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| Titel |
Retrieving mesospheric water vapour from observations of volume scattering radiances |
| VerfasserIn |
P. Vergados, M. G. Shepherd |
| 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 ; 27, no. 2 ; Nr. 27, no. 2 (2009-02-02), S.487-501 |
| Datensatznummer |
250016389
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| Publikation (Nr.) |
 copernicus.org/angeo-27-487-2009.pdf |
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| Zusammenfassung |
| This study examines the possibility for a theoretical approach in the
estimation of water vapour mixing ratios in the vicinity of polar mesospheric
clouds (PMC) using satellite observations of Volume Scattering Radiances
(VSR) obtained at the wavelength of 553 nm. The PMC scattering properties
perturb the underlying molecular Rayleigh scattered solar radiance of the
background atmosphere. As a result, the presence of PMC leads to an
enhancement in the observed VSR at the altitude of the layer; the PMC VSRs
are superimposed on the exponentially decreasing with height Rayleigh VSR, of
the PMC-free atmosphere. The ratio between the observed and the Rayleigh VSR
of the background atmosphere is used to simulate the environment in which the
cloud layer is formed. In addition, a microphysical model of ice particle
formation is employed to predict the PMC VSRs. The initial water vapour
profile is perturbed until the modelled VSRs match the observed, at which
point the corresponding temperature and water vapour profiles can be
considered as a first approximation of those describing the atmosphere at the
time of the observations. The role of temperature and water vapour in the
cloud formation is examined by a number of sensitivity tests suggesting that
the water vapour plays a dominant role in the cloud formation in agreement
with experimental results. The estimated water vapour profiles are compared
with independent observations to examine the model capability in the context
of this study. The results obtained are in a good agreement at the peak of
the PMC layer although the radiance rapidly decreases with height below the
peak. This simplified scenario indicates that the technique employed can give
a first approximation estimate of the water vapour mixing ratio, giving rise
to the VSR observed in the presence of PMC. |
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