Arctic oscillation

(meteorology) Atmospheric pressure fluctuations (positive and negative phases) between the polar and middle latitudes (above 45° North) that strengthen and weaken the winds circulating counterclockwise from the surface to the lower stratosphere around the Arctic and, as a result, modulate the severity of the winter weather over most Northern Hemisphere middle and high latitudes. Also known as the Northern Hemisphere annular mode.

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The Arctic oscillation (AO) is the dominant pattern of non-seasonal sea-level pressure variations north of 20N latitude, and it is characterized by pressure anomalies of one sign in the Arctic with the opposite anomalies centered about 37-45N. The North Atlantic oscillation is a close relative of the AO and there exist arguments about whether one or the other is more fundamentally representative of the atmosphere's dynamics; Ambaum et al. argue that the NAO can be identified in a more physically meaningful way [1].

See also

• John Michael Wallace

External links

• AO page
• Overview of Arctic Climate Indices

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