New Approaches to Understanding Wildfires

Forecasting fire-weather interactions, assessing emissions, and understanding social impacts

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NCAR researchers and colleagues have flown over raging forest fires, gathering data from infrared cameras and other sensors, for more than a decade. The knowledge gained from field campaigns, satellite sensors, and advanced computer modeling is sharpening understanding of the erratic behavior of wildfires and their interaction with land, atmosphere, wildlife, and people. (Photo courtesy of the Canadian Forest Service.) Persistent drought and hot weather are expected to make the 2007 wildland fire season unusually severe. Spring fires caused extensive damage in the Southeast and in southern California, and experts warn that much of the West is vulnerable to large blazes this summer. These conditions follow a record-breaking 2006 season which, by early October, had seen an unprecedented 9.93 million acres burned, almost twice the average for the past decade.

In 2006, Science reported that warmer summer temperatures appear to be increasing the duration and intensity of the wildfire season in the western United States through longer summers, more droughts, and earlier snowmelt. Compared to the years 1970–86, major fires have increased fourfold since then, and total burn area has increased sixfold.

Wildfires have major impacts on regional and global pollution and can affect climate and weather. They could even complicate efforts to regulate greenhouse gases.

"Climate, vegetation structure, and fire regimes interact with one another and with human activities," explains Guy Brasseur, director of NCAR's Earth and Sun Systems Lab. "Integrated approaches will be required to adapt to altered fire activities resulting from climate change, especially in terms of social and economic practices. NCAR wants to be at the forefront of the research on these issues."

What's in the smoke?

Wildfire smoke contains a number of atmospheric pollutants that can damage human health. Some of the pollutants that NCAR scientists study include:

  • Carbon monoxide, a toxic gas that is also an ozone precursor. An urban area downwind of a wildfire might see levels of carbon monoxide that exceed the Environmental Protection Agency's standards.
  • Atmospheric mercury, which can fall or rain out after a wildfire and enter watersheds, where interaction with microbes converts it into methyl mercury, a neurotoxin.
  • Ozone, which inflames and impairs lungs and can trigger asthma attacks. It also damages plants and materials and influences climate.
  • Volatile organic compounds (VOCs), composed of hydrocarbons and partially oxidized compounds that, when mixed with some types of industrial pollution, make smog worse.
  • Fine particulate matter (particles of soot and ash) that is too small for the human respiratory system to filter out. Its effects range from irritation to an increased risk of cancer.



NCAR scientists study a wide range of wildfire topics, their work ranging from forecasting fire and weather to modeling emissions, assessing mercury, and analyzing social impacts. Here's a look at recent developments in wildfire research at NCAR.

Forecasting weather-fire systems

NCAR scientist Janice Coen is approaching wildfire as a high-impact weather forecasting challenge.

"People can think of this approach as a weather forecast model that exchanges feedbacks with another model, such as a land surface, ocean, or sea ice model. But in this case, the fire model takes wind and humidity information from the atmospheric model, calculates how the fire would behave and grow, and provides releases of heat, water vapor, and smoke back into the atmospheric model."

In conjunction with colleague Ned Patton, Coen is working on WRF-Fire, a module of the Weather Research and Forecasting model (WRF) that will allow the university community to study fire-weather interactions and fire impacts on air quality. She's trying to improve short-range weather forecasting techniques and develop methods to verify forecasts. Along with university colleagues, she's also developing techniques for assimilating fire mapping and weather data.

Coen has a special interest in how multiple fires interact with each other by modifying their surrounding atmosphere, a research question that is especially applicable to backfires. A backfire is a small fire set intentionally ahead of a major wildfire to prevent the wildfire's advance by consuming fuels in its path.

"If the backfire is too intense or set too far away, it becomes another uncontrollable fire," Coen says. "Backfires sometimes escape and are blamed for large losses." She cites a case in which more than one hundred homeowners filed suit against the Forest Service, claiming that a backfire set during Montana's Bitterroot fires of 2000 was responsible for destroying their homes.

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