A link between cyclones and wildfires

Asheville Citizen-Times (Tennessee): Geographers from Appalachian State University and UNC Greensboro have found a piece of the global warming/climate change puzzle related to the occurrence of wildfires in the northern Rocky Mountains. Peter T. Soulé, a professor in Appalachian’s Department of Geography and Planning, and UNCG geography professor Paul A. Knapp looked at 105 years of weather data related to mid-latitude cyclones (MLC) – low-pressure weather systems that affect precipitation and temperature. They looked for anomalies in the average maximum temperatures that occurred between the first of August and the end of October from 1905-2004.

“As we searched records maintained by the National Climate Data Center, we found that these mid-latitude cyclones which drastically reduce the air temperature are occurring less often and later in the year compared to what is typically expected during this three-month period,” Soulé said. When a MLC occurs, temperatures can drop as much as 35 degrees Fahrenheit compared to the western region’s typical highs, Soulé explained.

The weather data were then compared to the number of hectares burned in the northern Rockies during the past 65 years and they found a significantly larger number of wildfires occurred in the Rockies when MLCs and their cooler temperatures occurred later in the season. One hectare equals 2.47 acres. Their findings were published in Geophysical Research Letters. The research also was included in the research highlights section of the journal Nature.

“Everybody thinks it’s mostly the rainfall that accompanies these weather events that affects wildfires, but it’s really the big drop in temperature that helps the fires calm down and makes them easier to control,” Soulé said. “About 20 percent of the variation in fires can be explained by the changes in the mid-latitude cyclone activity. If we are not getting these events as frequently and they are occurring later, then that has an impact on fire activity.”

The relationship of climate to the occurrence and severity of wild fires is a topic of great interest to researchers. For instance, a strong connection between global warming and an increase in fire activity has been documented in the mid-elevation /forests/ of Alaska, Canada and parts of the western United States, according to work done by researchers at the University of Arizona and the University of California Merced.

Understanding changing weather patterns and their impact on wildfires may help agencies such as the U.S. Forest Service plan budgets for fighting fire and allocate resources based on the fire season cycle occurring in the United States, according to research published by Anthony Westerling at the University of California Merced. “It’s important to be aware when climatic conditions are more favorable for large fires,” Soulé said. “When you look at climate change and global warming, this is a small piece of the puzzle but an interesting and important piece that has a direct impact on people and their environment.”