A cloud-to-ground lightning density due to progressing climate change in Poland

This research focuses on the climatology of cloud-to-ground (CG) lightning flashes based on PERUN lightning detection network managed by IMGW-PIB (Institute of Meteorology and Water Management – National Research Institute) during period 2002 to 2020. To present statistical data converted from raw lightning data, a grid cell with dimensions of 10 km × 10 km was used in order to standardize the results and refer to research conducted in other countries. As a result of the research, it can be concluded that the PERUN system detected 8,626,200 CG flashes during the 18-year period under study. Lightning data were used to determine the spatial distribution of CG flashes, number of thunderstorm days, the annual distribution or the hours of lightning occurrence. The average annual value of CG flashes varies from 0,5 to 3,5 flashes km−2·yr−1. The highest electrical activity occurs in central Poland (Mazovian Lowland) and the lowest in the Pomeranian Lake District. As a result of the research, it is possible to identify a storm trail that begins near Kraków-Częstochowa Upland and ends at the Masurian Lake District. The month with the highest electrical activity in Poland is July, while the highest electrical activity of thunderstorms occurred in 2017. Positive current flashes accounted for 4% of all detected CG flashes, with the greatest activity in June but since 2015, there has been visible increasing activity of thunderstorms carrying CG's with positive current. As a result of the analysis, it was also possible to identify a growing tendency of CG flashes in the area of whole country.