Scientists find that stratospheric intrusions can increase the effects of Santa Ana winds on wildfires

This important research about a little known weather phenomenon that affects wildfires was conducted by government employees working for the National Oceanic and Atmospheric Administration (NOAA) and the University of Colorado at Boulder. However, to get a copy of this taxpayer-funded research, you will have to pay $38 to a private organization, John Wiley & Sons, Inc., a corporation that for the year that ended April 30, 2015 had $1.8 billion in revenue and a net income of $176 million. In that year, 64 percent of their revenue came from journal subscriptions.

While some government and university employees may be able to access this and other research papers, they can only do it because their employer pays tens or hundreds of thousands of dollars in subscription fees to these private companies. The employees can seamlessly read the papers, and don’t always realize that non-employees can’t.

Gowers Weblog has an exhaustive article about this issue in which he lists the exorbitant subscription fees paid by some universities in the United States.

He noted, for example, that the state universities in Arizona pay a total of $2.7 million to just one of these private outfits, Elsevier.

The authors of the paper are Andrew O. Langford (U. of Colo.), R. B. Pierce (NOAA), and P. J. Schultz (NOAA).

The University of Colorado and NOAA have graciously allowed this brief summary of the publicly-funded research to be released — to the public:


Southern Californians and writers love to blame the hot, dry Santa Ana winds for tense, ugly moods, and the winds have long been associated with destructive wildfires. Now, NOAA researchers have found that on occasion, the winds have an accomplice with respect to fires, at least: Natural atmospheric events known as stratospheric intrusions, which bring extremely dry air from the upper atmosphere down to the surface, adding to the fire danger effects of the Santa Anas, and exacerbating some air pollution episodes.

Springs Fire
Satellite image of the smoke on 2 May 2013, the first day of the Springs Fire northwest of Los Angeles. The photo was taken by the Moderate Resolution Imaging Spectroradiometer (MODIS) instrument on NASA’s Terra satellite.

The findings suggest that forecast models with the capacity to predict stratospheric intrusions may provide valuable lead time for agencies to issue air quality alerts and fire weather warnings, or to reallocate fire fighting resources before these extreme events occur.

“The atmosphere could give us an early warning for some wildfires,” said Andrew Langford, a research chemist at NOAA’s Earth System Research Laboratory in Boulder, Colorado, and lead author of the study. Researchers at NOAA’s National Environmental Satellite, Data, and Information Service (NESDIS) and the Cooperative Institute for Research in Environmental Sciences (CIRES) at the University of Colorado Boulder coauthored the work, which was accepted for publication this week in the American Geophysical Union journal Geophysical Research Letters.

The authors took a detailed look at the May 2013 “Springs Fire” that burned 25,000 acres about 50 miles northwest of Los Angeles. The researchers used a NOAA forecast model that incorporates satellite observations of ozone, wind data, and other atmospheric information to detect the occurrence of the intrusions.

The analysis showed that in the early hours before the Springs Fire, a tongue of air characteristic of the stratosphere—extremely dry and very high in ozone from the stratosphere’s ozone layer—reached to the surface in southern California and extended as far south as Baja California.

The researchers found that ground-based monitoring stations near the fire’s origin also confirmed the telltale signs of the intrusion right before the fire broke out: A large drop in relative humidity and a rise in ozone. As the day went on, a combination of factors accelerated the fire: Low humidity, persistent high winds, dry condition of the grasses and other vegetation, clear skies and bright sunlight, and very warm surface temperatures. A few days later, cloudy skies, a drop in temperature, a shift in winds, and widespread rainfall helped extinguish the fire.

The stratospheric intrusion also had another downside during the Springs Fire: it added ozone from the upper atmosphere to the urban and fire-related pollution produced in the lower atmosphere. On the second and third days of the fire, this helped to push levels of ozone—which can harm people’s lungs and damage crops—over the federal ozone limit at 24 monitoring sites across southern California. Monitors as far away as Las Vegas also saw a spike in ozone on the third day of the fire. The observed exceedances of the ozone standard were unusual for the region for that time period, suggesting that the stratospheric intrusions were a contributing factor.

“Stratospheric intrusions are double trouble for Southern California,” said Langford. “We knew that the intrusions can add to surface ozone pollution. Now we know that they also can contribute to the fire danger, particularly during La Niña years when deep intrusions are more frequent, as recently shown by our NOAA colleagues at the Geophysical Fluid Dynamics Laboratory. The good news is that with models and observations, we can get an early warning from the atmosphere in some cases.”

The authors note that stratospheric intrusions have previously been implicated in the explosive development of wildland fires in New Jersey and Michigan, but have not previously been connected to fires in southern California or to the Santa Ana winds. The frequent occurrence of stratospheric intrusions above the west coast during the fall, winter, and spring suggests that similar circumstances may have played a role in other major southern California fires, including the series of destructive fires that burned more than 800,000 acres in October of 2003, and burned nearly a million acres in October of 2007, say the authors.


(UPDATE July 12, 2015: We contacted one of the authors, Andrew Langford, and he sent us a copy of the paper, which has not been copyedited and typeset yet.)

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Thanks and a tip of the hat go out to Barbara.

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Author: Bill Gabbert

After working full time in wildland fire for 33 years, he continues to learn, and strives to be a Student of Fire.

3 thoughts on “Scientists find that stratospheric intrusions can increase the effects of Santa Ana winds on wildfires”

  1. This article makes sense but not only Santa Ana winds enhanced by stratospheric deep intrusions could triggered fires. Around mid-March 2006, a mega deep stratospheric intrusions triggered enormous bush fires in Texas. We should review more carefully in many places the real cause of triggering factors and include it. Also there is a growing interest in the literature for the impact of theses intrusions on severe weather triggering.

  2. Here is a link from the NOAA GIBBS (Global ISCCP B1 Browse System) archive satellite image site showing an 18 UTC (1100 PDT) May 2, 2013 GOES-15 Water Vapor Imagery (WVI) screen shot of a rather massive stratospheric intrusion (dark orange/yellow band) off the coast of California with a dry intrusion evident all throughout the state of California (light to moderate yellow).

    It is reasonable to infer that with southwest winds, the dark orange stratospheric intrusion present in this satellite WV image would be the same one that would have passed over the Springs Fire site on May 2-3, 2013; and the same one used in the above authors’ research.

    Stratospheric intrusions, dry intrusions, and dry slots indicate very dry air aloft. They are responsible for abrupt surface to near-surface drying, strong and gusty winds, and Haines Indices of 5-6 according to ‘the literature’ and research on those atmospheric mechanisms. The stratosphere is very high in ozone and high ozone areas also manifest themselves as dry intrusions and dry slots.

  3. “There was a desert wind blowing that night. It was one of those hot dry Santa Anas that come down through the mountain passes and curl your hair and make your nerves jump and your skin itch. On nights like that every booze party ends in a fight. Meek little wives feel the edge of the carving knife and study their husbands’ necks. Anything can happen. You can even get a full glass of beer at a cocktail lounge.”
    From “Red Wind” aptly describes it, long time Raymond Chandler fan, here.
    Wait until you write a paper, or help write it, someone plagiarizes it, then you find it behind the paywall-with the perp who stole the data taking credit-happened to a friend of mine.
    However no taxpayer money was involved….


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