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December 20, 2006

Satellite Data Helps Pinpoint Wildfire Threats

Data from NASA satellites is advancing efforts that may soon allow scientists to predict when and where wildfires occur.

While information from satellites and instruments have recently let scientists more quickly determine the exact location of wildfires and to monitor their movement, this research offers a step toward predicting their development and could complement data currently used in calculating fire potential across much of the United States.

By studying shrublands prone to wildfire in southern California, scientists found that NASA satellite data accurately detected and mapped two key factors: plant moisture and fuel condition - or greenness - the amount of living plant material in an area. Moisture levels and fuel condition, combined with the weather, play a major role in the development, rate of spread, and intensity of wildfires.

"This represents an advance in our ability to predict wildfires using data from recently launched instruments," said lead author Dar Roberts, University of California-Santa Barbara. "We have come a long way in just the past 5 to 10 years and continue to gather much better data on the variables critical in wildfire development and spread."

To find out how well NASA satellites could detect these factors, researchers sampled live fuel moisture, a critical measure used in determining fire danger, from several different plant species in sites across Los Angeles County, Calif. This ground-based data, collected by the Los Angeles County Fire Department over a five year period, were then compared to greenness and moisture measures from NASA's Moderate Resolution Imaging Spectrometer and Airborne Visible/Infrared Imaging Spectrometer. The space-based data were often closely linked to the field measurements, suggesting the instruments can be used to determine when conditions are favorable for wildfires.

"Improving the role of satellite data in wildfire prediction and monitoring through efforts like these is critical, since traditional field sampling is limited by high costs, and the number and frequency of sites you can sample," said Roberts. "This new data on the relative greenness of a landscape also allows us to see how conditions are changing compared to the past."

The satellite data worked best on landscapes with just one major plant type. The amount of vegetation cover in an area and its growth rate also influence the reliability of satellite data for wildfire prediction.

Although scientists have long known about the importance of moisture conditions in wildfire development, this research suggests that other factors may be just as significant. "While live fuel moisture values are critical in the development of wildfires, it's clearly not the last word. Even if vegetation is extremely dry, there are a number of other factors that influence whether a fire will develop and how quickly it spreads, including the ratio of live to dead foliage, plant type, seasonal precipitation, and weather conditions," said Roberts. "In Southern California, if a strong Santa Ana wind event occurs before our first major rainfall in the fall or winter, the risk for wildfire is significantly heightened."

As researchers continue to better understand wildfire development, they are also creating fire spread computer models that use wind speed and direction forecasts to determine where fires will travel. And in the near future, scientists will likely be able to map the overall impact of a wildfire on the landscape and environment, including the amount of carbon dioxide released into the atmosphere.

On the Web:

http://www.nasa.gov