A huge tower of smoke generated by Australian forest fires in late 2019 set a new record for the tallest and largest storms generated by the fire ever measured. It may also represent a new class of volcanic-scale “pyrocumulonimbus” events, scientists said at an online press conference on Dec. 11 at the fall meeting of the American Geophysical Union.
A particularly intense fire wave in South East Australia during the country’s 2019-2020 black summer forest fire season caused a “super outbreak” of 32 pyrocumulonimbus trees, or pyroCB, from December 29 to December 31 (SN: 3 / 4/20). The resulting smoke from smoke thrown high was so massive that it rose up to 35 kilometers into the atmosphere, into the stratosphere, well above the heights that jet planes fly (SN: 15/06/20). Combined with a second large plume on January 4, they injected three times more aerosol particles into the stratosphere than any previously recorded pyrocb event.
Such a lasting and intense event “wasn’t like anything we’ve seen before,” eclipsing the previous headline, a vast cloud of fire that formed over the Pacific Northwest in 2017, said David Peterson, a U.S. Naval Research meteorologist. Laboratory in Monterey, California. The Australian outbreak "surpassed this unprecedented event at almost every level". As for the large amount of aerosols sent into the stratosphere, Australian feathers were on par with the strongest volcanic eruptions in the last 25 years.
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It is not yet clear what impact these particles have on the atmosphere, weather patterns and the ozone layer. Scientists detected remnants of the 2017 pen up to 10 months; black summer feather particles still linger, Peterson said. His work will appear in an upcoming issue of npj Climate and Atmospheric Science.
It is unclear whether these events will become more common as the weather warms. PyroCb clouds require very large and intense fires and conditions that allow thunderstorms, including humidity, several kilometers into the atmosphere. Such conditions may be more common in some regions due to climate change.