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Changing correlation structures of the Northern Hemisphere atmospheric circulation from 1000 to 2100 AD

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Raible, C. C. and Lehner, F. and González Rouco, J. Fidel and Fernández Donado, Laura (2014) Changing correlation structures of the Northern Hemisphere atmospheric circulation from 1000 to 2100 AD. Climate of the past, 10 (2). pp. 537-550. ISSN 1814-9324

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Official URL: http://dx.doi.org/10.5194/cp-10-537-2014


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Abstract

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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© Author(s) 2014. This work is distributed under the Creative Commons Attribution 3.0 License. This work is supported by the Sinergia project FUPSOL funded by the Swiss National Science Foundation. 20th Century Reanalysis data is provided by the NOAA/OAR/ESRL PSD, Boulder, Colorado, USA (from their website at http://www.esrl.noaa.gov/psd/). The CCSM3 simulations are performed on the super computing architecture of the Swiss National Supercomputing Centre (CSCS). LFD and JFGR were supported by CGL 2011-29677-602-02, CGL 2011-29672-602-01, and the FPU grant AP2009-4061.

Uncontrolled Keywords:Atlantic oscillation; Climate variability; 20th-century reanalysis; Last millennium; Reconstructions; Simulations; Temperature; Winter; Model; Nao
Subjects:Sciences > Physics > Astrophysics
Sciences > Physics > Astronomy
ID Code:36093
Deposited On:03 Mar 2016 15:14
Last Modified:10 Dec 2018 15:05

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