Journal cover Journal topic
Atmospheric Chemistry and Physics An interactive open-access journal of the European Geosciences Union
Atmos. Chem. Phys., 17, 2229-2253, 2017
http://www.atmos-chem-phys.net/17/2229/2017/
doi:10.5194/acp-17-2229-2017
© Author(s) 2017. This work is distributed
under the Creative Commons Attribution 3.0 License.
Research article
14 Feb 2017
Impact of a moderate volcanic eruption on chemistry in the lower stratosphere: balloon-borne observations and model calculations
Gwenaël Berthet1, Fabrice Jégou1, Valéry Catoire1, Gisèle Krysztofiak1, Jean-Baptiste Renard1, Adam E. Bourassa2, Doug A. Degenstein2, Colette Brogniez3, Marcel Dorf4,a, Sebastian Kreycy4, Klaus Pfeilsticker4, Bodo Werner4, Franck Lefèvre5, Tjarda J. Roberts1, Thibaut Lurton1, Damien Vignelles1, Nelson Bègue6, Quentin Bourgeois7, Daniel Daugeron1, Michel Chartier1, Claude Robert1, Bertrand Gaubicher1, and Christophe Guimbaud1 1Laboratoire de Physique et Chimie de l'Environnement et de l'Espace (LPC2E), Université d'Orléans, CNRS UMR7328, Orléans, France
2Institute of Space and Atmospheric Studies, University of Saskatchewan, Saskatoon, Canada
3Laboratoire d'Optique Atmosphérique, Université Lille 1 Sciences et Technologies, CNRS UMR8518, Villeneuve d'Ascq, France
4Institute of Environmental Physics, University of Heidelberg, Heidelberg, Germany
5Laboratoire Atmosphères Milieux Observations Spatiales, UPMC, Université Paris 06, Université Versailles Saint Quentin, CNRS UMR8190, LATMOS-IPSL, Paris, France
6Laboratoire de l'Atmosphère et des Cyclones, UMR8105 CNRS, Université de la Réunion, Saint-Denis de la Réunion, France
7Department of Meteorology and Bolin Centre for Climate Research, Stockholm University, Stockholm, Sweden
anow at: Max Planck Institute for Chemistry, Department of Atmospheric Chemistry, Mainz, Germany
Abstract. The major volcanic eruption of Mount Pinatubo in 1991 has been shown to have significant effects on stratospheric chemistry and ozone depletion even at midlatitudes. Since then, only moderate but recurrent volcanic eruptions have modulated the stratospheric aerosol loading and are assumed to be one cause for the reported increase in the global aerosol content over the past 15 years. This particularly enhanced aerosol context raises questions about the effects on stratospheric chemistry which depend on the latitude, altitude and season of injection. In this study, we focus on the midlatitude Sarychev volcano eruption in June 2009, which injected 0.9 Tg of sulfur dioxide (about 20 times less than Pinatubo) into a lower stratosphere mainly governed by high-stratospheric temperatures. Together with in situ measurements of aerosol amounts, we analyse high-resolution in situ and/or remote-sensing observations of NO2, HNO3 and BrO from balloon-borne infrared and UV–visible spectrometers launched in Sweden in August–September 2009. It is shown that differences between observations and three-dimensional (3-D) chemistry-transport model (CTM) outputs are not due to transport calculation issues but rather reflect the chemical impact of the volcanic plume below 19 km altitude. Good measurement–model agreement is obtained when the CTM is driven by volcanic aerosol loadings derived from in situ or space-borne data. As a result of enhanced N2O5 hydrolysis in the Sarychev volcanic aerosol conditions, the model calculates reductions of ∼ 45 % and increases of ∼ 11 % in NO2 and HNO3 amounts respectively over the August–September 2009 period. The decrease in NOx abundances is limited due to the expected saturation effect for high aerosol loadings. The links between the various chemical catalytic cycles involving chlorine, bromine, nitrogen and HOx compounds in the lower stratosphere are discussed. The increased BrO amounts (∼ 22 %) compare rather well with the balloon-borne observations when volcanic aerosol levels are accounted for in the CTM and appear to be mainly controlled by the coupling with nitrogen chemistry rather than by enhanced BrONO2 hydrolysis. We show that the chlorine partitioning is significantly controlled by enhanced BrONO2 hydrolysis. However, simulated effects of the Sarychev eruption on chlorine activation are very limited in the high-temperature conditions in the stratosphere in the period considered, inhibiting the effect of ClONO2 hydrolysis. As a consequence, the simulated chemical ozone loss due to the Sarychev aerosols is low with a reduction of −22 ppbv (−1.5 %) of the ozone budget around 16 km. This is at least 10 times lower than the maximum ozone depletion from chemical processes (up to −20 %) reported in the Northern Hemisphere lower stratosphere over the first year following the Pinatubo eruption. This study suggests that moderate volcanic eruptions have limited chemical effects when occurring at midlatitudes (restricted residence times) and outside winter periods (high-temperature conditions). However, it would be of interest to investigate longer-lasting tropical volcanic plumes or sulfur injections in the wintertime low-temperature conditions.

Citation: Berthet, G., Jégou, F., Catoire, V., Krysztofiak, G., Renard, J.-B., Bourassa, A. E., Degenstein, D. A., Brogniez, C., Dorf, M., Kreycy, S., Pfeilsticker, K., Werner, B., Lefèvre, F., Roberts, T. J., Lurton, T., Vignelles, D., Bègue, N., Bourgeois, Q., Daugeron, D., Chartier, M., Robert, C., Gaubicher, B., and Guimbaud, C.: Impact of a moderate volcanic eruption on chemistry in the lower stratosphere: balloon-borne observations and model calculations, Atmos. Chem. Phys., 17, 2229-2253, doi:10.5194/acp-17-2229-2017, 2017.
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Short summary
Since the last major volcanic event, i.e. the Pinatubo eruption in 1991, only moderate eruptions have regularly injected sulfur into the stratosphere, typically enhancing the aerosol loading for several months. We investigate here for the first time the chemical perturbation associated with the Sarychev eruption in June 2009, using balloon-borne instruments and model calculations. Some chemical compounds are significantly affected by the aerosols, but the impact on stratospheric ozone is weak.
Since the last major volcanic event, i.e. the Pinatubo eruption in 1991, only moderate eruptions...
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