Water Balance in the Murray-Darling Basin and the recent drought as modelled with WRF

The Weather Research and Forecasting (WRF) modelling system is developed as a collaborative partnership between the National Center for Atmospheric Research (NCAR), the National Oceanic and Atmospheric Administration (the National Centers for Environmental Prediction (NCEP) and the Forecast Systems Laboratory (FSL)), the Air Force Weather Agency (AFWA), the Naval Research Laboratory, Oklahoma University, and the Federal Aviation Administration (FAA) in the USA as well as the wider research community. The version used in this study is the Advanced Research WRF (ARW) maintained at NCAR. WRF was run over the Murray-Darling Basin (MDB) from 1985 through 2007. The model used the following physics schemes: WRF Single Moment 5-class microphysics scheme; the Rapid Radiative Transfer Model (RRTM) longwave radiation scheme; the Dudhia shortwave radiation scheme; Monin-Obukhov surface layer similarity; Noah land-surface scheme; the Yonsei University boundary layer scheme and the Kain-Fritsch cumulus physics scheme. The model simulation uses boundary conditions from the NCEP/NCAR reanalysis with an outer 50km resolution nest and an inner 10km resolution nest that covers the whole MDB. Both nests used 30 vertical levels spaced closer together in the planetary boundary layer. The simulation is evaluated against gridded surface temperature and precipitation observations created as part of the Australian Water Availability Project (AWAP). The WRF simulation is found to reproduce the climate of the MDB reasonably well. WRF was able to improve on the climate produced by the NCEP/NCAR reanalysis which provided the boundary conditions for the WRF simulation. Investigation of the time series of precipitation and soil moisture anomalies show that WRF is able to capture the recent drought in the MDB. While the overall time series captured the drought well the spatial patterns associated with the anomalies produced by WRF differed from those found in the AWAP dataset. Further work will investigate the reasons for these spatial differences as well as WRFs performance at shorter time scales.