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| Titel |
Simulations of stratospheric sudden warmings in the Berlin troposphere-stratosphere-mesosphere GCM |
| VerfasserIn |
P. Erlebach, U. Langematz, S. Pawson |
| Medientyp |
Artikel
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| Sprache |
Englisch
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| ISSN |
0992-7689
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| Digitales Dokument |
URL |
| Erschienen |
In: Annales Geophysicae ; 14, no. 4 ; Nr. 14, no. 4, S.443-463 |
| Datensatznummer |
250012260
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| Publikation (Nr.) |
 copernicus.org/angeo-14-443-1996.pdf |
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| Zusammenfassung |
| Stratospheric sudden warming events in the
Northern Hemisphere of the Berlin TSM GCM are investigated. In about 50% of the
simulated years (13 out of 28), major midwinter warmings occur. This agrees well
with observations but, whereas real events tend to occur approximately every
second season, those in the model are clustered, most of them occur in the
period between years 15/16 and years 24/25. In most other years, minor warming
events take place. The warming events are found earlier in the winter than in
reality. Many of the observed characteristics of warming events are well
captured by the model: pulses of wave activity propagate out of the troposphere;
these transient events force the zonal-mean zonal wind in the stratosphere and
coincide with increases of the temperature at the North Pole and cooling at low
levels in the tropics; temperature changes of opposite sign are modelled at
higher levels. Synoptically, the modelled stratosphere evolves quite
realistically before the warmings: the cyclonic vortex is displaced from the
Pole by an amplifying anticyclone. After minor warmings, the stratosphere
remains too disturbed as the cyclonic centre does not return to the North Pole
as quickly as in reality. In the aftermath of major warmings the cyclonic vortex
is not fully eroded and the anticyclonic circulation does not develop properly
over the Pole; furthermore, the wintertime circulation is not properly restored
after the event. |
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