Total lightning activity in thunderstorms over Paris

Overview & Synopsis

A statistical study of two groups of storms that occurred in the Paris area (France) during summer 2000 has been realized. The first group includes 26 high radar reflectivity (HRR) storms with radar reflectivity values exceeding 60 dBZ while the second one includes 19 moderate radar reflectivity (MRR) storms with a maximum radar reflectivity value between 50 and 55 dBZ. The radar reflectivity was provided by a C-band radar and the total lightning activity (cloud-to-ground (CG) and intra-cloud (IC) flashes) was provided by the French Météorage network and a Safir device. HRR storms seem to be characterized by a longer lifetime, and a more extended convective area. On average, they produce more CG and IC flashes than MRR storms. However, a large variability in the number, the rate, and the type of flashes is observed. The HRR storms producing the highest IC flash rates (above 100 min− 1) exhibit the lowest CG flash proportion (1.2 and 4.3%). Most of the HRR storms exhibit a peak lightning activity when the radar reflectivity is strong at low level within the cloud. However, several cases of these storms show a large time lag between the strong lightning production and the presence of high radar reflectivity values at low level. Some possible explanations of these observations, taking into account cloud dynamics, microphysics and lightning initiation, are discussed.