On the reality, stability, and usefulness of southern hemisphere teleconnections

A brief review is presented of published regional and hemispheric analyses of climatic data from the southern hemisphere. Besides several hemispheric analyses, regional analyses exist for southern Africa, Australia, New Zealand, and South America. These point to the importance to climatic variability of several features of the southern hemisphere atmospheric circulation, viz. the Walker Circulation or 'Southern Oscillation', the latitude of the subtropical high pressure maximum, the strength of the mid-latitude westerlies, and the eccentricity of the circumpolar flow. A new hemispheric analysis of precipitation data is used to illustrate some of the links between these features. The existence of some apparently significant correlations between climatic elements and circulation indices at lags of order 12 months are noted. These lead to a hypothesis linking anomalous circulation at high latitudes to the subsequent behaviour of the Southern Oscillation. Unfortunately there is evidence that the patterns and sequences of correlations do not remain constant with time. At best we seem unable to account for more than about one-third of the variance In Australian rainfall, even for favoured locations and seasons, in terms of its correlation with the Southern Oscillation. While relationships undoubtedly exist, some doubt as to their stability means that these relationships could be misleading as aids to long-range forecasting.