Impact of Hunga-Tonga on Antarctic Stratospheric Aerosols and Polar Stratospheric Clouds

Abstract

The explosive January 2022 Hunga-Tonga volcanic eruption injected plumes of SO2 and H2O well into the stratosphere.  Although the amount of injected SO2 was modest, the amount of H2O reaching the stratosphere was unprecedented with the potential to significantly impact radiative and chemical processes for an extended period.  We utilize observations from the CALIOP (Cloud-Aerosol Lidar with Orthogonal Polarization) lidar on the CALIPSO (Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observations) satellite and the MLS (Microwave Limb Sounder) on the Aura satellite to investigate the impact of the Hunga-Tonga volcanic sulfate aerosol and H2O enhancements on polar stratospheric cloud (PSC) processes in the Antarctic.  The CALIOP observations provide information on particulate aerosol/PSC morphology and composition in unprecedented detail, while the MLS is providing complementary measurements of gas-phase HNO3 and H2O, the major constituents of all PSC particles. The combined analyses of these datasets have enabled better PSC composition discrimination and provide valuable new insight into processes such as PSC-catalyzed chlorine activation and PSC particle growth kinetics.  The more than 17 years of CALIOP and MLS measurements have uniquely captured the primary aspects of the seasonal and multi-year variability of PSCs in the Arctic and Antarctic, enabling the development of a state-of-the-art reference PSC data record and climatology. In this paper, we first examine the initial transport of the Hunga-Tonga volcanic sulfate aerosol and water vapor enhancements to the polar latitudes of the Southern Hemisphere during the 2022 austral fall and winter and investigate their potential effect on PSC processes during the 2022 Antarctic winter.  We then examine the impact of the persistent stratospheric H2O enhancements from Hunga-Tonga on PSCs during the early part of the 2023 Antarctic winter.  To put the Hunga-Tonga volcanic aerosol enhancement over Antarctica in perspective, we also compare its characteristics with two previous events during the CALIPSO era where volcanic aerosols clearly produced a significant enhancement in the Antarctic winter/spring stratosphere: Puyehue-Cordón Caulle (2011) and Calbuco (2015).