Variability of southeast Queensland rainfall and climate indices

Abstract

This paper presents a study of variability of climate indices and rainfall in southeast Queensland (SE Qld). Using high-resolution gridded rainfall data for all of Australia and global sea surface temperatures (SST), the relationship between rainfall Australia-wide and in SE Qld in particular with SST indices and the Southern Oscillation Index (SOI) have been investigated. It is found that SE Qld is more subject to the breakdown of correlations between the SOI and rainfall than any other part of Australia. Model predictions suggest that this is probable in the future. Considering only timescales longer than interannual, it was found that SSTs in the central tropical Pacific Ocean (TPO) (represented by the Nino-4 index) correlated best with SE Qld rainfall. Eastern TPO (Nino-3) SSTs and the SOI produced successively weaker correlations. The time series of the second modes of variability of SSTs over the Pacific and Indian Oceans were shown to have limited impact on SE Qld rainfall variability. The data was split into periods before and after 1946, when Australian mean rainfall changed (Pittock, 1975). While the SOI correlations with rainfall in SE Australia were similar in both periods, in SE Qld the correlations were very weak in the earlier period (0.06) but very strong in the latter (0.72). The Nino-4 index correlated better than the Nino-3 index in both periods, but they showed smaller changes from the earlier to the latter periods than the SOI.