Water vapour is highly variable in both time and space, and understanding its distribution in the atmosphere is essential to understanding short time scale weather systems and climatic conditions on a longer time scale.   However, due to lack of sufficient observations it is under-observed in time and space and its analysis remains a difficult problem in weather forecasting and related climate applications. 

The emergence of new and cost-effective satellite technology such as GPS has provided greater opportunities to fill the lack of information on fast-changing water vapour in time and space throughout the column of the atmosphere.   It offers the possibility of observing the distribution of water vapour with unprecedented coverage and a temporal resolution of the order of 10min (Bevis et al, 1992).  In addition, the capability of GPS to produce continuous and high temporal resolution measurements has been shown to benefit weather forecasts and in particular improve the precipitation field (Marcus et al, 2007).    

The Bureau of Meteorology ACCESS-R NWP model is a key component of the operational weather forecast systems in Australia. We have compared ACCESS-R model moisture fields and radiosonde data with Total Precipitable Water fields generated from Victorian GPS sites to provide an indication of the utility of the data for improving moisture analysis. The databases used and the data processing methodology will be discussed in the paper.