG) flashes with a main positive layer located between 2 and 4 km height and (b) high altitude negative dipole class, dominated by negative intracloud (IC) with a main positive layer at 5 km height. Dominant positive dipole can also be separated into two categories with (a) a dominant positive dipole located between 4.5 and 10 km high, −CG dominance, weak flash rate and (b) higher altitude dominant positive dipole, +IC dominance and a larger +CG fraction. The synergistic use of LMA and Météorage observations independently gives a rational type and polarity classification with regard to the vertical charge structure.

This study develops a lightning data assimilation (LDA) scheme for the regional, convection-permitting numerical weather prediction (NWP) model AROME-France. The LDA scheme intends to assimilate total lightning, i.e., cloud-to-ground (CG) and inter- and intra-cloud (IC), of the future Meteosat Third Generation (MTG) Lightning Imager (LI; MTG-LI). MTG-LI proxy data are created, and flash extent density (FED) fields are derived. An FED forward observation operator (FFO) is trained based on modeled, column-integrated graupel mass from 24 storm days in 2018. The FFO is successfully verified for 2 independent storm days. With the FFO, the LDA adapts a 1-dimensional Bayesian (1DBay) retrieval followed by a 3-dimensional variational (3DVar) assimilation approach that is currently run operationally in AROME-France for radar reflectivity data. The 1DBay retrieval derives relative humidity profiles from the background by comparing the FED observations to the FED inferred from the background. Retrieved relative humidity profiles are assimilated as sounding data. The evaluation of the LDA comprises different LDA experiments and four case studies. It is found that all LDA experiments can increase the background integrated water vapor (IWV) in regions where the observed FED exceeds the FED inferred from AROME-France outputs. In addition, IWV can be reduced where spurious FED is modeled. A qualitative analysis of 6 h accumulated rainfall fields reveals that the LDA is capable of locating and initiating some local precipitation fields better than a radar data assimilation (RDA) experiment. However, the LDA also leads to rainfall accumulations that are too high at some locations. Fractions skill scores (FSSs) of 6 h accumulated rainfall are overall similar for the developed LDA and RDA experiments. An approach aiming at mitigating effects due to differences in the optical extents of lightning flashes and the area of the corresponding cloud was developed and included in the LDA; however, it does not always improve the FSS.

SOFT-IO-LI is a new tool merging space and ground based lightning observations and aircraft NOx measurements to provide a database of new parameters characterizing lightning-NOx air masses observed at the global scale, to the scientific community.The tool takes lightning-NOx air masses measured by IAGOS (In-service Aircraft for a Global Observing System) a European Research Infrastructure for global observations of atmospheric composition using commercial aircraft. FLEXPART the Lagrangian transport and dispersion model is used, together with ERA5 reanalysis weather data from ECMWF, to perform a backward trajectory of these air masses, resulting in hourly mass residence times for lightning-NOx particles for the days prior to the flight measurements.We will present, for IAGOS transatlantic flights, the comparison of these mass residence times with ground based NLDN (National Lightning Detection Network) and space based GLM (Global Lightning Mapper) lightning observations, as well as with ABI (Advanced Baseline Imager) cloud data. We will show that SOFT-IO-LI is capable of relating lightning events and chemical species observed in situ, in order to determine characteristics of the different lightning-related air masses.

The north-western Mediterranean basin often experiences thunderstorms with heavy precipitation and intense lightning activity causing damages to this densely populated area. This study is conducted within the framework of the EXAEDRE (EXploiting new Atmospheric Electricity Data for Research and the Environment) project that aims to better monitor the thunderstorms in this area through a better understanding of the physical processes that drive the dynamics, the microphysics and the electrical activity of the convective systems. These thunderstorms can exhibit distinct vertical charge structures (normal and anomalous) that produce lightning flashes with different properties. The goal of this study is to compare these characteristics (CG production, flash polarity...) according to both charge structures as measured in Corsica. The study evaluates the properties of both types of Corsican storms at the electrical cell scale. Hence, observations of the LMA (Lightning Mapping Array) SAETTA network, deployed in Corsica, are used to document in 3D the total lightning activity. Complementary 2D lightning observations recorded by the French LLS (Lightning Locating System) METEORAGE are also used. We also add Météo France weather radar data to document the cumulative rainfall associated to each electrical cell. A clustering algorithm is applied on the lightning data to identify and track the cells. Then we extract lightning and radar data for each cell to document the evolution of several lightning-related parameters during their lifetime. We also apply a recently published method to automatically infer the vertical structure of the electrical charge regions within each cell. These algorithms allow us to create a database of hundreds of electrical cells in Corsica for the period of study (June – October 2018). We first introduce the different observations and methodologies applied here. Then we present the geographical and temporal distribution of the normal and anomalous cells over the study period. Finally we compare the electrical properties associated to these different vertical charge structure configuration. Overall, anomalous cells represented around 15% of the cells population in Corsica over the study period. Anomalous storms produced less lightning jumps per cell but produced more CGs relative to the total number of flashes per cell. We also show that anomalous cells tend to form shorter flashes. The relationship between number of CGs and cumulative rainfall in Corsica for both charge structure is linear and in accordance with previous results.

Coincident Geostationary Lightning Mapper (GLM) and National Lightning Detection Network (NLDN) observations are used to build a generator of realistic lightning optical signal in the perspective to simulate Lightning Imager (LI) signal from European NLDN-like observations. Characteristics of GLM and NLDN flashes are used to train different machine-learning (ML) models, which predict simulated pseudo-GLM flash extent, flash duration, and event number per flash (targets) from several NLDN flash characteristics. Comparing statistics of observed GLM targets and simulated pseudo-GLM targets, the most suitable ML-based target generators are identified. The simulated targets are then further processed to obtain pseudo-GLM events and flash-scale products. In the perspective of lightning data assimilation, flash extent density (FED) is derived from both observed and simulated GLM data. The best generators simulate accumulated hourly FED sums with a bias of 2% to the observation while cumulated absolute differences remain of about 22%. A visual comparison reveals that hourly simulated FED features local maxima at the similar geolocations as the FED derived from GLM observations. However, the simulated FED often exceeds the observed FED in regions of convective cores and high flash rates. The accumulated hourly area with FED. > flashes per 5 km 3 5 km pixel simulated by some pseudoGLM generators differs by only 7%-8% from the observed values. The recommended generator uses a linear support vector regressor (linSVR) to create pseudo-GLM FED. It provides the best balance between target simulation, hourly FED sum, and hourly electrified area.

All evolution stages of cloud-to-ground (CG) lightning flashes, both positive (+CG) and negative (-CG), generate electromagnetic radiation, which can be used for their investigation. We focus on the electromagnetic activity immediately following the first return stroke (RS). We combine measurements of the broadband receiver BLESKA and the lightning mapping array (LMA) network SAETTA, capable of detecting sources of narrowband very high frequency (VHF) radiation. The French lightning location system Météorage provided us with the information about 2D location, polarity and peak currents for studied CG and intracloud (IC) discharges. From our data collected in the northwestern Mediterranean region from September to December 2015, we have selected and investigated the electromagnetic activity following 16 +CG and 38 -CG flashes. Using the data from individual SAETTA stations we found that 36 -CG flashes exhibited a fast decrease in the counts and in the power of VHF radiation sources immediately after the RS pulse. The maximum count of 2000 VHF radiation sources was detected by the closest SAETTA station at an average time delay of 66 μs after the RS pulse peak. At a delay of 1.85 ms after the RS pulse peak or sooner, the VHF radiation rate decreased below 1500 VHF radiation sources, with the median value of this time equal to 195 μs, and kept decreasing. In the case of all inspected +CG flashes, we observed an unexpectedly fast increase in the counts of the VHF radiation sources and their power after the RS pulse. Up to 161.95 ms after the RS pulse, the VHF radiation rate decreased below 1500 VHF radiation sources, with the median value of this time equal to 34.53 ms, much longer than in case of –CGs. At the same time, we observed a visible sequence of bipolar pulses lasting up to 50 ms in the magnetic-field waveforms recorded by BLESKA, with the amplitude of the biggest pulse varying from 2 to 10 nT. This observed longer presence of VHF radiation after +CG flashes may be caused by a potential difference between the end of neutralized RS channel and the positive charge layer in the thundercloud in case of +CGs, which might result in a new electrical breakdown. Then a stepwise propagation of a new negative leader inside the thundercloud is possible, emitting electromagnetic radiation in a wide range of frequencies. This radiation can be detected by narrowband LMA stations in the form of VHF radiation sources, same as by a broadband receiver in the form of pulses.

This study aims at simulating satellite-measured lightning observations with numerical weather prediction (NWP) system variables. A total of eight parameters, calculated with the AROME-France NWP system variables, were selected from a literature review to be used as proxies for satellite lightning observations. Two different proxy types emerged from this literature review: microphysical and dynamical proxies. Here, we investigate which ones are best related to satellite lightning and calibrate an empirical relationship between the best parameters and lightning data. To obtain those relationships, we fit machine learning regression models to our data. In this study, pseudo flash extent accumulation (FEA) observations are used because no actual geostationary lightning observations are available yet over France, and non-geostationary satellite lightning data represent a sample that is too small for our study. The performances of each proxy and machine learning regression model are evaluated by computing fractions skill scores (FSSs) with respect to observed FEA and proxy-based FEA. The present study suggests that microphysical proxies are more suited than the dynamical ones to model satellite lightning observations with the AROME-France NWP system. The performances of multivariate regression models are also evaluated by combining several proxies after a feature selection based on a principal component analysis and a proxy correlation study, but no proxy combination yielded better results than microphysical proxies alone. Finally, different accumulation periods of the FEA had little influence, i.e. similar FSS, on the regression model's ability to reproduce the observed FEA. In future studies, the microphysical-based relationship will be used as an observation operator to perform satellite lightning data assimilation in storm-scale NWP systems and applied to NWP forecasts to simulate satellite lightning data.

The north-western Mediterranean basin often experiences thunderstorms with heavy precipitation, strong wind, lightning activity and sometimes waterspouts/tornadoes. One of the objectives of the EXAEDRE (EXploiting new Atmospheric Electricity Data for Research and the Environment) project is to better monitor the thunderstorms in this area through a better understanding of the physical processes that drive the dynamics, the microphysics and the electrical activity of the convective systems. Characteristics of the electrical activity such as flash rate, charge layer distribution or flash polarity are good proxies for thunderstorm monitoring and good evidences of the storm severity. The 29th October 2018, an intense trough developed over Mediterranean Sea between Balearic Islands and Corsica. This storm, called ADRIAN, produced several hazards (heavy precipitation, strong winds, intense lightning activity and hailstorm) in Corsica. Two tornadoes and one waterspout were observed in the morning at Porto Vecchio (EF2 tornado and waterspout) and Aleria (EF1 tornado), causing significant damages. In this study, we take a look at electrical and microphysical characteristics of the two tornadic cells. For that, observations of the LMA (Lightning Mapping Array) SAETTA network, deployed in Corsica, are used to document in 3D the total lightning activity. Complementary 2D lightning observations recorded by the French national lightning detection network METEORAGE are also investigated. We also use weather radar data from the Météo France network. A clustering algorithm is applied on both the lightning and radar data to identify and track the cells to document the evolution of several lightning-related and microphysical characteristics during the lifetime of each cell. We also applied a new method based on lightning leader velocity to automatically infer the vertical and horizontal structure of the electrical charge regions within each electrical cell. We first introduce the different observations and methodologies applied here. Then the main electrical properties of the tornadic cells (e.g. flash duration, vertical flash extension, charge layer, flash type and polarity) and microphysical characteristics as well as their temporal evolution are presented. Overall, the studied electrical cells produced few cloud-to-ground lightning flashes predominantly of negative polarity. The peaks of electrical activity occurred when tornadoes hit the land and these storms presented all an anomalous charge structure.

This study is a multi-instrumental analysis of a ~20-hour duration northwestern Mediterranean storm on September 21, 2019 that produced 21 sprites recorded with a video camera, of which 19 (90 %) were dancing sprites. A dancing sprite is a phenomenon in which sequences of sprites appear in succession with time intervals of no more than a few hundred milliseconds. For the most part, the individual sprites are a consequence of discrete strokes from one extended lightning flash. In this case, we find that 87.5% of the sprite sequences were triggered by distinct positive cloud-to-ground (+CG) strokes. The time between successive sprite parent (SP)+CG strokes within the same dancing sprite was between 40 and 516 ms, and the distance ranged between 2 and 87 km. The storm size and vertical development were analyzed from the infrared radiometer onboard Meteosat Second Generation satellite and the lightning activity was documented with several lightning location systems (LLS): the French LF network (Météorage), the GLD360 network operated by Vaisala company, the VHF SAETTA Lightning Mapping Array (LMA) system located in Corsica. Additionally, the vertical electric field at the time of the dancing sprites was measured with a broadband ELF vertical dipole whip antenna ~700 km away from the storm. The SAETTA LMA allows to map the SP+CG flashes in their both full extent and temporal evolution, and to infer the charge structure of the parent storm. We show that the SP+CG flashes followed a common propagation: they originated from the convective and very electrically active regions of the storm, and then escaped and extended horizontally far (tens of km) into the stratiform cloud region. Most of the sprites were triggered by +CG strokes in the stratiform region often following flash development resembling cutoff of a long negative leader. Additionally, we present a detailed analysis of two dancing sprite events in which the SP+CGs triggered new bidirectional breakdown with fast moving leaders that extended into the stratiform cloud region and resulted in new SP+CG strokes. In both events, we find in both LLS and ELF vertical electric field records, that the last sprite sequence was triggered by three almost simultaneous +CG strokes.

The EXAEDRE (EXploiting new Atmospheric Electricity Data for Research and the Environment) project aims at better understanding North-western Mediterranean Sea thunderstorms through coupled observational- and modelling-based studies with a dedicated focus on the lightning activity and its properties at flash, storm and regional scale. In this work, the lightning activity is measured by the VHF Lightning Mapping Array (LMA) network SAETTA and the operational French lightning detection network Meteorage. SAETTA VHF sources are merged in flashes based on a DBSCAN algorithm (L2 SAETTA dataset). Meteorage strokes and pulses are then combined to SAETTA flashes based on temporal and pulse/stroke-dependent spatial criteria (L2b SAETTA-Meteorage dataset). Four categories of flashes can then be investigated: 1) CG L2b flashes with at least one CG stroke, 2) pure IC L2b flashes as detected by Meteorage with only IC pulses, 3) No-MTRG flashes which are only detected by SAETTA flashes with no concurrent Meteorage records, and 4) No-SAETTA flashes which were only reported by Meteorage with no concurrent SAETTA records. Several lightning parameters have been investigated for the first three L2b flash categories listed above. It includes among others the flash duration, the vertical flash extension, the 2D horizontal flash extension, the 10/50/90 percent quantile of flash altitude, the flash trigger altitude, the stroke/pulse number per flash, and the flash vertical extension. Based on the L2b database built from the SAETTA and Meteorage records of the entire year 2018, No-MTRG flashes have tendency to be rather small in terms of 2D flash extension or short in duration. They also statically exhibit a similar distribution of their 10/50/90 percent quantile of flash altitude. CG L2b flashes exhibit mainly altitudes below 8 km while the majority of pure IC flashes show distinct distribution of 10/50/90 percent quantile flash altitude. Three trigger altitude ranges, i.e. 4-5 km, 7-9 km, 11-12 km are found in the three studied categories. Finally, for the studied year, less +CG flashes occurred compared to the -CG flashes while CG flashes with more ground connections have the tendency to last longer and to be larger. First we will introduce the instruments and the data. We will then present the different methodologies applied here to generate the L2b dataset with some typical lightning observations. We will then discuss on the characteristics of the different parameters listed above.

The aim of this study is to enhance our understanding about the microphysical structure of convective cloud systems and its relationships to the ambient electrical field, and to assess the capability of a model to capture the cloud electrical properties. This study relies on the EXAEDRE (EXploiting new Atmospheric Electricity Data for Research and the Environment) aircraft campaign that took place from 13 September to 8 October 2018 in Corsica Island. Eight electrified convective systems were successfully sampled during the campaign by the French Falcon 20 aircraft (e.g. RASTA Doppler cloud radar, microphysics probes, electric field mills) and ground-based platforms (Lightning Mapping Array network, Météorage operational lightning locating system and Météo-France weather radars). In this study, a multi-cell thunderstorm which developed over the complex topography of Corsica Island on 17 September 2018 was selected to investigate and to understand the physical processes linking lightning occurrence, electrification efficiency, cloud microphysics and dynamics. The detailed analysis results using the unprecedented airborne and ground-based dataset and their comparison to the numerical simulation results with a horizontal grid spacing of 1 km comprising the explicit electrical scheme CELLS (Cloud Electrification and Lightning Scheme) implemented in the cloud resolving model Meso-NH has been conducted. The key results will be presented at the conference.

The north-western Mediterranean basin often experiences thunderstorms with heavy precipitation, strong wind, lightning activity and sometimes waterspouts/tornadoes. One of the objectives of the EXAEDRE (EXploiting new Atmospheric Electricity Data for Research and the Environment) project is to better monitor the thunderstorms in this area through a better understanding of the physical processes that drive the dynamics, the microphysics and the electrical activity of the convective systems. Characteristics of the electrical activity such as flash rate, charge layer distribution or flash polarity are good proxies for thunderstorm monitoring and good evidences of the storm severity. The 29th October 2018, an intense trough developed over Mediterranean Sea between Balearic Islands and Corsica. This storm, called ADRIAN, produced several hazards (heavy precipitation, strong winds, intense lightning activity and hailstorm) in Corsica. Two tornadoes and one waterspout were observed in the morning at Porto Vecchio (EF2 tornado and waterspout) and Aleria (EF1 tornado), causing significant damages. In this study, we take a look at electrical and microphysical characteristics of the two tornadic cells. For that, observations of the LMA (Lightning Mapping Array) SAETTA network, deployed in Corsica, are used to document in 3D the total lightning activity. Complementary 2D lightning observations recorded by the French national lightning detection network METEORAGE are also investigated. We also use weather radar data from the Météo France network. A clustering algorithm is applied on both the lightning and radar data to identify and track the cells to document the evolution of several lightning-related and microphysical characteristics during the lifetime of each cell. We also applied a new method based on lightning leader velocity to automatically infer the vertical and horizontal structure of the electrical charge regions within each electrical cell. We first introduce the different observations and methodologies applied here. Then the main electrical properties of the tornadic cells (e.g. flash duration, vertical flash extension, charge layer, flash type and polarity) and microphysical characteristics as well as their temporal evolution are presented. Overall, the studied electrical cells produced few cloud-to-ground lightning flashes predominantly of negative polarity. The peaks of electrical activity occurred when tornadoes hit the land and these storms presented all an anomalous charge structure.