Looking into the forces that drive wildfires

Pioneer Fire northeast of Boise, Idaho, August, 2016. USFS photo.

High Country News has an excellent article written by Douglas Fox that looks under the hood, so to speak, at the science that causes wildfires to burn the way they do. There are forces, unknown until the last decade or two, that are major influences on the spread of a fire, such as the 100 mph flamethrower-like jets of flame that may have contributed to the deaths on the 1994 South Canyon fire near Glenwood Springs, Colorado.

Mr. Fox writes in illuminating detail about state-of-the-art research being conducted by Janice Coen, David Kingsmill, Craig Clements, Mark Finney, Michael Reeder, and Brian Potter, as well as legacy research done by the the U.S. military in the 1940s that provided data on how to design incendiary bombs to burn down many of the buildings in Hamburg, Germany on July 27, 1943 in order to demoralize the workers in Germany’s critical U-boat industry.

Most of the article is about recent research on wildfires, but here is an excerpt about the military’s work in the 1940s in northwest Utah that facilitated the attack on Hamburg by the British that killed at least 42,000 people.

…The U.S. Army’s Chemical Warfare Service had commissioned Standard Oil Development Company to construct a row of steep-roofed European-style apartment buildings. Erich Mendelsohn, an architect who had fled Nazi Germany, specified every detail: 1 1/4-by-2-inch wood battens, spaced 5 7/8 inches apart, to hold the roof tiles; 1-inch wood flooring underlain by 3 1/2-inch cinderblocks, and so on — all to replicate the dwellings of German industrial workers. The wood was maintained at 10 percent moisture to mimic the German climate. Rooms were outfitted with authentic German curtains, cabinets, dressers, beds and cribs — complete with bedding — laid out in traditional floor plans.

Then, military planes dropped various combinations of charges on the buildings, seeking the most efficient way to penetrate the roofs and lace the structures with flame.

Those experiments offered clues on what factors could cause firestorms. And in the years following World War II, scientists would study Hamburg and other bombing raids to derive basic numbers for predicting when a firestorm might form: the tons of munitions dropped per square mile, the number of fires ignited per square mile, and the minimum area that must burn. They concluded that Hamburg’s unusually hot weather set the stage for the firestorm, by making the atmospheric layers above the city more unstable and thus easier for a smoke plume to punch through. Scientists theorized that this powerful rise had drawn in the winds that whipped the flames into even greater fury.

NASA releases video about Suomi NPP fire-detecting satellite

NASA released a video this week that explains some of the features of the Suomi National Polar-orbiting Partnership (Suomi NPP) satellite that was launched October 28, 2011. The Visible Infrared Imaging Radiometer Suite (VIIRS) on the satellite is a 22-band radiometer designed to collect infrared and visible light data to observe wildfires, movement of ice, and changes in landforms. It has a resolution of 375 meters, much better than the MODIS satellite data with 1,000-meter resolution. The MODIS was launched in 1999.

The combination of the VIIRS data (that is updated twice a day), weather forecasts, and fire behavior modeling software developed by Janice Coen and Wilfrid Schroeder, can result in more useful fire spread forecasts for fire managers.

The National Center for Atmospheric Research studies fire behavior

Janice Coen at the National Center for Atmospheric Research is studying how weather and fire interact in order to develop a wildfire prediction system to forecast fire behavior.

Articles at Wildfire Today tagged “Janice Coen” about the fire behavior research she is conducting.

Colorado to use new system to predict wildland fire behavior

Janice Coen Gov. John Hickenlooper sign bill
Gov. John Hickenlooper traveled to an Arvada fire station to sign the bill that will implement a wildfire prediction system. Dr. Janice Coen, one of the developers of the system, is on the left. Photo provided by COHOUSEDEMS.

The Governor of Colorado signed a bill Wednesday that authorizes the state to spend $1.2 million over the next two years on a “revolutionary” wildfire prediction system that uses weather data, groundbreaking computer modeling, and high resolution satellite imagery to predict the spread of fires up to 18 hours in advance.

Below is an excerpt from an article at the (Colorado Springs) Gazette:

…”This bill will predict the intensity and the direction of fires 12 to 18 hours ahead of time. That is really important so we know where to direct our planes, the aircraft we had a bill for last year, and our firefighters,” said Rep. Tracy Kraft-Tharp, D-Arvada, who introduced the bill. “This is really revolutionary.”

Under the new law, the Division of Fire Prevention and Control will contract with a nonprofit Colorado-based research organization with expertise in atmospheric science to predict wildfire behavior. The National Center for Atmospheric Research, a federally funded program headquartered in Boulder, is the only state agency that meets that criteria. NCAR has used modeling to accurately recreate the behavior of historic fires, including the Yarnell Hill fire that killed 19 Arizona firefighters in 2013.

She said the new technology could be in place by next spring and will work with the state’s new aerial fire fleet, a multimillion-dollar investment into wildfire detecting and fighting aircraft lawmakers made in 2013…

Janice Coen at the National Center for Atmospheric Research is one of the scientists working on this program. We have written about her work previously:

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

Simulation of winds affecting the Yarnell Hill Fire

This is an animation developed by Janice Coen, Ph.D., a Project Scientist at the National Center for Atmospheric Research in Boulder, Colorado. It simulates through a coupled weather-wildland fire environment model the spread of the Yarnell Hill Fire and the wind direction and speed. The arrows indicate the wind direction; the length of the arrows vary with the wind speed. On June 30, 2013 19 members of the Granite Mountain Hotshots were overrun by the fire when the winds from a thunderstorm cell north of the fire changed the direction of spread of the fire by about 90 degrees, surprising the firefighters on the south side of the fire, resulting in their entrapment.

See if you can tell when conditions worsened for the Hotshots.

Dr. Coen’s description of the simulation:

It begins at 2 am on 6/30/13. The fire is initialized in the model using the ~3 am VIIRS active fire detection map. Each frame is 1 minute apart, the sequence extends until 8:15 pm on 6/30. The fatality occurred around 4:45 PM. The color bar on the right indicates the heat flux (watts per square meter) from the fire, with more intensely burning areas in bright yellow and white, and less intensely burning areas in darker reds.
In the simulation, solar heating stirs up the boundary layer circulations throughout the day. Convection occurs in outer domains (not shown) to the northeast, creating high-based convective clouds as air flows south/southeast over the Mogollon Rim. Rain falls into a very dry boundary layer, creating a broad gust front that reaches the south edge of the fire at frame 936, which is 51 minutes after the fatality, so the simulated rush through the fatality site is about an hour slow.

The map below shows the approximate location of the fire at 4:30 p.m. on June 30, 2014, about 15 minutes before the Hotshots were entrapped at the deployment site (X) on the south side.

Yarnell Hill Fire, estimated perimeter at 4:30 p.m. June 30, 2014
Yarnell Hill Fire, estimated perimeter at 4:30 p.m. June 30, 2014. Source: Arizona State Forestry Division.

Better satellite imagery enables improved wildfire mapping and growth predictions

Higher resolution imagery becoming available from satellites will enable more accurate mapping and spread prediction of wildfires.

Higher resolution imagery becoming available from satellites will enable more accurate mapping and spread prediction of wildfires. Since we created Wildfire Today in 2008 we have frequently displayed maps showing fire data collected by the Moderate-resolution Imaging Spectroradiometer (MODIS) instrument package, such as the one below of the Falls Fire near Elsinore, California in August. The red squares represent heat detected by MODIS before the fire spread east across the South Main Divide and down through the bowl where the Decker Fire fatalities occurred in 1959. Click on the image to see a larger version.

Map of Falls Fire at 1:47 p.m. PDT, August 5, 2013
Map of Falls Fire at 1:47 p.m. PDT, August 5, 2013, showing heat detected by a satellite. The red squares indicating heat can be as much as a mile in error. (click to enlarge)

MODIS, launched in 1999 with its 1,000-meter resolution system, is starting to show its age. Better technology is now available and is orbiting 512 miles above the Earth on the Suomi National Polar-orbiting Partnership (Suomi NPP) satellite launched October 28, 2011 . The Visible Infrared Imaging Radiometer Suite (VIIRS) on the satellite is a 22-band radiometer designed to collect infrared and visible light data to observe wildfires, movement of ice, and changes in landforms. It has a resolution of 375 meters, much better than the MODIS. The new Landsat 8 satellite launched in February has a resolution of 30 meters for most of its sensors, and 100 meters for thermal infrared. This will be a game changer. In March we published a test image of the Galena Fire taken with Landsat 8.

Below is a comparison of data from MODIS and VIIRS. Click on it to see a larger version.

VIIRS vs MODIS
When observing wildfires, satellites provide different levels of detail, depending on which instrument is used. The image at left, produced from data generated by the MODIS instrument aboard NASA’s Aqua satellite, uses 1-kilometer pixels (a bit over half a mile across) to approximate a fire burning in Brazil from March 26 to 30, 2013. The image at right, produced with data from the new VIIRS instrument, shows the same fire in far greater detail with 375-meter pixels (a bit over 1,200 feet across). (Image courtesy Wilfrid Schroeder, University of Maryland.)

Last month we told you about a proposed satellite, called FUEGO – Fire Urgency Estimator in Geosynchronous Orbit, which would survey the entire western United States every two minutes or less and could detect a fire that is about 10 feet in diameter. Assuming that the data from the satellite could be transmitted to the appropriate dispatch center within a minute or two, this could be a major step toward keeping fires small… IF the fire agencies have the appropriate initial attack policies in place and an adequate number of firefighting resources, both ground and air-based, to respond and arrive at the fire within the first 10 to 30 minutes. But since the cost of the satellite could be several hundred million dollars, it probably will never be built or launched.

Two scientists who have been working with some of the new data that is available now are Janice Coen of the National Center for Atmospheric Research in Boulder, Colorado, and Wilfrid Schroeder with the Department of Geographical Sciences, University of Maryland. They intend to transition the new refined spatial resolution VIIRS and Landsat-8 fire detection data and a new weather forecast-fire spread model into operations in the next two to three years. Mr. Schroeder told us that some of the higher resolution data should replace the MODIS data on the GEOMAC website in the next one to two months. In the meantime you can see some early versions of it on an experimental basis at a website they created.

The two of them recently published a paper documenting the development of a new wildfire spread model (think newer version of BEHAVE) that, coupled with high resolution numerical weather prediction and the actual location of a fire as detected by the 375-meter resolution VIIRS, predicts the fire behavior and spread of a fire, displaying it on a map. The model can be run after the overflights of the satellite every 12 hours using updated weather forecast information and the current location of the fire.

Their paper is HERE, and a description of the concept written by Ms. Coen is below.
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