Analyzing the Variation of Precipitable Water Vapor with Ground-Based GPS Over Taiwan

Water vapor plays an important role in weather prediction. Thus, it would be helpful to use Precipitable Water Vapor (PWV) data from Global Positioning System (GPS) signals to understand weather phenomena. Approximately 100 ground GPS stations that cooperate with approximately 500 ground weather stations were used in this study. The hourly Zenithal Wet Delay (ZWD) values during the observation period of between 2006 and 2011 were estimated. The PWV which was converted from the ZWD variations were compared with the rainfall observations. The results indicated that the PWV amplitudes were between 10.98 and 13.10 mm and always occurred at the end of July. The magnitudes of the PWV annual growth rate were between 0.68 and 0.83 mm/year. Although the end of July with the greatest monthly average PWV values, the rainfall magnitude on this period is smaller than that during the typhoons, which only occurred for a few days. The PWV also increased during typhoons. Because this affect was short-term, it did not contribute to the PWV monthly average seriously.