Southern California Fires Demand New Techniques in Fire Science

Firefighters battle fire in San Marcos, California

Wildfires menace southern California, thousands evacuated

Southern California’s fire ecology is unlike that of anywhere else in the United States. Fire control strategies developed for mountain forests don’t have the same results here. So can science help uncover new answers to help Southern California communities manage and live with wildfires?

The fires in Southern California are genuinely different than in the rest of the United States, breaking the well-established rules of fire control developed elsewhere in the country. Research into what makes these fires so different is critical to more effective firefighting.

Southern California Fires Demand New Techniques in Fire Science

Fires in Escondido, California on Thursday May 15, 2014. Image credit: Gregory Bull/AP

I know what you’re going to say: Clear firebreaks! Build with stone! Set controlled burns! Southern California is different. Those techniques don’t always work in the unusual geography, or aren’t earthquake-safe. Read on to learn why you really shouldn’t scoff at California for being so flammable.

Southern California is coastal desert with more deserts inland, not at all like the mountainous forests that regularly catch fire in other parts of the country. This geography leads to Santa Ana winds that drive fires over firebreaks. Meanwhile the chaparral scrublands don’t respond well to controlled burns. Not only do the controlled burns not reduce the risk of another fire, but flat-out removing vegetation just causes invasive weeds to grow that burn hotter and faster than the native plants! Luckily, a research program is dedicated to looking at just fires in Southern California, learning how they’re different and using that statistical data to develop new plans on how to best mitigate the risk.

Last year, the U.S. Geological Survey produced an educational video on just why fires in Southern California are so different than elsewhere, and how they’re using data to develop new strategies in fire prevention and fire science. Given the severe drought in California and the potential for a hot El Niño summer, let’s hope some of the science helps firefighters generate ideas for more effectively combatting fires this summer.

If you dislike learning via video, the USGS also provides a full transcript you can read instead.

California Heat Wave

Wildfire approaching homes in San Marcos, California. Image credit: AP Photo

Santa Ana Winds, Fire Tornados, and the California Fires

After months of drought, summer is starting with fires in southern California. The fires are being amplified by Anabatic winds, with smoke cyclone and fire tornadoes spinning out of the flames.

MODIS

Image credit: NASA/MODIS

The MODIS Satellite managed to get some rapid-response images of the scene. Smoke is clearly visible in the true-colour image, but the fire damage is easier to spot as magenta splotches in a sea of bright green in the false-colour image.

 Smoke Cyclones and Fire Tornados

Even small temperature differences are enough to spawn a funnel. If a column of hot air rises rapidly inside a pool of cool air, through the conservation of angular momentum any rotation will amplify as the tower of air grows. More hot air gets pulled horizontally along the ground before rising within the column, feeding the funnel. Air cools as it rises, eventually tumbling down the outside of the tower. This cooler air reinforces the structure by stabilizing it and keeping it contained.

Change in winds created this twister in Fallbrook

Santa Ana Winds

Southern California is subject to adiabatic winds, more commonly known as the Santa Ana winds. They’re driven by the pressure differential between the hot, dry interior, and the cooler, moist coast.

Santa Ana windsThe pressure difference draws air up and over the mountains. As winds flow down-slope, they compress, heating up as they gain speed. The result is very strong, hot, dry winds blasting the coast. During fire season, these winds make a bad situation worse by drying out vegetation into fuel. The strong gusts quite literally fanning the flames, building flare-ups into raging fires.

NOAA fireThis past week, the Santa Ana winds combined with a wriggle in the jet stream producing already record-breaking high temperatures, making containing the fires that much more difficult.

Science of the Fiery Dust Devil Spawned by a Controlled Burn

Take a swirling dust devil, pick up some tumbleweeds, add fire, and the result looks like an elemental monster straight out of a video game. But it isn’t a computer-generated effect; it’s 100% real science.

dust devilsThomas Rogers was working on a controlled burn at Rocky Mountain Arsenal National Wildlife Refuge when a dust devil spawned and quickly evolved into a swirling mass of hot air, drawing in the fire and nearby tumbleweeds to create a swirling inferno.

The science behind this incredible, bizarre video of earth, wind and fire

Most people are familiar with (or have even seen) a dust devil before. Dust devils are rapidly rotating columns of air that form over large, flat patches of land on days with hot temperatures and light winds. Under the right conditions, the land may be able to heat up enough to cause the air immediately above the surface to quickly start to rise.

When the winds are just right, it may cause the rising column of air to begin to rotate much in the same way that a tornado does. As the column of air continues to rise, it stretches out, causing the column of air to spin more quickly, which kicks up dust and dirt and creates a dust devil.

Some dust devils can reach the intensity of an EF-0 tornado, blowing around light objects and doing damage to poorly constructed buildings. Several people are known to have died from flying debris caused by dust devils.

The same general principle extends to firenadoes. When the right conditions are present, the incredibly intense heat caused by the wildfire allows the air to quickly rise, stretch out, and rotate, creating the “tornado” of fire and smoke.

firenadoesRegarding the question of whether or not they’re dangerous…it’s a spinning column of fire reaching a hundred feet into the sky. Of course it’s dangerous. The whirl wouldn’t be able to survive outside of the wildfire itself, so it wouldn’t spread beyond the fire to terrorize a town, but the intense winds are enough to help spread the fire and send it further out of control.

Firenadoes have made the news several times in the last few weeks, including the one spotted in California (pictured at the top of this post), and an incredible shot of one in Missouri .

firenadoesThis is not a new phenomenon. The odds of people spotting firenadoes increases with the frequency of wildfires. Not only do more fires provide more chances for these whirls to form, but the fact that almost everyone has a smartphone these days allows people to take a picture and share it with the world the moment they spot one.

Dust Devil Pulls Burning Tumbleweeds Into A Hellish Firenado

Dust Devil Pulls Burning Tumbleweeds Into A Hellish Firenado

As terrifying as the tumbleweed firenado is, the firefighters were prepared for the possibility of accidental fires as part of their controlled burn.

Here’s the most scientific explanation I could find, and that’s just for a computer-simulated fire whirl created under controlled conditions. Link to the paper.

Flow Structure of a Fixed-frame Type Fire Whirl

flame interactionUPDATE:

May 2014 San Diego County wildfires

The severe weather conditions contributed to the spread of at least 14 fires, with 10 of them receiving names. At least nine of the wildfires are believed to have originated from the Bernardo Fire, which ignited on May 13, 2014.Those fires were later collectively dubbed as the San Diego Complex Fire by CAL FIRE.

Governor Jerry Brown and the state of California declared a state of emergency for the county and affected areas.

May_2014_Bernardo_Fire_Burn_Area

A CAL FIRE fire map of the Bernardo Fire’s burn areas, as indicated in red. The fire had burnt a total of 1,550 acres of land. The Bernardo Fire was also responsible for most of the wildfires burning in San Diego County in May 2014 (collectively known as the San Diego Complex Fire).

Driving Through San Diego Wildfire – state of emergency

 

Wildfires roar in California, teens arrested for arson

wildfires in CATwo teens were arrested Thursday evening after police say they started at least two brush fires in San Diego’s Escondido area, as a number of larger fires rage across the county. Two teens were arrested Thursday evening after police say they started at least two brush fires in San Diego’s Escondido area, as a number of larger fires rage across the county.

Man arrested for arson in California fire

Authorities arrested a man for arson Friday in one of 10 fires that raged through San Diego County this week, as U.S. Marines and their families were forced to flee Camp Pendleton due to a new fire on the base.

Marine Corps Camp PendletonAlberto Serrato, 57,  pleaded not guilty Friday to arson in connection with a 105-acre fire in suburban Oceanside — one of the smaller fires. The fire started Wednesday and is fully contained. Serrato was arrested Thursday in Oceanside and faces up to seven years in prison if convicted.

At least 10 blazes broke out in San Diego County between Tuesday and Thursday. Together, the fires burned through more than 10,000 acres in the San Diego area, killing one person and causing more than $20 million in damage.

At least eight houses, an 18-unit condominium complex and two businesses were destroyed, and tens of thousands of people were told to leave their homes.


 

Check the CalFire official map and incident updates for the latest information on the California fires. Use their guide on how to reduce your fire hazard, and learn how the hazard can be reduced through controlled burns.

Resources:

Southern California Fires

io9 – We come from the future

Santa Ana Winds and the California Fires

2014 California wildfires

Gov. Jerry Brown declares state of emergency in San Diego

Man arrested for arson in California fire as Marines, families

 

MODIS Satellite Imagery – Active Fire Mapping Program

Stop Disasters! as an Emergency Manager

 

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