Preprints
https://doi.org/10.5194/acp-2021-448
https://doi.org/10.5194/acp-2021-448

  07 Jul 2021

07 Jul 2021

Review status: this preprint is currently under review for the journal ACP.

The 2019 Raikoke volcanic eruption part 2: Particle phase dispersion and concurrent wildfire smoke emissions

Martin John Osborne1,2, Johannes de Leeuw3, Claire Witham1, Anja Schmidt3,4, Frances Beckett1, Nina Kristiansen1, Joelle Buxmann1, Cameron Saint1, Ellsworth J. Welton5, Javier Fochesatto5,6, Ana R. Gomes7, Ulrich Bundke7, Andreas Petzold7, Franco Marenco1,8, and Jim Haywood1,2 Martin John Osborne et al.
  • 1Met Office, FitzRoy Road,Exeter, Devon, EX1 3PB, United Kingdom
  • 2University of Exeter, Laver Building, North Park Road, Exeter, Devon, EX4 4QE, United Kingdom
  • 3University of Cambridge, Department of Chemistry, Lensfield Road, Cambridge, CB2 1EW, United Kingdom
  • 4University of Cambridge, Department of Geography, 20 Downing Place, Cambridge CB2 1BY, United Kingdom
  • 5NASA Goddard Space Flight Center, Greenbelt, Maryland, USA
  • 6Department of Atmospheric Sciences, University of Alaska Fairbanks, Fairbanks, Alaska, 99775 USA
  • 7Institute of Energy and Climate Research 8: Troposphere, Forschungszentrum Jülich, Jülich, 52425, Germany
  • 8Climate and Atmosphere Research Centre (CARE-C), Cyprus Institute, Nicosia, Cyprus

Abstract. Between 27 June and 14 July 2019 aerosol layers were observed by the United Kingdom (UK) Raman lidar network in the upper troposphere and lower stratosphere. The arrival of these aerosol layers in late June caused some concern within the London Volcanic Ash Advisory Centre (VAAC) as according to dispersion simulations the volcanic plume from the 21 June 2019 eruption of Raikoke was not expected over the UK until early July. Using dispersion simulations from the Met Office Numerical Atmospheric-dispersion Modelling Environment (NAME), and supporting evidence from satellite and in-situ aircraft observations, we show that the early arrival of the stratospheric layers was not due to aerosols from the explosive eruption of the Raikoke volcano, but due to biomass burning smoke aerosols associated with intense forest fires in Alberta, Canada that occurred four days prior to the Raikoke eruption. We use the observations and model simulations to describe the dispersion of both the volcanic and forest fire aerosol clouds, and estimate that the initial Raikoke ash aerosol cloud contained around 15 Tg of volcanic ash, and that the forest fires produced around 0.2 Tg of biomass burning aerosol. The operational monitoring of volcanic aerosol clouds is a vital capability in terms of aviation safety and the synergy of NAME dispersion simulations and lidar data with depolarising capabilities allowed scientists at the Met Office to interpret the various aerosol layers over the UK, and attribute the material to their sources. The use of NAME allowed the identification of the observed stratospheric layers that reached the UK on 27 June as biomass burning aerosol, characterised by a particle linear depolarisation ratio of 9 %, whereas with the lidar alone the latter could have been identified as the early arrival of a volcanic ash/sulphate mixed aerosol cloud. In the case under study, given the low concentration estimates, the exact identification of the aerosol layers would have made little substantive difference to the decision making process within the London VAAC. However, our work shows how the use of dispersion modelling together with multiple observation sources enabled us to create a more complete description of atmospheric aerosol loading.

Martin John Osborne 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-2021-448', Anonymous Referee #1, 05 Aug 2021
  • RC2: 'A well-written paper describing a unique study of multiple clouds', Larry Mastin, 31 Aug 2021
  • RC3: 'Referee comment on acp-2021-448', Anonymous Referee #3, 16 Sep 2021

Martin John Osborne et al.

Martin John Osborne et al.

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Short summary
Using the Met Office NAME dispersion model, supported by satellite and ground based remote sensing observations, we describe the dispersion of aerosols from the 2019 Raikoke eruption and the concurrent wild fires in Alberta Canada. We show how the synergy of dispersion modelling and multiple observation sources allowed observers in the London VAAC to arrive at a more complete picture of the aerosol loading at altitudes commonly used by aviation.
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