A pan-Eurasian pattern of Northern Hemisphere wintertime sea level pressure variability

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Monday, 24 January 2011
A pan-Eurasian pattern of Northern Hemisphere wintertime sea level pressure variability
Washington State Convention Center
Brian V. Smoliak, University of Washington, Seattle, WA; and J. M. Wallace

The dominant pattern of Eurasian monthly-mean wintertime (DJFM) sea level pressure (SLP) variability in the NCEP-NCAR reanalyses, 1958 to 2010, is characterized by a single, broad center of action over northwestern Russia that extends eastward to the Pacific coastline. Results of a series of objective analyses including empirical orthogonal function (EOF) analysis in hemispheric and regional domains, rotated EOF analysis, and empirical orthogonal teleconnection (EOT) analysis define the pattern as the third leading pattern of Northern Hemisphere (NH) wintertime SLP variability, explaining approximately 10% of hemispherically-integrated variance. The robust pan-Eurasian pattern is exemplified by EOT3 of NH SLP.

Linear regression and compositing techniques are used in conjunction with the standardized expansion coefficient time series associated with EOT3 of SLP to investigate its signature in other climatological fields, how the pattern relates to climatological mean features, and the impacts of variability associated with the pattern on time scales of days to months. The pattern's positive (negative) polarity is associated with an expansion (contraction) of the Siberian High on its western flank, accompanied by cold (warm) surface air temperature anomalies and decreased (increased) storminess across the northern tier of the continent. The pattern's influence is discernible on shorter time scales from Europe to southern China, particularly as it affects the frequency of cold air outbreaks.

The pan-Eurasian pattern is most extensive during wintertime, but exhibits two peaks in the fraction of hemispherically-integrated SLP variance it explains, one in autumn and one in spring. During autumn it is the leading pattern of NH SLP variability.