Diagnosing the synoptic influences driving changes in climate extremes over southern Australia during the last century
Lisa V. Alexander, Monash Univ., Clayton, Vic., Australia
Australia is known as “the land of droughts and flooding rains”, however the southern part of the continent has sustained an unprecedented period of drought in the past decade putting huge stress on the water resources of the major metropolitan areas. Previous studies have indicated that there has been a shift in the synoptic systems affecting southern Australia enhancing the recent large-scale drying. However most studies have been based on reanalyses data which only cover the last 50 years or so and have generally focused on changes in average climate conditions. Since extreme events are more likely to impact communities, the aim here is to gain a long term perspective of the large-scale drivers of extreme temperature and rainfall events by extending previous analysis to cover the past century. For the first time, a high quality daily surface pressure dataset is created for Australia using in-situ sub-daily observations between 1907 and 2006. Synoptic patterns are identified from this dataset using a clustering technique called self organizing maps (SOMs). The outcome is a dataset of spatially complete daily synoptic patterns back to the beginning of the 20th century. Trends in each of these patterns are then investigated over this century long timescale. In addition, trends in the daily synoptic systems driving extreme temperature and precipitation events in major Australian cities are analyzed to investigate changes in the large-scale mechanisms which are driving these events.
Session 12B, Climate and weather extremes
Thursday, 15 January 2009, 8:30 AM-9:45 AM, Room 129B
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