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This article gives an overview of the electrical characteristics of the thundercloud and the predominant mechanisms that are at the origin. The specific cloud that can produce lightning is described and the parameters that control its... more
This article gives an overview of the electrical characteristics of the thundercloud and the predominant mechanisms that are at the origin. The specific cloud that can produce lightning is described and the parameters that control its development and its organization are discussed. According to the variety of the scales of time and space associated with the mechanisms that occur within the thundercloud, it is difficult to simulate them both experimentally and numerically. Thus, the advances in the knowledge of the thunderstorm electricity have been sometimes relatively slow and have raised a lot of debates. Furthermore, in-situ observation remains difficult because of the hostility of the thundercloud medium for instrumentation, sensors, aircraft or other carriers of sensors. The responses to the questions in the domain of thundercloud electricity can sometimes remain speculative. However, recent detection techniques and laboratory experiments allow a better knowledge of the cloud e...
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Transient Luminous Events are optical effects of lightning induced electric fields in the upper atmosphere. They were serendipitously discovered in 1989 by low-light video recordings of sprites above thunderstorms over the US. Since 1993... more
Transient Luminous Events are optical effects of lightning induced electric fields in the upper atmosphere. They were serendipitously discovered in 1989 by low-light video recordings of sprites above thunderstorms over the US. Since 1993 airborne and ground based campaigns to perform TLE observations have been carried out in several countries in all five continents. Space shuttle and, more recently, satellite
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This paper reviews scientific advances achieved by a North-South network between 2006 and 2016. These scientific advances concern solar terrestrial physics, atmospheric physics and space weather. This part B is devoted to the results and... more
This paper reviews scientific advances achieved by a North-South network between 2006 and 2016. These scientific advances concern solar terrestrial physics, atmospheric physics and space weather. This part B is devoted to the results and capacity building. Our network began in 1991, in solar terrestrial physics, by our participation in the two projects: International Equatorial Electrojet Year IEEY [1992-1993] and International Heliophysical Year IHY [2007-2009]. These two projects were mainly focused on the equatorial ionosphere in Africa. In Atmospheric physics our research focused on gravity waves in the framework of the African Multidisciplinary Monsoon Analysis project n°1 [2005-2009 ], on hydrology in the Congo river basin and on lightning in Central Africa, the most lightning part of the world. In Vietnam the study of a broad climate data base highlighted global warming. In space weather, our results essentially concern the impact of solar events on global navigation satellit...
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Research Interests: Geology, Geophysics, Geofísica, Lightning, Geophysical, and 3 moreStorms, Tle, and Lightning Connector
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This contribution reports the design, realization and operation of a novel digital low frequency radio camera towards an exploration of the Earth's electromagnetic environment with particular emphasis on lightning discharges and... more
This contribution reports the design, realization and operation of a novel digital low frequency radio camera towards an exploration of the Earth's electromagnetic environment with particular emphasis on lightning discharges and subsequent atmospheric effects such as transient luminous events. The design of the digital low frequency radio camera is based on the idea of radio interferometry with a network of radio receivers which are separated by spatial baselines comparable to the wavelength of the observed radio waves, i.e., ~1-100 km which corresponds to a frequency range from ~3-300 kHz. The key parameter towards the realization of the radio interferometer is the frequency dependent slowness of the radio waves within the Earth's atmosphere with respect to the speed of light in vacuum. This slowness is measured with the radio interferometer by using well documented radio transmitters. The digital low frequency radio camera can be operated in different modes. In the imaging...
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We present recent observations, performed in France with a multi-component infrasound station, of gravity waves produced by a thunderstorm. The wave amplitude reaches 100 Pa at periods increasing from few tens of minutes up to few hours... more
We present recent observations, performed in France with a multi-component infrasound station, of gravity waves produced by a thunderstorm. The wave amplitude reaches 100 Pa at periods increasing from few tens of minutes up to few hours during the thunderstorm evolution. The thunderstorm evolution has been determined by using meteorological radars, satellites and lightning maps. The gravity wave activity is
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A new instrument composed by a high speed camera, two high energy detectors, a E-field antenna and a VHF antenna were installed at the Eagle Nest tower (northeast of Spain) during summer 2011. With this equipment several lightning flashes... more
A new instrument composed by a high speed camera, two high energy detectors, a E-field antenna and a VHF antenna were installed at the Eagle Nest tower (northeast of Spain) during summer 2011. With this equipment several lightning flashes to the tower and its vicinity have been observed. This paper presents two examples: the first was an upward negative leader triggered by a close cloud-to-ground flash and the second was an upward negative flash not associated with previous lightning activity. The paper also presents 3D mapping of leaders of two upward lightning.
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Lightning flashes and surface rainfall are two manifestations of thunderstorms, both consequences of physical processes in the cloud involving hydrometeors of different sizes and types. For several decades, observations using various... more
Lightning flashes and surface rainfall are two manifestations of thunderstorms, both consequences of physical processes in the cloud involving hydrometeors of different sizes and types. For several decades, observations using various techniques have shown the general trend for both activities to be tightly related and to quantify the relationship. In several regions of the world, rainfall produced by convective systems has been estimated from surface detection, from ground radar scans or from space observations, and the rate of lightning flashes generated by the same systems was determined in parallel using various detection systems. Among the parameters used to quantify the relationship between rainfall and lightning, the Rain-yield Per Flash (RPF) which is the rainfall volume or mass divided by the lightning frequency, has been estimated in different regions and in several convection regimes. The values obtained from many studies can range from less than 1 × 107 kg fl-1 in continental and arid regimes to about 3000 × 107 kg fl-1 in oceanic regime. The variation of the RPF has been attributed to various causes in the literature, according to the techniques of rainfall estimation, the region of the storm activity, the type and the phase of the storms involved, and the type of flash considered. Surface-detected rainfall can provide larger RPF values than rainfall detected at altitude because of evaporation. The RPF values are obviously lower when considering total lightning activity and higher when the storm systems cover an extended stratiform zone. A large difference is observed between oceanic and continental storms. The RPF is much larger in oceanic convective clouds, especially in warm pool. The main reason for this contrast is the weakness of the updrafts over the ocean compared to over the land. In ocean storms, the width and the height of the mixed-phase cloud region, where the non-inductive charging processes occur, are too small for the development of electrification.
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EuroSprite 2003/2005 campaigns have yielded 165 sprites during several nights of organized thunderstorms. A comprehensive study of the characteristics of the storm systems and their cloud-to-ground lighting strokes has started. The key... more
EuroSprite 2003/2005 campaigns have yielded 165 sprites during several nights of organized thunderstorms. A comprehensive study of the characteristics of the storm systems and their cloud-to-ground lighting strokes has started. The key dataset consists of 5-minute radar reflectivity composites over France, Meteorage lightning detection data, Meteosat cloud top temperatures and the image database of sprites and their times of occurrence. Radar data availability limits the analysis to include only events occurring over France. The following analyses are presented: 1) Evolution of radar reflectivity (and cloud top temperature) area sizes over time 2) Overview plots of positive, negative and sprite-associated lightning overlaid over radar images, occurring over a relatively long period, before, during and after the sprites 3) A statistical summary of peak current/radar reflectivity/cloud top temperature values in the vicinity of cloud- to-ground lightning strokes that do and do not prod...
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. A numerical model called PICASSO [Production d'Ions Corona Au Sol Sous Orage (French) and Production of Corona Ions at the Ground Beneath Thundercloud (English)], previously designed, is used to describe the evolution of the... more
. A numerical model called PICASSO [Production d'Ions Corona Au Sol Sous Orage (French) and Production of Corona Ions at the Ground Beneath Thundercloud (English)], previously designed, is used to describe the evolution of the principal electrical parameters below a thunderstorm, taking into account the major part played by corona ions. In order to improve the model restitution of a real situation, various improvements are performed: an initial vertical distribution of aerosol particles is introduced instead of the previously used uniform concentration; time and space calculation steps are adjusted according to the electric field variation rate; the upper boundary condition is improved; and the coefficients of ion attachment are reconsidered with an exhaustive bibliographic study. The influence of the ion attachment on aerosol particles, on the electric field and charge density aloft, is studied by using three different initial aerosol particle concentrations at ground level and two types of initial vertical distributions: uniform and non-uniform. The comparison between field data and model results leads to adjust the initial aerosol particle concentration over the experimental site at the value of 5000 cm-3 which appears to be highly realistic. The evolutions of the electric field and of the charge density at altitude are greatly influenced by the aerosol concentration. On the contrary, the surface intrinsic field, defined as the electric field that would exist underneath a thundercloud if there were no local charges, is weakly affected when the model is forced by the surface field. A good correlation appears between the success in the triggered lightning attempts and this intrinsic field evaluation. Therefore, when only the surface field is available, the model can be used in a triggered lightning experiment.
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The PEACH (Projet en Electricité Atmosphérique pour la Campagne HyMeX – the Atmospheric Electricity Project of HyMeX Program) project is the Atmospheric Electricity component of the HyMeX (Hydrology cycle in the Mediterranean Experiment)... more
The PEACH (Projet en Electricité Atmosphérique pour la Campagne HyMeX – the Atmospheric Electricity Project of HyMeX Program) project is the Atmospheric Electricity component of the HyMeX (Hydrology cycle in the Mediterranean Experiment) 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; 5 September–6 November 2012), four European Operational Lightning Locating Systems (OLLSs) (ATDNET, EUCLID, LINET, ZEUS) and the HyMeX Lightning Mapping Array network (HyLMA) were used to locate and characterize the lightning activity over the Southeastern Mediterranean at flash, storm and regional scales. Additional research instruments like slow antennas, video cameras, micro-barometer and microphone arrays were also operated. All these observations in conjunction with operational/research ground-based and airborne radars, ra...