"This was the mother of all pyroCbs. Normally, when you see something like this, you think volcanic eruptions — that's what normally puts a lot of material into the stratosphere — but it's all coming from these wildfire-driven thunderstorms." US Navy Research Laboratory meteorologist Dr. David Peterson
The 2017 fire season in North America was one of the most brutal ever recorded. One such fire started in the state of Washington on August 22, and it eventually combined with 18 other fires in the province of British Columbia to create a massive wildfire that became the largest in the province’s history. But it was what happened on August 12 that worried scientists. Intense heat, along with the correct atmospheric conditions, triggered four thunderstorms to form within five hours, according to researchers at NASA. The storms, named pyrocumulonimbus or pyroCb, sent smoke soaring into the stratosphere where it eventually encircled the Northern Hemisphere. What the US Navy research concluded was that the thunderstorms acted as a “giant chimney” blowing the smoke to high altitudes, similar to what a moderate volcanic eruption does.
Karen Graham of Digital Journal writes:
A pyrocumulonimbus storm combines smoke and fire with the features of a violent thunderstorm. Pollutants from these storms are blown into the stratosphere.Dr. Peterson explained that like regular thunderstorms, pyroCbs are very tall and produce lightning, but pyroCbs are also filled with smoke. "You end up with this very dirty thunderstorm. Essentially, this is a giant chimney taking smoke from the surface to high altitudes, at least to aircraft-cruising altitudes."
The impact of volcanic eruptions on the climate system has been recognized for several decades, but pyroCb research is relatively new, originating at NRL in the early 2000s, according to Peterson. While such major volcanic events are sporadic, Peterson said, pyroCb events occur every year, however, scientists have not studied these storms enough to understand their full impact on our climate.
But what makes B.C.'s 2017 fire season so interesting and the center of the NRL study was an event that occurred on the night of August 12, 2017. A combination of the intense heat from the fires burning in a remote region of the province, combined with the right atmospheric conditions, generated a series of four thunderstorms in a 5-hour period.
A satellite map from the early hours of Aug. 13, 2017, shows how B.C. wildfires, in pink, triggered large thunderstorms, in green. (Naval Research Laboratory)The intensity of the stratospheric injection from the pyroCb event "produced a high-altitude smoke layer that encircled the Northern Hemisphere over several months,” Peterson said. “This event provides the best opportunity to date for highlighting pyroCb activity as an important consideration in the climate system.”