Research On Precipitable Water Vapor Retrieval Using Ground-based GPS Data

Water vapor plays a very crucial role in the weather. With the change of time and space it is very important to weather forecasting especially to the monitoring and prediction of meso-scale and micro-scale disastrous weather. We are short of knowledge about the variations and structure of water vapor because of the limited spatio-temporal measurements of routine observing technology. Compared with other observational means, GPS technology provides a new means for sensing water vapor with the advantages of real-time, continuity, high precision, easily maintained and renovated, economical and unaffected by weather et al. GPS/MET has become a front-subject of geodesy and meteorological research at present.Firstly, in this paper we introduced the present research status of GPS/MET at home and abroad. On the basis of research results of predecessors, we detailly analyzed the basic equation of GPS sensing water vapor. Then we introduced the use of GAMIT and the basic processes of data processing, expatiated several models and mapping functions of zenith hydrostatic delay, analyzed the errors of precipitable water vapor retrieval using ground-based GPS data.Secondly, through the test of using GAMIT, we verified the previous findings on quasi-real-time GPS sensing water vapor issues and put forward different solution. Especially for the period, we proved that the best time is 12 hours.Finally, we compared GPS water vapor data with sounding data, they had the same trend of water vapor. Its RMS was 3.49mm.We also analyzed the atmospheric precipitable water vapor at she shan GPS station in August 25, 2008. It suggested that the water vapor content increasing and keeping a higher value foreshadowed the emergence of rainfall process well and maintained good agreement with rainfall process, which had a good indicative significance for rainstorm weather analysis and forecasting.