Authors: G Wendler J Conner B Moore M Shulski M Stuefer
Publish Date: 2010/11/07
Volume: 104, Issue: 3-4, Pages: 459-472
Abstract
Wildfires are a common experience in Alaska where on average 3775 km2 burn annually More than 90 of the area consumed occurs in Interior Alaska where the summers are relatively warm and dry and the vegetation consists predominantly of spruce birch and cottonwood Summers with above normal temperatures generate an increased amount of convection resulting in more thunderstorm development and an amplified number of lightning strikes The resulting dry conditions facilitate the spread of wildfires started by the lightning Working with a 55year dataset of wildfires for Alaska an increase in the annual area burned was observed Due to climate change the last three decades have shown to be warmer than the previous decades Hence in the first 28 years of the data two fires were observed with an area burned greater than 10000 km2 while there were four in the last 27 years Correlations between the Palmer Drought Severity Index and the Canadian Drought Code against both the number of wildfires and the area burned gave relatively low but in some cases significant correlation values Special emphasis is given to the fire season of 2004 in which a record of 27200 km2 burned These widespread fires were due in large part to the unusual weather situation Owing to the anticyclonic conditions of the summer of 2004 the composite anomaly of the 500 mb geopotential height showed above normal values The dominance of a ridge pattern during summer resulted in generally clear skies high temperatures and below normal precipitation Surface observations confirmed this the summer of 2004 was the warmest and third driest for Interior Alaska in a century of climate observations The fires lasted throughout the summer and only the snowfalls in September terminated them at least one regenerated in spring 2005 Smoke from the forest fires affected the air quality This could be demonstrated by measurements of visibility fine particle matter transmissivity of the atmosphere and CO concentrationWe would like to thank the following persons Thor Weatherby provided lightning data and Sue Christensen supplied data on fire starts and area burned both are with the Alaska Fire Service AFS Sharon Alden AFS and Heather Angeloff ACRC contributed in helpful discussions Financial support was given by the State of Alaska to the Alaska Climate Research Center ACRC and by Vice Chancellor for Research V Sharpton
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