Hurrell North Atlantic Oscillation (NAO) Index (PC-Based)

The principal component (PC)-based indices of the North Atlantic Oscillation (NAO) are the time series of the leading Empirical Orthogonal Function (EOF) of SLP anomalies over the Atlantic sector, 20°-80°N, 90°W-40°E. These indices are used to measure the NAO throughout the year, tracking the seasonal movements of the Icelandic low and Azores high.
Positive values of the NAO index are typically associated with stronger-than-average westerlies over the middle latitudes, more intense weather systems over the North Atlantic and wetter/milder weather over western Europe.

To Access Resource:

Questions? Email Resource Support Contact:

  • Phillips, Adam
    asphilli@ucar.edu
    UCAR/NCAR - Climate and Global Dynamics Laboratory

Temporal Range

  • Begin:  1899-01-01
    End:  2017-08-31

Keywords

Resource Type dataset
Temporal Range Begin 1899-01-01
Temporal Range End 2017-08-31
Temporal Resolution Monthly; Seasonal; Annual
Bounding Box North Lat 80
Bounding Box South Lat 20
Bounding Box West Long -90
Bounding Box East Long 30
Spatial Representation N/A
Spatial Resolution N/A
Related Links

Hurrell North Atlantic Oscillation (NAO) Index (Station-Based) : The station-based counterpart to the PC-based NAO Index.
Additional Information N/A
Resource Format NETCDF
Standardized Resource Format NetCDF
Asset Size N/A
Legal Constraints

Dash and its services comply with policies set by UCAR and NCAR.
Access Constraints citation: NAO Index Data provided by the Climate Analysis Section, NCAR, Boulder, USA, Hurrell (2003). Updated regularly. Accessed DD Month YYYY. [list date you accessed the data].
Software Implementation Language N/A

Resource Support Name Phillips, Adam
Resource Support Email asphilli@ucar.edu
Resource Support Organization UCAR/NCAR - Climate and Global Dynamics Laboratory
Distributor N/A
Metadata Contact Name Phillips, Adam
Metadata Contact Email asphilli@ucar.edu
Metadata Contact Organization UCAR/NCAR - Climate and Global Dynamics Laboratory

Author Hurrell, James
Publisher UCAR/NCAR - Climate and Global Dynamics Laboratory
Publication Date 1995-01-01
Digital Object Identifier (DOI) Not Assigned
Alternate Identifier N/A
Resource Version N/A
Topic Category climatologyMeteorologyAtmosphere
Progress onGoing
Metadata Date 2023-11-12T10:05:02
Metadata Record Identifier climatedataguide.ucar.edu::node.740
Metadata Language eng
Suggested Citation Hurrell, James. (1995). Hurrell North Atlantic Oscillation (NAO) Index (PC-Based). UCAR/NCAR - Climate and Global Dynamics Laboratory. https://climatedataguide.ucar.edu/node/740. Accessed 24 October 2025.

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