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Atmospheric Chemistry and Physics An interactive open-access journal of the European Geosciences Union
https://doi.org/10.5194/acp-2017-425
© Author(s) 2017. This work is distributed under
the Creative Commons Attribution 3.0 License.
Research article
19 May 2017
Review status
This discussion paper is under review for the journal Atmospheric Chemistry and Physics (ACP).
Equatorward dispersion of high-latitude volcanic plume and its relation to the Asian summer monsoon: a case study of the Sarychev eruption in 2009
Xue Wu1,2, Sabine Griessbach1, and Lars Hoffmann1 1Jülich Supercomputing Centre, Forschungszentrum Jülich, Jülich, Germany
2Key Laboratory of Middle Atmosphere and Global Environment Observation, Institute of Atmospheric Physics, Chinese Academy of Sciences, Beijing, China
Abstract. Tropical volcanic eruptions have been widely studied for their significant contribution to the stratospheric aerosol loading and global climate impacts, but the impact of high-latitude volcanic eruptions on the stratospheric aerosol layer is not clear and the pathway of transporting aerosol from high-latitudes to the tropical stratosphere is not well understood. In this work, we focus on the high-latitude volcano Sarychev (48.1°N, 153.2°E), which erupted during the Asian summer monsoon (ASM) season in 2009, and the influence of ASM on the equatorward dispersion of the volcanic plume. First, the sulfur dioxide (SO2) emission rate and plume height of the Sarychev eruption are estimated with SO2 observations of the Atmospheric Infrared Sounder (AIRS) and a backward trajectory approach, using the Lagrangian particle dispersion model Massive–Parallel Trajectory Calculations (MPTRAC). Then, the transport and dispersion of the plume are simulated using the derived emission rate time series. The transport simulations are compared with SO2 observations from AIRS and validated with aerosol observations from the Michelson Interferometer for Passive Atmospheric Sounding (MIPAS). The simulations show that about 4% of the emissions were transported to the tropical stratosphere within 50 days after the beginning of the eruption, and the plume dispersed towards the tropical tropopause layer (TTL) through isentropic transport above the subtropical jet. The simulations and MIPAS aerosol data both show that in the vertical range of 360–400 K, the equatorward transport was primarily driven by anticyclonic Rossby wave breaking enhanced by the ASM in boreal summer. The volcanic plume was entrained along the anticyclone flows and reached the TTL as it was transported south-westwards into the deep tropics downstream of the anticyclone. Further, the ASM anticyclone influenced the pathway of aerosols by isolating an aerosol hole inside of the ASM, which was surrounded by aerosol-rich air outside. This transport barrier was best indicated using the potential vorticity gradient approach. Long-term MIPAS aerosol detections show that after entering the TTL, the aerosol from the Sarychev eruption remained in the tropical stratosphere for about 10 months and ascended slowly. The ascent speed agreed well with the ascent speed of water vapour tape recorder. In contrast, by running a hypothetical simulation for a wintertime eruption, it is confirmed that under winter circulations, the equatorward transport of the plume would be suppressed by the strong subtropical jet and weak wave breaking events. In this hypothetic scenario, high-latitude volcanic eruption would not be able to contribute to the tropical stratospheric aerosol layer.

Citation: Wu, X., Griessbach, S., and Hoffmann, L.: Equatorward dispersion of high-latitude volcanic plume and its relation to the Asian summer monsoon: a case study of the Sarychev eruption in 2009, Atmos. Chem. Phys. Discuss., https://doi.org/10.5194/acp-2017-425, in review, 2017.
Xue Wu et al.
Xue Wu et al.

Video supplement

Video supplement to "Equatorward dispersion of the Sarychev volcanic plume in June 2009 and its relation to the Asian summer monsoon"
Xue Wu
https://doi.org/10.5446/21886
Video supplement to "Equatorward dispersion of the Sarychev volcanic plume in June 2009
Xue Wu
https://doi.org/10.5446/21887
Xue Wu et al.

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Short summary
This study is focused on the Sarychev eruption in 2009. Based on Lagrangian model simulation and satellite data, the equatorward transport of the plume and aerosol from the Sarychev eruption is confirmed, and the transport is facilitated by the Asian summer monsoon anticyclonic circulations. The aerosol transported to the tropics remained for months and dispersed upward, which could make the Sarychev eruption have a similar global climate impacts as a tropical volcanic eruption.
This study is focused on the Sarychev eruption in 2009. Based on Lagrangian model simulation and...
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