Retrieval Of Precipitable Water Vapor Using Ground-based Gps Within Extreme Weather

Retrival of atmospheric precipitation water vapor with ground-based GPS inversion atmospheric precipitation water vapor has become hotspot research within GNSS remote sensing application and numerical weather prediction. It has been received much more attenion because of high spatiotemporal resolution, high precision, not being affected by weather conditions as well as real-time monitoring, compared with the traditional methods.The thesis intented to study on the characteristics of GPS precipitation water vapor changes within context of four typhoon events according to GPS satellite reference station network data and weather station data in Hong Kong.Firstly, it introduced basics of ground-based GPS water vapor remote sensing. Atmospheric vertical stratification structure and the characteristics of ground meteorological parameters were described.The methodology of retrieval of precipitable water vapor using ground-based GPS data and its factors were introduced in detail.Then, the precision and applicability of three zenith delay model such as Saastamoinen model, Hopfield model and Black model were evaluated.After comparing the effects of ground meteorological elements on zenith delay model, it provided the schemes for processing pressure and temperature.The result shows some effects appeared in the calculation of zenith tropospheric delay.Moreover, troposphere mapping function was introduced in detail,such as NMF, VMF1 and GMF.Both VMF1 and GMF provided similar precision within context of severe weather.Furthermore, Hong Kong sounding station data were used to build the formula model of weighted mean temperature Tm.The results show that the proposed model can eliminate the periodic error influencing on Bevis formula, and the Tm model based on historical record shows better performance in a long time.According to the relationship between the error of Bevis empirical formula and ground temperature, one piecewise linear correction method was proposed, which can effectively eliminate the periodic error of Bevis empirical formula.Finally, the Hong Kong satellite reference station network data was used to study the characteristics of GPS water vapor changes during four typhoon events.The analysis shows that GPS/PWV has better accuracy and reliability, it can provide effective approach for monitoring of typhoon.In addition, within consideration of temperature, pressure and relative humidity, GPS/PWV is a promising for severe weather forecasting.