Here are some details on the index:
Updated standardized values for the PDO index, derived as the leading PC of monthly SST anomalies in the North Pacific Ocean, poleward of 20N. The monthly mean global average SST anomalies are removed to separate this pattern of variability from any "global warming" signal that may be present in the data.
For more details, see:
Zhang, Y., J.M. Wallace, D.S. Battisti, 1997: ENSO-like interdecadal variability: 1900-93. J. Climate, 10, 1004-1020.
Mantua, N.J. and S.R. Hare, Y. Zhang, J.M. Wallace, and R.C. Francis,1997: A Pacific interdecadal climate oscillation with impacts on salmon production. Bulletin of the American Meteorological Society, 78, pp. 1069-1079. (available via the internet at url: http://www.atmos.washington.edu/~mantua/abst.PDO.html)
Data sources for this index are: UKMO Historical SST data set for 1900-81; Reynold's Optimally Interpolated SST for January 1982-latest
These data (Jan 1900 - Dec. 1998) are available in an Excel 5.0 spreadsheet or in a simple text file.
last updated 8 Nov 1998.