The Black Summer fire season of 2019-2020 in southeastern Australia contributed to an intense ‘super outbreak’ of fire-induced and smoke-infused thunderstorms, known as pyrocumulonimbus (pyroCb). More than half of the 38 observed pyroCbs 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. We connect cause and effect of this event by quantifying the fire characteristics, fuel consumption, and meteorology contributing to the pyroCb spatiotemporal evolution. Emphasis is placed on the unusually long duration of sustained pyroCb activity and anomalous persistence during nighttime hours. The ensuing stratospheric smoke plumes are compared with plumes injected by significant volcanic eruptions over the last decade. The Australian super outbreak is also compared with pyroCb events observed in North America during 2020-2021, including recent airborne measurements inside an active pyroCb. As the second record-setting stratospheric pyroCb event in the last four years, the Australian super outbreak offers new clues on the potential scale and intensity of this increasingly extreme fire-weather phenomenon in a warming climate.
Dr. Dave Peterson is a meteorologist at the US Naval Research Laboratory in Monterey, CA. He has broad scientific interests in both meteorology and satellite remote sensing. Dave currently supports the US Navy’s global aerosol modeling efforts, with a focus on extreme wildfires and smoke transport. He is a leading expert on thunderstorms caused by intense wildfires (pyrocumulonimbus), and the ensuing impact on stratospheric composition. Dave also serves as an interface between operational meteorologists, atmospheric chemistry scientists, and modelers, especially during large field experiments.