Cloud-to-Ground Lightning in Canada: 20 Years of CLDN Data

This study presents the spatial and temporal features of more than 45 million cloud-to-ground (CG) lightning flashes recorded by the Canadian Lightning Detection Network for the years 1999-2018. Although sensor upgrades have improved the detection efficiency and location accuracy of CG lightning, the large-scale spatial patterns remain about the same as found in a previous study covering the years 1999-2008. Analyses, using equal-area squares with 10 km sides, describe the regional and seasonal characteristics of negative and positive flashes, the percentage and flash density of positive lightning, and the first-stroke peak currents of both polarities. Lightning activity over the provinces and territories is greatest in the summer, varying from 95.9% to 76.8% of the annual activity in the Northwest Territories and Ontario, respectively. Winter lightning is rare, usually occurring in extreme southern Ontario and the Atlantic Provinces, as well as over offshore regions west of Vancouver Island and the coastal waters off Nova Scotia. Preliminary analysis suggests that, compared with the 1999-2008 period, the majority of western and northern Canada has experienced more lightning days during the 2009-2018 period, whereas much of eastern Canada has experienced fewer lightning days. A statistical analysis performed on 154 stations across Canada found that the decadal increases (decreases) at 5 (31) stations were significant at the 90% confidence level or higher, and 4 (16) of these were significant at the 95% confidence level.