Smoke with Induced Rotation and Lofting (SWIRL) Generated by the February 2009 Australian Black Saturday PyroCb Plume.

The discovery of smoke‐induced dynamical anomalies in the stratosphere associated with the 2019/2020 Australian New Year pyrocumulonimbus (pyroCb) super outbreak initiated a new field of study involving aerosol/weather anomalies. This paper documents the dynamical anomalies associated with the February 2009 Australian Black Saturday pyroCb outbreak. Positive potential vorticity anomalies (indicating anticyclonic rotation) with horizontal extent ∼1000 km and vertical thickness ∼2 km are associated with the plume, which we classify as a Smoke With Induced Rotation and Lofting (SWIRL). The SWIRL initially formed east of Australia, but then moved westward, crossing over Australia, and continuing to Africa. The SWIRL lasted for nearly three weeks (13 February–4 March), traveling ∼27,000 km and rising from potential temperatures of ∼410–500 K (altitudes ∼18–21 km). The altitude of the SWIRL is corroborated with coincident satellite‐based profiles of H2O, CO, HCN, O3, and aerosol extinction. A vertical temperature dipole (±3 K) accompanied the PV anomaly, as verified with coincident Global Navigation Satellite System radio occultation temperatures. The SWIRL dissipated as it passed over Africa. Operational ECMWF forecasts with early initialization (13 February) and late initialization (21 February) are examined. In the early case, the forecasted PV anomaly disappeared within 4 days, as expected due to lack of smoke heating in the forecast model. In the late case, while the forecasted PV anomaly was weaker than in the reanalyzes, a remnant anomaly remained out to 10 days. Plain Language Summary: Large bushfires in February 2009 in Australia led to large thunderstorms called pyrocumulonimbus (pyroCb) that injected significant amounts of smoke high into the atmosphere. When this smoke was warmed by absorbing sunlight it became buoyant and started to rise and rotate. This feature has been named a Smoke With Induced Rotation and Lofting (SWIRL) and had previously been observed in large pyroCbs that occurred around New Year's Day 2020 and in Canadian fires that occurred in 2017. The February 2009 SWIRL was a pancake‐like structure 1000 km across and 2 km thick. It lasted for three weeks, traveling over 27,000 km, and rising from 18 to 21 km in altitude. The SWIRL was observed both in weather maps and in satellite observations of gases such as water vapor, carbon monoxide, and ozone. Forecasting the SWIRL is difficult because current numerical weather models either do not consider smoke heating or lack inputs of pyroCb events as they are occurring in real time. Key Points: The February 2009 Australian Black Saturday pyroCbs injected a smoke plume into the stratosphere that induced a mesoscale anticycloneThe anticyclone was 1000 km across and 2 km thick and traveled 27,000 km in three weeks as it rose from 18 to 21 km in altitudeSatellite trace gas and aerosol anomalies coincide with potential vorticity anomalies, confirming smoke‐induced dynamical perturbations [ABSTRACT FROM AUTHOR]