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| Titel |
Influence of upper stratosphere and mesosphere on the stratosphere/troposphere coupling |
| VerfasserIn |
B. Christiansen |
| Konferenz |
EGU General Assembly 2009
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 11 (2009) |
| Datensatznummer |
250026955
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| Zusammenfassung |
| In the winter mid- and high latitudes there is a substantial coupling
between the stratosphere and the troposphere. This coupling has the
form of a downward propagation of anomalies with a time-scale of 10-60
days. The physical mechanism involves upward propagating planetary waves
originating in the troposphere and it is still unclear to what extent
the stratosphere is active in controlling the downward propagation.
The purpose of this paper is to investigate the influence of
the upper stratosphere and mesosphere on the statistics of the
stratosphere/troposphere coupling. A batch of perpetual January
experiments with the AGCM ARPEGE has been calculated. This batch includes
experiments where the uppermost model levels - above a threshold level
that varies between 1 and 10 hPa - have been restrained, either by
applying a strong damping or by forcing constant conditions.
We conclude that restraining the upper model atmosphere has profound
consequences on the stratosphere/troposphere coupling. In particular we
find that the delay between the stratosphere and the troposphere gets
shorter when the threshold altitude decreases. The influence on the AO/NAO
and tropospheric time-scales are also investigated. |
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