Global Atmospheric Data From Champ And Grace-A: Overview And Results

The German geoscience satellite CHAMP (CHAllenging Minisatellite Payload) provides global atmospheric measurements almost continuously since early 2001. It currently generates a unique and operationally available long-term set of GPS radio occultation (RO) data. RO data from the US-German GRACE-A satellite (Gravity Recovery and Climate Experiment) are in addition operationally available since May 22, 2006. Data and analysis results from both satellites are provided to the international scientific community and stimulated several activities to improve GPS RO data analysis and the application in atmospheric research and for global weather forecasts. The data are currently in use by more than 40 research groups worldwide. A near-real time data provision from CHAMP and GRACE was installed and is demonstrated by GFZ within the GEOTECHNOLOGIEN research project NRT-RO (Near-Real-Time Radio Occultation) funded by the German Federal Ministry of Education and Research (BMBF). An average delay between measurement aboard the satellites and provision of corresponding analysis results below 2 h is operationally reached. This successful research activity was one of the preconditions for the beginning of the operational GPS RO data use to improve global weather forecasts in 2006 by Met Office and ECMWF (European Centre for Medium-Range Weather Forecasts). This result is a milestone and a breakthrough for the acceptance of the innovative GPS RO data in Numerical Weather Prediction (NWP).