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| Titel |
Modelling the impact of noctilucent cloud formation on atomic oxygen and other minor constituents of the summer mesosphere |
| VerfasserIn |
B. J. Murray, J. M. C. Plane |
| 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 ; 5, no. 4 ; Nr. 5, no. 4 (2005-03-29), S.1027-1038 |
| Datensatznummer |
250002668
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| Publikation (Nr.) |
 copernicus.org/acp-5-1027-2005.pdf |
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| Zusammenfassung |
| The formation, evolution and eventual sublimation of noctilucent
clouds (NLC) may have a significant effect on the odd oxygen and
hydrogen chemistry of the high latitude summer mesosphere. Three
mechanisms are considered here: the direct uptake of atomic oxygen
on the surface of the ice particles; the redistribution of water
vapour, which changes the photochemical source of odd hydrogen
species; and the direct photolysis of the ice particles themselves
to produce odd hydrogen species in the gas phase. A 1-D
photochemical model is employed to investigate the potential
importance of these mechanisms. This shows, using the recently
measured uptake coefficients of O on ice, that the heterogeneous
removal of O on the surface of the cloud particles is too slow by at
least a factor of 5x103 to compete with gas-phase O
chemistry. The second and third mechanisms involve the solar
Lyman-α photolysis of H2O in the gas and solid phase,
respectively. During twilight, Lyman-α radiation is severely
attenuated and these mechanisms are insignificant. In contrast, when
the upper mesosphere is fully illuminated there is a dramatic impact
on the O profile, with depletion of O at the base of the cloud layer
of close to an order of magnitude. A correspondingly large depletion
in O3 is also predicted, while H, OH, HO2 and
H2O2 are found to be enhanced by factors of 3-5. In fact,
rocket-borne mass spectrometer measurements during summer have
revealed local H2O2 enhancements in the region of the
clouds. Rocket-borne measurements of atomic O and O3 profiles
in the presence of mesospheric clouds in the daytime are highly
desirable to test the predictions of this model and our
understanding of the genesis of mesospheric clouds. |
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