Temporal variation of relations between tropical sea-surface temperatures and New South Wales rainfall

Principal component analysis (PCA) of Pacific and Indian Ocean sea-surface temperatures (SSTs) revealed six dominant patterns in each season. PCA of New South Wales district rainfall with varimax rotation identified major patterns of rainfall variability. Each of the latter patterns characterised the rainfall variability of a subregion of the State. Correlations between the SST principal components (PCs) and rainfall PCs showed that some of the SST patterns were significantly related to the rainfall patterns. However, running correlations between the SST PCs and the rainfall PCs revealed instabilities in the relationships over the period 1933–87. Changes in the relationships were different for each season and also for each rainfall subregion. The SST patterns which were found to be related to the rainfalls were strongly related to the Southern Oscillation Index (SOI). The main features of the changes observed in the SST-rainfall relationships were similar to those in the SOI-rainfall relationships although the SST-rainfall relationships were generally weaker than the SOI-rainfall relations.