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| Titel |
Diurnal variations in middle-atmospheric water vapor by ground-based microwave radiometry |
| VerfasserIn |
D. Scheiben, A. Schanz, B. Tschanz, N. Kämpfer |
| 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. 14 ; Nr. 13, no. 14 (2013-07-23), S.6877-6886 |
| Datensatznummer |
250018769
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| Publikation (Nr.) |
 copernicus.org/acp-13-6877-2013.pdf |
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| Zusammenfassung |
In this paper, we compare the diurnal variations in middle-atmospheric water
vapor as measured by two ground-based microwave radiometers in the Alpine
region near Bern, Switzerland. The observational data set is also compared to
data from the chemistry–climate model WACCM. Due to the small diurnal
variations of usually less than 1%, averages over extended time periods are
required. Therefore, two time periods of five months each, December to April
and June to October, were taken for the comparison.
The diurnal variations from the observational data agree well with each other
in amplitude and phase. The linear correlation coefficients range from 0.8 in
the upper stratosphere to 0.5 in the upper mesosphere. The observed diurnal
variability is significant at all pressure levels within the sensitivity of
the instruments. Comparing our observations with WACCM, we find that the
agreement of the phase of the diurnal cycle between observations and model is
better from December to April than from June to October. The amplitudes of
the diurnal variations for both time periods increase with altitude in WACCM,
but remain approximately constant at 0.05 ppm in the
observations.
The WACCM data are used to separate the processes that lead to diurnal
variations in middle-atmospheric water vapor above Bern. The dominating
processes were found to be meridional advection below 0.1 hPa, vertical
advection between 0.1 and 0.02 hPa and (photo-)chemistry above 0.02 hPa. The
contribution of zonal advection is small. The highest diurnal variations in
water vapor as seen in the WACCM data are found in the mesopause region
during the time period from June to October with diurnal amplitudes of 0.2
ppm (approximately 5% in relative units). |
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