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| Titel |
Dehydration in the tropical tropopause layer estimated from the water vapor match |
| VerfasserIn |
Y. Inai, F. Hasebe, M. Fujiwara, M. Shiotani, N. Nishi, S.-Y. Ogino, H. Vömel, S. Iwasaki, T. Shibata |
| 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 ; 13, no. 17 ; Nr. 13, no. 17 (2013-09-02), S.8623-8642 |
| Datensatznummer |
250085662
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| Publikation (Nr.) |
 copernicus.org/acp-13-8623-2013.pdf |
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| Zusammenfassung |
| We apply the match technique, whereby the same air mass is observed more than
once and such cases are termed a "match", to study the dehydration process
associated with horizontal advection in the tropical tropopause layer (TTL)
over the western Pacific. The matches are obtained from profile data taken by
the Soundings of Ozone and Water in the Equatorial Region (SOWER) campaign
network observations using isentropic trajectories calculated from European
Centre for Medium-Range Weather Forecasts (ECMWF) operational analyses. For
the matches identified, extensive screening procedures are performed to
verify the representativeness of the air parcel and the validity of the
isentropic treatment, and to check for possible water injection by deep
convection, consistency between the sonde data and analysis field referring
to the ozone conservation. Among the matches that passed the screening tests,
we identified some cases corresponding to the first quantitative value of
dehydration associated with horizontal advection in the TTL. The statistical
features of dehydration for the air parcels advected in the lower TTL are
derived from the matches. The threshold of nucleation is estimated to be
146 ± 1% (1σ) in relative humidity with respect to ice
(RHice), while dehydration seems to continue until
RHice reaches about 75 ± 23% (1σ) in the
altitude region from 350 to 360 K. The efficiency of dehydration expressed
by the relaxation time required for the supersaturated air parcel to approach
saturation is empirically determined from the matches. A relaxation time of
approximately one hour reproduces the second water vapor observation
reasonably well, given the first observed water vapor amount and the history
of the saturation mixing ratio during advection in the lower TTL. |
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