Southern Oscillation Index


Southern Oscillation Index gives an indication of the development and intensity of El Niño or La Niña events in the Pacific Ocean.

Basic dataSOI
SourceAustralian Bureau of Meteorology (ABM)

Sustained negative values of the SOI below -8 often indicate El Niño episodes. These negative values are usually accompanied by sustained warming of the central and eastern tropical Pacific Ocean, a decrease in the strength of the Pacific Trade Winds, and a reduction in winter and spring rainfall over much of eastern Australia and the Top End.

Sustained positive values of the SOI above +8 are typical of a La Niña episode. They are associated with stronger Pacific Trade Winds and warmer sea temperatures to the north of Australia. Waters in the central and eastern tropical Pacific Ocean become cooler during this time.

Frequency of collectionMonthly
Frequency of disseminationMonthly
Temporal disaggregation Monthly
Spatial disaggregationNational