Alaska's exceptional 2004 fire season

A total area of 26,669 km² (6.59 million acres) burned from forest fires in Alaska during the summer of 2004, setting a new record in the 50-year database. The unusually warm and dry weather was a predominant factor for the wildfire season in which it was the warmest on record and drought-like conditions produced the 3rd driest summer for Interior Alaska in nearly 100 years of observations. There was increased thunderstorm development producing a record number of lightning strikes almost five times the normal seasonal total. Only the first snowfall in September terminated a large percentage of the fires, however, at least one fire southeast of Fairbanks regenerated in spring 2005. Climatological guidance in the late spring gave no indication for the abnormally warm and dry conditions that were experienced during the summer of 2004. Smoke from the fires resulted in extremely poor air quality at locations across the state. The fine particulate matter load in Fairbanks was very high with a maximum of above 1000 µg/m³, exceeding the most dangerous EPA established category “hazardous” by a factor of two. In addition, an hourly CO concentration observation in Fairbanks reached 10.3 ppm, the highest value ever measured in summer. The weather conditions, lightning, and wildfires for the summer of 2004 will be discussed and placed in historical context. In addition, the influence of the smoke on local air quality, visibility, and surface radiation will be shown.