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How extreme south-west rainfalls have changed
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How extreme south-west rainfalls have changed

J. K Ruprecht, Yun Li, Eddy Campbell, Pandora Hope, Department of Environment, CSIRO (Commonwealth Scientific and Industrial Research Organisation) and BMRC (Bureau of Meteorology Research Centre)
Climate note, 1, IOCI (Indian Ocean Climate Initiative), 1st
2005
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How extreme south-west rainfalls have changed_IOCI Stage 2_Climate Note 1 seriesView
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Abstract

Climate Climatic changes Climatic extremes Rain and rainfall
South-west WA can experience extreme rainfall in winter with frontal systems and in summer with tropical storms. In the mid-1970s in south-west WA there was a shift to consistently drier conditions (see IOCI Climate Note 5/05) for annual and seasonal rainfall. Research sponsored by IOCI suggests that both natural climate variability and the enhanced greenhouse effect have played a role. However, it is much more difficult to determine if there has been a shift in extreme rainfall. At the relatively frequent level of extreme events, such as less than a one-in-10 year annual maximum rainfall event (20- 60mm recorded at various locations), observed statistics give us some insight, but for extremes at the rare or disaster level, there is very little understanding at this point in time. The data for many rainfall stations in the south-west indicate that larger storms do not appear as often now in winter, but the magnitude of annual winter maxima is not significantly changed. There are also observations that summer rainfall events (one-in-10 year) are typically random and have not altered significantly over the last 100 years. Continuing research by IOCI is building our understanding of factors driving these changes, but projections of change in rare events are perhaps only able to be investigated by modelling studies at the very edge of our current capability in climate science.

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