Statistical analysis of Eastern Australian rainfall events and their interaction with El Nino-Southern Oscillation and Southern Annular Mode — Australian Meteorological and Oceanographic Society

Statistical analysis of Eastern Australian rainfall events and their interaction with El Nino-Southern Oscillation and Southern Annular Mode (#2010)

Matthew A Jones 1 , George J Takacs 1
  1. University of Wollongong, Wollongong, NSW, Australia

Eastern Australian rain events and their correlations with the Southern Oscillation and the Southern Annular Mode have been analysed, revisiting and expanding on the work of Nicholls (1993) for more stations and a longer time period. A rain event is here defined as a single rain day or a stretch of consecutive rainfall days. The annual rainfall, number of events in a year, the average length of events and average intensity of events have been studied using data for 56 stations in the eastern Australian states from the Bureau of Meteorology High Quality Daily Rainfall dataset. Finally, least squares regression models are compared to Theil-Sen estimator models to determine whether different conclusions may be drawn based on the estimator used. Most stations indicated significant positive correlations between annual rainfall and the other three variables. When correlations between the latter variables are analysed, approximately half of the stations indicate significant correlations with greater spatial variance than the annual rainfall correlations. Correlations between annual rainfall and the SOI are significantly positive across eastern Australia. Positive correlations also exist at all stations between the SOI and the other variables with varying significance. Correlations with SAM are much less significant and there is no clear pattern across the variables. The least squares regression confidence intervals generally agreed with those for the Theil-Sen estimator, and so similar conclusions are drawn. The observations agree well with those of Nicholls (1993), indicating there has been no significant change in the behavior of these events since 1988. It is clear that there must be other influences on these rain events which have not been considered such as land cover, air pressure or other large scale modes of variability such as the Indian Ocean Dipole. These, along with the seasonality of rain events, are potential areas for future study.

  1. Nicholls, N. and Kariko, A., 1993. East Australian rainfall events: Interannual variations, trends, and relationships with the Southern Oscillation. Journal of Climate, 6(6), pp.1141-1152.
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