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| Titel |
Diurnal variations of reactive chlorine and nitrogen oxides observed by MIPAS-B inside the January 2010 Arctic vortex |
| VerfasserIn |
G. Wetzel, H. Oelhaf, O. Kirner, F. Friedl-Vallon, R. Ruhnke, A. Ebersoldt, A. Kleinert, G. Maucher, H. Nordmeyer, J. Orphal |
| 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. 14 ; Nr. 12, no. 14 (2012-07-25), S.6581-6592 |
| Datensatznummer |
250011345
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| Publikation (Nr.) |
 copernicus.org/acp-12-6581-2012.pdf |
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| Zusammenfassung |
| The winter 2009/2010 was characterized by a strong Arctic vortex with
extremely cold mid-winter temperatures in the lower stratosphere associated
with an intense activation of reactive chlorine compounds (ClOx) from
reservoir species. Stratospheric limb emission spectra were recorded during
a flight of the balloon version of the Michelson Interferometer for Passive
Atmospheric Sounding (MIPAS-B) from Kiruna (Sweden) on 24 January 2010
inside the Arctic vortex. Several fast limb sequences of spectra (in time
steps of about 10 min) were measured from nighttime photochemical
equilibrium to local noon allowing the retrieval of chlorine- and
nitrogen-containing species which change rapidly their concentration around
the terminator between night and day. Mixing ratios of species like ClO,
NO2, and N2O5 show significant changes around sunrise, which
are temporally delayed due to polar stratospheric clouds reducing the direct
radiative flux from the sun. ClO variations were derived for the first time
from MIPAS-B spectra. Daytime ClO values of up to 1.6 ppbv are visible in a
broad chlorine activated layer below 26 km correlated with low values (below
0.1 ppbv) of the chlorine reservoir species ClONO2. Observations are
compared and discussed with calculations performed with the 3-dimensional
Chemistry Climate Model EMAC (ECHAM5/MESSy Atmospheric Chemistry). Mixing
ratios of the species ClO, NO2, and N2O5 are well reproduced
by the model during night and noon. However, the onset of ClO production and
NO2 loss around the terminator in the model is not consistent with the
measurements. The MIPAS-B observations along with Tropospheric
Ultraviolet-Visible (TUV) radiation model calculations suggest that polar
stratospheric clouds lead to a delayed start followed by a faster increase
of the photodissoziation of ClOOCl and NO2 near the morning terminator
since stratospheric clouds alter the direct and the diffuse flux of solar
radiation. These effects are not considered in the EMAC model simulations
which assume a cloudless atmosphere. |
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