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| Titel |
Methane as a diagnostic tracer of changes in the Brewer–Dobson circulation of the stratosphere |
| VerfasserIn |
E. E. Remsberg |
| 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. 7 ; Nr. 15, no. 7 (2015-04-07), S.3739-3754 |
| Datensatznummer |
250119616
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| Publikation (Nr.) |
 copernicus.org/acp-15-3739-2015.pdf |
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| Zusammenfassung |
| This study makes use of time series of methane (CH4) data from the
Halogen Occultation Experiment (HALOE) to detect whether there were any
statistically significant changes of the Brewer–Dobson circulation (BDC)
within the stratosphere during 1992–2005. The HALOE CH4 profiles are in
terms of mixing ratio versus pressure altitude and are binned into latitude
zones within the Southern Hemisphere and the Northern Hemisphere. Their separate time
series are then analyzed using multiple linear regression (MLR) techniques.
The CH4 trend terms for the Northern Hemisphere are significant and
positive at 10° N from 50 to 7 hPa and larger than the tropospheric
CH4 trends of about 3% decade−1 from 20 to 7 hPa. At 60° N the trends are
clearly negative from 20 to 7 hPa. Their combined trends indicate an
acceleration of the BDC in the middle stratosphere of the Northern Hemisphere
during those years, most likely due to changes from the effects of wave
activity. No similar significant BDC acceleration is found for the Southern
Hemisphere. Trends from HALOE H2O are analyzed for consistency. Their
mutual trends with CH4 are anti-correlated qualitatively in the middle
and upper stratosphere, where CH4 is chemically oxidized to H2O.
Conversely, their mutual trends in the lower stratosphere are dominated by
their trends upon entry to the tropical stratosphere. Time series residuals
for CH4 in the lower mesosphere also exhibit structures that are
anti-correlated in some instances with those of the tracer-like species HCl.
Their occasional aperiodic structures indicate the effects of transport
following episodic, wintertime wave activity. It is concluded that observed
multi-year, zonally averaged distributions of CH4 can be used to
diagnose major instances of wave-induced transport in the middle atmosphere
and to detect changes in the stratospheric BDC. |
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