(abbrev. AO)- The Arctic Oscillation is a pattern in which atmospheric pressure at polar and middle latitudes fluctuates between negative and positive phases. The negative phase brings higher-than-normal pressure over the polar region and lower-than-normal pressure at about 45 degrees north latitude. The negative phase allows cold air to plunge into the Midwestern United States and western Europe, and storms bring rain to the Mediterranean. The positive phase brings the opposite conditions, steering ocean storms farther north and bringing wetter weather to Alaska, Scotland and Scandinavia and drier conditions to areas such as California, Spain and the Middle East. In recent years research has shown, the Arctic Oscillation has been mostly in its positive phase. Some researchers argue that the North Atlantic Oscillation is in fact part of the AO.
The Arctic Oscillation is a seesaw pattern in which atmospheric pressure at polar and mid-latitudes fluctuates between positive and negative phases. AO and its regional manifestation, the North Atlantic Oscillation (NAO) vary on seasonal and decadal time scales and affect the climate of the U.S., Europe and Asia. Specifically, the NAO is the pressure seesaw between the Azores and Iceland.
the seesaw pattern of alternating atmospheric pressure at polar and mid-latitudes. The positive phase produces a strong polar vortex, and the negative phase produces the opposite.