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| Titel |
Changing correlation structures of the Northern Hemisphere atmospheric circulation from 1000 to 2100 AD |
| VerfasserIn |
C. C. Raible, F. Lehner, J. F. González-Rouco, L. Fernández-Donado |
| Medientyp |
Artikel
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| Sprache |
Englisch
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| ISSN |
1814-9324
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| Digitales Dokument |
URL |
| Erschienen |
In: Climate of the Past ; 10, no. 2 ; Nr. 10, no. 2 (2014-03-19), S.537-550 |
| Datensatznummer |
250116937
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| Publikation (Nr.) |
 copernicus.org/cp-10-537-2014.pdf |
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| Zusammenfassung |
| Atmospheric circulation modes are important concepts in understanding the
variability of atmospheric dynamics. Assuming their spatial patterns to be
fixed, such modes are often described by simple indices from rather short
observational data sets. The increasing length of reanalysis products allows
these concepts and assumptions to be scrutinised. Here we investigate the
stability of spatial patterns of Northern Hemisphere teleconnections by using
the Twentieth Century Reanalysis as well as several control and transient
millennium-scale simulations with coupled models. The observed and simulated
centre of action of the two major teleconnection patterns, the North
Atlantic Oscillation (NAO) and to some extent the Pacific North American
(PNA), are not stable in time. The currently observed dipole pattern of the
NAO, its centre of action over Iceland and the Azores, split into a
north–south dipole pattern in the western Atlantic with a wave train pattern
in the eastern part, connecting the British Isles with West Greenland and the
eastern Mediterranean during the period 1940–1969 AD. The PNA centres of
action over Canada are shifted southwards and over Florida into the Gulf of
Mexico during the period 1915–1944 AD. The analysis further shows that
shifts in the centres of action of either teleconnection pattern are not
related to changes in the external forcing applied in transient simulations
of the last millennium. Such shifts in their centres of action are
accompanied by changes in the relation of local precipitation and temperature with the
overlying atmospheric mode. These findings further undermine the assumption
of stationarity between local climate/proxy variability and large-scale
dynamics inherent when using proxy-based reconstructions of atmospheric modes, and
call for a more robust understanding of atmospheric variability on decadal
timescales. |
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