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Atmospheric Chemistry and Physics An interactive open-access journal of the European Geosciences Union
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Volume 18, issue 2 | Copyright
Atmos. Chem. Phys., 18, 1217-1239, 2018
https://doi.org/10.5194/acp-18-1217-2018
© Author(s) 2018. This work is distributed under
the Creative Commons Attribution 4.0 License.

Research article 31 Jan 2018

Research article | 31 Jan 2018

MIPAS observations of volcanic sulfate aerosol and sulfur dioxide in the stratosphere

Annika Günther1, Michael Höpfner1, Björn-Martin Sinnhuber1, Sabine Griessbach2, Terry Deshler3, Thomas von Clarmann1, and Gabriele Stiller1 Annika Günther et al.
  • 1Karlsruhe Institute of Technology, Institute of Meteorology and Climate Research, Karlsruhe, Germany
  • 2Forschungszentrum Jülich GmbH, Institute for Advanced Simulation, Jülich, Germany
  • 3University of Wyoming, Department of Atmospheric Science, Laramie, Wyoming, USA

Abstract. Volcanic eruptions can increase the stratospheric sulfur loading by orders of magnitude above the background level and are the most important source of variability in stratospheric sulfur. We present a set of vertical profiles of sulfate aerosol volume densities and derived liquid-phase H2SO4 (sulfuric acid) mole fractions for 2005–2012, retrieved from infrared limb emission measurements performed with the Michelson Interferometer for Passive Atmospheric Sounding (MIPAS) on board of the Environmental Satellite (Envisat). Relative to balloon-borne in situ measurements of aerosol at Laramie, Wyoming, the MIPAS aerosol data have a positive bias that has been corrected, based on the observed differences to the in situ data. We investigate the production of stratospheric sulfate aerosol from volcanically emitted SO2 for two case studies: the eruptions of Kasatochi in 2008 and Sarychev in 2009, which both occurred in the Northern Hemisphere midlatitudes during boreal summer. With the help of chemical transport model (CTM) simulations for the two volcanic eruptions we show that the MIPAS sulfate aerosol and SO2 data are qualitatively and quantitatively consistent with each other. Further, we demonstrate that the lifetime of SO2 is explained well by its oxidation by hydroxyl radicals (OH). While the sedimentation of sulfate aerosol plays a role, we find that the long-term decay of stratospheric sulfur after these volcanic eruptions in midlatitudes is mainly controlled by transport via the Brewer–Dobson circulation. Sulfur emitted by the two midlatitude volcanoes resides mostly north of 30°N at altitudes of ∼10–16km, while at higher altitudes ( ∼ 18–22km) part of the volcanic sulfur is transported towards the Equator where it is lifted into the stratospheric overworld and can further be transported into both hemispheres.

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Satellite-borne data of sulfur dioxide and a new data set of sulfate aerosol volume densities, as retrieved from MIPAS measurements, are studied in the upper-troposphere–lower-stratosphere region. General patterns of enhanced aerosol are in agreement with SO2. Via chemical transport model simulations for two volcanic eruptions in the Northern Hemisphere midlatitudes, we show that the volcanic enhancements in MIPAS SO2 and sulfate aerosol are consistent in terms of mass and transport patterns.
Satellite-borne data of sulfur dioxide and a new data set of sulfate aerosol volume densities,...
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