Talks and Poster Presentations (with Proceedings-Entry):

E. Fragner:
"Estimation of the integrated water vapor from GNSS data over the Austrian territory";
Poster: 4th Oersted International Science Team Conference (OIST-4), Kopenhagen; 2002-09-23 - 2002-09-27; in: "OIST-4", Kopenhagen (2002), ISBN: 87-7478-484-6; 241 - 244.

English abstract:
GPS has become an important tool both in navigation and in precise point positioning. So far, the water vapor content of the troposphere was considered as one of the limiting error sources. In view of the interest of meteorologists in the wet component of the troposphere as a valuable tool for Numerical Weather Prediction, the potential of ground based GPS measurements for estimating tropospheric water vapor has been demonstrated by several projects e.g. MAGIC , COST-716. Nowadays the accuracy of water vapor estimates based on microwave data is comparable to radiosonde and radiometer data. Compared to these measurements GPS lacks of vertical resolution but offers a low cost monitoring of water vapor with high temporal resolution.

We make use of the continuous measurements of the GPS/GLONASS reference station network in Austria extended with surrounding stations of the IGS and EUREF-network. Currently the network under consideration consists of about 25 sites with a distance of 50 - 120 km. We calculate the zenith wet delays for a period of 7 days in February 2002. Subsequently the results will be compared to contributions of different processing centers of the COST-716 project "Exploitation of Ground Based GPS for Climate and NWP" and with zenith path delay estimates provided by the IGS. Special attention is paid on the use of rapid ephemeris instead of the IGS final orbits. Furthermore we investigate the impact of additional GLONASS data in terms of improving the amount and distribution of the observation data. On the other hand we have to keep in mind that GLONASS data might harm the estimates due to imperfect available satellite orbits.

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