Large scale climatic patterns control large lightning fire occurrence in Canada and Alaska forested areas

Large lightning-caused fires in the forested areas of Canada and Alaska account for most of the area burnt and are one of the main determiners of the age mosaic of the landscape. Generally such fires occur when positive mid-troposphere pressure anomalies persist for more than ten days during the fire season. Mid-troposphere anomalies are part of teleconnection patterns which are created by internal atmospheric and coupled sea/air dynamics. Large lightning fire occurrence and area burnt data were used to define eight major centres of large fire variability (Fire Regions) in the forested areas of Canada and Alaska between 1959 and 1999. Preferred positions of persistent positive mid-troposphere anomalies correlated with the Fire Regions during large fire events. Active fire weather showed overall strong relationships with Pacific Decadal Oscillation (PDO) at interdecadal timescales and with El Nino Southern Oscillation (ENSO) and Arctic Oscillation (AO) mostly at interannual (2 to 7 years) frequency bands. PDO- and ENSO-related large fire occurrence was more frequent in the western regions, whereas AO-related large fires were more frequent in the eastern regions. (Abstract shortened by UMI.)...