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  • 1 Institute of Geodesy and Geophysics, University of Technology Vienna, Austria
  • 2 Institute of Geodesy and Geophysics, University of Technology Please ask the editor of the journal.
  • 3 Institute of Geodesy and Geophysics, University of Technology Please ask the editor of the journal.
  • 4 Institute of Geodesy and Geophysics, University of Technology Please ask the editor of the journal.
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VLBI observations at various stations all over the globe have been carried out since the beginning of the eighties. As VLBI allows to determine tropospheric parameters such as hydrostatic and wet zenith path delays stable and long time series of these parameters exist that can be used for climatological studies. From the wet zenith delays information about trends and periodic variations of the amount of water vapour in the troposphere can be obtained. For example a trend of ~+0.7 mm/year in the wet zenith delay will correspond to a trend of ~ +0.1 mm/year in precipitable water. For assessing the reliability of the linear trends and the amplitudes of annual and semiannual components, data from VLBI, GPS, and the ECMWF (European Centre for Medium-Range Weather Forecasts) were compared. Good agreement was found for the seasonal variations, though the linear trends showed some disagreement. Possible reasons for this disagreement are discussed. Finally, the effect of El Niño events on tropospheric mapping functions and on length-of-day time series is shown.

  • Boehm J, Schuh H 2004: Geophys. Res. Lett., 31, L01603, DOI:10.1029/2003GL018984.

    () 31 Geophys. Res. Lett. : L01603.

  • Boehm J, Schuh H, Tesmer V, Schmitz-Huebsch H 2003: In: Proceedings of the 16th Working Meeting on European VLBI for Geodesy and Astrometry. Verlag des Bundesamtes für Kartographie und Geodaesie, Leipzig, 237-245.

    , , .

  • Niell A E 1996: J. Geoph. Res., 101, 3227-3246.

    () 101 J. Geoph. Res. : 3227 -3246.

  • Niell A E 2001: Physics and Chemistry of the Earth, 26, 475-480.

    () 26 Physics and Chemistry of the Earth : 475 -480.

  • Niell A E, Coster A J, Solheim F S, Mendes V B, Toor P C, Langley R B, Upham C A 2001: J. Atm. Oceanic Techn., 18, 830-850.

    () 18 J. Atm. Oceanic Techn. : 830 -850.

  • Roberts D H, Lehar J, Dreher J W 1987: The Astronomical Journal, 93, 968-989.

    () 93 The Astronomical Journal : 968 -989.

  • Thompson A R, Moran J M, Swenson jr G W 2001: Interferometry and synthesis in radio astronomy. John Wiley and sons

    Interferometry and synthesis in radio astronomy , ().

  • Titov O, Tesmer V, Boehm J 2001: In: AUSLIG Technical Report, 7, AUSLIG, Canberra