How useful are teleconnection patterns for explaining variability in extratropical storminess?

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e-mail: ivar@gfi.uib.no

ABSTRACT

This empirical study relates the extratropical storminess in the Northern Hemisphere to the large-scale flow using gamma regression models. Time series of storminess are derived using the monthly mean variance of highpass filtered sea-level pressure from the 6-hourly NCEP/NCAR reanalysis data for the 54 extended winters (Oct-Mar) between 1950–2003. Five teleconnection patterns were found to be statistically significant factors at the 5% level for storminess in the Euro-Atlantic region: the North Atlantic Oscillation (NAO), the East Atlantic pattern, the Scandinavian pattern, the East-Atlantic/Western-Russia pattern and the Polar/Eurasian pattern. In the North Pacific the dominant factor is found to be the Pacific North American (PNA) pattern. It is also shown that the relationship between teleconnection patterns and storminess to a large extent is accounted for by a basic relation between storminess and the local mean SLP but with a few notable exceptions. In particular the East Atlantic pattern is identified as an important non-local factor for storminess over the Labrador Sea and the PNA pattern as an important non-local factor for storminess north of the Aleutian low.

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