The 2019 Raikoke volcanic eruption – Part 2: Particle-phase dispersion and concurrent wildfire smoke emissions

Martin J Osborne,Nina Kristiansen,Ellsworth J Welton,Johannes De Leeuw,Ulrich Bundke,Franco Marenco,Joelle Buxmann,Frances Beckett,Anja Schmidt,Andreas Petzold,Claire Witham,Ana R Gomes,Javier Fochesatto,Cameron Saint,Jim Haywood

doi:10.5194/acp-22-2975-2022

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 4 d 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–sulfate 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.

Highlights

Explosive volcanic eruptions can inject volcanic ash and sulfur dioxide (SO2) into the stratosphere that can have residence times of many months or even years (e.g. Langmann, 2014; Carn et al, 2017)
The 2010 eruption of the Icelandic volcano Eyjafjallajökull caused widespread disruption to air travel across Europe for several weeks and had a significant financial impact on several large airlines (Gertisser, 2010). To mitigate these risks the International Civil Aviation Authority designates nine centres to act as Volcanic Ash Advisory Centres (VAACs), each of which is responsible for issuing warnings and information to national aviation authorities and the wider aviation community
The Met Office acts as the London VAAC and formulates guidance products using a combination of dispersion model simulations (Jones et al, 2007; Webster et al, 2012; Dacre et al, 2015), satellite observations (Millington et al, 2012; Francis et al, 2012), and ground-based and aircraft observations (Turnbull et al, 2012; Marenco et al, 2016; Osborne et al, 2019)

Summary

Introduction

Explosive volcanic eruptions can inject volcanic ash and sulfur dioxide (SO2) into the stratosphere that can have residence times of many months or even years (e.g. Langmann, 2014; Carn et al, 2017). The damage to engines and airframes resulting from an aircraft encountering volcanic aerosol clouds can cause significant costs to airlines, with a single encounter potentially costing tens of millions of Euros (Miller and Casadeval, 1999; Prata and Tupper, 2009). The 2010 eruption of the Icelandic volcano Eyjafjallajökull caused widespread disruption to air travel across Europe for several weeks and had a significant financial impact on several large airlines (Gertisser, 2010) To mitigate these risks the International Civil Aviation Authority designates nine centres to act as Volcanic Ash Advisory Centres (VAACs), each of which is responsible for issuing warnings and information to national aviation authorities and the wider aviation community. The Met Office acts as the London VAAC and formulates guidance products using a combination of dispersion model simulations (Jones et al, 2007; Webster et al, 2012; Dacre et al, 2015), satellite observations (Millington et al, 2012; Francis et al, 2012), and ground-based and aircraft observations (Turnbull et al, 2012; Marenco et al, 2016; Osborne et al, 2019)

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Conclusion