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| Titel |
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 |
| VerfasserIn |
G. Wetzel, H. Oelhaf, O. Kirner, R. Ruhnke, F. Friedl-Vallon, A. Kleinert, G. Maucher, H. Fischer, M. Birk, G. Wagner, A. Engel |
| Medientyp |
Artikel
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| Sprache |
Englisch
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| ISSN |
1680-7316
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| Digitales Dokument |
URL |
| Erschienen |
In: Atmospheric Chemistry and Physics ; 10, no. 3 ; Nr. 10, no. 3 (2010-02-01), S.931-945 |
| Datensatznummer |
250008022
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| Publikation (Nr.) |
 copernicus.org/acp-10-931-2010.pdf |
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| Zusammenfassung |
| 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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