Stratospheric Aerosol and Ozone Responses to the Hunga Tonga-Hunga Ha'apai Volcanic Eruption: Insights from Chemistry and Dynamics

The Hunga Tonga-Hunga Ha'apai (HTHH) eruption on January 15, 2022, was one of the most explosive volcanic events of the 21st century so far. According to satellite-based measurements, 0.4 Tg of sulfur dioxide (SO2) was injected into the stratosphere during the eruption. Using observations and model simulations, we investigate changes in the chemical composition of the stratosphere one year after the HTHH eruption and examine the key physical and chemical processes influencing ozone (O3) concentrations. Injected SO2 was oxidized into sulfate during the first two months and transported from the tropics to the Antarctic by the Brewer-Dobson circulation within one year. In mid-to-low latitudes, enhanced sulfate aerosol increased O3 concentrations in the middle stratosphere but declined in the lower stratosphere. In addition to the chemical processes, sulfate aerosols also reduced polar low-stratospheric O3 concentrations through enhanced Antarctic upwelling anomalies. We suggest that catalytic NOx ozone loss cycles, sulfate aerosols radiative effects, and vertical transport processes are the main factors influencing stratospheric ozone variations.