Hotter and drier nights mean more runaway fires

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Nighttime fires have become more intense and more intense in recent decades, as hot and dry nights are more common, according to a new study led by the Earth Research Institute at the Institute for Environmental Sciences (CIRES) at the University of Colorado at Boulder. It’s becoming more frequent.

Forty years ago, cool and damp nights regularly rescued firefighters. “Flammable nights” were rare. Now, due to climate change, nights are warming faster than days, and the team found that there are 11 flammable nights each year in the western United States, a 45% surge.

“Night is an important time to slow down speed violations fire— And the wildfire night brakes aren’t working, ”said Jennifer Balch, CIRES Fellow, director of Earth Lab at CIRES and lead author of the February 16 survey. Nature..

The new analysis relied on vapor pressure deficiency (VPD), an important measure of atmospheric thirst. If the VPD is relatively low, the air is cold and moist and no fire will occur. Fire extinguishing activities take advantage of these night conditions to extinguish the flames. However, if the VPD is high, the air will be hot, dry, dry and ready for combustion.

And first, the team analyzed 81,000 global fire satellite observations and hourly climate data to identify the exact VPD turning point when it was hot and dry at night. In the last 40 years, researchers have discovered an additional week of flammable nights a year in one-fifth of the world’s flammable lands. And in the western United States, it increased further: 11 nights — an increase of 45% over 40 years (1979-2020).

The team also used new remote sensing and modeling techniques to assess the hourly fire progression of tens of thousands of fire events. And they found that night fires were 7.2% more intense worldwide between 2003 and 2020. In the western United States, that number was much higher, at 28%.

Balch and her team also reported:

  • Between 1979 and 2020, flammable night time increased by 36%. Compared to this, flammable time during the day increased “only” by 27%.
  • Certain ecosystems, such as evergreens, hardwoods, shrubs, and grasslands, have been hit harder than others.
  • And they expect changes in fire emissions due to frequent nighttime weaknesses and smoldering burns.

“People tend to pay more attention to the daytime conditions. When the fire is most active. But not enough attention is paid at night. In cool conditions, the fire slows down or completely. It tends to extinguish the fire, “says postdoctoral fellow Adam Mahood. Co-author of the paper with Earth Lab.And night is really important: human caused Climate change The team says that in the last 70 years, nights have been relatively warmer than a day and only get worse from here.

The recent devastating fires of December 2021 in Midwestern Kansas and the Marshall fires in Boulder County, Colorado further emphasize the importance of better understanding the climate-related factors of wildfires. ..

“As nighttime warming continues, we expect more wildfires to run wilder, faster, and bigger,” said Balti, associate professor of geography at CU Boulder. “That is, firefighters can’t take a break the night before and have to fight the flames 24/7.”

The additional authors of this publication are: Maxwell Joseph and Michael Koontz from Earth Lab at CIRES. CIRES Earth Lab and Hydrosat Inc. Joseph McGlinchy; John Abazoglow of the University of California, Merced. Megan Katau from Boise State University. A. Park Williams at the University of California, Los Angeles and Lamont-Doherty Earth Observatory at Columbia University.

Dryer, warmer night air makes some western wildfires more active at night

For more information:
Jennifer Balti, warming weakens nighttime barriers to global fires, Nature (2022). DOI: 10.1038 / s41586-021-04325-1..

Quote: Hotter and drier nights, more runaway fires acquired on February 16, 2022 from https: // (2022) February 16th, 2016)

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Hotter and drier nights mean more runaway fires

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