Environmental & Climate Sciences Department Seminar

There are about 45 flashes per second worldwide. About 90% of the flashes occur in cloud. A lightning flash is triggered when the ambient electric field exceeds a threshold. The ambient electric field is due to zones of electrical charges spreading within the thundercloud. Electrical charges are exchanged during hydrometeor collisions and are carried by the hydrometeors which are transported within the cloud. Consequently the lightning properties (e.g. flash rate; lightning type, i.e. intra-cloud and cloud-to-ground; flash extension; triggering altitude...) are strongly related to the microphysical, dynamical and electrification processes occurring in the parent storms.

At the flash scale, a lightning flash is not a continuous phenomenon but is in fact composed of successive events, also called flash components, with different physical properties in terms of discharge propagation, radiation type, current properties, space and time scales.

First a brief description of lightning detection techniques will be given. Then examples of flashes observed simultaneously by different instruments and replaced in their cloud context will be presented. Properties of the lightning activity will be discussed according to the dynamical and microphysical characteristics of the parent thunderclouds based on observational and modeling-based studies. Finally the EXAEDRE (EXploiting new Atmospheric Electricity Data for Research and the Environment) project will be introduced with an emphasis on the airborne field campaign scheduled between mid-September and mid-October 2018 in Western Mediterranean Sea.