Observations and modelling of the winter thunderstorm on 4 February 2022 at the Milešovka meteorological observatory

Abstract

The study analyses a winter thunderstorm that passed over the Milešovka meteorological observatory on 4 February 2022, between 2300 and 2330 UTC. Lightning was recorded directly over the observatory by both the observer and the EUCLID lightning network at 2320 UTC. To analyse the state of the atmosphere at the time when the lightning occurred, we used data from the X‐band Doppler polarimetric radar and the Ka‐band Doppler polarimetric vertical profiler, both located at the observatory. We also applied data from the Meteosat Second Generation satellite, and data from standard meteorological instruments located at the observatory. In addition, we run our cloud electrification model to simulate cloud electrification of the winter thunderstorm to find out whether the model develops conditions suitable for the occurrence of lightning and if so, under what circumstances. Our results show that the lightning appeared at the very end of the storm passage defined by high radar reflectivity. At the same time, it is clear from the radar observations that before lightning occurred, the cloud contained hydrometeors (graupel, cloud or rain water, and ice or snow) which are commonly associated with charge separation by collisions. Our analysis of the radar data also suggests that in at least several parts of the cloud the electric field was strong. Although the cloud top height was very low compared to summer storms, the model results indicate conditions suitable for lightning occurrence. However, uncertainty remains on how to properly formulate the initial conditions for model simulations for this type of storm which was shallow and occurs rarely in winter.