Research On Ground-based GPS Atmospheric Water Vapor Retrieval And Water Vapor Tomography

GPS meteorology theory has made it possible to detect the atmospheric water vapor by the ground-based GPS,whose network and continuous GPS sites provide the good conditions for the ground-based GPS water vapor retrieval.GPS meteorology is stepping into the operational application stage from the research.So the ground-based GPS vapor retrieval accuracy and the meteorological application and the three-dimensional water vapor density accuracy have been the research hot-spots.According to the above contents,this thesis carries out an experiment of the ground-based GPS water vapor retrieval with data from continuous GPS sites and NCEP materials in Hong Kong.1.Based on the NCEP materials from Oct 2014 to Oct 2016 in Hong Kong,this thesis established the weighted mean temperature local model.The weighted mean temperature bias is 3.4 degree calculated by local model in Oct and the PWV bias is 1mm.2.This thesis found terrain fit using GSP sites with cubic equation model bias is little,but the other sites have a high bias.So the model of terrain fit should be determined by actual terrain and the equation of 2-degree is best for Hong Kong.According to the studying,this thesis found that plane gradient factors improved little accuracy of PWV results.3.The thesis established PWV fit using terrain fit model and found that when the terrain fit model bias is under 1km the PWV bias could be under 1mm.The whole day sequentially pictures based terrain fit show that the PWV fit not only has good results but also could be judged the trend and variation of water vapor obviously.4.According to the height difference problem based on traditional vertical stratification method using flats,this thesis proposed a new method of three-dimensional water vapor using surface,and take a comparison from the time of filter,the length of plane grid and the model of surface fit.The results have been improved under 3km and above 6km using the three-dimensional water vapor based on surface fit compared traditional method,but the accuracy between 3kmand 6km is decayed.At last the thesis proposed the combination method to calculate the three-dimensional water vapor density,the results show that the accuracy and correlation have been improved.