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| Titel |
On the impact of the temporal variability of the collisional quenching process on the mesospheric OH emission layer: a study based on SD-WACCM4 and SABER |
| VerfasserIn |
S. Kowalewski, C. von Savigny, M. Palm, I. C. McDade, J. Notholt |
| 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 ; 14, no. 18 ; Nr. 14, no. 18 (2014-09-24), S.10193-10210 |
| Datensatznummer |
250119064
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| Publikation (Nr.) |
 copernicus.org/acp-14-10193-2014.pdf |
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| Zusammenfassung |
| The mesospheric OH Meinel emissions are subject of many theoretical and
observational studies devoted to this part of the atmosphere. Depending on
the initial vibrational level of excitation the altitude of the considered OH
Meinel emission is systematically shifted, which has important implications
for the intercomparison of different studies considering different transition
bands. Previous model studies suggest that these vertical shifts are
essentially caused by the process of collisional quenching with atomic
oxygen. Following this hypothesis, a recent study found experimental evidence
of a coherent seasonality at tropical latitudes between vertical shifts of
different OH Meinel bands and changes in atomic oxygen concentrations.
Despite the consistent finding of the above mentioned hypothesis, it cannot
be excluded that the actual temporal variability of the vertical shifts
between different OH Meinel bands may in addition be controlled or even
dominated by other processes. It remains an open question whether the
observed temporal evolution is indeed mainly controlled by the modulation of
the collisional quenching process with atomic oxygen. By means of
a sensitivity study which employs a quenching model to simulations made with
the SD-WACCM4 chemistry climate model, we aim at assessing this question.
From this study we find that the observed seasonality of vertical OH Meinel
shifts is only partially controlled by temporal changes in atomic oxygen
concentrations, while molecular oxygen has another noticeable impact on the
vertical OH Meinel shifts. This in particular becomes evident for the diurnal
variability of vertical OH Meinel shifts, which reveal only a poor
correlation with the atomic oxygen species. Furthermore, changes in the
H + O3 source gases provide another mechanism that can
potentially affect the diurnal variability in addition. By comparison with
limb radiance observations from the SABER/TIMED satellite this provides an
explanation for the less evident diurnal response between changes in
O concentrations and vertical OH Meinel shifts. On the other hand, at
seasonal timescales the coherency between both quantities is again evident in
SABER/TIMED but less pronounced compared to our model simulations. |
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