NASA scientists fly through Wash. wildfire-triggered thunderstorm for research
The research could improve climate models and help determine what happens to the chemistry of smoke in the stratosphere
By Evan Bush
The Seattle Times
SEATTLE — Wildfire smoke from the Williams Flats fire, burning on the Colville Indian Reservation, triggered a thunderstorm Thursday, and for one of the only times ever, scientists were able to fly through its clouds, photograph the phenomenon from a jet and take measurements from inside.
The phenomenon, called a pyrocumulonimbus or PyroCb, “is essentially a thunderstorm that is created or driven by a wildfire,” said David Peterson, a meteorologist with the Naval Research Laboratory, giddy after Thursday’s flight. “The heating from the fire produces an updraft column and under certain favorable weather conditions, you can build a cloud on that plume.”
These high-altitude thunderheads can produce thunder and lightning but rarely dump precipitation.
Peterson said he could see smoke being injected just below the stratosphere during the thunderstorm.
Peterson’s research is part of a joint National Oceanic and Atmospheric Administration and National Aeronautics and Space Administration (NASA) project to better understand wildfire smoke’s impact on air quality and the climate.
Scientists’ observations, data and photographs from the Williams Flats fire could form the basis of pioneering new research about the poorly understood phenomenon of wildfire-induced thunderstorms, which only recently have been studied in detail.
The research could improve climate models, help determine what happens to the chemistry of smoke in the stratosphere and answer other mysteries about wildfire-fueled thunderstorms.
For several weeks, researchers have been flying throughout the West on a NASA DC-8 airplane stationed in Boise, Idaho. The plane, equipped with scientific instruments, travels through wildfire smoke so scientists can photograph, measure and collect data. The researchers spent much of the week darting in and out of smoke from the Williams Flats fire, which has burned some 43,000 acres, according to the federal fire-tracking database InciWeb.
“As we fly into this deep smoke, the light goes down, and the sun gets orange,” said Rebecca Hornbrook, an atmospheric chemist at the National Center for Atmospheric Research. “It’s like a weird sepia-toned orange-ish hue.”
Sometimes, the smoke smells like a campfire or barbecue. Other times, an acrid and unpleasant smell overtakes the airplane cabin, said Hornbrook, who uses the flights to detect volatile organic compounds in wildfire smoke.
Thursday’s wildfire-fueled thunderstorm was the first produced in the continental United States this year.
Scientists couldn’t detect PyroCb plumes until the early 2000s, when satellite technology developed the ability to pinpoint the wildfire-fueled thunderstorms, said Philippe Papin, a postdoctoral atmospheric scientist at the U.S. Naval Research Laboratory.
Wildfire-fueled thunderstorms don’t produce much precipitation that reaches the ground, Papin said, but they can create lightning strikes that reach the ground that have the potential to start new fires.
The clouds are so high and there’s so much smoke in the air to collect condensation, “if anything is falling out of these clouds, it’s small pieces of dirty ice,” Peterson said.
The scientists don’t know exactly how many PyroCbs are produced each year, though active fire years can see 25 to 30 in North America alone, Peterson said.
The size and intensity of wildfires has increased in recent years. Climate change is expected to continue that trend.
More wildfires don’t necessarily produce more PyroCbs, the researchers said. Extreme or large fires don’t necessarily make them more likely. Meteorological conditions, such as moisture and instability, must be just right to produce wildfire-fueled thunderstorms, said Melinda Berman, a UCLA student involved in the research.
It’s also not yet clear how fire-caused thunderstorms affect the climate system.
When volcanoes erupt, they spew ash into the air, and send sulphur dioxide gas into the stratosphere, where it cools and converts to tiny sulphate particles, Peterson said. Those particles reflect solar radiation, which scientists believe causes global cooling.
Peterson said large wildfire-fueled thunderstorms inject a ”similar amount of material into the stratosphere” as volcanic events, but instead of sulphur, the storms emit carbon-based smoke, which absorbs sunlight and rises.
What impact the high-altitude smoke has on surface temperatures hasn’t been studied enough, Peterson said.
In 2017, several wildfires in British Columbia produced smoke-fueled thunderclouds, which transported smoke into the stratosphere, according to an article published Thursday in the journal Science. Satellites could detect smoke in the stratosphere for more than eight months. The scientists wrote that the findings could help scientists understand the potential effects of nuclear winter.
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