BOULDER -- Beginning September 1, scientists from the National Center for Atmospheric Research (NCAR) will fly a highly instrumented C-130 research aircraft around and over dangerous wildfires that may ignite this season within the United States. To seize wildfire opportunities, the airplane is reserved for four or five flights over a six-week period out of Jefferson County Airport, northwest of Denver.
"We're most interested in understanding the violent, unpredictable fires that kill firefighters," says Lawrence Radke, NCAR co-principal investigator for the Wildfire Experiment (WiFE). "We need to be able to predict the course of a dangerous fire to develop the most effective strategy for suppressing it."
WiFE is funded by the National Science Foundation, which also sponsors NCAR and owns the NCAR-operated research aircraft. The National Aeronautics and Space Administration (NASA) Ames Research Center and the U.S. Forest Service's Riverside Fire Research Laboratory will provide additional scientists, observers, and instruments. The Rocky Mountain Area Aviation and Fire Coordination Center will help the scientists decide which fires to observe and will coordinate flights around the fires.
The ultimate goal of the research is to understand wildfire behavior well enough to predict the course of a particular fire. The flights will test a unique set of remote-sensing tools to determine their combined effectiveness in observing fires. In addition, NCAR chemists will analyze emissions from the burning biomass.
Wildfires typically burn five million acres in the United States annually, costing hundreds of millions of dollars. The price tag will mount as urban development continues to encroach on forests nationwide.
According to Radke, large, violent wildfires often generate their own controlling weather. The released heat can spawn deep convection, even thunderstorms, with strong and dangerous winds. So-called fire whirls, cousins of tornadoes, can hurl flaming logs and other burning debris miles away, setting other areas ablaze. Such vortices already occur at all scales in our solar-heated atmosphere, and they intensify locally near fires.
The C-130's speed, range, and endurance will improve the researchers' chances of getting to a fire in time to observe it during a dramatic and dangerous phase. The plane will circle the fires at 150 knots or less, cruising between the minimum safe altitude and 10,000 feet.
Among the instruments on board will be NCAR's new Thermacam, a digital, high-resolution infrared imager with a sensing range between -40 and 3600 degrees Fahrenheit. Fires can reach 2200 degrees F; a glowing candle tip, 1300. Built by Inframetrics, Inc., the Thermacam will gaze out of an opening in one of the airplane's windows and straight through smoke. The result will be color video images of hot, swirling air and flames, detailing their motion, size, structure, and temperature. Other instruments aboard the C-130 include a passive microwave imager, an electric field meter, and NASA's fire-imaging spectrometer. The microwave imager targets areas of woody, fire-feeding vegetation by measuring the weight of burnable biomass per square meter. Spotting the blaze's next meal can help observers determine its future path. The instrument may also prove useful in detecting the moisture content of surface vegetation, a key factor in fire intensity and spread.
Co-leader of WiFE is NCAR's Terry Clark, whose atmospheric fire models reproduce in computers many of the fine-scale structures frequently observed in wildfires. Clark and Radke are now eager to observe these "fire fingers" in nature and to quantify their structures. Both radiation and the convection that results from fire-atmosphere interactions affect fire spread. To understand those effects, Clark must first see how fire fronts lap at or "finger" unburned fuel. WiFE measurements will be used to validate physically based models like Clark's, which can then help improve the fire-spread models used by firefighters.
Meanwhile, chemists on board will be measuring emissions above the blaze, some of which will shed light on the chemical reactivity of the fire plume, its combustion efficiency, and the total carbon emitted. Other chemicals of interest emitted by fires are methyl halides, which have properties similar to those of chlorofluorocarbons, the infamous CFCs that attack the ozone layer and also contribute to global warming. Many of the human-produced halides have been banned, but naturally formed ones are still rising into the stratosphere, where they join in the ozone-destruction cycle. WiFE will help clarify how much wildfires contribute to the methyl halide balance in the stratosphere. Says NCAR chemist Elliot Atlas, "We chemists don't get to explore big fires very much. This is a real opportunity for us."
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.