• Southern Oscillation Index;
  • Phases;
  • Rainfall probability distributions;
  • Cluster analysis


Phases of the Southern Oscillation Index (SOI) have been identified using cluster analysis. The monthly phases are associated with amounts of rainfall expressed in terms of probability distributions for various locations in eastern Australia. The phase representing rapid rise in SOI indicates above median rainfall during Southern Hemisphere autumn and spring at the locations analysed. The phase representing consistently positive SOI generally corresponds with above median rainfall amounts while the phase representing consistently negative SOI corresponds with below median rainfall amounts. As SOI phases relate to actual rainfall amounts, expressed in terms of probability distributions, the phases have, for instance, direct application to agricultural decision support programmes.