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Refractivity Biases in GNSS Occultation Data

  • G. Beyerle
  • S. Heise
  • J. Kaschenz
  • G. König-Langlo
  • C. Reigber
  • T. Schmidt
  • J. Wickert

Abstract

An analysis of atmospheric refractivity profiles observed by the georesearch satellite CHAMP between May 2001 and October 2004 reveals a negative bias compared to ECMWF meteorological fields at altitudes below 5 km. In order to separate bias contributions caused by critical refraction from contributions induced by the receiver tracking process a comprehensive end-to-end simulation study was performed. The simulations are based on radiosonde profiles obtained aboard research vessel “POLARSTERN”. Within a subset of 3039 profiles recorded on the Atlantic Ocean between 60°N and 60°S, 1202 profiles (39.6%) are found with vertical refractivity gradients below the threshold value of −157 km−1. Critical refraction layers occur mainly between 1 km and 2.5 km altitude, above 3 km the occurrence of critical refraction can be disregarded. End-to-end simulations using these 3039 refractivity profiles confirm that four quadrant carrier phase extraction outperforms the two quadrant method currently implemented on CHAMP. Within regions of low signal-to-noise ratios “open-loop” tracking methods yield improvements with respect to the current “fly-wheeling” method.

Keywords

Global Position System Phase Noise Radio Occultation Radio Occultation Data Global Position System Radio Occultation 
These keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.

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Copyright information

© Springer-Verlag Berlin Heidelberg 2006

Authors and Affiliations

  • G. Beyerle
    • 1
  • S. Heise
    • 1
  • J. Kaschenz
    • 1
  • G. König-Langlo
    • 2
  • C. Reigber
    • 1
  • T. Schmidt
    • 1
  • J. Wickert
    • 1
  1. 1.Deptartment 1, Geodesy & Remote SensingGeoForschungsZentrum Potsdam (GFZ)PotsdamGermany
  2. 2.Alfred Wegener Institute for Polar and Marine ResearchBremerhavenGermany

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