13 May 2022
13 May 2022
Status: a revised version of this preprint is currently under review for the journal ACP.

The effect of ash, water vapor, and heterogeneous chemistry on the evolution of a Pinatubo-size volcanic cloud

Mohamed Abdelkader1, Georgiy Stenchikov1, Andrea Pozzer2, Holger Tost3, and Jos Lelieveld2 Mohamed Abdelkader et al.
  • 1Division of Physical Sciences and Engineering, King Abdullah University of Science and Technology, Thuwal 23955-6900, Saudi Arabia
  • 2Air Chemistry Department, Max Planck Institute for Chemistry, Mainz, 55128, Germany
  • 3Institute for Atmospheric Physics, Johannes Gutenberg University of Mainz, Mainz, 55128, Germany

Abstract. We employ the atmospheric chemistry general circulation model (EMAC) with gas phase, heterogeneous chemistry, and detailed aerosol microphysics to simulate the 1991 Pinatubo volcanic cloud. We explicitly account for the interaction of simultaneously injected SO2, volcanic ash, and water vapor and conducted multiple ensemble simulations with different injection configurations to test the simulated SO2, SO42-, ash masses, stratospheric aerosol optical depth, surface area density (SAD), and the stratospheric temperature response against available observations. We find that the SO2, SO42- masses and stratospheric aerosol optical depth (SAOD) are sensitive to the initial height of the volcanic cloud. The volcanic cloud interacts with tropopause and stratopause, and its composition is shaped by heterogeneous chemistry coupled with the ozone cycle. The height of the volcanic cloud in our simulations is also affected by dynamic processes within the cloud, i.e., heating and lofting of volcanic products. The mass of the injected water vapor has a moderate effect on the cloud evolution when volcanic materials are released in the lower stratosphere because it freezes and sediments as ice crystals. However, the injected water vapor at a higher altitude accelerates the oxidization of SO2 which is sensitive to the injected water vapor mass (via hydroxyl production and reaction rate). The coarse ash comprises 98 % of ash injection mass, which sediments within a few days, but aged sub-micron ash could stay in the stratosphere for a few months providing SAD for heterogeneous chemistry. The presence of ash accelerates the SO2 oxidation that leads to a faster formation of the sulfate aerosol layer in the first two months after the eruption and has to be accounted for in modeling the impact of large-scale volcanic injections on climate and stratospheric chemistry.

Mohamed Abdelkader et al.

Status: final response (author comments only)

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse
  • RC1: 'Comment on acp-2022-177', Anonymous Referee #1, 27 May 2022
    • AC1: 'Reply on RC1', Mohamed AbdelKader, 23 Jun 2022
  • RC2: 'Comment on acp-2022-177', Anonymous Referee #2, 15 Aug 2022
    • AC2: 'Reply on RC2', Mohamed AbdelKader, 25 Sep 2022

Mohamed Abdelkader et al.

Mohamed Abdelkader et al.


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Short summary
We study the effect of injected volcanic ash, water vapor, and SO2 on the development of the volcanic cloud and the stratospheric aerosol optical depth (AOD). Both are sensitive to the initial injection height and to the aging of the volcanic ash shaped by heterogeneous chemistry coupled with the ozone cycle. The manuscript explains the large differences in AOD for different injection scenarios which could improve the estimate of the radiative forcing of volcanic eruptions.