A comparison of precipitable water vapor obtained from GPS and radiosonde

In order to account for the validity of precipitable water vapor (PWV) obtained from Global Positioning System (GPS), we compared PWV obtained from GPS (GPS_PWV) and that obtained from radiosonde (SONDE PWV). We used radiosonde data from 14 stations in Japan, and also GPS data of GEONET stations established by Geographical Survey Institute (GSI) near radiosonde stations during January 1999 and December 2000 in the present investigation. The antenna phase center of GEONET. Varies by elevation angle of microwave path from GPS satellites, and we applied an antenna specific phase characteristic model to the GPS_PWV. When we estimated GPS_PWV without the antenna specific phase characteristic model, average difference between GPS_PWV and SONDE_PWV (GPS_PWV-SONDE_PWV : PWV difference) was -3.7mm. This average PWV difference varied by each antenna/monument type. On the other hand, when we estimated GPS_PWV with the antenna specific phase characteristic model, it decreased to 1.8mm. This PWV difference did not vary by antenna/ monument type. We also compared two kinds of PWV at 00UTC and those at 12UTC. At 12UTC, GPS_PWV was usually lower than SONDE_PWV when PWV increased. When it is rainy or very humid, GPS_PWV tended to be much lower than SONDE_PWV. This tendency was caused by the fact that the sensor of the , hygrometer of radiosonde was wet. Finally, we investigated a relationship between PWV difference and distance between \u27 GPS station and the position of radiosonde, but could not find a clear correlation between them.publishe