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A tropical West Pacific OH minimum and implications for stratospheric composition

Rex, M. and Wohltmann, I. and Ridder, T. and Lehmann, R. and Rosenlof, K. and Wennberg, P. and Weisenstein, D. and Notholt, J. and Krüger, K. and Mohr, V. and Tegtmeier, S. (2014) A tropical West Pacific OH minimum and implications for stratospheric composition. Atmospheric Chemistry and Physics, 14 (9). pp. 4827-4841. ISSN 1680-7316.

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Most of the short-lived biogenic and anthropogenic chemical species that are emitted into the atmosphere break down efficiently by reaction with OH and do not reach the stratosphere. Here we show the existence of a pronounced minimum in the tropospheric column of ozone over the West Pacific, the main source region for stratospheric air, and suggest a corresponding minimum of the tropospheric column of OH. This has the potential to amplify the impact of surface emissions on the stratospheric composition compared to the impact when assuming globally uniform OH conditions. Specifically, the role of emissions of biogenic halogenated species for the stratospheric halogen budget and the role of increasing emissions of SO_2 in Southeast Asia or from minor volcanic eruptions for the increasing stratospheric aerosol loading need to be reassessed in light of these findings. This is also important since climate change will further modify OH abundances and emissions of halogenated species. Our study is based on ozone sonde measurements carried out during the TransBrom cruise with the RV Sonne roughly along 140–150° E in October 2009 and corroborating ozone and OH measurements from satellites, aircraft campaigns and FTIR instruments. Model calculations with the GEOS-Chem Chemistry and Transport Model (CTM) and the ATLAS CTM are used to simulate the tropospheric OH distribution over the West Pacific and the transport pathways to the stratosphere. The potential effect of the OH minimum on species transported into the stratosphere is shown via modeling the transport and chemistry of CH_2Br_2 and SO_2.

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Wennberg, P.0000-0002-6126-3854
Additional Information:© 2014 Author(s). This work is distributed under the Creative Commons Attribution 3.0 License. Published by Copernicus Publications on behalf of the European Geosciences Union. Received: 16 October 2013, Published in Atmos. Chem. Phys. Discuss.: 5 November 2013. Revised: 26 March 2014. Accepted: 27 March 2014. Published: 15 May 2014. We thank two anonymous reviewers and in particular M. Manning for very useful comments on the original manuscript, which significantly improved the paper. We thank Ru-Shan Gao (NOAA) for his contributions and sharing his data. This work was supported by the European Community within the SHIVA project (grant no. 226224) and the StratoClim project (grant no. 603557). TransBrom was financed by the BMBF (grant no. 03G0731A). Susan Tegtmeier and Viktoria Mohr were funded by the WGL project TransBrom. We thank ECMWF for providing ERA Interim data. Edited by: W. T. Sturges.
Funding AgencyGrant Number
European Community226224
European Community603557
Bundesministerium für Bildung und Forschung (BMBF)03G0731A
Issue or Number:9
Record Number:CaltechAUTHORS:20140627-110737071
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Official Citation:Rex, M., Wohltmann, I., Ridder, T., Lehmann, R., Rosenlof, K., Wennberg, P., Weisenstein, D., Notholt, J., Krüger, K., Mohr, V., and Tegtmeier, S.: A tropical West Pacific OH minimum and implications for stratospheric composition, Atmos. Chem. Phys., 14, 4827-4841, doi:10.5194/acp-14-4827-2014, 2014.
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:46553
Deposited By: Ruth Sustaita
Deposited On:27 Jun 2014 19:10
Last Modified:03 Oct 2019 06:45

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