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Abbs, D. J., Aryal, S., Campbell, E., Palmer, M., Rafter, A. S., and Bates, B. (2006). Impact of climate variability and climate change on rainfall extremes in Western Sydney and surrounding areas : Phase 1 report to the Upper Parramatta River Catchment Trust C/1030. Aspendale, Vic.: CSIRO Atmospheric Research. 66 p.
< http://www.cmar.csiro.au:8000/e-print/open/abbsdj_2006a.pdf >

The CSIRO Climatic Extremes research group (CER) is investigating rainfall intensity-frequencyduration (IFD) and depth-area curves for western Sydney and surrounding areas for present day and projected future conditions in collaboration with the Upper Parramatta River Catchment Trust and its partners. The other objectives of the project are:
· Assess the impact of decadal-scale climate fluctuations on rainfall frequency characteristics (subsidiary).
· Obtain a “broad brush” understanding of the likely changes in average and extreme rainfall under enhanced greenhouse conditions (core).
· Quantify the likely future changes to the rainfall frequency characteristics of the study area due to global warming (core).
The proposed work plan consists of four components couched within a three-year timeframe. The objectives of Components 1 to 3 are to provide information on rainfall IFD and depth-area curves for durations less than 6 hr for present day and projected future conditions, respectively. This information is critical for flood design applications.
Component 1 will develop a statistical model of extreme rainfall events for the study area, and will provide a list of candidate extreme events that can be explored using high resolution downscaling. The main task undertaken in Component 1 is the statistical analysis of observations at daily rain gauges and recording rain gauges (pluviometers) within and adjacent to the study area. The following steps are involved:
1.1 Clean rainfall data set prepared,
1.2 Spatial model(s) developed and applied to available data for durations of less than 1 hour to 72 hours,
1.3 Initial characterisation of IFD and depth-area curves for present day conditions,
1.4 Comparison of IFD and depth-area curves with those obtained from high resolution dynamical downscaling.
Step 1.1 is a major activity in terms of length of time involved. Section 4 of this report is concerned with the progress made in this Component.
Component 4 of the project is the high resolution dynamical downscaling of extreme rainfall events for the current climate and the climates of 2030 and 2070. This component is being undertaken as a joint project with the AGO. The tasks are:
4.1 Identification of candidate cases,
4.2 High-resolution simulation of extreme rainfall events at a grid spacing of approximately 5km,
4.3 Analysis of downscaled events and preparation of IFD and depth-area curves for durations of less than 1 hour to 72 hours. (Author abstract).

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