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Other research product . 2021

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

Clyne, Margot; Lamarque, Jean-Francois; Mills, Michael J.; Khodri, Myriam; Ball, William; Bekki, Slimane; Dhomse, Sandip S.; +16 Authors
Open Access
English
Published: 04 Mar 2021
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 grid cell near the location of the volcanic eruption, or whether it is injected as a longitudinally averaged band around the Earth.
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Funded byView all
NSF| Decadal Prediction Following Volcanic Eruptions
Project
  • Funder: National Science Foundation (NSF)
  • Project Code: 1430051
  • Funding stream: Directorate for Geosciences | Division of Atmospheric and Geospace Sciences
,
SNSF| SPARC International Project office
Project
  • Funder: Swiss National Science Foundation (SNSF)
  • Project Code: 20FI21_138017
  • Funding stream: Infrastructure | Research Infrastructure
,
EC| STRATOCLIM
Project
STRATOCLIM
Stratospheric and upper tropospheric processes for better climate predictions
  • Funder: European Commission (EC)
  • Project Code: 603557
  • Funding stream: FP7 | SP1 | ENV
,
UKRI| Reconciling Volcanic Forcing and Climate Records throughout the Last Millennium (Vol-Clim)
Project
  • Funder: UK Research and Innovation (UKRI)
  • Project Code: NE/S000887/1
  • Funding stream: NERC
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