The wildfires raging across the western United States in 2000 were among the worst of the past half-century. They burned seven million acres of land and cost 1.6 billion dollars in damage. Now a team of researchers, led by Anthony Westerling of the Scripps Institution of Oceanography at the University of California, San Diego, has developed a wildfire forecast system to help prepare for future fires.
"This promises to be a valuable tool for scheduling fire management," Westerling says. "The western United States has been pooling its resources together for fire suppression. A lot of important decisions are made early in the year about prepositioning equipment and personnel. Anything we can do to provide a forecast of where fires are likely to occur is going to save a lot of money, time and effort."
Westerling and colleagues from the Scripps Institution, the Desert Research Institute and the U.S. Geological Survey used statistical methods developed for climate predictions to analyze 20 years' worth of data. They focused on past levels of moisture and amounts of flammable vegetation-the so-called fire fuel availability. "This forecasting model is based on our understanding of fuels that are available for fires to burn," Westerling explains. "We looked at the correlations between the Palmer Drought Severity Index-which summarizes moisture characteristics in soil and vegetation-and acres burned, or fire frequency. The previous climate tells us how much fuel has been produced, and how moist that fuel is going into the fire season, so that's what's driving this forecast."
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Using this information, the researchers came to some interesting conclusions. Fires in California, for example, are more likely to occur after a wet winter followed by a dry winter. The wet winter produces a lot of vegetation and then the arid winter dries it out so that it burns more easily. For this year's wildfire season, the scientists are optimistic. Although the available fuel is dry, there isn't much of it left to burn after 2000.