Comment on egusphere-2022-1480

Abstract

<strong class="journal-contentHeaderColor">Abstract.</strong> The lifetime of sulfur dioxide (SO₂) in the Earth's atmosphere varies from orders of hours to weeks, mainly depending on whether cloud water is present or not. The volcanic eruption on Ambae Island, Vanuatu, in July 2018 injected a large amount of SO₂ into the upper troposphere and lower stratosphere (UT/LS) region with abundant cloud cover. In-cloud removal is therefore expected to play an important role during long-range transport and dispersion of SO₂. In order to better represent the rapid decay processes of SO₂ observed by the Atmospheric InfraRed Sounder (AIRS) and the TROPOspheric Monitoring Instrument (TROPOMI) in Lagrangian transport simulations, we simulate the SO₂ decay in a more realistic manner compared to our earlier work, considering gas phase hydroxyl (OH) chemistry, aqueous phase hydrogen peroxide (H₂O₂) chemistry, wet deposition, and convection. The either newly developed or improved chemical and physical modules are implemented in the Lagrangian transport model Massive-Parallel Trajectory Calculations (MPTRAC) and tested in a case study for the July 2018 Ambae eruption. To access the dependencies of SO₂ lifetime on the complex atmospheric conditions, sensitivity tests are conducted by tuning the control parameters, changing the release height, predefined OH climatology data, the cloud pH value, the cloud cover and other. Wet deposition and aqueous phase H₂O₂ oxidation remarkably increased the decay rate of the SO₂ total mass, which leads to a rapid and more realistic depletion of the Ambae plume. The improved representation of chemical and physical of SO₂ loss processes described here is expected to lead to more realistic Lagrangian transport simulations of volcanic eruption events with MPTRAC in future work.