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Troposphere gradients from the ECMWF in VLBI analysis

Abstract

Modeling path delays in the neutral atmosphere for the analysis of Very Long Baseline Interferometry (VLBI) observations has been improved significantly in recent years by the use of elevation-dependent mapping functions based on data from numerical weather models. In this paper, we present a fast way of extracting both, hydrostatic and wet, linear horizontal gradients for the troposphere from data of the European Centre for Medium-range Weather Forecasts (ECMWF) model, as it is realized at the Vienna University of Technology on a routine basis for all stations of the International GNSS (Global Navigation Satellite Systems) Service (IGS) and International VLBI Service for Geodesy and Astrometry (IVS) stations. This approach only uses information about the refractivity gradients at the site vertical, but no information from the line-of-sight. VLBI analysis of the CONT02 and CONT05 campaigns, as well as all IVS-R1 and IVS-R4 sessions in the first half of 2006, shows that fixing these a priori gradients improves the repeatability for 74% (40 out of 54) of the VLBI baseline lengths compared to fixing zero or constant a priori gradients, and improves the repeatability for the majority of baselines compared to estimating 24-h offsets for the gradients. Only if 6-h offsets are estimated, the baseline length repeatabilities significantly improve, no matter which a priori gradients are used.

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References

  • Boehm J, Schuh H (2001) Spherical harmonics as a supplement to global tropospheric mapping functions and horizontal gradients. In: Behrend D, Rius A (eds). Proceedings of the 15th working meeting on European VLBI for geodesy and astrometry. Institut d’Estudis Espacials de Catalunya, Barcelona, Spain, pp 143–148

    Google Scholar 

  • Boehm J, Ess M, Schuh H (2005) Asymmetric mapping functions for CONT02 from ECMWF. In: Vennebusch M, Nothnagel A (eds) Proceedings of the 17th working meeting on European VLBI for geodesy and astrometry. Istituto di Radioastronomia, Noto Italy, pp 64–68

    Google Scholar 

  • Boehm J, Werl B, Schuh H (2006) Troposphere mapping functions for GPS and very long baseline interferometry from European Centre for Medium-Range Weather Forecasts operational analysis data. J Geophys Res 111:B02406. doi:10.129/2005JB003629

    Article  Google Scholar 

  • Chen G, Herring TA (1997) Effects of atmospheric azimuthal asymmetry on the analysis from space geodetic data. J Geophys Res 102(B9):20489–20502

    Article  Google Scholar 

  • Davis JL, Herring TA, Shapiro II, Rogers AEE, Elgered G (1985) Geodesy by radio interferometry: effects of atmospheric modelling errors on estimates of baseline length. Radio Sci 20(6):1593–1607

    Google Scholar 

  • Davis JL, Elgered G, Niell AE, Kuehn CE (1993) Ground-based measurements of the gradients in the ‘wet’ radio refractivity of air. Radio Sci 28(6):1003–1018

    Google Scholar 

  • Haas R, Nothnagel A, Schuh H, Titov O (1999) Explanatory supplement to the section ‘Antenna Deformation’ of the IERS conventions (1996) DGFI report no. 71, Deutsches Geodätisches Forschungsinstitut (DGFI), Munich, pp 26–29

  • MacMillan DS (1995) Atmospheric gradients from very long baseline interferometry observations. Geophys Res Lett 22(9):1041–1044

    Article  Google Scholar 

  • MacMillan DS, Ma C (1997) Atmospheric gradients and the VLBI terrestrial and celestial reference frames. Geophys Res Lett 24(4):453–456

    Article  Google Scholar 

  • Niell AE (1996) Global mapping functions for the atmosphere delay at radio wavelengths. J Geophys Res 101(B2):3227–3246

    Article  Google Scholar 

  • Niell AE (2001) An a priori hydrostatic gradient model for atmospheric delay. In: Behrend D, Rius A (eds) Proceedings of the 15th working meeting on European VLBI for geodesy and astrometry. Institut d’Estudis Espacials de Catalunya, Barcelona Spain, pp 133–136

    Google Scholar 

  • Niell AE (2006) Interaction of atmosphere modeling and analysis strategy. In: Behrend D, Baver KD (eds) Proceedings of IVS 2006 general meeting, NASA/CP-2006

  • Petrov L, Boy JP (2004) Study of the atmospheric pressure loading signal in VLBI observations. J Geophys Res 109, No. B03405. doi:10.1029/2003JB002500

  • Ray R (1999) A global ocean tide model from TOPEX/Poseidon Altimetry/GOT99.2 – NASA/TM-1999-209478, Goddard Space Flight Center/NASA, Greenbelt

  • Scherneck HG (1991) A parameterized solid earth tide model and ocean tide loading effects for global geodetic baseline measurements. Geophys J Int 106:677–694

    Article  Google Scholar 

  • Schlueter W, Himwich E, Nothnagel A, Vandenberg NR, Whitney A (2002) IVS and its important role in the maintenance of the global reference systems. Adv Space Res 30(2):145–150

    Article  Google Scholar 

  • Schubert SD, Rood RB, Pfaendtner J (1994) An assimilated data set for earth science applications. Bull Am Meteor Soc 74:2331–2342

    Article  Google Scholar 

  • Titov O, Tesmer V, Boehm J (2004) OCCAM v. 6.0 software for VLBI data analysis. In: Vandenberg NR, Baver KD (eds) Proceedings of international VLBI service for geodesy and astrometry 2004 general meeting, NASA/CP-2004–212255

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Correspondence to Johannes Boehm.

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Boehm, J., Schuh, H. Troposphere gradients from the ECMWF in VLBI analysis. J Geod 81, 403–408 (2007). https://doi.org/10.1007/s00190-007-0144-2

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  • DOI: https://doi.org/10.1007/s00190-007-0144-2

Keywords

  • Troposphere modeling
  • Troposphere gradients
  • VLBI
  • ECMWF