Climatic Research Unit : Data

Southern Oscillation Index (SOI)

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 (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

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

Filename Size Description
soi.dat 14 kilobytes SOI
soi_dar.dat 12 kilobytes Pressure data for Darwin
soi_tah.dat 12 kilobytes Pressure data for Tahiti

Filename	Size	Description
soi.dat	14 kilobytes	SOI
soi_dar.dat	12 kilobytes	Pressure data for Darwin
soi_tah.dat	12 kilobytes	Pressure data for Tahiti

Last updated: January 2010, Phil Jones & Mike Salmon

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