GPS Radio Occultation with CHAMP: Comparison of Atmospheric Profiles from GFZ Potsdam and IGAM Graz

A major application of the CHAMP occultation data is the preparation of processing systems for future occultation missions. The University of Graz (IGAM) uses data and analysis results to prepare for the ACE+ multi-satellite occultation mission, which is currently foreseen to be launched in 2008. We compare vertical profiles of refractivity, derived by GFZ and IGAM, with ECMWF data (European Centre for Medium-Range Weather Forecasts) and discuss the deviations. Good agreement is observed in the upper troposphere and stratosphere. The magnitude of the observed refractivity bias in the lower troposphere depends significantly on the quality control criterion. The bias can be nearly eliminated by the application of the Full Spectrum Inversion analysis method down to ∼1 km above the Earth's surface.