Tuesday, 13 November 2001
A potential wildfire feedback mechanism in the Alaskan boreal forest: do fire scars increase lightning activity?
Previous numerical modeling studies have suggested a potential feedback mechanism between fire disturbance boreal forests and fire return frequency via a change in convective activity. Lightning strike data provided by the Alaska Fire Service is used to investigate such potential links between wildfire burn scars and local convective activity in Alaskan boreal forests. Lightning induced wildfires are responsible for the majority of acreage burned annually in North American boreal forests. Satellite derived radiant temperatures of burn scars indicate that disturbed regions maintain temperatures greatly in excess of the surrounding vegetation for more than a decade after the fire. Furthermore, surface heterogeneity within burn scars and abrupt changes in surface characteristics as a result of fire provide ideal triggering mechanisms for local convective development. Our initial hypothesis that convective development, and hence lightning strike activity, would be enhanced over burn scars as a result of high surface temperatures was contradicted by our analysis of the lightning strike data. We discuss these findings in the context of changes in the radiation balance and surface energy budget resulting in changes in surface characteristics in boreal forest following a fire and throughout succession.