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Atmospheric Chemistry and Physics An interactive open-access journal of the European Geosciences Union
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Preprints
https://doi.org/10.5194/acp-2020-889
© Author(s) 2020. This work is distributed under
the Creative Commons Attribution 4.0 License.
https://doi.org/10.5194/acp-2020-889
© Author(s) 2020. This work is distributed under
the Creative Commons Attribution 4.0 License.

  07 Oct 2020

07 Oct 2020

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This preprint is currently under review for the journal ACP.

The 2019 Raikoke volcanic eruption: Part 1 Dispersion model simulations and satellite retrievals of volcanic sulfur dioxide

Johannes de Leeuw1, Anja Schmidt1,2, Claire S. Witham3, Nicolas Theys4, Isabelle A. Taylor5, Roy G. Grainger5, Richard J. Pope6,7, Jim Haywood3,8, Martin Osborne3,8, and Nina I. Kristiansen3 Johannes de Leeuw et al.
  • 1Department of Chemistry, University of Cambridge, Cambridge, UK
  • 2Department of Geography, University of Cambridge, Cambridge, UK
  • 3Met Office, Exeter, UK
  • 4Royal Belgian Institute for Space Aeronomy (BIRA-IASB), Brussels, Belgium
  • 5COMET, Sub-Department of Atmospheric, Oceanic and Planetary Physics, University of Oxford, Oxford, UK
  • 6School of Earth and Environment, University of Leeds, Leeds, UK
  • 7National Centre for Earth Observation, University of Leeds, Leeds, UK
  • 8College of Engineering, Mathematics, and Physical Sciences, University of Exeter, Exeter, UK

Abstract. Volcanic eruptions can cause significant disruption to society and numerical models are crucial for forecasting the dispersion of erupted material. Here we assess the skill and limitations of the Met Office’s Numerical Atmospheric-dispersion Modelling Environment (NAME) in simulating the dispersion of the sulfur dioxide (SO2) cloud from the 21–22 June 2019 eruption of the Raikoke volcano (48.3° N, 153.2° E). The eruption emitted around 1.5 ± 0.2 Tg of SO2, which represents the largest volcanic emission of SO2 into the stratosphere since the 2011 Nabro eruption. We simulate the temporal evolution of the volcanic SO2 cloud across the Northern Hemisphere (NH) and compare our model simulations to high-resolution SO2 measurements from the Tropospheric Monitoring Instrument (TROPOMI) and the Infrared Atmospheric Sounding Interferometer (IASI) satellite SO2 products.

We show that NAME accurately simulates the observed location and horizontal extent of the SO2 cloud during the first 2–3 weeks after the eruption, but is unable, in its standard configuration, to capture the extent and precise location of very high-concentration regions within the volcanic cloud. Using the Fractional Skill Score as metric for model skill, NAME shows skill in simulating the horizontal extent of the cloud for 12–17 days after the eruption where vertical column densities (VCD) of SO2 (in Dobson Units, DU) are above 1 DU. For SO2 VCDs above 20 DU, which are predominantly observed as small-scale features within the SO2 cloud, the model shows skill on the order of 2–4 days only. The lower skill for these high-concentration regions is partly explained by the model-simulated SO2 cloud in NAME being too diffuse compared to TROPOMI retrievals. Reducing the standard diffusion parameters used in NAME by a factor of four results in a slightly increased model skill during the first five days of the simulation, but on longer timescales the simulated SO2 cloud remains too diffuse when compared to TROPOMI measurements.

We find that the temporal evolution of the NH-mean SO2 mass burden simulated by NAME strongly depends on the fraction of SO2 mass emitted into the lower stratosphere, which is uncertain for the 2019 Raikoke eruption. When emitting 0.9–1.1 Tg of SO2 into the lower stratosphere (11–18 km) and 0.4–0.7 Tg into the upper troposphere (8–11 km), both NAME and TROPOMI show a similar peak in SO2 mass burden (1.4–1.6 Tg of SO2) with an average SO2 e-folding time of 14–15 days in the NH.

Our work demonstrates the large potential of using high-resolution satellite retrievals to identify and rectify limitations in dispersion models like NAME, which will ultimately help to improve dispersion modelling efforts of volcanic SO2 clouds.

Johannes de Leeuw et al.

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Johannes de Leeuw et al.

Video supplement

Movie of the 2019 Raikoke volcanic eruption: Sulfur dioxide and sulfate dispersion as simulated by NAME Johannes de Leeuw https://doi.org/10.5281/zenodo.3992052

Johannes de Leeuw et al.

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Short summary
Using the NAME dispersion model in combination with high-resolution SO2 satellite data from TROPOMI we investigate the dispersion of volcanic SO2 from the 2019 Raikoke eruption. NAME accurately simulates the dispersion of SO2 during the first 2–3 weeks after the eruption and we demonstrate the potential of using high-resolution satellite data to identify and rectify limitations in dispersion models, which will ultimately help to improve efforts to forecast the dispersion of volcanic clouds.
Using the NAME dispersion model in combination with high-resolution SO2 satellite data from...
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