The daily geopotential height anomalies at 14 pressure levels are shown for the previous 120 days as indicated, and they are normalized by standard deviation using 1979-2000 base period. The anomalies are calculated by subtracting 1979-2000 daily climatology, and then averaged over the polar cap poleward of 65°S.
The blue (red) colors represent a strong (weak) polar vortex. The black solid lines show the zero anomalies.
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