Forecasting long-lived wildfires
Without the most updated data about a fire’s current state, however, CAWFE could not reliably produce a longer-term prediction of an ongoing fire. This is because the accuracy of all fine-scale weather simulations declines significantly after a day or two, thus affecting the simulation of the blaze. An accurate forecast would also have to include updates on the effects of firefighting and of such processes as spotting, in which embers from a fire are lofted in the fire plume and dropped ahead of a fire, igniting new flames.
Until now, the kind of real-time data that would be needed to regularly update the model has not been available. Satellite instruments offered only coarse observations of fires, providing images in which each pixel represented an area a little more than a half mile across (1 kilometer by 1 kilometer). These images might show several places burning, but they could not distinguish the boundaries between burning and non-burning areas, except for the largest wildfires.
The release notes that to solve the problem, Coen’s co-author, Wilfrid Schroeder of the University of Maryland, have produced higher-resolution fire detection data from a new satellite instrument, the Visible Infrared Imaging Radiometer Suite (VIIRS), which is jointly operated by NASA and the National Oceanic and Atmospheric Administration (NOAA). Launched in 2011, this new tool provides coverage of the entire globe at intervals of twelve hours or less, with pixels about 1,200 feet across (375 meters). The higher resolution enabled the two researchers to outline the active fire perimeter in much greater detail.
Coen and Schroeder then fed the VIIRS fire observations into the CAWFE model. By restarting the model every 12 hours with the latest observations of the fire extent — a process known as cycling — they could accurately predict the course of the Little Bear fire in 12- to 24-hour increments during five days of the historic blaze. By continuing this way, it would be possible to simulate the entire lifetime of even a very long-lived fire, from ignition to extinction.
“The transformative event has been the arrival of this new satellite data,” said Schroeder, a professor of geographical sciences who is also a visiting scientist with NOAA. “The enhanced capability of the VIIRS data favors detection of newly ignited fires before they erupt into major conflagrations. The satellite data has tremendous potential to supplement fire management and decision support systems, sharpening the local, regional, and continental monitoring of wildfires.”
Keeping firefighters safe
The researchers said that forecasts using the new technique could be particularly useful in anticipating sudden blowups and shifts in the direction of the flames, such as what happened when nineteen firefighters perished in Arizona last summer.
In addition, they could enable decision makers to look at several newly ignited fires and determine which pose the greatest threat.
“Lives and homes are at stake, depending on some of these decisions, and the interaction of fuels, terrain, and changing weather is so complicated that even seasoned managers can’t always anticipate rapidly changing conditions,” Coen said. “Many people have resigned themselves to believing that wildfires are unpredictable. We’re showing that’s not true.”
— Read more Janice L. Coen and Wilfrid Schroeder, “Use of spatially refined satellite remote sensing fire detection data to initialize and evaluate coupled weather-wild fire growth model simulation,” Geophysical Research Letters (22 October 2013) (DOI: 10.1002/2013GL057868)
