The SOI is defined as the normalized pressure difference between Tahiti and Darwin. There are several slight variations in the SOI values calculated at various centres. Here we supply the SOI (from CRU) which is based on the method given by Ropelewski and Jones (1987).

Time Interval: Monthly
Time Coverage: 1866 to Aug 2021
Update Status: Periodically updated

Get Data:

SOI: Standard PSL Format (What is standard format?)
SOI: Original Format

Source:
Data is from CRU via the page http://www.cru.uea.ac.uk/cru/data/soi/.
References:

1. Allan, R.J., Nicholls, N., Jones, P.D. and Butterworth, I.J., 1991: A further extension of the Tahiti-Darwin SOI, early SOI results and Darwin pressure. J. Climate, 4, 743-749.
2. Ko"nnen, G.P., Jones, P.D., Kaltofen, M.H. and Allan, R.J., 1998: Pre-1866 extensions of the Southern Oscillation Index using early Indonesian and Tahitian meteorological readings. J. Climate, 11, 2325-2339.
3. Ropelewski, C.F. and Jones, P.D., 1987: An extension of the Tahiti-Darwin Southern Oscillation Index. Monthly Weather Review, 115, 2161-2165.

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