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| Titel |
The role of water-vapour photodissociation on the formation of a deep minimum in mesopause ozone |
| VerfasserIn |
I. M. Vardavas, J. H. Carver, F. W. Taylor |
| Medientyp |
Artikel
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| Sprache |
Englisch
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| ISSN |
0992-7689
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| Digitales Dokument |
URL |
| Erschienen |
In: Annales Geophysicae ; 16, no. 2 ; Nr. 16, no. 2, S.189-196 |
| Datensatznummer |
250013156
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| Publikation (Nr.) |
 copernicus.org/angeo-16-189-1998.pdf |
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| Zusammenfassung |
A one-dimensional atmospheric photochemical
model with an altitude grid of about 1.5 km was used to examine the structure of
the global mean vertical ozone profile and its night-time-to-daytime variation
in the upper atmosphere. Two distinct ozone layers are predicted, separated by a
sharp drop in the ozone concentration near the mesopause. This naturally
occurring mesopause ozone deep minimum is primarily produced by the rapid
increase in the destruction of water vapour, and hence increase in HOx,
at altitudes between 80 and 85 km, a region where water-vapour photodissociation
by ultraviolet radiation of the solar Lyman-alpha line is significant, and where
the supply of water vapour is maintained by methane oxidation even for very dry
conditions at the tropospheric-stratospheric exchange region. The model
indicates that the depth of the mesopause ozone minimum is limited by the
efficiency with which inactive molecular hydrogen is produced, either by the
conversion of atomic hydrogen to molecular hydrogen via one of the reaction
channels of H with HO2, or by Lyman-alpha photodissociation of water
vapour via the channel that leads to the production of molecular hydrogen. The
ozone concentration rapidly recovers above 85 km due to the rapid increase in O
produced by the photodissociation of O2 by absorption of ultraviolet
solar radiation in the Schumann-Runge bands and continuum. Above 90 km, there is
a decrease in ozone due to photolysis as the production of ozone through the
three-body recombination of O2 and O becomes slower with decreasing
pressure. The model also predicts two peaks in the night-time/daytime ozone
ratio, one near 75 km and the other near 110 km, plus a strong peak in the
night-time/daytime ratio of OH near 110 km. Recent observational evidence
supports the predictions of the model.
Key words. Atmospheric composition and structure ·
Middle atmosphere · Thermosphere · Transmission and scattering of radiation |
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