EGUsphere EGUsphere EGUsphere EGUsphere Copernicus Publications Göttingen, Germany 10.5194/egusphere-2025-1396 Radiative impact of increased middle atmospheric water vapour in the aftermath of the Hunga 2022 volcanic eruption at two locations in the Northern Hemisphere Bell Alistair https://orcid.org/0009-0009-7987-140X 1 2 Murk Axel 1 2 Stober Gunter https://orcid.org/0000-0002-7909-6345 1 2 Institute of Applied Physics, University of Bern, Bern, Switzerland Oeschger Centre for Climate Change Research, University of Bern, Bern, Switzerland 16 04 2025 2025 1 22 Copyright: © 2025 Alistair Bell et al. 2025 This work is licensed under the Creative Commons Attribution 4.0 International License. To view a copy of this licence, visit https://creativecommons.org/licenses/by/4.0/ This article is available from https://egusphere.copernicus.org/preprints/2025/egusphere-2025-1396/ The full text article is available as a PDF file from https://egusphere.copernicus.org/preprints/2025/egusphere-2025-1396/egusphere-2025-1396.pdf

Increases in middle atmosphere water vapour as a result of the 2022 Hunga volcanic eruption have now been detected almost globally, with above-average mixing ratios predicted to persist until around 2032. Changes in the middle atmosphere water vapour volume mixing ratio impact chemical reactions in this section of the atmosphere, can result in more favorable conditions for polar stratospheric and mesospheric cloud formation, and have a significant radiative effect on the middle atmosphere and below. For this reason, precise radiative transfer calculations are important to make accurate and precise assessments of changes to both long-wave and short-wave fluxes, and how this may impact the heating rates at different heights in the atmosphere. In this study, water vapour profiles from two microwave radiometers deployed at two different latitudes in Europe are used to analyse changes in water vapour in the aftermath of the Hunga volcano, and a line-by-line radiative transfer model is used to analyse the thermal impact of this increase over Bern, Switzerland, and Ny-Ålesund, Svalbard.