Modelling and analysis of rainfall extremes in the Greater Sydney region.

How extreme rainfall events may change under future climate scenarios is of great interest to a large section of the community. As part of the revision of Australian Rainfall and Runoff, possible changes in rainfall intensity-frequency-duration (IFD) curves due to anthropogenic climate change will be quantified. These will be used to provide advice to practitioner on how these changes can be included into design and planning decisions.

Concentrating on the Greater Sydney region, two different limited area models will be used to downscale reanalysis data as well as global climate model data under both the current climate and a future climate scenario. For the current climate, IFD curves will be calculated from the downscaled reanalysis and climate model data. These results will be compared with the updated IFD curves under the current climate which have recently been prepared by the Bureau of Meteorology. If the results differ, a method of correcting the downscaled results will be identified.

Future changes to rainfall IFD curves will be assessed relative to the current climate case. If necessary, the dynamically downscaled results for the future climate will be adjusted using the approach identified and applied to those for the current climate. This will ensure that any advice on climate change will be relevant to the baseline revised IFDs prepared by the BoM and will be able to be adopted by users.

This presentation will give an overview of the modelling being carried out in this project.