Trends in Australian rainfall over the period 1901 to 2002 are analysed with the aim of evaluating and assessing long-term trends. In particular, this study examines long-term trends in Australian rainfall with the aim of identifying any continentalscale patterns that could be described as ‘unusual’. All-Australia annual average rainfall and all-Australia average decile time series indicate a positive long-term trend over the full period. Trend maps indicate that much of this trend is the result of increases in summer half-year rainfall over western, northern and central Australia that have occurred over the latter part of the record 1952-2002. While significant negative trends in winter half-year rainfall over southwest Western Australia are evident, there is little evidence that they are part of any continental-scale trends, at least not on 100 or 50-year time-scales. Empirical Orthogonal Teleconnection patterns (EOTs) of annual rainfall provide a means for delineating independent spatial modes. These indicate that much of the variance in all-Australian rainfall can be attributed to the first two modes that cover much of central eastern Australia and central western Australia. In addition, the pattern of positive trends comprises at least two modes, which, being linearly independent, indicate that the large-scale pattern of increases is itself unusual in a historical context.
I. N. Smith (Wed,) studied this question.