Future Heatwaves in NSW from the NARCliM ensemble ; MODSIM2017, 22nd International Congress on Modelling and Simulation. Modelling and Simulation Society of Australia and New Zealand

Abstract

NARCliM (NSW/ACT Regional Climate Modelling project) is a regional climate modelingproject for the Australian area. It provides a comprehensive dynamically downscaled climate dataset for theCORDEX-AustralAsia region at 50km resolution, with a finer 10km resolution across South-East Australia.NARCliM data is being used by the NSW and ACT governments to design their climate change adaptationplans. Data is available through the AdaptNSW website (http://climatechange.environment.nsw.gov.au/).NARCliM uses WRFv3.3 regional climate model (RCM) to perform an ensemble of simulations for the presentand the projected future climate. WRF is run in three different model configurations (different combinationsof physical parametrizations) that have been shown to perform well in South-East Australia and were chosenbased on performance and independence. These three RCMs are simulating three different periods: 1990-2009,2020-2040 and 2060-2080. Four different GCMs (MIROC-medres 3.2, ECHAM5, CGCM 3.1 and CSIROmk3.0) from CMIP3 provide initial and boundary conditions for the WRF simulations. These GCMs werechosen through a process that considered model performance, independence and diversity in projected futurechanges. This GCM-RCM matrix gives an ensemble of 12 simulations for each period.Heatwaves are here defined using the Excess Heat Factor metric. Its characteristics, including duration,frequency and intensity, are examined. Compared to observations, the NARCliM ensemble displays a goodability to simulate heatwaves across NSW with almost all present-day biases being non-significant. By 2070,robust increases in heatwave frequency, duration and peak amplitudes are found across NSW and the ACT.Western NSW is projected to have the most significant increases in peak amplitude. Most of NSW is projectedto experience about 20 more heatwave-days a year by 2070 compared to the present. In many locations this ismore than a doubling of the current number of heatwave days.