Climatic Research Unit : Data
Southern Oscillation Index (SOI)
Data updated to June 2016 (5 Nov 2016)
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 calculate the SOI based on the method given by Ropelewski and Jones (1987).
It uses a second normalization step, and was the Climate Analysis Centre's standard method in 1987.
The reader is also referred to Allan et al. (1991) and Können et al. (1998) for details of
the early pressure sources and methods used to compile the series from 1866 onwards.
- 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.
- Können, 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.
- Ropelewski, C.F. and Jones, P.D., 1987: An extension of the Tahiti-Darwin Southern Oscillation Index. Monthly Weather Review 115, 2161-2165.
|File format (SOI)
for year = 1866 to endyear
format(i5,12f7.2,f8.2) year, 12 * monthly value, annual value
Missing values represented by -99.99 and -10.00
|File format (Station pressure)
for year = 1855 to endyear
format(i5,12i6) year, 12 * monthly value
Missing values represented by -989, -990 and -10
Divide by 10 for millibars
||12 kilobytes||Pressure data for Darwin
||12 kilobytes||Pressure data for Tahiti
Last updated: January 2010, Phil Jones & Mike Salmon