Southern oscillation index
From Glossary of Meteorology
Southern Oscillation index
A measure of the state of the Southern Oscillation.
A common index used for this purpose is the sea level pressure at Tahiti minus the sea level pressure at Darwin, Australia, divided by the standard deviation of that quantity. It is closely associated with El Niño and is thus often referred to as ENSO (El Niño–Southern Oscillation).
