Global Atmospheric Sounding with GPS Radio Occultation aboard CHAMP

  • Jens Wickert
  • Torsten Schmidt
  • Georg Beyerle
  • Stefan Heise
  • Christoph Reigber


The German CHAMP (CHAllenging Minisatellite Payload) satellite provides continuously GPS radio occultation data since February 2001. The measurements are analyzed by an operational satellite orbit and occultation processing system at GFZ. In total, more than 200,000 precise globally distributed vertical profiles of refractivity, temperature and water vapor are provided as of June 2005. The operational ground infrastructure from GFZ allows for the demonstration of a rapid data analysis since February 2003. A mean delay between measurement and provision of atmospheric excess phase data of ∼4 hours is continuously reached. Results of various validation studies with data from meteorological analyzes of the European Centre for Medium-Range Weather Forecasts (ECMWF) and the global radiosonde network indicate an excellent quality of the CHAMP data. But in the lower troposphere systematic deviations are observed, the known negative refractivity bias of the occultation data. It is most pronounced in the Tropics and is also observed by other GPS occultation instruments. The CHAMP data stimulated a number of studies to investigate the observed bias and to improve the GPS occultation data quality in the lower troposphere. First radio occultation measurements from the GRACE-B (Gravity Recovery And Climate Experiment) satellite are available for a 25 h period on July 28/29, 2004.

Key words

GPS radio occultation CHAMP GRACE atmospheric profiling 


Unable to display preview. Download preview PDF.

Unable to display preview. Download preview PDF.


  1. Ao, C. O., T. K. Meehan, G. A. Hajj, A. J. Mannucci, and G. Beyerle, Lower-troposphere refractivity bias in GPS occultation retrievals, J. Geophys. Res., 108(D18), doi:10.1029/2002JD003,216, 2003a.Google Scholar
  2. Ao, C. O., W. B. Schreiner, and J. Wickert, First report on the CHAMP radio occultation intercomparison study, JPL Publication, 03-016, 2003b.Google Scholar
  3. Beyerle, G., M. E. Gorbunov, and C. O. Ao, Simulation studies of GPS radio occultation measurements, Radio Sci., 38(5), doi:10.1029/2002RS002,800, 2003a.Google Scholar
  4. Beyerle, G., J. Wickert, T. Schmidt, and C. Reigber, Atmospheric sounding by GNSS radio occultation: An analysis of the negative refractivity bias using CHAMP observations, J. Geophys. Res., p. doi:10.1029/2003JD003922, 2003b.Google Scholar
  5. Beyerle, G., T. Schmidt, G. Michalak, J. Wickert, and C. Reigber, GPS radio occultation with GRACE: Atmospheric profiling utilizing the zero difference technique, Geophys. Res. Lett., in print, 2005a.Google Scholar
  6. Beyerle, G., T. Schmidt, J. Wickert, S. Heise, C. Reigber, and G. König-Langlo, An analysis of refractivity biases detected in GPS radio occultation data: Results from simulation studies, aerological soundings and CHAMP satellite observations, paper available via, 2005b.Google Scholar
  7. Dunn, C., et al., Instrument of GRACE-GPS Augments Gravity Measurements, GPS World, Feb. 1, 2003.Google Scholar
  8. Foelsche, U., G. Kirchengast, A. Gobiet, A. Steiner, A. Löscher, J. Wickert, and T. Schmidt, The CHAMPCLIM project: An overview, in Earth Observation with CHAMP: Results from Three Years in Orbit, edited by C. Reigber, P. Schwintzer, H. Lühr, and J. Wickert, pp. 615–620, Springer Verlag, 2005.Google Scholar
  9. Gobiet, A., U. Foelsche, A. Steiner, M. Borsche, G. Kirchengast, and J. Wickert, Validation of stratospheric temperatures in ECMWF operational analyses with CHAMP radio occultation data, Geophys. Res. Lett., 32(12), doi:10.1029/2005GL022,617, 2005.Google Scholar
  10. Hajj, G. A., L. C. Lee, X. Pi, L. J. Romans, W. S. Schreiner, P. R. Straus, and C. Wang, COSMIC GPS ionospheric sensing and space weather, Terrestrial, Atmospheric and Oceanic Science, 11, 2000.Google Scholar
  11. Hajj, G. A., et al., CHAMP and SAC-C atmospheric occultation results and intercomparisons, J. Geophys. Res., 109(D06109), doi:10.1029/2003JD003,909, 2004.Google Scholar
  12. Healy, S., and J. Eyre, Retrieving temperature, water vapor and surface pressure information from refractive-index profiles derived by radio occultation: A simulation study, Quart. J. Roy. Meteorol. Soc., 126, 1661–1683, 2000.CrossRefGoogle Scholar
  13. Healy, S., A. Jupp, and C. Marquardt, Forecast impact experiment with gps radio occultation measurements, Geophys. Res. Lett., 32(3), doi: 10.1029/2004GL020,806, 2005.Google Scholar
  14. Healy, S. B., and J.-N. Thepaut, Assimilation experiments with CHAMP GPS radio occultation measurements, Q. J. R. Meteorol. Soc., subm., 2005.Google Scholar
  15. Heise, S., J. Wickert, G. Beyerle, T. Schmidt, and C. Reigber, Global monitoring of tropospheric water vapor with GPS radio occultation aboard CHAMP, Adv. Space Res., in print, 2005.Google Scholar
  16. Jakowski, N., A. Wehrenpfennig, S. Heise, C. Reigber, H. Lühr, L. Grunwaldt, and T. K. Meehan, GPS radio occultation measurements of the ionosphere from CHAMP: Early results, Geophys. Res. Lett., 29(10), doi:10.1029/2002RS002763, 2002.Google Scholar
  17. König, R., G. Michalak, and K. Neumayer, Remarks on champ orbit products, in Observation of the Earth System from Space, edited by R. Rummel, C. Reigber, M. Rothacher, G. Boedecker, U. Schreiber, and J. Flury, Springer Verlag, 2005a.Google Scholar
  18. König, R., G. Michalak, K. Neumayer, R. Schmidt, S. Zhu, H. Meixner, and C. Reigber, Recent developments in CHAMP orbit determination at GFZ, in Earth Observation with CHAMP: Results from Three Years in Orbit, edited by C. Reigber, P. Schwintzer, H. Lühr, and J. Wickert, Springer Verlag, 2005b.Google Scholar
  19. Kuo, Y.-H., S. V. Sokolovskiy, R. A. Anthes, and F. Vandenberghe, Assimilation of GPS radio occultation data for numerical weather prediction, Terrestrial, Atmospheric and Oceanic Sciences, 11(1), 157–186, 2000.Google Scholar
  20. Kuo, Y.-H., T.-K. Wee, S. Sokolovskiy, C. Rocken, W. Schreiner, D. Hunt, and R. A. Anthes, Inversion and error estimation of GPS radio occultation data, J. Meteorol. Soc. Jpn., 1B(82), 507–531, 2004.CrossRefGoogle Scholar
  21. Kuo, Y.-H., W. S. Schreiner, J. Wang, D. L. Rossiter, and Y. Zhang, Comparison of GPS Radio occultation soundings with radiosondes, Geophys. Res. Lett., 32, l05817, doi:10.1029/2004GL021443, 2005.Google Scholar
  22. Kursinski, E. R., G. A. Hajj, J. T. Schofield, R. P. Linfield, and K. R. Hardy, Observing Earth’s atmosphere with radio occultation measurements using Global Positioning System, J. Geophys. Res., 19(D19), 23,429–23,465, 1997.Google Scholar
  23. Larsen, G., K. Lauritsen, F. Rubek, and M. Sørensen, Processing of CHAMP radio occultation data using GRAS SAF software, in Earth Observation with CHAMP: Results from Three Years in Orbit, edited by C. Reigber, P. Schwintzer, H. Lühr, and J. Wickert, pp. 543–548, Springer Verlag, 2005.Google Scholar
  24. Loiselet, M., N. Stricker, Y. Menard, and J. Luntama, GRAS — MetOps GPS based atmospheric sounder, ESA Bulletin, May, 102, 38–44, 2000.Google Scholar
  25. Marquardt, C., K. Schöllhammer, G. Beyerle, T. Schmidt, J. Wickert, and C. Reigber, Validation and data quality of CHAMP radio occultation data, in First CHAMP Mission Results for Gravity, Magnetic and Atmospheric Studies, pp. 384–396, Springer Verlag, 2003.Google Scholar
  26. Randel, W. J., F. Wu, and W. R. Rios, Thermal variability of the tropical tropopause region derived from GPS/MET observations, J. Geophys. Res., 108(4024), doi: doi:10.1029/2002JD002595, 2003.Google Scholar
  27. Reigber, C., P. Schwintzer, H. Lühr, and J. Wickert (Eds.), Earth Observation with CHAMP: Results from Three Years in Orbit, Springer Verlag, 2005.Google Scholar
  28. Rocken, C., Y.-H. Kuo, W. Schreiner, D. Hunt, S. Sokolovskiy, and C. McCormick, COSMIC system description, Terrestrial, Atmospheric and Oceanic Sciences, 11, 21–52, 2000.Google Scholar
  29. Rocken, C., et al., Analysis and validation of GPS/MET data in the neutral atmosphere, J. Geophys. Res., 102(D25), 29,849–29,866, 1997.CrossRefGoogle Scholar
  30. Sausen, R., and B. Santer, Use of changes in tropopause height to detect human influences on climate, Met. Zeitschrift, 12(3), 131–136, 2003.CrossRefGoogle Scholar
  31. Schmidt, T., J. Wickert, G. Beyerle, and C. Reigber, Tropical tropopause parameters derived from GPS radio occultation measurements with CHAMP, J. Geophys. Res., 109(D13105), doi:10.1029/2004JD004566, 2004.Google Scholar
  32. Schmidt, T., S. Heise, J. Wickert, G. Beyerle, and C. Reigber, GPS radio occultation with CHAMP and SAC-C: global monitoring of thermal tropopause parameters, Atmosph. Chemistry and Physics, 5, 1473–1488, 2005a.CrossRefGoogle Scholar
  33. Schmidt, T., J. Wickert, G. Beyerle, R. König, R. Galas, and C. Reigber, The CHAMP atmospheric processing system for Radio occultation measurements, in Earth Observation with CHAMP: Results from Three Years in Orbit, edited by C. Reigber, P. Schwintzer, H. Lühr, and J. Wickert, Springer Verlag, 2005b.Google Scholar
  34. Sokolovskiy, S. V., Tracking tropospheric radio occultation signals from low Earth orbit, Radio Sci., 36(3), 483–498, 2001.CrossRefGoogle Scholar
  35. Takahashi, H., et al., Scientific satellite EQUARS for remote sensing of the equatorial atmosphere, 7th Latin-American Conference on Space Geophysics, Atibaia, April, 2004.Google Scholar
  36. Tapley, B., and C. Reigber, GRACE (Gravity Recovery and Climate Experiment), in McGraw-Hill Yearbook of Science & Technology, 2004.Google Scholar
  37. Tett, S., et al., Estimation of natural and anthropogenic contributions to twentieth century temperature change, JGR, 107, 4306, 10.1029/2000JD000,028, 2002.CrossRefGoogle Scholar
  38. v. Engeln, A., J. Teixeira, J. Wickert, and S. Buehler, Detecting the planetary boundary layer using CHAMP data, Geophys. Res. Lett., 32, doi:10.1029/2004GL022,168, 2005.Google Scholar
  39. Wang, D. Y., et al., Cross-validation of MIPAS/ENVISAT and GPS-RO/CHAMP temperature profiles, J. Geophys. Res., 109, doi:10.1029/2004JD004963, 2004.Google Scholar
  40. Ware, R., et al., GPS sounding of the atmosphere from low Earth orbit: Preliminary results, Bull. Am. Meteorol. Soc., 77(1), 19–40, 1996.CrossRefGoogle Scholar
  41. Wickert, J., The CHAMP radio occultation experiment: Algorithms, Processing system, and First results (in German), Scientific Technical Report 02/07, GFZ Potsdam, 2002.Google Scholar
  42. Wickert, J., Comparison of vertical refractivity and temperature profiles from CHAMP with radiosonde measurements, Scientific Technical Report 04/19, GFZ Potsdam, ISSN 1610-0956, 2004.Google Scholar
  43. Wickert, J., A. Pavelyev, Y. A. Liou, T. Schmidt, C. Reigber, A. Pavelyev, K. Igarashi, and S. Matyugov, Amplitude variations in the GPS signals as a possible indicator of the ionospheric structures, Geophys. Res. Lett., 31, l24801, doi:10.1029/2004GL020607, 2004a.CrossRefGoogle Scholar
  44. Wickert, J., T. Schmidt, G. Beyerle, R. König, C. Reigber, and N. Jakowski, The radio occultation experiment aboard CHAMP: Operational data processing and validation of atmospheric parameters, J. Meteorol. Soc. Jpn., 82(1B), 381–395, 2004b.CrossRefGoogle Scholar
  45. Wickert, J., C. Ao, and W. Schreiner, GPS based atmospheric sounding with CHAMP: Comparison of data analysis and results from GFZ, JPL and UCAR, GFZ Scientific Technical Report, in preparation, Potsdam, 2005a.Google Scholar
  46. Wickert, J., G. Beyerle, R. König, S. Heise, L. Grunwaldt, G. Michalak, C. Reigber, and T. Schmidt, GPS radio occultation with CHAMP and GRACE: A first look at a new and promising satellite configuration for global atmospheric sounding, Ann. Geophysicae, 23(653–658), 2005b.Google Scholar
  47. Wickert, J., T. Schmidt, G. Beyerle, G. Michalak, R. König, S. Heise, and C. Reigber, GPS radio occultation with CHAMP and GRACE: Recent results, in Proc. OPAC-2 workshop, Graz September 2004, edited by G. Kirchengast, U. Foelsche, and A. K. Steiner, Springer Verlag, 2005c.Google Scholar
  48. Wickert, J., et al., Atmosphere sounding by GPS radio occultation: First results from CHAMP, Geophys. Res. Lett., 28(17), 3263–3266, 2001.CrossRefGoogle Scholar

Copyright information

© Springer-Verlag Berlin Heidelberg 2006

Authors and Affiliations

  • Jens Wickert
    • 1
  • Torsten Schmidt
    • 1
  • Georg Beyerle
    • 1
  • Stefan Heise
    • 1
  • Christoph Reigber
    • 1
  1. 1.Department 1, Geodesy & Remote SensingGeoForschungsZentrum Potsdam (GFZ)PotsdamGermany

Personalised recommendations