SOIL-MOISTURE PREDICTION OVER THE AUSTRALIAN CONTINENT

This paper describes an attempt to model soil moisture over the Austra lian continent with an integrated system of dynamic models and a Geogr aphic Information System (CIS) data base. A land surface scheme with i mproved treatment of soil hydrological processes is described. The non -linear relationships between soil hydraulic conductivity, matric pote ntial and soil moisture are derived from the Broadbridge and White soi l model. For a single location, the prediction of the scheme is in goo d agreement with the measurements of the Hydrological and Atmospheric Pilot Experiment (HAPEX). High resolution atmospheric and geographic d ata are used in soil moisture prediction over the Australian continent . The importance of reliable land surface parameters is emphasized and details are given for deriving the parameters from a GIS. Predicted s oil moisture patterns over the Australian continent in summer, with a 50 km spatial resolution, are found to be closely related to the distr ibution of soil types, apart from isolated areas and times under the i nfluence of precipitation. This is consistent with the notion that the Australian continent in summer is generally under water stress. In co ntrast, predicted soil temperatures are more closely related to radiat ion patterns and changes in atmospheric circulation. The simulation ca n provide details of soil moisture evolution both in space and time, t hat are very useful for studies of land use sustainability, such as pl ant growth modelling and soil erosion prediction.