Climatic Research Unit : Data

North Atlantic Oscillation (NAO)


The NAO is traditionally defined as the normalized pressure difference between a station on the Azores and one on Iceland. An extended version of the index can be derived for the winter half of the year by using a station in the southwestern part of the Iberian Peninsula (Hurrell, 1995). Here we give data for SW Iceland (Reykjavik), Gibraltar and Ponta Delgada (Azores). The NAO calculated from Gibraltar and SW Iceland is also given (Jones et al., 1997).

See also :

December 2000: The values for Gibraltar have been altered. New documentation will be in a paper currently in preparation by Jones, Briffa and Osborn.

File format (NAO)
for year = 1821 to 2000
  format(i5,12f7.2,f8.2) year, 12 * monthly value, annual value
Missing values represented by -99.99

File format (Station pressure)
format(i1,i5,i5,a) ?,startyear,endyear,name
for year = startyear to endyear
  format(i5,12i6) year, 12 * monthly value
Missing values represented by -10
Divide by 10 for millibars

Filename SizeDescription
nao.dat 18 kilobytesNAO
nao_azo.dat 10 kilobytesPressure data for Ponta Delgada, Azores
nao_gib.dat 14 kilobytesPressure data for Gibraltar
nao_ice.dat 14 kilobytesPressure data for South-West Iceland


Last updated: June 2016, Tim Osborn

These datasets are made available under the Open Database License.
Any rights in individual contents of the datasets are licensed under the
Database Contents License under the conditions of Attribution and Share-Alike.
Please use the attribution Climatic Research Unit, University of East Anglia