NCAR Scientists Seek Clues To Wildfires During Alaska Prescribed Burn

"There are still a lot of unanswered questions about what goes on inwildfires, 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 withuniform fuels in a location where, with good luck, we can be in a goodposition to observe it with our high-speed infrared imager. This isexactly the kind of conditions we need."

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

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

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

Both radiation and the convection that results from fire-atmosphereinteractions affect fire spread. To understand those effects, the teammust first see how fire fronts lap at, or "finger," unburned fuel. TheNCAR researchers are eager to observe more high-intensity fires, wherethey 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 thatfirefighters can take with them to the fire," explains Radke. "That'snot practical today, but with the current pace of computer technology weforesee more practical applications of this work in the early 21stcentury."

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

Conditions for igniting the burn

The Frostfire burn plan puts public health and safety foremost (seehttp://www.fsl.orst.edu/fera/burnplan.html). Each day the Alaska FireService will make the "go/no-go" decision on ignition according tocurrent and predicted weather conditions and administrativeconsiderations such as the availability of firefighting resources.Ignition may take from two to several days to complete, withfirefighters on site for many more days to monitor and mop up theresidual burning. The fire will not be lit unless conditions are withinprescribed limits for wind speed and direction, lack of atmosphericinversion, relative humidity, and fuel moisture. Updates on theprobability of ignition are posted at the Frostfire Web site: http://www.fsl.orst.edu/fera/frostfire.html.

Frostfire is coordinated by the USDA Forest Service and the Universityof Alaska, Fairbanks. In addition to NCAR, NSF, and NASA, cooperatingagencies include the Bureau of Land Management, Bonanza CreekExperimental Forest/Caribou-Poker Creeks Research Watershed, the AlaskaDepartment 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 atmosphericand related sciences.

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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 workingduring the initial blacklining phase. During the following helitorchphase, media will be able to view the burn from Cleary Summit or PokerFlat. Contact Sue Mitchell, 907-455-6378, fnsm@uaf.edu.

UCAR and NCAR news: http://www.ucar.edu/publications/newsreleases/1999.To subscribe via e-mail send name, title, affiliation, postal address,fax, and phone number to butterwo@ucar.edu.