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@ARTICLE{Osborne:903140,
      author       = {Osborne, Martin John and de Leeuw, Johannes and Witham,
                      Claire and Schmidt, Anja and Beckett, Frances and
                      Kristiansen, Nina and Buxmann, Joelle and Saint, Cameron and
                      Welton, Ellsworth J. and Fochesatto, Javier and Gomes, Ana
                      R. and Bundke, Ulrich and Petzold, Andreas and Marenco,
                      Franco and Haywood, Jim},
      title        = {{T}he 2019 {R}aikoke volcanic eruption part 2: {P}article
                      phase dispersion and concurrent wildfire smoke emissions},
      reportid     = {FZJ-2021-04864},
      year         = {2021},
      abstract     = {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.},
      cin          = {IEK-8},
      cid          = {I:(DE-Juel1)IEK-8-20101013},
      pnm          = {2111 - Air Quality (POF4-211)},
      pid          = {G:(DE-HGF)POF4-2111},
      typ          = {PUB:(DE-HGF)25},
      doi          = {10.5194/acp-2021-448},
      url          = {https://juser.fz-juelich.de/record/903140},
}