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Jim Hurrell, Senior Scientist

NAO/NAM Climate Indices

Introduction to NAO Indices

Reference Information

To learn more about how the spatial structure and time series of the NAO are defined, please see Hurrell et al. (2003)

Index Description Updated Thru Next Update Format
NAO Station Based (DJFM)Winter (December through March) index of the NAO based on the difference of normalized sea level pressure (SLP) between Lisbon, Portugal and Stykkisholmur/Reykjavik, Iceland since 1864.
Detailed Description, Timeseries Plot		DJFM 2008June 2009 HTML Table / ascii / Microsoft Excel File (.xls)
NAO Station Based (Monthly)Monthly index of the NAO based on the difference of normalized sea level pressures (SLP) between Ponta Delgada, Azores and Stykkisholmur/Reykjavik, Iceland since 1865. March 2003 Unknown*HTML Table
NAO Station Based (3 month seasons)Seasonal (DJF,MAM,JJA,SON) indices of the NAO are based on the difference of normalized sea level pressure (SLP) between Ponta Delgada, Azores and Stykkisholmur/Reykjavik, Iceland since 1865. Detailed Description May 2004Unknown*HTML Table
NAO Station Based (Annual)The annual index of the NAO is based on the difference of normalized sea level pressure (SLP) between Ponta Delgada, Azores and Stykkisholmur/Reykjavik, Iceland since 1865. Detailed Description May 2004Unknown*HTML Table
CPC NAO Projection Based (Daily)The daily NAO index is constructed by projecting the daily (00Z) 500mb height anomalies over the Northern Hemsiphere onto the loading pattern of the NAO since 1950. Detailed Description TodayTomorrow ascii (Last 120 days) / ascii (1950-Current) / Teleconnections Data Archive
CRU NAO Station Data (Monthly)Sea level pressure (SLP) data from the Azores (1865-2002), Gibraltar (1821-2007), and Reykjavik, Iceland (1821-2007). Dec. 2007UnknownCRU NAO Data
Updated CRU NAO Data
NAO PC Based (DJFM)The principal component (PC) time series of the leading EOF of seasonal (December through March) SLP anomalies over the Atlantic sector (20-80N, 90W-40E), available since 1899.
Detailed Description, Timeseries Plot		DJFM 2008May 2009 HTML Table
NAO PC Based (DJF)The principal component (PC) time series of the leading EOF of DJF (December through February) SLP anomalies over the Atlantic sector (20-80N, 90W-40E), available since 1899.
Plot of Spatial Pattern, Timeseries		DJF 2008May 2009 HTML Table
NAO PC Based (MAM)The principal component (PC) time series of the leading EOF of MAM (March through May) SLP anomalies over the Atlantic sector (20-80N, 90W-40E), available since 1899.
Plot of Spatial Pattern, Timeseries		MAM 2007May 2009 HTML Table
NAO PC Based (JJA)The principal component (PC) time series of the leading EOF of JJA (June through August) SLP anomalies over the Atlantic sector (20-80N, 90W-40E), available since 1899.
Plot of Spatial Pattern, Timeseries		JJA 2007May 2009 HTML Table
NAO PC Based (SON)The principal component (PC) time series of the leading EOF of SON (September through November) SLP anomalies over the Atlantic sector (20-80N, 90W-40E), available since 1899.
Plot of Spatial Pattern, Timeseries		SON 2007May 2009 HTML Table
NAO PC Based (Annual)The principal component (PC) time series of the leading EOF of annual SLP anomalies over the Atlantic sector (20-80N, 90W-40E), available since 1899.
Plot of Spatial Pattern, Timeseries		2007May 2009 HTML Table
Northern Annular Mode (DJFM) The NAM (or Arctic Oscillation) is defined as the first EOF of NH (20-90N) winter SLP data. The normalized PC values are available since 1899.
Detailed Description, Plots		DJFM 2008May 2009 HTML Table

Reference Information

Correct reference for all NAO/NAM timeseries taken directly from this webpage:

NAO Index Data provided by the Climate Analysis Section, NCAR, Boulder, USA, Hurrell (1995).