Climatic Research Unit : Data
North Atlantic Oscillation (NAO)
Please read the note in the File Format section
regarding incorrect documentation of the format
that may have caused you to incorrectly process this data.
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).
- Hurrell, J.W., 1995: Decadal trends in the North Atlantic Oscillation and relationships to regional temperature and precipitation. Science 269, 676-679.
- Jones, P.D., Jónsson, T. and Wheeler, D., 1997: Extension to the North Atlantic Oscillation using early instrumental pressure observations from Gibraltar and South-West Iceland. Int. J. Climatol. 17, 1433-1450.
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
March 2004 - Erratum:
The format given above was previously incorrectly given as (i5,13f7.2)
If you used this fixed format to read the values you would suffer two errors:
If you used free-format reading it should have worked correctly.
- Loss of precision: second decimal place would not be read
- Bad missing data: missing values would be read as -99.9 so may not be detected as missing by your program
Please accept our apologies for incorrectly documenting this dataset
|File format (Station pressure)
for year = startyear to endyear
format(i5,12i6) year, 12 * monthly value
Missing values represented by -10
Divide by 10 for millibars
||10 kilobytes||Pressure data for Ponta Delgada, Azores
||14 kilobytes||Pressure data for Gibraltar
||14 kilobytes||Pressure data for South-West Iceland
Last updated: March 2004, Mike Salmon