L'analyse de 561 jours d'orage sur 6 années de données de l'imageur d'éclair 3D Saetta a permis d'identifier des nuages convectifs en région Corse présentant une structure électrique anormale et apparaissant par flux de sud de poussières désertiques africaines. L'explication physique des processus électriques apporte les bases pour comprendre ce que l'imageur permet de déduire sur la structure électrique des cellules orageuses. Des hypothèses microphysiques et radiatives conduisant à un faible contenu en gouttelettes d'eau surfondue à l'origine de cette électrisation anormale sont explorées en s'appuyant sur l'analyse du contexte en aérosols et des conditions météorologiques environnantes. The analysis of 561 days of thunderstorms over 6 years of data from the 3D lightning imager Saetta has allowed to identify convective clouds in Corsica region with an abnormal electrical structure and appearing by southern flow of African desert dust. The physical explanation of the electrical processes brings the basis to understand what the imager allows to deduce about the electrical structure of thunderstorm cells. Microphysical and radiative hypotheses leading to a low content of supercooled droplets at the origin of this abnormal electrification are explored by relying on the analysis of the aerosol context and the surrounding meteorological conditions.
<p><span><span>The north-western Mediterranean basin often experiences thunderstorms with heavy precipitation, strong wind, lightning activity </span><span>and sometimes waterspouts/tornadoes</span><span>. 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. </span><span>C</span><span>haracteristics </span><span>of the electrical activity </span><span>such as flash rate, charge layer </span><span>distribution</span><span> or flash polarity are good proxies for thunderstorm monitoring and good evidences of the storm severity.</span></span></p><p><span>The 29<sup>th</sup> 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.</span></p><p><span>In this study, we take a look at electrical and microphysical characteristics of the two tornadic cells. </span><span>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 M&#233;t&#233;o 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.</span></p><p><span><span>We first introduce the different observations and methodologies applied here. Then the main electrical properties </span></span><span><span>of the tornadic cells </span></span><span><span>(e.g. flash duration, vertical flash extension, charge layer, flash type and polarity) </span></span><span><span>and microphysical characteristics </span></span><span><span>as well as their temporal evolution are presented. </span></span><span><span>Overall, t</span></span><span><span>h</span></span><span><span>e </span></span><span><span>studied electrical cells</span></span><span><span> produced few cloud-to-ground lightning </span></span><span><span>flashes</span></span><span> </span><span><span>p</span></span><span><span>redominantly of negative polarity. </span></span><span><span>The peaks of electrical activity occurred when tornadoes </span></span><span><span>hit the land and </span></span><span><span>these storms presented </span></span><span><span>all </span></span><span><span>an anomalous charge structure. </span></span></p>
<p><span>The north-western Mediterranean basin often experiences thunderstorms with heavy precipitation </span><span>and </span><span>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. </span><span>These t</span><span>hunderstorms can exhibit d</span><span>istinct</span><span> vertical charge structure</span><span>s</span><span> (</span><span>normal</span><span> and anomalous) that produce lightning </span><span>flashes</span><span> with different</span> <span>properties</span><span>. </span><span>The goal of this study is to compare these </span><span>characteristics (CG production, flash polarity...</span><span>)</span> <span>according</span><span> to both charge structure</span><span>s as measured</span><span> in Corsica. </span></p><p><span>T</span><span>h</span><span>e</span><span> study </span><span>evaluates</span><span> the</span> <span>properties</span><span> of </span><span>both types of </span><span>Corsican </span><span>storms at the </span><span>electrical cell s</span><span>cale</span><span>. </span><span>Hence</span><span>, 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 </span><span>LLS (Lightning Locating System)</span><span> METEORAGE are also </span><span>used</span><span>. </span><span>We also add</span><span>&#160;M&#233;t&#233;o France</span><span> weather radar </span><span>data</span><span> to </span><span>document</span><span> the cumulative rainfall associated to each </span><span>electrical </span><span>cell. </span><span>A clustering algorithm is </span><span>applied on the lightning data</span><span> to identify and track the cells. </span><span>Then we extract lightning and radar data for each cell</span> <span>to </span><span>document</span><span> the evolution of several lightning-related </span><span>parameters </span><span>during th</span><span>eir</span><span> lifetime. We also </span><span>apply</span> <span>a </span><span>recently published</span> <span>method</span><span>&#160;</span><span>to automatically </span><span>infer </span><span>the vertical structure of the electrical charge regions </span><span>within each cell. These algorithms allow us to create a database of </span><span>hundreds</span><span> of electrical cells in Corsica </span><span>for the period of study (June &#8211; October 2018)</span><span>. </span></p><p><span>We first introduce the different </span><span>observations</span><span> and methodologies applied here. </span><span>Then we present the geographical and temporal distribution of the </span><span>normal and anomalous</span><span> cells over the study period. </span><span>Finally</span> <span>we </span><span>compare the </span><span>electrical properties </span><span>associated to </span><span>these </span><span>different vertical charge structure configuration.</span> <span>O</span><span>verall, anomalous cells represented around 15% of the cells population in Corsica over the study period. </span><span>A</span><span>nomalous</span> <span>storms</span> <span>produced </span><span>less</span> <span>lightning jumps</span><span> per cell </span><span>but produced more CGs</span> <span>relative to the total number of flashes per cell</span><span>. We also show that anomalous cells </span><span>tend to </span><span>form</span><span>&#160;</span><span>s</span><span>horter flashes</span><span>.</span> <span>The relationship between number of C</span><span>G</span><span>s and </span><span>cumulative</span><span> rain</span><span>fall</span> <span>in </span><span>Corsica</span> <span>for both charge structure </span><span>is linear and in accordance with </span><span>previous </span><span>results</span><span>. </span></p>
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
hi@scite.ai
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.