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Seminar: Dr. David Peterson | Naval Research Laboratory

In-Person PHYS 401


Physics : 401

Date & Time

October 4, 2023, 11:00 am12:00 pm


TITLE: Pyrocumulonimbus and its Role in the Climate System:
What is known and unknown?

ABSTRACT: Pyrocumulonimbus (pyroCb) are fire-induced and smoke-infused thunderstorms that serve as the primary pathway for smoke to reach the upper troposphere and lower stratosphere (UTLS).The magnitude of smoke plumes observed in the UTLS has increased significantly in recent years, rivaling or exceeding the impact from all volcanic eruptions observed over the last decade, with the potential for significant climate feedbacks on seasonal and hemispheric scales. The Black Summer fire season of 2019-2020 in southeastern Australia contributed to an unprecedented pyroCb ‘super outbreak’ that took place over 51 non-consecutive hours. More than half of the 38 observed pyroCb updraft pulses injected smoke particles directly into the stratosphere, producing two of the three largest smoke plumes observed at such altitudes to date. Over the course of three months, these plumes encircled a large swath of the Southern Hemisphere while continuing to rise, in a manner consistent with existing nuclear winter theory. Fewer than three years earlier, a large pyroCb outbreak in Canada produced a persistent smoke plume that encircled a portion of the Northern Hemisphere. We summarize what the community has learned from these extreme events and identify science questions that remain unanswered. A recently-developed pyroCb inventory facilitates the first analysis of regional, seasonal, monthly, and inter-annual variability worldwide, including during the extreme 2023 fire season in Canada. Unique in-situ and remotely-sensed measurements of pyroCb activity observed during the 2019 FIREX-AQ field experiment identify the fire characteristics, cloud microphysical properties, and smoke plume chemistry associated with this extreme fire-weather phenomenon.