Wildfire Chemistry Model Assesses Long Range Fire Effects

"We are headed in a new direction," said Los Alamos scientist Manvendra Dubey. "Our fire modeling started as a crisis forecasting initiative where we modeled terrain, atmospheric conditions and heat, which creates its own wind, to predict wildfire behavior and enhance safety. Now we will be exploiting our fire safety modeling codes for air quality and climate change applications."

In a paper presented today at the American Geophysical Union fall meeting in San Francisco, Dubey and fellow Los Alamos scientist Rodman R. Linn described a scheme to track volatile organics released into the atmosphere from wood heating and burn simulations that will allow them to compute gas and smoke emissions from wildfires. These results, added to Los Alamos' wildfire model developed for fire safety applications, will allow prediction of effects on the air at a wide variety of distances.

Los Alamos is the only institution that has a physical and mechanistic model to simulate wildfires at extremely high resolution on scales as small as a few meters. Los Alamos also has the supercomputing power to perform realistic, three-dimensional wildfire simulations that also explore wildfire chemistry.

During the 1990s, Los Alamos began using its supercomputers to predict the unfolding of crisis events. Because fires are a series of small, intense physical phenomena affected by both terrain and atmospheric conditions, their spread could not be reliably predicted before the availability of supercomputers.

At Los Alamos, a sitewide Environmental Impact Statement has identified wildfire as the greatest threat to Los Alamos operations. Over the past several years, several nearby catastrophic blazes have intensified efforts to refine the model to a high degree of resolution. Extensive knowledge of the terrain and the types of fuels present have produced a unique data set to incorporate into the model and use to test a variety of scenarios for wildfire risk assessment.

After modeling blazes like the 1994 South Canyon fire in Glenwood Springs, Colorado, in which 14 firefighters were killed, and the Calabasas fire near Malibu, California, in 1996, scientists began working with the U.S. Forest Service and with Los Angeles County to simulate burn patterns.

In addition to causing damage on the ground, fires are a leading source of chemicals in the atmosphere:

* Firefighters' lungs show significant damage, compared to the general population,

* the Southwestern United States experienced dramatic visual and public health effects from the 1998 forest fires in Mexico, and

* the cumulative effect of biomass burning will have worldwide consequences to the atmosphere.

To better anticipate and cope with these effects, the Los Alamos scientists intend to extend their wildfire model to include physical chemistry components. A study of near-field toxic emissions of species like cyanide and smoke will be combined with the analysis of more long-range pollutants like ozone and carbon dioxide and their effects. The researchers hope to develop unique indicators of biomass burning to quantify the global significance of wildfires.

"Our model tries to represent the combined effects of small-scale details into large-scale effects," said Linn. "With this model, we can ask local, regional and global questions and share the capability with the larger global change community."

Los Alamos National Laboratory is operated by the University of California for the U.S. Department of Energy.