Climate Dynamics

, Volume 26, Issue 7–8, pp 751–764 | Cite as

Shifts in the synoptic systems influencing southwest Western Australia

  • Pandora K. HopeEmail author
  • Wasyl Drosdowsky
  • Neville Nicholls


A self-organising map is used to classify the winter circulation affecting southwest Western Australia (SWWA) into 20 different synoptic types. The changes in the frequency of these types and their links to observed rainfall are analysed to further understand the significant, prolonged, rainfall drop observed in this region since 1975. The temporal variability of the different synoptic types link well with the observed rainfall changes. The frequency of the troughs associated with wet conditions across SWWA has declined markedly since 1975 while the frequency of the synoptic types with high pressure over the continent, associated with dry conditions, has increased. Combining the frequency of the synoptic systems with the amount of observed rainfall allows a quantitative analysis of the rainfall decline. The decreased frequency of the troughs associated with very wet conditions accounts for half of the decline. Reductions in the amount of rainfall precipitating from each system also contribute to the decline. Large-scale circulation changes, including increases in the mean sea-level pressure and a decrease in the general baroclinicity of the region have been associated with the rainfall decline. These changes are suggested to be linked to increasing levels of greenhouse gases. Due to the strong link between the number of trough types and the rainfall over SWWA, the shifts in the frequency of these synoptic types could be used as a tool to assess simulated rainfall changes, particularly into the future.


Cyclone Australian Region Synoptic Situation Rainfall Change Synoptic System 
These keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.



This research was supported by the Indian Ocean Climate Initiative (IOCI). Thank you to Debbie Hudson, who provided guidance in the early stages of this project and to Vaughan Barras, who provided helpful suggestions.


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Copyright information

© Springer-Verlag 2006

Authors and Affiliations

  • Pandora K. Hope
    • 1
    Email author
  • Wasyl Drosdowsky
    • 1
  • Neville Nicholls
    • 1
  1. 1.Bureau of Meteorology Research CentreMelbourneAustralia

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