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Atmospheric Chemistry and Physics An interactive open-access journal of the European Geosciences Union
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© Author(s) 2020. This work is distributed under
the Creative Commons Attribution 4.0 License.
© Author(s) 2020. This work is distributed under
the Creative Commons Attribution 4.0 License.

  14 Sep 2020

14 Sep 2020

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This preprint is currently under review for the journal ACP.

Model physics and chemistry causing intermodel disagreement within the VolMIP-Tambora Interactive Stratospheric Aerosol ensemble

Margot Clyne1,2, Jean-Francois Lamarque3, Michael J. Mills3, Myriam Khodri4, William Ball5,6,7, Slimane Bekki8, Sandip S. Dhomse9, Nicolas Lebas4, Graham Mann9,10, Lauren Marshall9,11, Ulrike Niemeier12, Virginie Poulain4, Alan Robock13, Eugene Rozanov5,6, Anja Schmidt11,14, Andrea Stenke6, Timofei Sukhodolov5, Claudia Timmreck12, Matthew Toohey15,16, Fiona Tummon6,17, Davide Zanchettin18, Yunqian Zhu2, and Owen B. Toon1,2 Margot Clyne et al.
  • 1Department of Atmospheric and Oceanic Sciences, University of Colorado, Boulder, CO, USA
  • 2Laboratory for Atmospheric and Space Physics, Boulder, CO, USA
  • 3National Center for Atmospheric Research, Boulder, CO, USA
  • 4LOCEAN, Sorbonne Universités/UPMC/CNRS/IRD, Paris, France
  • 5PMOD WRC Physical Meteorological Observatory Davos and World Radiation Center, Davos Dorf, Switzerland
  • 6Institute for Atmospheric and Climate Science, ETH Zurich, Switzerland
  • 7Department of Geoscience and Remote Sensing, TU Delft, the Netherlands
  • 8LATMOS/IPSL, Sorbonne Université, UVSQ, CNRS, Paris, France
  • 9School of Earth and Environment, University of Leeds, Leeds, UK
  • 10National Centre for Atmospheric Science, University of Leeds, UK
  • 11Department of Chemistry, University of Cambridge, UK
  • 12Max Planck Institute for Meteorology, Hamburg, Germany
  • 13Department of Environmental Sciences, Rutgers University, New Brunswick, NJ, USA
  • 14Department of Geography, University of Cambridge, UK
  • 15Institute for Space and Atmospheric Studies, University of Saskatchewan, Canada
  • 16GEOMAR Helmholtz Centre for Ocean Research Kiel, Kiel, Germany
  • 17Swiss Federal Office for Meteorology and Climatology MeteoSwiss, Payerne, Switzerland
  • 18Department of Environmental Sciences, Informatics and Statistics, Ca’Foscari University of Venice, Mestre, Italy

Abstract. 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 gridcell near the location of the volcanic eruption, or whether it is injected as a longitudinally averaged band around the Earth.

Margot Clyne et al.

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Margot Clyne et al.

Margot Clyne et al.


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Latest update: 29 Sep 2020
Publications Copernicus
Short summary
This study finds how and why five state-of-the-art global climate models with interactive stratospheric aerosols differ when simulating the aftermath of large volcanic injections as part of the Model Intercomparison Project on the climatic response to Volcanic forcing (VolMIP). We identify and explain the consequences of significant disparities in the underlying physics and chemistry currently in some of the models, which are problems likely not unique to the models participating in this study.
This study finds how and why five state-of-the-art global climate models with interactive...