What is the Arctic Oscillation Index?

The Arctic Oscillation (AO) is a climate index of the state of the atmospheric circulation over the Arctic. It consists of a positive phase, featuring below average geopotential heights , which are also referred to as negative geopotential height anomalies , and a negative phase in which the opposite is true.

How is the NAO calculated?

The standard NAO Index is calculated by taking the difference between normalized surface pressure anomaly from a 30 years mean of a northern and a southern station (Equation 1).

What does a positive NAO index mean?

The positive NAO phase represents a stronger than usual difference in pressure between the two regions. Winds from the west dominate, bringing with them warm air, while the position of the jet stream enables stronger and more frequent storms to travel across the Atlantic.

Why is the NAO important?

What is the NAO and why is it important? When the NAO is in its positive phase, low pressure anomalies over the Icelandic region and throughout the Arctic combine with high-pressure anomalies across the subtropical Atlantic to produce stronger-than-average westerlies across middle latitudes.

What does a high Arctic Oscillation mean?

The Arctic Oscillation (AO) is a back-and-forth shifting of atmospheric pressure between the Arctic and the mid-latitudes of the North Pacific and North Atlantic. When the AO is strongly positive, a strong mid-latitude jet stream steers storms northward, reducing cold air outbreaks in the mid-latitudes.

How is Arctic Oscillation measured?

The degree to which Arctic air penetrates into middle latitudes is related to the AO index, which is defined by surface atmospheric pressure patterns. The Arctic oscillation index is defined using the daily or monthly 1000 hPa geopotential height anomalies from latitudes 20° N to 90° N.

How does the North Atlantic Oscillation work?

It is an “oscillation” because the changes in atmospheric pressure are essentially a back-and-forth switching between two prevailing patterns, or modes: a “positive mode,” in which a strong subtropical high is located over the Azores islands in the central North Atlantic while a strong low-pressure system is centred …

Who is the NAO?

We have three key strategic objectives to ensure we achieve our vision: The National Audit Office (NAO) helps Parliament hold government to account for the way it spends public money. We do this by auditing the finances of public bodies and scrutinising public spending to assess facts and value for the taxpayer.

What makes Azores high?

The ultimate cause is probably related to the inherent distribution of continents and oceans. Large east-west circulations exist in heating between subtropical continents and oceans.

Where is the Azores high today?

North East Atlantic Ocean
The current position of AZORES HIGH is at North East Atlantic Ocean (coordinates 37.12148 N / 8.52842 W) reported 352 days ago by AIS.

What causes the NAO?

Positive NAO This occurs because the polar-front jet stream tends to be free of large undulations (Rossby waves), and the jet stream’s westerly winds funnel storms over the Mid-Atlantic states, between the strong North Atlantic pressure cells, and over northern Europe.

What causes negative Arctic Oscillation?

When the difference is strong, the AO is in positive mode. When the difference is less strong, the AO is in its negative mode. The AO can persist in either phase anywhere from days to months. Pressure differences manifested in the AO affect Earth’s atmosphere and people’s lives, particularly in winter.

What is Atlantic Multidecadal Oscillation?

The Atlantic Multidecadal Oscillation (AMO) is a climate cycle that affects the sea surface temperature (SST) of the North Atlantic Ocean based on different modes on multidecadal timescales.

What is Antarctic Oscillation?

The Antarctic oscillation (AAO, to distinguish it from the Arctic oscillation or AO) is a low-frequency mode of atmospheric variability of the southern hemisphere. It is also known as the Southern Annular Mode (SAM).

Where is the North Atlantic Current?

North Atlantic Current. North Atlantic Current, also called North Atlantic Drift, part of a clockwise-setting ocean-current system in the North Atlantic Ocean , extending from southeast of the Grand Bank, off Newfoundland, Canada, to the Norwegian Sea , off northwestern Europe. It constitutes the northeastward extension of the Gulf Stream ;

What is a North Atlantic Current?

The North Atlantic Current (NAC), also known as North Atlantic Drift and North Atlantic Sea Movement, is a powerful warm western boundary current within the Atlantic Ocean that extends the Gulf Stream northeastward.