Validation of WRF Downscaling Capabilities Over Western Australia to Detect Rainfall and Temperature Extremes

When evaluating the merits of regional climate simulations, one of the most compelling arguments for this high resolution, dynamical downscaling approach is its ability to simulate the extremes of temperature and precipitation with greater skill than lower resolution models. A historical (1970-2000), ensemble regional climate simulation using WRF was performed over Western Australia at a 50km, 10km and 5km resolution in order to evaluate the effectiveness of the model in simulating annually extreme climate events as defined by the core climate indices of the CCI/CLIVAR/JCOMM Expert Team on Climate Change Detection and Indices (ETCCDI). Five temperature and five precipitation indices were chosen and the capacity of the simulation to detect the temporal and spatial structure of these indices was assessed. Validation took place through comparisons to observational CSIRO Australia Water Availability Project (AWAP) daily gridded minimum and maximum temperature and precipitation data and RCM simulations driven by ERA-Interim lateral boundary conditions over the same area. The study is part one of a two part project to examine future changes in extreme temperature and precipitation in the region and the influence of land cover change and anthropogenic greenhouse gases on these changes.