Nightfall no Longer Offers a Reliable Reprieve for Western US Firefighters
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For decades, firefighting crews counted on falling temperatures and rising humidity at night to dampen wildfire activity, allowing them to rest, regroup and prepare for the next day.
Over the last 20 years though, satellite measurements have confirmed a change reported in the western US by firefighters on the ground: a dramatic increase in nighttime fire activity by larger fires. Previous studies attributed the increase to warmer, drier nights, conditions that help to maintain the flammability of fuels.
New research from NOAA, the University of Washington and the U.S. Forest Service has investigated other weather conditions that influence fire behavior, the extent to which these factors have been changing over recent decades and how they may have contributed to changes in nighttime fire behavior.
“We looked for simultaneous changes in winds, atmospheric mixing and fuel moisture that might enhance nocturnal fire activity,” said lead author Andy Chiodi, a University of Washington scientist working with NOAA’s Pacific Marine Environmental Laboratory. “Our results show that, indeed, all the atmospheric measures that influence wildfires have changed towards supporting more intense nocturnal fire behavior.”
The findings were published in the Journal of Climate.
The implication of these findings, said Chiodi, is that researchers need to better understand the interplay of each of these factors in driving increases in nocturnal fire activity, which not only complicate firefighters’ jobs, but also could jeopardize public safety.
In 2022, a study led by the US Forest Service confirmed that the amount of fire radiative power, or the amount of heat generated by burning, detected at night over the contiguous U.S. by two NASA satellites (VIIRS and MODIS) increased by approximately 50 percent during the 2003-2020 study period. That study found the change was most pronounced for the larger fires burning in drier heavy fuels that experienced more active nighttime burning.
read more at research.noaa.gov.
