Southern Oscillation

There is a lot of random variation in this time series, but the index remains low for much of 1987 and is relatively high in 1988 and 1989. These periodic highs and lows indicate autocorrelation.

The Southern Oscillation Index is defined as the barametric pressure difference between Tahiti and the Darwin Islands at sea level. The southern oscillation is a predictor of El Nino which in turn is thought to be a driver of world-wide weather. Specifically, repeated southern oscillation values less than -1 typically defines an El Nino. The time series plot shows the index between January 1984 and December 1987.