Map (Positive Phase)
Plotted Historical Time Series : (January 1950-February 1997)
Table Archive of Indices Dating Back to 1950
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Table showing Calendar months when specific teleconnection patterns are important
The Polar/ Eurasian pattern appears only in the winter, and is the most prominent mode of low-frequency variability during December and February. The pattern consists of one main anomaly center over the polar region, and separate centers of opposite sign to the polar anomaly over Europe and northeastern China. Thus, the pattern reflects major changes in the strength of the circumpolar circulation, and reveals the accompanying systematic changes which occur in the midlatitude circulation over large portions of Europe and Asia.
The polar/Eurasian pattern exhibits strong intradecadal and interdecadal variability, with several consecutive winters of a positive phase of the pattern often followed by several winters having a negative phase of the pattern. For example, the winters from 1964/65 through 1969/70 were dominated by a negative phase of the pattern, followed by a five-year period from 1971/72 through 1975/76 dominated by a positive phase of the pattern. A negative phase then returned for much of the decade between 1976/77 and 1985/86, followed by a prolonged positive phase of the pattern from 1988/89 through 1992/93. These prolonged positive phases of the pattern reflected below-normal heights throughout the polar region and an enhanced circumpolar vortex, in combination with above-normal heights over much of Europe and eastern Asia. In contrast, the prolonged negative phases of the pattern reflected above-normal heights throughout the polar region and a weaker than normal polar vortex, in combination with below-normal heights over much of Europe and eastern Asia.