Scientists confirm that nighttime wildfire activity is increasing

Firefighting agencies need to make changes to deal with the the new normal

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Day-night proportion of fire activity
Fig. 9 from the study below showing the proportions of heat detected on wildfires at night, vs. during the day. The MODIS (black) time series spans 2003–2020 and the VIIRS (red) time series spans 2012–2020. The horizontal dotted line at 28% indicates the CONUS-wide value detected by MODIS from 2003–2020.

In a study of wildfires in the conterminous United States from 2003 to 2020 researchers found that while fire activity increased during the day in the 18-year period, it increased even more at night.

Heat sensing data from satellites showed significant increasing trends in nighttime wildfire fire activity, with a +54%, +42% and +21% increase in the annual nighttime sum of Fire Radiative Power (FRP), annual nighttime active fire pixel counts, and annual mean nighttime per-pixel values of FRP, respectively, in the latter half of the study period. Activity during the day increased also, with rates of +36%, +31%, and +7% respectively.

Analysis of coincident 1000-hour fuel moistures indicated that as fuels dried out, satellites detected increasingly larger and more intense wildfires with higher probabilities of nighttime persistence.

The information above is from the study “Large wildfire driven increases in nighttime fire activity observed across CONUS from 2003–2020,” by Patrick H. Freeborn, W. Matt Jolly, Mark A. Cochrane, and Gareth Roberts.

Average wildfire size, US, 1985-2000 (except Alaska)

The reason wildfires typically exhibit less activity at night is due to diurnal changes in weather. Nighttime generally brings lower temperatures, higher relative humidity, decreasing winds, and higher fuel moistures in light fuels.

But a warming climate with occasional multi-year droughts and higher temperatures can lead to nighttime higher temperatures and lower humidities. Drought will lower the fuel moistures in live and dead vegetation. These changes can result in fuels at night remaining available for significant and continuous fire spread. This is causing wildfires to burn with more intensity, spread more quickly, and have more resistance to control 24 hours a day.

Annual temperature change

About 15 to 20 years ago firefighters could usually count on wildfire activity slowing significantly at night as long as the wind was not extreme. Night shift crews could make good progress constructing direct fireline near the edge of fires. In the last few years weather and fuel conditions that permit direct attack by ground personnel, day or night, are less common. Fires are getting larger. Megafires that blacken 100,000 acres are no longer rare.

So now what?

As fires show increasing resistance to control we need to ramp up our fuel treatments, including prescribed fires, by a factor of 10. Less than full suppression of carefully selected fires when the season-ending weather event is on the horizon can have a place also, if they are very carefully planned and actively tracked and managed using all of the predictive tools available run by very smart, experienced personnel.

We also need to realize that we will never be able to prevent all wildfires from burning into populated areas, so property owners must realize they have to live with fire, using FireWise principles. Here are six things that need to be done to protect fire-prone communities.

And, community destruction during extreme wildfires is a home ignition problem. Here is an excerpt from the article written by Jack Cohen and Dave Strohmaier:

Uncontrollable extreme wildfires are inevitable; however, by reducing home ignition potential within the Home Ignition Zone we can create ignition resistant homes and communities. Thus, community wildfire risk should be defined as a home ignition problem, not a wildfire control problem. Unfortunately, protecting communities from wildfire by reducing home ignition potential runs counter to established orthodoxy.

We also have to realize that the fire suppression manpower staffing model that was created 50 years ago is obsolete. The agencies that fight wildfires, especially the federal agencies, need to increase the numbers of Interagency Hotshot Crews and engine crews. The crews must be configured and managed to allow personnel to have a reasonable amount of down time at the home unit even during the busiest times of the fire year. They can’t be away from home 90 percent of the time and expect to have a decent work/life balance. One National Forest will begin a pilot program in 2022 increasing the sizes of Hotshot and Engine crews to 30 and 10 people, respectively. This is intended to improve work/life balance and increase the availability of resources.

The reforms in the just-passed infrastructure bill to improve the pay and working conditions of firefighters must be implemented immediately. Slow-walking those improvements, a tactic too often used by the Federal agencies, should not be tolerated.

Technology needs to be adopted to make firefighting more safe and efficient. Firefighters down to the crew supervisor level should have access to real time data about the location of the fire and other firefighting resources 24 hours a day. Communications capabilities need to be robust and bomb proof.

On the afternoon of November 16, 2021 we initiated a 24-hour online poll on Twitter, asking for firefighters’ observations about nighttime wildfire activity.

Typos, let us know HERE, and specify which article. Please keep in mind our commenting ground rules before you post a comment.

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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.

9 thoughts on “Scientists confirm that nighttime wildfire activity is increasing”

  1. Hi Bill,

    Is everybody ignoring the probably that the amount of fuel has been increasing Smoky The Bear and the Spotted Owl etc???

    And you have been reporting how the wildfires are now creating their own local tornadoes as the high needles wh burn up ion minutes to consume all the atmospheric oxygen in the near vicinity. The hot carbon monoxide, carbon dioxide combustion products, burning twigs and atmospheric nitrogen go straight up. Hence, spot fires form miles ahead without the need of the normal strong afternoon wild.

    Have a good day, Jerry

  2. Nope, nobody’s ignoring that. I think we’re all pretty aware of an increased fuel loading as a result of how good we’ve been at suppressing fire.

  3. Beginning in 2007, every uptick in acreage above the line labeled as 60 can be explained by big boxing and burning. None of these analyses consider the impacts of purposeful burning in managed fires or “full suppression” using our massive new (since 2007) ignition capabilities. Academics don’t understand what’s happening and can’t factor in what they can’t see. The agencies are in denial about their actions for public relations, political, and legal reasons. It’s a mess and without admitting the role firefighters play in final fire sizes there is no meaningful analysis including this one. Why don’t we demand that agency administrators track acres burned on purpose and miles of indirect line, for starters.

  4. Hi Brody,

    “Nope, nobody’s ignoring that.” Do you really believe that the Government Authorities responsible for maintaining Government Lands (Forest Service and Bureau of Land Management) publicly recognize the MISTAKES that they have CAUSED??? And do you really believe that the “Environmentalists” who promote the importance of the Spotted Owl over the proper harvesting of the timber growing on public lands recognize this???

    Have a good day, Jerry

  5. You use the word activity to perhaps describe fire behavior. Activity could be many things including numbers of fires. I think you are speaking to night time intensities?? but you simply state “Night time fire activity is increasing” Just sayin

  6. Hey Jerry, it’s not 1990 anymore; there are more issues afoot than the Spotted Own and timber sales. Most of the stuff that’s burning is standing dead timber that the timber companies won’t touch- and it my neck of the woods that is due to accessibility and the ability to even sell it. I’m so tired of hearing dinosaurs complain.

  7. Hi Frank,
    I will agree that we need to at least try to track acres burned as backburns, or at least intentionally lit, but understand it is probably difficult to be accurate. I think your estimates of these numbers are high, but anecdotally have seen > 20-30% of a fire’s acreage to be backburn acres. I see it in active fire plans where containment lines are set (or used) miles ahead of a fire and backburning operations are anchored to these lines.

    I am all for us using more fire on the landscape, but I don’t think the peak of fire season is when we should be adding these acres.

    Anecdotally, I have posed the question to peers about how many acres on wildfires are intentionally lit. Nobody has a good answer, but I have seen guesses from 20 – 50%!

  8. Wow, great analysis as usual Frank Carroll. You must have loads of data? Care to list names of fires you’ve analyzed? Since you began with 2007 to say that all of the average size of fire increase above 60 is caused by intentional ignition, feel free to name all the fires that year you analyzed, so we can come along on your journey.

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