First remote sensing measurements of ClOOCl along with ClO and ClONO2 in activated and deactivated Arctic vortex conditions using new ClOOCl IR absorption cross sections

Active chlorine species play a dominant role in the catalytic destruction of stratospheric ozone in the polar vortices during the late winter and early spring seasons. Recently, the correct understanding of the ClO dimer
Active chlorine species play a dominant role in the catalytic destruction of stratospheric ozone in the polar vortices during the late winter and early spring seasons. Recently, the correct understanding of the ClO dimer cycle was challenged by the release of new laboratory absorption cross sections (Pope et al., 2007) yielding significant model underestimates of observed ClO and ozone loss (von Hobe et al., 2007). Under this aspect, nocturnal Arctic stratospheric limb emission measurements carried out by the balloon version of the Michelson Interferometer for Passive Atmospheric Sounding (MIPAS-B) from Kiruna (Sweden) on 11 January 2001 and 20/21 March 2003 have been reanalyzed with regard to the chlorine reservoir species ClONO2 and the active species, ClO and ClOOCl (Cl2O2). New laboratory measurements of IR absorption cross sections of ClOOCl for various temperatures and pressures allowed for the first time the retrieval of ClOOCl mixing ratios from remote sensing measurements. High values of active chlorine (ClOx) of roughly 2.3 ppbv at 20 km were observed by MIPAS-B in the cold mid-winter Arctic vortex on 11 January 2001. While nighttime ClOOCl shows enhanced values of nearly 1.1 ppbv at 20 km, ClONO2 mixing ratios are less than 0.1 ppbv at this altitude. In contrast, high ClONO2 mixing ratios of nearly 2.4 ppbv at 20 km have been observed in the late winter Arctic vortex on 20 March 2003. No significant ClOx amounts are detectable on this date since most of the active chlorine has already recovered to its main reservoir species ClONO2. The observed values of ClOx and ClONO2 are in line with the established polar chlorine chemistry. The thermal equilibrium constants between the dimer formation and its dissociation, as derived from the balloon measurements, are on the lower side of reported data and in good agreement with values recommended by von Hobe et al. (2007). Calculations with the ECHAM/MESSy Atmospheric Chemistry model (EMAC) using established kinetics show similar chlorine activation and deactivation, compared to the measurements in January 2001 and March 2003, respectively.
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Author:Gerald Wetzel, Hermann Oelhaf, Oliver Kirner, Roland Ruhnke, Felix Friedl-Vallon, Anne Kleinert, Guido Maucher, Herbert Fischer, Manfred Birk, Georg Wagner, Andreas Engel
URN:urn:nbn:de:hebis:30-80705
DOI:http://dx.doi.org/10.10.5194/acp-10-931-2010
ISSN:1680-7316
ISSN:1680-7324
Parent Title (English):Atmospheric chemistry and physics, 10.2010, S. 931-945
Publisher:European Geosciences Union
Place of publication:Katlenburg-Lindau
Document Type:Article
Language:English
Date of Publication (online):2010/02/01
Date of first Publication:2010/02/01
Publishing Institution:Universitätsbibliothek Johann Christian Senckenberg
Release Date:2010/09/24
Volume:10
Pagenumber:15
First Page:931
Last Page:945
Note:
© Author(s) 2010. This work is distributed under the Creative Commons Attribution 3.0 License.
HeBIS PPN:228924111
Institutes:Geowissenschaften
Dewey Decimal Classification:550 Geowissenschaften
Sammlungen:Universitätspublikationen
Licence (German):License LogoCreative Commons - Namensnennung 3.0

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