Sea Surface Temperatures and Australian Winter Rainfall

A rotated principal component analysis of Australian winter (June–August) rainfall revealed two large-scale patterns of variation which together accounted for more than half of the total rainfall variance. The first pattern was a broadband stretching from the northwest to the southeast corners of the country. The second was centered in the eastern third of the continent. The two patterns were correlated to sea surface temperatures in the Indian and Pacific oceans. The first rainfall pattern was best related to the difference in sea temperatures between the Indonesian region and the central Indian Ocean. The second rainfall pattern was related to equatorial Pacific sea surface temperatures. This relationship reflects the influence of the Southern Oscillation on both sea surface temperatures and Australian rainfall but the relationship between the first rainfall pattern and the difference between Indonesian and central Indian Ocean sea surface temperatures is largely independent of the Southern Oscillation. This sea surface temperature difference may be another factor influencing Australian rainfall, some-what separate from the well-known effect of the Southern Oscillation.