Advancement of GNSS Radio Occultation Retrieval in the Upper Stratosphere

  • A. Gobiet
  • G. Kirchengast
Chapter

Abstract

Radio occultation (RO) observations promise to become a valuable basis for global climatologies of refractivity, temperature, geopotential height, and humidity in the near future. The continuous RO data stream from the CHAMP and SAC-C missions enables to create such climatologies for the first time. This paper describes two simulation studies designed to evaluate and enhance high altitude RO retrieval algorithms for climate applications. The results showed that the ionospheric correction of bending angles is remarkably robust under various conditions and that proper statistical optimization/high altitude initialization is vital for a good retrieval performance. Biased background information or inappropriate high-altitude initialization can cause biases in the retrieved temperature profiles down to below 20 km. An enhanced high altitude retrieval scheme was developed, focusing on background bias reduction. It proved to be effective applied to a large sample of simulated occultation events especially in the formerly most critical regions. The results show that near bias-free global climatologies (temperature biases <0.5 K between 8 and 35–40 km) based on RO-measurements are feasible. The presented enhanced high altitude retrieval scheme is currently under evaluation with data from the CHAMP mission and will be further developed to finally serve as part of the retrieval chain for creating RO based global climatologies.

Keywords

Covariance Assimilation Hunt Geophysics Lidar 

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Copyright information

© Springer-Verlag Berlin Heidelberg 2004

Authors and Affiliations

  • A. Gobiet
    • 1
  • G. Kirchengast
    • 1
  1. 1.Institute for Geophysics, Astrophysics, and Meteorology (IGAM)University of GrazGrazAustria

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