Knowable Magazine has an interesting article by Alexandra Witze on a variety of physics principles that affect wildland fires. She covers the research by Michael Gollner of the University of Maryland on how embers start spot fires, how Janice Coen, an atmospheric scientist who studies wildland fires at the National Center for Atmospheric Research in Boulder, Colorado monitored the start of the Camp Fire as she sat in the back of a room at a conference, and the real time radar signature of the firenado (fire tornado) at the Carr Fire.
Below is an excerpt from a section about embers propagating spot fires.
It turns out that a single ember, or a handful of embers, can’t build up that much heat if it lands on a material such as a deck or a roof. But put one or two dozen embers into Gollner’s device and the heat flux goes up dramatically, he and his colleagues report in the March Fire Safety Journal. “You start to have re-radiation between them,” he says. “It glows, under the wind — it’s just beautiful.”
Just a small pile of embers can generate about 40 times the heat you’d feel from the sun on a hot day. That’s as much heating, and sometimes more, as comes from the fire itself. It’s also enough to ignite most materials, such as the wood of a deck.
So if there are a lot of embers flying ahead of a fire, but those embers land relatively far from one another, they may not build up the radiative heat needed to generate a spot fire. But if the embers pile up, perhaps blown by the wind into a crevice of a deck, they can smolder together and then trigger an ignition, Gollner says. Most homes that burn in the wildland-urban interface ignite from these embers, often hours after the fire front itself has passed.
Understanding the heat flux at these small scales can illuminate why some houses burn while others don’t. During the Tubbs fire, homes on one side of some streets were destroyed while those on the other side had hardly any damage. That may be because the first house that ignited radiated energy to its neighbor, which then burned neighboring homes like dominoes because of the radiative heat. When houses are closely packed together, there’s only so much homeowners can do to mitigate the danger by clearing brush and flammable material around the house.
Recent large fires may be harbingers of things to come, researchers say
Eiler Fire, Northern California, August 6, 2014. Photo by Bill Gabbert.
By Mari N. Jensen, University of Arizona College of Science
Wet winters no longer predict possible relief from severe wildfires for California, according to a new study from an international team that includes a University of Arizona scientist.
From 1600 to 1903, the position of the North Pacific jet stream over California was linked to the amount of winter precipitation and the severity of the subsequent wildfire season, the team found. Wet winters brought by the jet stream were followed by low wildfire activity, and dry winters were generally followed by higher wildfire activity.
After 1904, the connection between winter moisture brought by the jet stream from December through February and the severity of the wildfire season weakened. The weakened connection between precipitation and wildfires corresponds to the onset of a fire suppression policy on U.S. federal lands, the team reports in the March 4 issue of the Proceedings of the National Academy of Sciences.
The connection disappeared altogether after 1977.
Now, fuel buildup from decades of fire suppression in the 20th century plus rising temperatures from climate change means any year may have large fires, no matter how wet the previous winter, the team writes.
“The moisture availability over California is still strongly linked to the position of the jet stream, but fire no longer is,” said co-author Valerie Trouet, an associate professor of dendrochronology at the UA Laboratory of Tree-Ring Research.
The finding surprised Trouet.
“I didn’t expect there to be no relationship between jet stream dynamics and fire in the 20th century. I expected it to be maybe weaker than before, but not to completely disappear,” Trouet said.
California’s wet winter of 2016-2017 is a good example, she said. That winter was followed by many large fires in 2017, including the Tubbs fire in October and the Thomas fire in December. Twenty-four people died and 6,699 structures burned in those two fires, according to the California Department of Forestry and Fire.
“It’s not either climate change or historical fire management–it’s really a combination of the two that’s creating a perfect storm for catastrophic fires in California,” Trouet said.
To reconstruct California’s fire and moisture patterns and the position of the North Pacific jet stream for the past 400 years, the researchers combined instrumental and historical records of temperature, precipitation and fires with the natural archives of climate and fires stored in tree rings that go back in time for centuries.
Lead author Eugene R. Wahl of the National Oceanic and Atmospheric Administration said, “The method we used to determine the average winter jet stream conditions is a real advance. Coupled with independent precipitation and fire records, this is a state-of-the-art coupling of paleoclimate and paleoecology.”
The study is the first to show the close connection between winter precipitation in California and the position of the jet stream back to the year 1571, Trouet said. The study is also the first to examine the relationship of past winter precipitation, the position of the jet stream and past fire activity stretching back to 1600, she said.
The paper by Wahl, Trouet and two co-authors is, “Jet Stream Dynamics, Hydroclimate, and Fire in California from 1600 CE to Present.”
Initially, Wahl and co-author Eduardo Zorita of the Helmholz-Zentrum Geesthacht in Germany were working independently of Trouet and co-author Alan Taylor.
As part of a larger project to extend global reconstructions of temperature, precipitation and atmospheric circulation further into the past, Wahl and Zorita were figuring out how the North Pacific jet stream affected precipitation in California for centuries. Wahl, a paleoclimatologist at NOAA’s National Centers for Environmental Information in Boulder, Colorado, was a co-leader for the North America part of the larger project.
Trouet and Taylor of Penn State in University Park, Pennsylvania, had already reconstructed California’s fire history back to 1600, and Trouet had reconstructed the behavior of the North Atlantic jet stream back to 1725.
After Wahl heard Trouet give a presentation about her North Atlantic jet stream research, the four scientists joined forces to see whether there were links between the past behavior of the North Pacific jet stream and California’s fire and precipitation history.
“When the jet stream is positioned over California, it’s like a fire hose–it brings storms and moisture straight over California,” Trouet said. “What we see post-1900 is that the position of the jet stream is still an important driver of moisture to California–it brings moisture to California when it’s in the right position–but there’s a disconnect with fire.”
The likelihood that every year may be a high-fire year will be a significant societal challenge, Taylor said.
“Fire not being influenced by moisture anymore? That is surprising. It’s going to be a problem for people, for firefighters, for society,” he said. “The only thing we can control is fuels, so what it suggests is that we take that very seriously.
“The last three years may be a harbinger of things to come,” he said. “Between 1600 and 1903 there was not a single case of a high-precipitation year coupled with a high-fire year as occurred in 2017.”
The research team’s next step is to expand this research to see how the jet stream patterns correspond with fire in other types of forested ecosystems farther north.
The research was funded by the U.S. National Science Foundation, the U.S. Geological Survey’s Southwest Climate Science Center, the U.S. Department of Agriculture Forest Service, the German Science Foundation Cluster of Excellence Clisap, a George H. Deike, Jr. Research Grant, and the Swiss National Science Foundation.
Note from Bill. Even though the research was funded by universities and government agencies, you would still have to pay $10 to a private organization to read the report. It does not comply with Open Access policies.
A researcher who excavated 12 layers of soil deposits from the shore of an ancient lake near the river Jordan found evidence that fire had been used by humans in every layer. The soil layers were laid down by waters from the lake in between occupancies by the different societies of humans that inhabited the site 790,000 years ago. Nira Alperson-Afil from the Hebrew University of Jerusalem, Israel, concluded that humans would have had to have mastered the art of creating fire for it to have shown up in all 12 layers.
Previous research had shown that humans from this period could manipulate and use fire, but it was not clear whether they had the ability to create the fire themselves.
The researcher did not say if 790,000 years ago the users of fire had to obtain burning permits, get NEPA compliance, or write burn plans before they started their fires.
Hot-Dry-Windy Index for the area of the CR34 Fire in southeast Colorado February 13, 2019.
The Hot-Dry-Windy Index (HDW) is a new tool for firefighters to predict weather conditions which can affect the spread of wildfires.
It is described as being very simple and only considers the atmospheric factors of heat, moisture, and wind. To be more precise, it is a multiplication of the maximum wind speed and maximum vapor pressure deficit (VPD) in the lowest 50 or so millibars in the atmosphere.
On a website bearing the logos of the U.S. Forest Service, Michigan State University, and St. Cloud State University, you can click on the map to display the HDW for any area in the contiguous United States. Then the displayed chart shows the index for the preceding 10 days and the forecast for the next 7 days. For the current and following days you will see results of the Global Ensemble Forecast System (GEFS), which is a weather forecast model made up of 21 separate forecasts, one control (in red) and twenty perturbations. The reasoning for showing 21 different forecasts is to quantify the amount of uncertainty in a forecast by generating an ensemble of multiple forecasts, each minutely different, or perturbed, from the original observations.
The HDW only only uses weather information – fuels and topography are not considered by HDW at all. If the fuels are wet or have a high live or dead moisture content it will not be reflected in the data.
Another thing to keep in mind is that the rating which is shown on the percentile gradient compares the HDW to the average for that date, from 1979 to 2012, at that location on a 0.5-degree long/lat grid spacing, rather than to a year-long average.
Yesterday, February 13, the CR34 fire in southeast Colorado burned 3,800 acres. Judging from the way the smoke column was laying over it was pretty windy.
The CR34 Fire in southeast Colorado 10 miles south of Springfield, Wednesday afternoon February 13, 2019. Baca County Sheriff’s Office photo.
At the top of this page is the HDW prediction for yesterday at the location of the CR34 Fire, showing the predicted index for February 13 above the 95th percentile for that date.
The actual HDW below is centered on the most active day on the Pagami Creek Fire which was managed, rather than suppressed, for 25 days, until it ran 16 miles on September 12, 2011 eventually consuming over 92,000 acres of the Boundary Waters Canoe Area Wilderness in Minnesota. Eight USFS employees were caught out in front of the fire in canoes, with some of them having to deploy fire shelters. Like for the CR34 Fire, the HDW was well above the 95th percentile for the date.
Pagami Creek fire September 11, 2011. Photo: Superior National ForestPagami fire, Lake Polly, 9-12-2011. Photo: Hans Martin, USGS.
Last year a paper was published about the Hot-Dry-Index, written by Jessica M. McDonald, Alan F. Srock, and Joseph J. Charney.
A Canadian bird dog airplane disappears into smoke over the Highland Fire in South Dakota, July 1, 2012. Photo by Bill Gabbert.
According to a researcher with the University of Alberta, breathing smoke from a wildfire can be equivalent to smoking up to two packs of cigarettes a day, depending on the density.
Accumulating over time, smoke particles trapped in the lungs can cause “all kinds of problems,” Mike Flannigan of the university’s Department of Renewable Resources told the Associated Press. “The more we learn about smoke and health, the more we are finding out it is bad for us, which isn’t a surprise but it’s worse than we thought.”
The AP reported that Mr. Flannagin was scheduled to make a presentation at the British Columbia Lung Association’s annual workshop on air quality and health on February 6, 2019.
Last week at the Consumer Electronics Show in Las Vegas Hyundai displayed a scale model of a concept for an outlandish vehicle that they think could be useful for emergency responders and search and rescue organizations.
It truly looks like something out of a science fiction movie. And for now, anyway, it is just an idea since it hasn’t been manufactured.
Hyundai Elevate. Image from the video.
Their “Elevate” vehicle has four rubber tires and can travel down a road much like a regular car. Each wheel is driven by individual electric motors and is attached at the end of a “leg” that has three or four joints, or knees. The legs are folded unless the driver needs to navigate over rough, rocky terrain, or has to step over a five-foot wall, in which case the legs extend and can begin walking.
Hyundai Elevate in rescue ambulance mode. Image from the video.
There have been a number of wildfires that come to mind (in the U.S., Australia, Greece, and Portugal) in which residents fleeing by car became trapped on roads blocked by a fallen tree or traffic jams. Rescuers in an “elevated” vehicle might be able to quickly access the area, stepping over the trees or going off-road to bypass the obstacle. It could also be used as an all-terrain ambulance that could transport wildland firefighters out of terrain that is moderately steep and rocky.
Hyundai Elevate enabling access for person in wheelchair. Image from the video.
Hyundai admits that the Elevate is a pretty wild concept and has no plans to manufacture the vehicle, but is using the project to explore ideas and technologies that could be useful down the road.
In the video below a representative from Hyundai describes some of the features of the Elevate.
