Real time monitoring of PWV from SGCAN and its application test in numerical weather forecast

GPS data from Shanghai GPS Comprehensive and Application Network(SGCAN) in the summer of 2002 are analyzed. The Ultra-rapid orbit of IGS(IGU) is used directly in real-time processing. Reliable Precipitable Water Vapor (PWV) series can be obtained with the assistant of remote stations. Considering the effect of ocean tide, the accuracy of PWV can be improved. The difference between GPS/PVFV and Radiosonde observations is about 2mm. Comparison between the outputs of MM5 and GPS/PWV shows that GPS can be regarded as one means to real-time check up the result of MM5 numerical prediction. Continuous GPS/PWV series in the whole Meiyu season reflects the changing processes of PWV in detail before and after the onset of the Meiyu Season in the Yangtz River Delta in 2002 summer. The variations of GPS/PWV show that the onset of the Meiyu season was from southwest to northeast and completed in about 7 similar to 8 hours. The rainband moved back and forth among the Yangtz River Delta, Huaihe area and the south to the Yangtz river area in the Meiyu season. The statistics of PWV peaks and one-hour rain explain some short-term forecast ability of GPS/PWV for rainstorms. The humidity condition of numerical forecast model is optimized after GPS/PWV being interpolated to the grids of the initial field using the Cressman method. The accuracy of numerical forecast is improved. One example is provided in this paper which shows the potential of GPS/PWV in improving numerical forecast