Validation of CLIGEN parameter adjustment methods for Southeastern Australia and Southwestern Western Australia

Abstract

Global climate models (GCMs) are usually used for future climate projections. Model output from GCMs needs to be downscaled and stochastic weather generators such as Climate Generator (CLIGEN) are tools to downscale GCM output and to produce synthetic weather sequences that are statistically similar to the observed weather data. Two methods of adjusting CLIGEN parameters were developed to reproduce precipitation sequences for southeastern Australia (SEA), where significant changes in annual precipitation had occurred, and for southwestern Western Australia (SWWA), where the precipitation has shown a significant decreasing trend since the 1920s. The adjustment methods have been validated using observed precipitation data for these regions. However, CLIGEN outputs ultimately will be used as input to other simulation models. The objective of this research was to further validate the methods of CLIGEN parameter adjustment using conceptual hydrological models to simulate streamflow and to compare the streamflow using observed and CLIGEN-generated precipitation data. Six precipitation sites from SEA and SWWA were selected and synthetic time series of daily precipitation were generated for these sites. Conceptual hydrological models, namely, the Australian Water Balance Model and SimHyd, were used for flow simulation and were calibrated using recorded daily streamflow data from six gauging stations in SEA and SWWA. Both monthly and annual streamflow show statistically similar patterns using observed and CLIGEN-generated precipitation data. The adjustment methods for CLIGEN parameters are further validated and can be used to reproduce the significant changes, both abrupt and gradually decreasing, in streamflow for these two climatically contrasting regions of Australia.