The nature and impacts of thunderstorms in a northern climate

Abstract

Thunderstorms and associated lightning play an important role in the cycling of water and energy during the warm season, over the boreal and subarctic ecosystems of northern Canada, including the Mackenzie Basin. A variety of observational data sets and model-derived products have been used to characterize these storms, to examine their impacts on the forests of the Basin and on polar bear habitat in western Hudson Bay, and to assess predictive applications of lightning information. The convective storm season and resultant lightning activity are characterized as short but intense with a strong peak in cloud-to-ground (C-G) flashes during June and July. The maximum area of lightning activity varies in space and in time, and there is evidence that smoke from fires enhances the probability of positive CG flashes. Although fire occurrence in the Basin peaks in July, much of the burned area occurs in June. Fires have also significantly changed vegetation and permafrost conditions, resulting in a decrease in the stability of polar bear maternity den sites, the collapse of dens and deterioration of the surrounding habitat in western Hudson Bay. A tree-structured regression method for constructing statistical probability forecast models successfully predicts the probability of lightning in 3-h projection intervals out to 45-48 h. © 2008 Springer-Verlag Berlin Heidelberg.