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Arctic Oscillation (AO) Index Data

Abstract: The University of Washington Joint Institute for the Study of the Atmosphere and Ocean (JISAO) offers an Arctic Oscillation (AO) Index dataset. The Arctic Oscillation (AO) is defined as the leading EOF of
Northern Hemisphere sea-level pressure anomalies poleward of 20N, weighted by area (Thompson and Wallace, 1998).

The following indices are generated by projecting various anomaly fields onto the structure of the AO, defined here as the leading EOF
of SLP poleward of 20N based on all months January 1958 to April 1997. All units are arbitrary.
Related URL
Description: Access to AO Index documentation, graphs and data from 1899. Data
includes monthly means and seasonal (JFM) means.
Geographic Coverage
Spatial coordinates   
  N: 90.0   S: 75.0   E: 180.0   W: -180.0

Data Set Citation
Dataset Originator/Creator: David W. J. Thompson, John. M. Wallace,
Dataset Title: Arctic Oscillation (AO) Index Data
Dataset Release Place: Seattle, Washington, USA
Dataset Publisher: University of Washington Department of Atmospheric Sciences
Temporal Coverage
Start Date: 1851-01-01
Use Constraints Please cite the dataset originator if you use this data.
Data Set Progress
Distribution Media: Online (FTP)
Distribution Format: ASCII
Fees: None
Email: davet at
Contact Address:
Department of Atmospheric Sciences
Colorado State University
City: Fort Collins
Province or State: CO
Postal Code: 80523
Country: USA
David W. J. Thompson and John. M. Wallace, 1998: The Arctic
Oscillation signature in the wintertime geopotential height and
temperature fields. Geophys. Res. Lett., 25, No. 9, 1297-1300.
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Extended Metadata Properties
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Creation and Review Dates
DIF Creation Date: 1999-07-27
Last DIF Revision Date: 2018-02-05