Study models smoke intrusion during prescribed burn; yields better knowledge about smoke transport
Sep 9, 2016
Smoke from prescribed fires in the Deschutes National Forest has negatively affected the city of Bend; Oregon; nine times over the past 2 years. These smoke events threaten the ability of land managers to use prescribed burning as a tool to mitigate hazardous fuels in the wildland-urban interface around Bend. Further complicating the situation is the narrow window that managers have to safely conduct prescribed burns. Meteorological and fuel conditions only meet burn requirements about 9 days per year.
The station and Pacific Northwest Region partnered with the Deschutes National Forest to better understand meteorological conditions near Bend. This was part of an effort to increase the pace and scale of forest restoration while protecting air quality in nearby communities. To better understand when and how smoke intrusions from prescribed burns occur; scientists deployed up to 12 meteorological and smoke monitors during fall 2014 and spring 2015 in a 40-mile north-to-south transect from Sisters to Sunriver; Oregon.
Station scientists successfully modeled smoke intrusion in Bend using a high-resolution smoke model. They are now analyzing the data to determine how the predominant wind directions vary diurnally and seasonally. A better understanding of the conditions that cause smoke to drain into Bend will allow for more targeted burn windows. Specifically; will smoke from a prescribed burn be transported up-drainage during the day of the burn; only to reverse flow and be transported down-drainage (toward Bend) over night and in early morning hours? Or is the problem smoldering on the burn unit overnight that continues to generate smoke close to the ground; which is then transported into Bend? Answering these questions will inform decisions about when to start and stop ignitions.
This information is crucial for land managers wanting to use prescribed burning as a management tool while protecting air quality in nearby communities. Understanding the meteorological and fuel conditions that cause smoke to move in a certain direction will inform decisions about when to start and stop ignitions.