Near Real‐Time Sensing of PWV from SGCAN and the Application Test in Numerical Weather Forecast

Abstract

AbstractGPS data from Shanghai GPS Comprehensive Application Network (SGCAN) in summer of 2002 are analyzed. The ultra‐rapid orbits of IGS (IGU) are used directly in real‐time processing. Reliable Precipitable Water Vapor (PWV) series can be obtained with the assistance of remote stations. Considering the effect of ocean tide, the accuracy of PWV can be improved. The difference between GPS/PWV and Radiosonde observations is about 2mm. Comparison between the output of MM5 and GPS/PWV shows that GPS can be regarded as one means to verify the forecast of MM5 in near real time. Continuous GPS/PWV series in the whole Meiyu season reflect the changing processes of PWV in detail before and after the onset of Meiyu Season in Yangtze River Delta in 2002 summer. The variation of GPS/PWV shows that the onset of Meiyu season was from southwest to northeast and completed in about 7–8 hours. Rainband moved back and forth between Yangtze River Delta and Huaihe area in Meiyu season. The statistics of PWV peaks and one‐hour rain explains 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 gridpoints of background field using Cressman method. The accuracy of numerical forecast is improved. One example is provided in this paper which shows the potential of GPS/PWV for improving numerical forecast.