The North Atlantic Oscillation Index (NAO Index) is based on the pressure differences between the Azures (outside Portugal) and Iceland. The index yields both positive and negative values (phase of NAO) with pressure anomalies.
According to NOAA, both phases of the NAO are associated with changes in the intensity of the North Atlantic jet stream and storm track, and patterns of heat and precipitation extending from eastern North America to western and central Europe.
I Norway positive phase of the NAO is associated with mild and wet winter conditions, while negative phase is associated with cold winter weather. In 2010 the NAO index showed a strong negative phase, which contributed to an especially cold winter. In 2020, a positive NAO phase contributed an especially mild winter.
Verstat updates NAO index values from NOAA on a daily basis (it seems that NOAA updates its dataset on an irregualar basis). Below you will find Daily, Monthly, and Yearly averaged NAO index, by winter months.
The first graph shows the last 730 days NAO index values. All other graphs show only winter months.
Daily average NAO index value (all)
Daily winter average NAO index values
Monthly winter average NAO index values
Yearly winter average NAO index values
Data is from NOAA, please follow link for information on calculation method and data documentation.
Artikler relatert NAO-indeksen på norsk:
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