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| Titel |
The MIPAS HOCl climatology |
| VerfasserIn |
T. Clarmann, B. Funke, N. Glatthor, S. Kellmann, M. Kiefer, O. Kirner, B.-M. Sinnhuber, G. P. Stiller |
| 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 ; 12, no. 4 ; Nr. 12, no. 4 (2012-02-20), S.1965-1977 |
| Datensatznummer |
250010734
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| Publikation (Nr.) |
 copernicus.org/acp-12-1965-2012.pdf |
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| Zusammenfassung |
| Monthly zonal mean HOCl measurements by the Michelson Interferometer for Passive
Atmospheric Sounding (MIPAS) are presented for the period from June 2002 to
March 2004. Highest molar mixing ratios are found at pressure levels between
6 and 2 hPa, whereby largest mixing ratios occasionally exceed 200 ppt. The
mixing ratio maximum is generally higher at lower altitudes in the summer
hemisphere than in the winter hemisphere except for chlorine activation
conditions in polar vortices, where enhanced HOCl abundances are also found
in the lower stratosphere below about 10 hPa. During nighttime the maximum is
found at higher altitudes than during daytime. Particularly low values (below
80 ppt) during daytime are found in subpolar regions in the winter hemisphere
where HOCl photolysis is still strong but where HOCl precursors are less
abundant than at other latitudes. The Antarctic polar winter HOCl distribution
in 2002, the year of the split of the southern polar vortex, resembles northern
polar winters rather than other southern polar winters. Increased HOCl amounts
in response to the so-called Halloween solar proton event in autumn 2003 affect
the representativeness of data recorded during this particular episode.
Calculations with the EMAC model reproduce the measured HOCl distribution
reasonably well. MIPAS measurements confirm that the reaction rate constants
for HO2 + ClO ⟶ HOCl + O2 from the most recent JPL
recommendation allow much more realistic modelling of HOCl than reaction
rate constants from earlier recommendations. Modeled HOCl mixing ratios,
however, are still too low except in the polar winter stratosphere where the
model overestimates the HOCl abundance. |
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