GPS RADIO OCCULTATION WITH CHAMP AND GRACE: OVERVIEW, RECENT RESULTS AND OUTLOOK TO METOP

摘要

The German geoscience satellite CHAMP (CHAllenging Minisatellite Payload) almost continuously provides global atmospheric measurements since early 2001. It currently generates a unique long-term set of GPS radio occultation (RO) data. Around 400,000 occupation measurements were performed as of May 2006. Currently the mission is expected to last until 2008. Data and analysis results are provided to the international scientific community and stimulated several activities for GPS RO data analysis and application in atmospheric research and weather forecasts. The data are currently in use by more than 40 research groups and are also widely used for the preparation of the GRAS SAF (GNSS Receiver for Atmospheric Sounding Satellite Application Facility). First occultation measurements from the U.S.-German GRACE mission (Gravity Recovery and Climate Experiment) became available mid 2004; a first longer GRACE occultation campaign with duration of one month was performed in January/February 2006. During this campaign a first near-real-time provision of radio occultation data from a small multi-satellite configuration (CHAMP and GRACE-A) with average delay of around 4 hours between measurement and data provision was demonstrated. We review the current status of both occultation missions. Hereby we introduce the operational infrastructure used for space-based atmosphere sounding and characterize in more detail the scientific data analysis of both, neutral gas and ionosphere, occultation measurements at GFZ and DLR. Based on validation results with independent meteorological and ionospheric data we discuss advantages and weaknesses of CHAMP's data. We also present selected scientific results, achieved by analysing the long term data set from CHAMP: climatological studies of global tropopause and gravity wave characteristics. As outlook to the Metop mission we present a research project which was proposed within the announcement of opportunity and is related to the scientific analysis of the GPS occultation data from Metop. This project can contribute to the GRAS calibration/validation activities to ensure a high quality of the derived atmospheric data products from Metop.