Links between tropical indices and southern Australian rainfall

Links between southern Australian rainfall totals and tropical indices are investigated with the aim of identifying potential explanations for observed trends over the period 1950-2008. We find that, as has been noted in many previous studies, fluctuations in Indian Ocean sea surface temperature (SST) anomalies do not explain significantly more of interannual rainfall fluctuations than other indices which are dominated by El Nino Southern Oscillation events. It is proposed that a composite index, capturing SST variations in the Indian Ocean, the seas to the north of Australia, and the Pacific Ocean may be more useful in studying interannual variability. We also find that, while most indices can be significantly linked to rainfall fluctuations on interannual time scales, these links do not adequately describe the long-term trends. This suggests that the drivers of long-term trends in southern Australian rainfall do not involve the tropical oceans so much as changes in the large-scale atmospheric circulation. Copyright (C) 2010 Royal Meteorological Society