The kinematic and thermodynamic environment during cloud-to-ground lightning occurrence in Poland

This research identifies termodynamic and kinematic indices that positively influence elevated values of cloud-to-ground lightning flashes (CGs) in Poland. The analysis used data from the PERUN lightning detection system from IMGW-PIB and ERA5 (ECMWF) reanalyses for the period 2002-2020. In addition, a spatial-temporal distribution analysis was carried out for the period 1940-2022, covering the key parameters necessary for the appearance of convection. Results showed that thunderstorms most often occur in the summer, but also that there are increasingly favorable conditions for the appearance of organized multicellular systems in the spring. CG flashes most often form in a most-unstable convective available potential energy (MU CAPE) environment of about 1300 J/kg along with deep layer shear (DLS 0-6 km AGL) of 13-14 m/s. Using the WMAXSHEAR parameter, it was possible to conclude that overlapping CAPE and DLS values of about 500 m2/s2 imply increased electrical activity. At the same time, a high correlation with the Hail Size Index (HSI) parameter implies a positive relationship between the occurrence of hailstorms and an increased number of CGs generated in the case of supercells. The research also found a gradual increase over evaluated timeframe in air temperature, MU CAPE, MU Mixing Ratio and the MU WMAXSHEAR parameter for the area under study.