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Natural climate change and variability
Pacific Decadal Oscillation
The Pacific Decadal Oscillation, also known as the Pacific/North American
Pattern (PNA), is a wintertime pattern in atmospheric pressure like the NAO.
It involves a shift in atmospheric mass between the
Aleutian Low
and the high pressure system over western North America.
During the positive phase of the PNA, air pressure is lower than usual above the low and higher than usual above the high. The change in distribution of atmospheric mass affects the climate downstream in North America. The result is mild temperatures over much of North America, and unusually strong precipitation along the Gulf of Alaska and the Gulf of Mexico.
As with NAO, the PNA seems to be shifting toward more positive phases since 1977. Scientists who are interested in looking at the "big picture" are studying the connection between the NAO and the PNA, since both are affected by temperature and pressure conditions around the North Pole.
The PNA is most pronounced during January. The map to the right shows that when air pressure is lower than usual near the Aleutian Islands, it is higher than usual over western Canada.
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Links and resources
Pacific Decadal Oscillation
The Pacific Decadal Oscillation, also known as the Pacific/North American
Pattern (PNA), is a wintertime pattern in atmospheric pressure like the NAO.
It involves a shift in atmospheric mass between the
Aleutian Low
and the high pressure system over western North America.During the positive phase of the PNA, air pressure is lower than usual above the low and higher than usual above the high. The change in distribution of atmospheric mass affects the climate downstream in North America. The result is mild temperatures over much of North America, and unusually strong precipitation along the Gulf of Alaska and the Gulf of Mexico.
As with NAO, the PNA seems to be shifting toward more positive phases since 1977. Scientists who are interested in looking at the "big picture" are studying the connection between the NAO and the PNA, since both are affected by temperature and pressure conditions around the North Pole.
The PNA is most pronounced during January. The map to the right shows that when air pressure is lower than usual near the Aleutian Islands, it is higher than usual over western Canada.
Back to climate topics
Links and resources
