North Pacific Oscillation
Encyclopedia
The North Pacific Oscillation (NPO) is a teleconnection
pattern first described by Walker and Bliss and characterized by a north-south seesaw in sea level pressure over the North Pacific
.
Rogers, using surface atmospheric temperature from St. Paul, Alaska
and Edmonton
, identified two phases of the NPO, an Aleutian
below (AB) phase that correspond to a deepened and eastward shifted Aleutian low
and an Aleutian above (AA) phase that is the opposite.
During the positive (AB) phase sea level pressure is enhanced over a large region in the subtropics
that extend poleward to 40N° and reduced at higher latitudes, westerlies are enhanced over the central Pacific and winter temperature are mild along much of the North America west coast but cooler than usual over Eastern Siberia and the United States South-West, precipitations are higher than usual over Alaska
and the Great Plains.
The NPGO is the oceanic expression of the NPO.
Teleconnection
Teleconnection in atmospheric science refers to climate anomalies being related to each other at large distances...
pattern first described by Walker and Bliss and characterized by a north-south seesaw in sea level pressure over the North Pacific
Pacific Ocean
The Pacific Ocean is the largest of the Earth's oceanic divisions. It extends from the Arctic in the north to the Southern Ocean in the south, bounded by Asia and Australia in the west, and the Americas in the east.At 165.2 million square kilometres in area, this largest division of the World...
.
Rogers, using surface atmospheric temperature from St. Paul, Alaska
St. Paul, Alaska
St. Paul is a city in Aleutians West Census Area, Alaska, United States. It is the main settlement of Saint Paul Island in the Pribilofs, a small island group in the Bering Sea. Saint Paul Island is well known as a birdwatching haven. The population was 532 at the 2000 census.-Geography:St. Paul...
and Edmonton
Edmonton
Edmonton is the capital of the Canadian province of Alberta and is the province's second-largest city. Edmonton is located on the North Saskatchewan River and is the centre of the Edmonton Capital Region, which is surrounded by the central region of the province.The city and its census...
, identified two phases of the NPO, an Aleutian
Aleutian low
The Aleutian Low is a semi-permanent low pressure center located near the Aleutian Islands during the winter. It is one of the main centers of action in the atmospheric circulation of the Northern Hemisphere...
below (AB) phase that correspond to a deepened and eastward shifted Aleutian low
Aleutian low
The Aleutian Low is a semi-permanent low pressure center located near the Aleutian Islands during the winter. It is one of the main centers of action in the atmospheric circulation of the Northern Hemisphere...
and an Aleutian above (AA) phase that is the opposite.
During the positive (AB) phase sea level pressure is enhanced over a large region in the subtropics
Subtropics
The subtropics are the geographical and climatical zone of the Earth immediately north and south of the tropical zone, which is bounded by the Tropic of Cancer and the Tropic of Capricorn, at latitudes 23.5°N and 23.5°S...
that extend poleward to 40N° and reduced at higher latitudes, westerlies are enhanced over the central Pacific and winter temperature are mild along much of the North America west coast but cooler than usual over Eastern Siberia and the United States South-West, precipitations are higher than usual over Alaska
Alaska
Alaska is the largest state in the United States by area. It is situated in the northwest extremity of the North American continent, with Canada to the east, the Arctic Ocean to the north, and the Pacific Ocean to the west and south, with Russia further west across the Bering Strait...
and the Great Plains.
The NPGO is the oceanic expression of the NPO.