Radiative forcing and stratospheric ozone changes due to recent volcanic eruptions and major forest fires

The chemistry-climate model EMAC was used to simulate the period 2019 to 2023 with tropospheric meteorology slightly nudged to ERA5 data. Volcanic SO₂ injections were derived from aerosol extinction observations by OSIRIS and OMPS-LP which were also used for evaluation of the simulated aerosol, which includes organic particles from major forest fires that can linger in the lower stratosphere for more than 2 years. Our simulations consider several hundred explosive volcanic eruptions. The simulations of ozone chemistry include enhanced surface area density and fast heterogeneous chlorine activation on organic particles and will be compared with AURA-MLS observations. The effects of the major water vapour injection by the eruption of Hunga Tonga in 2022 on radiative transfer and chemistry were also analysed (as a contribution to SSIRC Hunga Tonga). 
For example, in 2022 the Hunga Tonga eruption increased the depth of the calculated  Antarctic ozone hole by about 12 DU. The Australian bushfire emissions enhanced the aerosol surface area which deepened the 2020 ozone hole by about 7 DU, with the largest changes near the vortex edge. The smoke effect is expected to increase with updated heterogeneous chemistry.
The computed global instantaneous aerosol radiative forcing by Hunga Tonga at the top of the atmosphere was about -0.12 W/m² in 2022. The injected water vapour by Hunga Tonga exerted a radiative forcing of about +0.04 W/m² in the first four months after the eruption. By the end of 2022, it nearly vanished due to dynamical and chemical adjustments. The absorbing aerosol from the Australian and Canadian forest fire emissions changed the stratospheric aerosol forcing from -0.2 W/m² to +0.3 W/m² in January 2020, and in January 2022 the remaining effect was about 0.05 W/m², reducing the negative forcing by the volcanoes. Continued interesting effects of the Hunga Tonga eruptions are expected for 2023, based on results from ongoing simulations.