Australian New Year's PyroCb impact on Stratospheric Composition

AbstractFollowing the Australian New Year's pyrocumulonimbus complex between 29-Dec-2019 and 4-Jan-2020, the Aura Microwave Limb Sounder (MLS) observed a plume with unprecedented enhancements of H2O and biomass-burning products (CO, HCN, CH3Cl, CH3CN, and CH3OH) in the lower/middle stratosphere, accompanied by depressions in stratospheric species (O3 and HNO3). The plume persisted for 110 days, circling the globe twice while ascending to 5.62 hPa (35 km). Air masses drawn o the main plume moved toward the developing Antarctic polar vortex but do not appear to have penetrated it. Comparison of species in the plume requires consideration of their measurements' spatial resolutions and background abundances. The apparent decay of some long-lived plume constituents is largely attributable to their coarsening spatial resolution with height, which reduces observed peak values. Differing HCN/H2O signatures indicate that multiple early plumes originated from different stratospheric injection events.