Author: Laurel Hamers / Source: Science News for Students
Wildfires are not known for their restraint.
They’ll jump rivers. They’ll spew whirling dervishes of flames. And they’ll double in size overnight.Take the Carr Fire, one of the most destructive California has ever seen. It sparked in the northern part of the state on July 23. Its source: the rim of a flat tire scraping a road’s pavement. As the blaze grew, it jumped the Sacramento River. Then it set off a flaming whirlwind near Redding that trapped and killed a firefighter. Crews didn’t fully contain the flames until August 30. By then, this wildfire had torched 930 square kilometers (359 square miles). Along the way, it destroyed more than 1,000 buildings and claimed seven lives.
“Once these fires are spreading fast enough and intensely enough, you can’t stop them,” says Ruddy Mell. He’s a combustion engineer with the U.S. Forest Service based in Seattle, Wash. (A combustion engineer is someone who studies how things burn.)
Federal and state agencies that manage wildfires rely on math to do their work. These agencies use computer programs known as fire models. Such models make it possible to predict how blazes will spread. They also allow the agencies to decide where to send firefighters and equipment — or to decide when an evacuation is needed. But the models can’t always predict when a fire will veer in a new direction or grow suddenly larger.
Now, scientists are developing newer, far better fire models. Those models include especially detailed data from satellites.
The newer computer models also are based on a better understanding of how fires can create their own weather, fanning their own flames.
Even on a computer, these fine-scale models take hours or days to run. That means they aren’t likely to replace more quick-and-dirty models created to respond in the heat of the moment. But they can help scientists figure out what’s driving a wildfire’s behavior — and learn how to better protect communities from going up in smoke.
Record burns
The National Interagency Fire Center (NIFC) is in Boise, Idaho. This year, it reports, wildfires are on track to cause at least as much damage in the United States as did last year. Indeed, those blazes burned a bigger area in 2017 than in almost any year since 1983. (That’s when researchers first began collecting consistent data.) As of September 24, 2018, 48,584 fires had torched at least 29,800 square kilometers (11,500 square miles) nationwide. That’s an area larger than Massachusetts. As of late September, NIFC reported more than 50 large fires burning in the West — 20 of them still uncontained.
In the past few years, wildfires have made extreme air pollution even worse in the western United States.
Lightning sparks many wildfires. These natural blazes are a healthy part of many ecosystems. But without meaning to, humans have made such fires worse. For years, experts who manage forests have worked hard to prevent natural fires from burning. That’s known as fire suppression. This policy has meant that there’s a lot of wood — a fire’s fuel — on the ground. And that’s made the fires that do ignite even more fierce.
Most disturbing, people start — whether accidentally or on purpose — 84 out of every 100 wildfires. That’s according to a March 2017 study in the Proceedings of the National Academy of Sciences. Our influence, the study suggests, has made the U.S. fire season three times as long as it would be naturally.
And climate change is likely worsening the problem. Much of the western United States will probably see an increase in the area of land burned over the next 30 years. That’s the finding of a December 2017 study in PLOS One. It had analyzed data on regional temperatures, wildfires and snowpacks. (Snowpack is the buildup of layers of snow during cold periods.)
Such natural disasters will be even more severe in the future, researchers suggested last month in Geophysical Research Letters. They concluded that heat waves and wildfires will be affected even more strongly by shifts in climate that come in cycles. A key example of those cyclic events: El Niños (El-NEEN-yohs). These are periods when surface waters around the equator in some areas of the Pacific Ocean warm, triggering shifts in climate across the globe.
Using math to model wildfire behaviors, though, is almost as hard as stopping the burn. Wildfires are influenced by a complex group of features. What types of plants cover the ground? Is the land flat or hilly? How fast does the wind blow? How hot is the region and how dry are its plants?
Fire managers take all of these into account. But the models they use are designed to guide fire control strategies during emergencies, where being able to respond fast is key. The math it uses cannot model all of the fine details. For example, it can’t take into account how fires interact with the atmosphere to create their own winds. That’s important, since those winds…
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