GFZ has started together with other large research centers of the German Helmholtz Association the "GPS Atmosphere Sounding" Project (GASP) on using ground-based (Subproject 1) and space-based (Subproject 2) GPS observations for applications in numerical weather prediction, climate research and space weather monitoring. Operational precision determination of water vapor in near real-time within dense German GPS network (~ 70 sites) is being carried out since May 2000 and has demonstrated an accuracy of better than 2 mm with a standard deviation at the level of better than +- 1 mm. The results are validated regulary with the local weather model LM1 of German Weather Service. Assimilation studies are in preparation. Space-based GPS sounding of the atmosphere and ionosphere is entering a new era with the German CHAMP sattelite: CHAMP is the first mission aiming at the quasi-continous monitoring of the atmosphere with GPS. Launched last summer, the satellite has only recently delivered its first set of atmospheric data. Once in full operation, CHAMP will deliver about 200-250 daily vertical profiles of temperature, tropospheric humidity and ionospheric electron content. Some first results and intercomparisons will be presented.

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Reigber, C.; Gendt, G.; Marquardt, C.; Dick, G.; Wickert, J. (2001): GASP -. APSG Meeting.