An evaluation of regional climate model simulations of present and future climate in Western Australia's wine regions

Rebecca Firth

Western Australia (WA) supports an industry for world class wine production that makes a signi_cant contribution to the state's economy. Winegrapes are particularly sensitive to climate and di_erent varieties are associated with wellestablished climatic niches that allow the production of premium quality wine. This inevitably makes viticulture particularly vulnerable to climate change, thus highlighting the necessity for climate change evaluations in viticulture regions. General circulation models (GCMs) provide information related to both past and future climate but their coarse resolution (100{250 km) limits their applicability to climate-viticulture research. Regional climate models (RCMs) provide a useful solution to this limitation by dynamically downscaling GCM simulations to regional scale outputs. This thesis evaluates the Weather Research and Forecasting (WRF) model as a RCM to simulate climate indices relevant to viticulture in WA's wine regions at a 5 km resolution under current and future climate. Climate simulations driven with ERA-Interim re-analysis for the current climate and three GCMs for both current and future climate were analysed. The focus of the analysis was on a selection of climate indices that are commonly used in climateviticulture research. Simulations of current climate were validated against an observational dataset to identify the errors in the simulations. Changes to the indices under future climate were then assessed through an analysis of future minus present climate. Results demonstrated that when WRF is driven with the re-analysis dataset, there was generally good agreement with observations for all of the indices, particularly for the temperature indices. However, the results for the GCM-forced simulations were less consistent. While the GCM-forced simulations performed reasonably well for the temperature indices, all simulations performed inconsistently for the precipitation indices. Climate projections showed signi_cant warming for all of the temperature indices and indicated potential risks to WA's wine growing regions under future climate, particularly in the north. There was less agreement between simulations with regards to the projections of the precipitation indices, hence greater uncertainty as to how these indices will change under future climate. However, the general indication was for drier conditions for WA's wine regions.

An evaluation of regional climate model simulations of present and future climate in Western Australia's wine regions

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