利用地基北斗站反演大气水汽总量的精度检验

The Accuracy Test of Retrieved Precipitation Water Vapor Based on Beidou Observations

采用上海市气象局建立的北斗气象站的2014年观测数据和我国自主研发的精密导航数据处理软件PANDA(position and navigation data analysist)实现了基于北斗数据的大气水汽总量(precipitable water vapor,PWV)反演,并将利用北斗卫星信号解算的大气水汽总量(W_(BD))结果与目前较为成熟的GPS卫星反演结果(W_(GPW))和无线电探空反演结果(W_(Radio))进行对比,研究表明:反演的W_(BD)与W_(GPS)的均方根误差均低于3.5 mm,反演的W_(BD)与W_(Radio)的均方根误差为3.6 mm,两种对比方式的相关系数均在0.95以上,反演方法以及地理位置的差异对于反演结果有一定影响;反演的W_(BD)能够很好地反映出大气中水汽的变化特征,对于气象短时临近预报、气候分析有指示作用。

The Beidou Navigation Satellite System is an independent system under construction in China.Observations of Beidou can be used to retrieve atmospheric precipitation water vapor(PWV) and provide information of water vapor with high precise and high real time.Beidou meteorological observation network is built by Shanghai Meteorological Bureau with PANDA(position and navigation data analysist) and M300C_GNSS,UNICORE-UB240 Beidou receivers,and the atmospheric precipitation water vapor is acquired.First,satellite data is received by Beidou meteorological observations and satellite orbit files are downloaded synchronously,and then zenith total delay(ZTD) is calculated by PANDA modules,and at last the PWV is retrieved based on surface meteorological parameters observed by automatic weather stations.Results of PWV retrieved by Beidou data(W_(BD)) are compared with both PWV retrieved by GPS data(W_(GPS)) and radiosonde data(W-(Radio),as the technology of them are mature.W_(GPS) is retrieved by two methods:One is GAMIT(GPS at MIT) with the method of double difference phase observation,the other is PANDA with the method of precise point positioning.W_(Radio) is retrieved by the method of water vapor integration from different pressure levels.The horizontal distance difference between corresponding observations is no more than 10 km,the elevation difference between GPS and Beidou observations is no more than5 m,and the elevation difference between radiosonde and Beidou observations is about 30 m.Results show that the root mean square error(RMSE) between W_(BD) and W_(GPS) is no more than 3.5 mm,the correlation coefficient between them is over 0.95,and the RMSE between W_(BD) and W_(GPS-P) is smaller than that between W_(bd) and W_(GPS-G),which means that the retrieve method has certain influence on results of PWV.The RMSE between W_(BD) and W_(GPS-Radio) is about 3.6 mm,the correlation coefficient between them is over 0.96,and W_(BD) is on the high side compared with W_(GPS-Radio).W_(BD) can well reflect the temporal changing characteristics of water vapor in the atmosphere and has corresponding relations with precipitation,which plays an important role in short-term weather forecast and climate analysis.The accuracy of W_(BD) relies much on the precise ephemeris of Beidou.With the development of the Beidou Navigation Satellite System,the accuracy of PWV based on Beidou observations can surpass that based on GPS observations.Therefore,making the best of the Beidou Navigation Statellite System and improving meteorological service with W_(BD) is important for the modernization of meteorology.