Clyne M. auteur aut IRD Lamarque J. F. auteur aut IRD Mills M. J. auteur aut IRD Khodri Myriam auteur aut IRD Ball W. auteur aut IRD Bekki S. auteur aut IRD Dhomse S. S. auteur aut IRD Lebas N. auteur aut IRD Mann G. auteur aut IRD Marshall L. auteur aut IRD Niemeier U. auteur aut IRD Poulain V. auteur aut IRD Robock A. auteur aut IRD Rozanov E. auteur aut IRD Schmidt A. auteur aut IRD Stenke A. auteur aut IRD Sukhodolov T. auteur aut IRD Timmreck C. auteur aut IRD Toohey M. auteur aut IRD Tummon F. auteur aut IRD Zanchettin D. auteur aut IRD Zhu Y. Q. auteur aut IRD Toon O. B. auteur aut IRD text journalArticle eng text/pdf reformatted digital access As part of the Model Intercomparison Project on the climatic response to Volcanic forcing (VolMIP), several climate modeling centers performed a coordinated pre-study experiment with interactive stratospheric aerosol models simulating the volcanic aerosol cloud from an eruption resembling the 1815 Mt. Tambora eruption (VolMIP-Tambora ISA ensemble). The pre-study provided the ancillary ability to assess intermodel diversity in the radiative forcing for a large stratospheric-injecting equatorial eruption when the volcanic aerosol cloud is simulated interactively. An initial analysis of the VolMIP-Tambora ISA ensemble showed large disparities between models in the stratospheric global mean aerosol optical depth (AOD). In this study, we now show that stratospheric global mean AOD differences among the participating models are primarily due to differences in aerosol size, which we track here by effective radius. We identify specific physical and chemical processes that are missing in some models and/or parameterized differently between models, which are together causing the differences in effective radius. In particular, our analysis indicates that interactively tracking hydroxyl radical (OH) chemistry following a large volcanic injection of sulfur dioxide (SO2) is an important factor in allowing for the timescale for sulfate formation to be properly simulated. In addition, depending on the timescale of sulfate formation, there can be a large difference in effective radius and subsequently AOD that results from whether the SO2 is injected in a single model grid cell near the location of the volcanic eruption, or whether it is injected as a longitudinally averaged band around the Earth. specialized 021 020 21 5 3317-3343 2021 1680-7316 https://www.documentation.ird.fr/hor/fdi:010080988 10.5194/acp-21-3317-2021 1680-7316 [F B010080988] https://www.documentation.ird.fr/hor/fdi:010080988 https://horizon.documentation.ird.fr/exl-doc/pleins_textes/divers21-03/010080988.pdf IRD - Base Horizon / Pleins textes 2021-04-01 2025-02-24 fdi:010080988 fre