NCAR scientists seek clues to wildfires during Alaska prescribed burn

July 08, 1999

BOULDER--Scientists from the National Center for Atmospheric Research (NCAR) will fly over a prescribed blaze in the Alaskan forest this month seeking clues to how violent and seemingly unpredictable forest fires spread. Between July 8 and July 31, if conditions are right, a multiagency team of researchers will observe the burn on 2,000 acres approximately 25 miles northeast of Fairbanks, Alaska. As of July 7, the chance of initiating the burn on July 8 is very likely at 75% probability. The U.S. Department of Agriculture's Forest Service is sponsoring the experiment, called Frostfire. NCAR's primary sponsor is the National Science Foundation.

"There are still a lot of unanswered questions about what goes on in wildfires, especially large ones," says NCAR scientist Lawrence Radke. While control and safety are paramount during the prescribed burn, "Frostfire offers the possibility of studying an intense fire with uniform fuels in a location where, with good luck, we can be in a good position to observe it with our high-speed infrared imager. This is exactly the kind of conditions we need."

Radke and NCAR scientist Terry Clark will collect data using NCAR's Thermacam imager mounted on a Forest Service Piper Navajo aircraft. The aircraft, which is based at the National Aeronautic and Space Administration's Ames Research Center in California, will also carry NASA investigator Robert Higgins and NASA's fire-imaging spectrometer.

NCAR's Thermacam is a digital, high-resolution infrared imager with a sensing range between 40 degrees below zero and 3600 degrees above zero Fahrenheit. The instrument, built by Inframetrics, produces color video images of hot, swirling air and flames, detailing their motion, size, structure, and temperature.

Clark and NCAR colleague Janice Coen create atmosphere-fire models that reproduce in computers many of the fine-scale structures frequently observed in explosive fires. "We're increasingly convinced that as fires become more violent, the vortex motions we see that look like 'fire fingers' become more important," says Radke.

Both radiation and the convection that results from fire-atmosphere interactions affect fire spread. To understand those effects, the team must first see how fire fronts lap at, or "finger," unburned fuel. The NCAR researchers are eager to observe more high-intensity fires, where they can look for fire fingers and quantify their structures.

The data they collect will be used to validate models like Clark's, which can then help improve the fire-spread models used by firefighters. "Ultimately we'd like to fit the model on a high-powered laptop that firefighters can take with them to the fire," explains Radke. "That's not practical today, but with the current pace of computer technology we foresee more practical applications of this work in the early 21st century."

About 60 researchers are involved in experiments planned for Frostfire, the first experimental fire in terrain dominated by permafrost. The collaborative effort focuses on boreal (northern) forest fires and climate change; carbon cycling; increased understanding of fire behavior; and long-term impacts on wildlife, soil erosion, and other ecosystem components.

Conditions for igniting the burn
The Frostfire burn plan puts public health and safety foremost (see Each day the Alaska Fire Service will make the "go/no-go" decision on ignition according to current and predicted weather conditions and administrative considerations such as the availability of firefighting resources. Ignition may take from two to several days to complete, with firefighters on site for many more days to monitor and mop up the residual burning. The fire will not be lit unless conditions are within prescribed limits for wind speed and direction, lack of atmospheric inversion, relative humidity, and fuel moisture.
Frostfire is coordinated by the USDA Forest Service and the University of Alaska, Fairbanks. In addition to NCAR, NSF, and NASA, cooperating agencies include the Bureau of Land Management, Bonanza Creek Experimental Forest/Caribou-Poker Creeks Research Watershed, the Alaska Department of Natural Resources, and the Canadian Forest Service.

NCAR is managed by the University Corporation for Atmospheric Research, a consortium of more than 60 universities offering Ph.D.s in atmospheric and related sciences. Writer: Zhenya Gallon

Note to Editors: Helicopter time will be on a space-available basis. Media may be escorted near the line where firefighters are working during the initial blacklining phase. During the following helitorch phase, media will be able to view the burn from Cleary Summit or Poker Flat. Contact Sue Mitchell, 907-455-6378, UCAR and NCAR news:
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National Center for Atmospheric Research/University Corporation for Atmospheric Research

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