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| Titel |
Is there a solar signal in lower stratospheric water vapour? |
| VerfasserIn |
T. Schieferdecker, S. Lossow, G. P. Stiller, T. Clarmann |
| 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 ; 15, no. 17 ; Nr. 15, no. 17 (2015-09-02), S.9851-9863 |
| Datensatznummer |
250120010
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| Publikation (Nr.) |
 copernicus.org/acp-15-9851-2015.pdf |
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| Zusammenfassung |
| A merged time series of stratospheric water vapour built from the Halogen Occultation
Instrument (HALOE) and the Michelson Interferometer for Passive Atmospheric Sounding (MIPAS)
data between 60° S and 60° N and 15 to 30 km and covering
the years 1992 to 2012 was analysed by multivariate linear regression,
including an 11-year solar cycle proxy. Lower stratospheric water vapour was
found to reveal a phase-shifted anti-correlation with the solar cycle, with
lowest water vapour after solar maximum. The phase shift is composed of an
inherent constant time lag of about 2 years and a second component following
the stratospheric age of air. The amplitudes of the water vapour response are
largest close to the tropical tropopause (up to 0.35 ppmv) and decrease with
altitude and latitude. Including the solar cycle proxy in the regression
results in linear trends of water vapour being negative over the full
altitude/latitude range, while without the solar proxy, positive water vapour
trends in the lower stratosphere were found. We conclude from these results
that a solar signal seems to be generated at the tropical tropopause which
is most likely imprinted on the stratospheric water vapour abundances and
transported to higher altitudes and latitudes via the Brewer–Dobson
circulation. Hence it is concluded that the tropical tropopause temperature
at the final dehydration point of air may also be governed to some degree by
the solar cycle. The negative water vapour trends obtained when considering
the solar cycle impact on water vapour abundances can possibly solve the
"water vapour conundrum" of increasing stratospheric water vapour
abundances despite constant or even decreasing tropopause temperatures. |
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