Wildfires have been erupting in southern California since Jan. 1. The fires’ spread is an effect of the Santa Ana winds, which happen when air from the desert region of the United States comes westward to California, where it is at a lower pressure.
“Those really strong winds result in an environment that is really conducive for the spread of the fire. So what that can do is push the flame front along quite a bit faster,” said Derek Mallia, an assistant professor at the University of Utah in atmospheric sciences.
Mallia added that the winds push the fires and distribute what are commonly called firebrands. As the wind blows, it carries the firebrands or embers downwind of the fire.
“It will basically inject these firebrands, in some cases upwards of a kilometer or a couple of miles out ahead of the fire, depending on how strong those winds are and how large those firebrands are,” he said. “And what they can do is deposit out ahead of the fire, and through that, they can start what we refer to as spot fires out ahead of the main fire line.”
These smaller spot fires eventually merge with the original fire, accelerating the speed at which the fires spread.
The first known fire in the area was the Lachman Fire. Though it was only known to have taken over eight acres, it was likely the fire that started the bigger fires, such as the Palisades Fire and the Eaton Fire.
Climate Change’s Impact
When it comes to climate change’s contribution to the fire, Mallia said it is debatable whether it played a big role in this particular fire.
“Granted, it has a big role in other fires as climate change is going to make things warmer and drier, which would help these fires really get out of control,” Mallia added.
William Anderegg, a professor in the School of Biological Sciences and director of the Wilkes Center for Climate Science and Policy, on the other hand, discussed how climate change has affected the extreme droughts in the West and made the land drier and more fire-prone.
The first weather phenomenon Anderegg mentioned was a La Niña year, the periodic cooling of the ocean’s surface in the central and eastern equatorial Pacific, resulting in drier-than-average winters. La Niña typically happens every three to five years.
“So we have climate change making fuels and soils really dry. We got a La Niña … then you have the Santa Ana winds, which, you know, create these really intense fire conditions, which are also a natural process,” Anderegg said. “But when you overlay that with really dry fuels, all you need is a single ignition source and then you get these fires. With the increased drought rates, I feel like that has been the pattern recently.”
Though fire is needed in forest ecosystems to send up seeds and repopulate the forest, Anderegg said they aren’t equipped for the severity of the fires that have started in Los Angeles this year.
As fires continue to spread throughout southern California, Anderegg said the best thing we can do is be prepared and think proactively to diminish these risks rather than reactively after the fires have already started. He added that restoring the “natural fire regime” before a fire hits is an important strategy in preventing severe wildfires in the future.
“That often involves maybe some sort of prescribed fire to remove a lot of the built-up fuels,” he said. “The goal really is to try to get it back to the kind of pre-European settlement structure of the forest.”
