Research On Method Of Real-time Retrieval Of Precipitable Water Vapor

Water vapor,as the complex and active part of the atmosphere,contributes a lot to the weather change.So the continuous and real-time monitoring to the water vapor can significantly improve the accuracy of the weather forecast in the short or medium term,and accumulate enormous essential data for the research of atmospheric circulation as well.Compared with the traditional detecting methods,GNSS provides a new way for the retrieval of precipitable water vapor(PWV),which is low-cost,high-resolution and free from the influence of weather changing.Therefore,this technology has been widely used in the meteorological department.This paper mainly focuses on the real-time sensing of water vapor and the atmosphere-related models.Main contents and conclusions are as follows:1.Based on the real-time precise point positioning(RT-PPP)technique,the research on the method of real-time retrieval of PWV is carried out in depth.Besides,the accuracy of PWV derived from GNSS observations is carefully analysed.2.With SuomiNet GPS measurements and synchronous meteorological observations,this paper assesses the performance of involving GPT or GPT2 model into the process of PWV estimating.The results show that the RMS values of GPT and GPT2 are 1.3 millimeter and 1.6 millimeter respectively.3.Because many existing weighted mean temperature models are built based on the regional radiosonde data and these models are just simply linear models which may involve obvious errors in certain areas,this paper proposes a new weighted mean temperature model using the ECMWF reanalyzed data.This model considers the annual and semi-annual variations,and has the RMS values of about 2.2K and 3.63 K when it is verified by ECMWF and GGOS integrated data respectively.4.GNSS observations of one month period for three stations from the International GNSS Service Multi-GNSS Experiment are processed using post precise point positioning technique.The accuracy of zenith total delay(ZTD)derived from GPS-only,BeiDou-only,GLONASS-only and combined GPS/BeiDou/GLONASS observations is investigated.The results show that the RMS values of retrieved ZTD for them in comparison with the IGS ZTD are 8.5mm,17.5 mm,9.7 mm and 8.6 mm separately.Then the accuracy of real-time ZTD derived from 20 globally distributed IGS stations using RT-PPP is evaluated as well.The RMS values of real-time ZTD derived from GPS observations are 9.84 mm and 6.45 mm respectively in comparison with IGS ZTD and post-PPP ZTD.