Sensitivity of radiative forcing by volcanic aerosol to the injection patterns for SO2 and H2O, studies with the CCM EMAC for 2022 to 2024

Our simulations with the chemistry climate model EMAC show an extreme sensitivity of aerosol properties and radiative and chemical implications to
the spatial distribution of the injections of Hunga SO₂ and water vapour. The main effects are modification of particle size and sedimentation by water 
uptake and lofting of aerosol by radiative heating with consequences for horizontal tranport and residence time of aerosol and water vapour. For Hunga we got an instantaneous radiative forcing by aerosol of -0.12 to -0.17 W/m² at the top of the atmosphere in the first 6 months after the eruption depending on injection patterns like the vertical distribution and the horizontal extent of the plume. How much water vapour is retained in the stratosphere strongly depends on the altitude and the horizontal size of the box into which water vapour is injected because of ice formation in case of supersaturation. Observations indicate that the vertical distributions of SO₂ and H₂O injections differ. We will present an extension of the published results and further sensitivity studies  to optimize the agreement in the temporal and spatial development of aerosol extinction and water vapour with observations by OSIRIS, SAGE III and MLS, including the effects of the Ruang eruption in April 2024. The study will contribute to the APARC-HTHH-MOC model comparison project.