Research On The Establishment Of Tropospheric Key Parameter Fusion Model And Its Applications

The troposphere is an important part of the geospatial environment and is closely related to human life.Tropospheric delay is a major source of error in space geodetic techniques and also an important meteorological signal associated with water vapor.Water vapor is the indicator of precipitation,evaporation and humidity balance and other related weather processes in the troposphere.It plays an extremely significant role in global atmospheric radiation,energy balance and water cycle and is closely linked with various weather phenomena and global climate events.Tropospheric delay and water vapor are two key parameters in the troposphere.However,many established tropospheric models are based on a single data source.Thus the spatio-temporal resolution and precision of these models are limited.Therefore,the establishment of tropospheric key parameter fusion model with higher precision and higher resolution and the study of its application in meteorology is an crucial issues of space geodetic technology.Moreover,they have important implications for related geoscience and meteorological science research.Under the above background,this paper first analyzes the principles and characteristics of the existing tropospheric delay model and water vapor monitoring measurements.This paper mainly focuses on some aspects as establishment of the multi-source high-precision zenith tropospheric delay(ZTD)model,the establishment of multi-source high-precision water vapor model,and the application of key tropospheric parameters in meteorological events:In this paper,a multi-source real-time tropospheric delay fusion model based on ground-based GNSS observation data,meteorological data and empirical model GPT2 w is proposed.The model coefficients as well as the system difference between the three models are estimated as parameters by the least squares method.The results show that: In Hong Kong,the ZTD derived from the tropospheric delay fusion model has an accuracy of 1.48 cm in the active troposphere period and 1.45 cm in the quiet troposphere period,which is significantly better than the traditional tropospheric GPT2 w and Saastamoinen models.Compared with GNSS models,it reaches higher spatial resolution but needs lower cost.In Zhejiang province,the ZTD estimated by the fusion model has an accuracy of 1.04 cm during the active troposphere period,0.96 cm during the quiet troposphere period,and 3.11 cm during the typhoon period,which is equivalent to the accuracy of GNSS tropospheric delay.Compared to the empirical model,the accuracy of the fusion model is improved by 2-5 cm.This paper build up a regional PWV fusion model with Gaussian Processes(GP)method using the water vapor data(Precipitable water vapor(PWV))provided by GNSS,the European Centre for Medium-range Weather Forecasts(ECMWF)and the radiosonde.The results show that: in Hong Kong,by combining GNSS and ECMWF water vapor data,the accuracy of PWV fusion is 3.87 mm in the active troposphere period and 3.97 mm in the quiet troposphere period,which show a 1.89 mm and 2.61 mm improvement than ECMWFPWV products.During the typhoon transit period in Japan,the PWV fusion model has an mean bias of 1.62 mm and mean RMS of 4.90 mm.The accuracy is improved by 1.57 mm than that of the ECMWF water vapor product(mean bias 1.10 is mm,mean RMS is 6.47 mm).Through the multi-source water vapor model established in this paper,the spatial and temporal distribution of PWV in Hong Kong and Japan is analyzed.It is found that the spatial distribution of water vapor content is closely related to the monsoon and typhoon,especially the wind speed and wind direction.Moreover,there is obvious cumulative process of water vapor before the strong convective precipitation caused by typhoon.The overall PWV time series showed a trend of increasing first and then decreasing.In conclusion,the variation of PWV has a good correspondence with the precipitation process.