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AO Index

The AO Index (Arctic Oscillation Index) describes the difference of the air pressure between the Arctic and mid-latitudes. The stronger this difference, the stronger the West Wind Drift blows air masses from the North Atlantic to northern Europe and Siberia. If the index weakens and becomes negative, polar air flows far south, bringing cold winters to Europe and Asia.


AO Index of the last 120 days:

AO Index of the last 120 days
(Click for a larger view)

Daily values from 1950 to date:

Daily values of the AO Index since 1950
(Click for a larger view)