Scientists said the wind-driven wildfires that are destroying Los Angeles’ arid landscape mark the latest in climate extremes that are likely to increase further as global temperatures continue to rise.
Erupting outside of the traditional wildfire season, California’s flames were spreading quickly on Wednesday.
Scientists now consider wildfires a year-round risk in California. The western US state has also seen increasingly larger conflagrations in recent years, with more areas burned amid drought conditions and changing climate trends.
“Climate change is reshaping regimes — the characteristic patterns of wildfires in a region,” said Kimberley Simpson, from the University of Sheffield’s School of Biosciences.
Just hours after weather warnings warned of extreme winds and dry conditions in the Los Angeles area last Tuesday night, parts of the iconic desert city were on fire.
Sparks leapt from highways and set roofs on fire. Palm trees burned like matchsticks against the night sky. On Wednesday morning, tens of thousands of people fled their homes as the fires were out of control.
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Los Angeles, located in a corner of the Southern California desert, is no stranger to strong winds and hot, dry weather, with its famous Santa Ana winds regularly blowing across the landscape toward the coast. Amid dry winter conditions, it is not uncommon for fast winds to develop, said Brent Walker of the UK Met Office.
However, the atmospheric event fueling the Los Angeles fires is not typical of Santa Ana. Instead, unusually strong winds are blowing on the back of an oddly shaped storm system over the lower Colorado River Valley, being amplified by what scientists call a “mountain wave” event.
A mountain wave phenomenon occurs when there are certain temperatures above a mountain range and specific winds passing over those mountains.
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“When these conditions align perfectly, the phenomenon behaves exactly like a wave in the ocean, when winds flow over mountains and then crash on the other side,” said scientist Paul Schlatter of the National Weather Service in Boulder, California. Colorado.
“Just the strength of these winds (from the storm system) and a little bit of the mountain surge increase is what’s really fueling these fires,” Schlatter said.
A similar mountain surge occurred around Colorado’s Marshall Fire on December 30, 2021, fueled by downslope winds gusting up to 185 km/h. It destroyed thousands of homes and businesses before being wiped out by blizzard the following night.
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“Any fire under these conditions will quickly get out of control,” Schlatter said.
This week’s snowstorms in the San Bernardino Mountains, about a two-hour drive from Los Angeles, may also be contributing to regional wind dynamics.
Meanwhile, meteorologists in the region expect a Santa Ana wind event later this week.
