上海GPS综合应用网对可降水汽量的实时监测及其改进数值预报初始场的试验

REAL TIME MONITORING OF PWV FROM SGCAN AND ITS APPLICATION TEST IN NUMERICAL WEATHER FORECAST

分析了 2 0 0 2年夏季上海GPS综合应用网 (简称SGCAN)的观测数据 ,实时处理中直接利用IGS(Interna tionalGPSService)超快速产品IGU(theUltrarapidorbitofIGS)轨道 ,在长基线辅助下考虑海潮的影响 ,得到了可靠的可降水汽量 (简称PWV)序列 ,监测结果与加密的Radiosonde观测比较 ,偏差为 2mm左右 .与MM5预报可降水量的比较说明GPS监测结果可以作为检验数值预报质量的工具之一 .2 0 0 2年夏季SGCAN监测的PWV时空变化过程反映了长江三角洲地区从西南到东北的详细入梅雨过程和特点 ,以及整个梅雨季节雨带在江淮地区来回摆动的情况 .一小时雨量与GPS PWV锋值的对应关系统计表明GPS PWV对雷暴雨具有一定的短期预报特性 .利用Cressman分析方法把GPS PWV插值到中尺度数值预报模式初始场的各个格点上 ,改进了数值预报初始湿度场的精度 ,提高了中尺度数值预报的准确性 ,反映了GPS

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/PWV 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 7～8 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.