Effect of Synoptic Systems on the Variability of the North Atlantic Oscillation.

Löptien, Ulrike and Ruprecht, Eberhard (2005) Effect of Synoptic Systems on the Variability of the North Atlantic Oscillation. Open Access Monthly Weather Review, 133 (10). pp. 2894-2904. DOI 10.1175/MWR3007.1.

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The North Atlantic Oscillation (NAO) represents the dominant mode of atmospheric variability in the North Atlantic region. In the present study, the role of the synoptic systems (cyclones and anticyclones) in generating the NAO pattern is investigated. To study the intermonthly variations of the NAO, NCEP–NCAR reanalysis data are used, and for the interdecadal variations the results of a 300-yr control integration
under present-day conditions of the coupled model ECHAM4/OPYC3 are analyzed. A filtering
method is developed for the sea level pressure anomalies. Application of this method to each grid point yields the low-frequency variability in the sea level pressure field that is due to the synoptic systems. The low-frequency variability of the filtered and the original data are in high agreement. This indicates that the low-frequency pressure variability, and with it the variability of the NAO, is essentially caused by the distribution of the synoptic systems. The idea that the distribution of the synoptic systems is the cause of the variation of the NAO is confirmed by high correlation between the latitudinal position of the polar front over the North Atlantic and the NAO index. Since most of the low-frequency variability in sea level pressure can be explained through the distribution of the synoptic systems, the NAO seems to be a reflection of the distribution of the synoptic systems, rather than the source for variations in the cyclone tracks.

Document Type: Article
Keywords: North Atlantic Oscillation, SFB460 Dynamics of Thermohaline Circulation Variability
Research affiliation: OceanRep > GEOMAR > FB1 Ocean Circulation and Climate Dynamics > FB1-ME Maritime Meteorology
Refereed: Yes
Open Access Journal?: Yes
DOI etc.: 10.1175/MWR3007.1
ISSN: 0027-0644
Date Deposited: 03 Dec 2008 16:50
Last Modified: 23 Jan 2019 12:02
URI: http://oceanrep.geomar.de/id/eprint/8082

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