Zonal winds and southeast Australian rainfall in global and regional climate models
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Southeast Australia is a region of high rainfall variability related to major climate drivers, with a long-term declining trend in cool-season rainfall. Projections of future rainfall trends are uncertain in this region, despite projected southward shifts in the subtropical ridge and mid-latitude westerlies. This appears to be related to a poor representation of the spatial relationships between rainfall variability and zonal wind patterns across southeast Australia in the latest Coupled Model Intercomparison Project ensemble, particularly in the areas where weather systems embedded in the mid-latitude westerlies are the main source of cool-season rainfall. Downscaling with regional climate models offers improvements in the mean rainfall climatology, and shows some ability to correct for poor modelled relationships between rainfall and zonal winds along the east coast of Australia. However, it provides only minor improvements to these relationships in southeast Australia, despite the improved representation of topographic features. These results suggest that both global and regional climate models may fail to translate projected circulation changes into their likely rainfall impacts in southeast Australia.
KeywordsRainfall Circulation Models Downscaling Australia
This research was supported by the Australian Research Council Centre of Excellence for Climate System Science, grant CE110001028, and Linkage project grant LP120200777. Jason Evans was supported by the Australian Research Council Future Fellowship FT110100576, with the WRF downscaled runs available thanks to the NSW Office of Environment and Heritage backed NSW/ACT Regional Climate Modelling (NARCliM) Project and the Eastern Seaboard Climate Change Initiative—East Coast Low Project (ESCCI-ECL). This research was undertaken with the assistance of resources provided at the NCI National Facility systems at the Australian National University through the National Computational Merit Allocation Scheme supported by the Australian Government. The authors also wish to thank two anonymous reviewers for their helpful comments.
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