26 Oct 2022
26 Oct 2022
Status: this preprint is open for discussion.

Including ash in UKESM1 model simulations of the Raikoke volcanic eruption reveal improved agreement with observations

Alice F. Wells1, Andy Jones2, Martin Osborne2, Lilly Damany-Pearce1, Daniel G. Partridge1, and James M. Haywood1,2 Alice F. Wells et al.
  • 1Department of Mathematics, University of Exeter, Exeter, EX4 4QE, United Kingdom
  • 2Met Office, Exeter, EX1 3PB, United Kingdom

Abstract. In June 2019 the Raikoke volcano located in the Kuril Islands, northeast of Japan, erupted explosively and emitted approximately 1.5 Tg ± 0.2 Tg of SO2 and 0.4–1.8 Tg of ash into the upper troposphere and lower stratosphere. Volcanic ash is usually neglected in modelling stratospheric climate changes since larger particles have generally been considered to be short-lived in terms of their stratospheric lifetime. However, recent studies have shown that the coagulation of mixed particles with ash and sulfate is necessary to model the evolution of aerosol size distribution more accurately. We perform simulations using a nudged version of the UK Earth System Model (UKESM1) that includes a detailed 2-moment aerosol microphysical scheme for modelling the oxidation of sulfur dioxide (SO2) to sulfate aerosol and the detailed evolution of aerosol microphysics in the stratosphere. We compare the model with a wide range of observational data. The current observational network including satellites and surface based lidars and high-altitude sun-photometers means that smaller-scale eruptions such as Raikoke provide unprecedented detail of the evolution of volcanic plumes and processes, but there are significant differences in the evolution of the plume detected using the various satellite retrievals. These differences stem from fundamental differences in detection methods between e.g. lidar and limb-sounding measurement techniques and the associated differences in detection limits and the geographical areas where robust retrievals are possible. This study highlights that, despite the problems in developing robust and consistent observational constraints, the balance of evidence suggests that including ash in the model emission scheme provides a more accurate simulation of the evolution of the volcanic plume within UKESM1.

Alice F. Wells et al.

Status: open (until 07 Dec 2022)

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse
  • CC1: 'Comment on egusphere-2022-1060', Kevin Ohneiser, 04 Nov 2022 reply
  • RC1: 'Comment on egusphere-2022-1060', Anonymous Referee #1, 15 Nov 2022 reply
  • RC2: 'Comment on egusphere-2022-1060', Anonymous Referee #2, 24 Nov 2022 reply

Alice F. Wells et al.

Alice F. Wells et al.


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Short summary
In 2019 the Raikoke volcano erupted explosively, emitting the largest injection of SO2 into the stratosphere since 2011. Observations indicated that a large amount of volcanic ash was also injected. Previous studies have identified that volcanic ash can prolong the lifetime of stratospheric aerosol optical depth which we explore in UKESM1. Comparisons to observations suggest that including ash in model emission schemes can improve the representation of volcanic plumes in global climate models.