In collaboration with the Office of Environment and Heritage (OEH) we are developing new, fine-scale climate projections for south-east Australia as part of the NSW and ACT Regional Climate Modelling project or NARCliM.

NARCliM will improve our ability to predict changes in temperature, wind and rainfall in the state which, in turn, will provide critical information to manage the impacts of climate change on health, settlements, agriculture, weather extremes and services, such as water and energy supplies.

NARCliM uses the Weather Research and Forecasting (WRF) model, a dynamical regional climate model that gives high resolution projections of temperature, rainfall and many other meteorological variables. WRF has been demonstrated to be effective in simulating temperature and rainfall in NSW (Evans & McCabe 2010 J. Geophys Res. 115) and provides a good representation of local topography and coastal processes. It was jointly developed by several major weather and research centres in the United States and is widely used internationally.

No model can perfectly represent the Earth’s climate – some regions of the modelled climate may be slightly hotter or drier, for example, than the climate we experience in reality. These differences are known as error or bias. To minimise potential bias from a single model, four global climate models (GCMs) are used as input to the regional model.

WRF has different settings which reflect uncertainties in our understanding of some physical processes. Varying these settings between model runs and using several different settings with each GCM provides a more realistic set of projections. Performing multiple model runs also captures more reliable information on rare, extreme weather events, such as heatwaves, heavy rain and drought.

There are four components to the NARCliM project.

Modelling

The modelling component is mainly being run and supervised at the Climate Change Research Centre at the University of NSW. WRF will be run with four separate GCMs (MIROC-medres 3.2, ECHAM5, CGCM 3.1 and CSIRO mk3.0). Each will be repeated three times for a total of 12 runs, using a single, representative emissions scenario: the IPCC high emissions scenario A2. Projections will be produced for several variables, including temperature, rainfall, wind, relative humidity, sea surface temperature and soil temperature.

Data storage

NARCliM will generate a very large dataset, estimated to be around 1 petabyte in size (1 million gigabytes), which will be systematically managed by OEH.

Data retrieval and access

NARCliM is designed to give the community easy access to both raw climate modelled data and, more importantly, information that combines the model projections into climate statistics that can be readily used by the public and agencies like local government. Inquiry, summary and visualisation tools are being developed using feedback from a user reference group. This will include tools to calculate fire weather hazard or extreme events, such as flood risk.

Synthesis reports

A report synthesising and interpreting the projected changes in climate across NSW will be jointly completed by staff from OEH and the Climate Change Research Centre at the University of NSW.