Abstract
Abstract. CHAMP (CHAllenging Minisatellite Payload) and GRACE (Gravity Recovery And Climate Experiment) formed a satellite configuration for precise atmospheric sounding during the first activation of the GPS (Global Positioning System) radio occultation experiment aboard GRACE on 28 and 29 July 2004. 338 occultations were recorded aboard both satellites, providing globally distributed vertical profiles of refractivity, temperature and specific humidity. The combined set of CHAMP and GRACE profiles shows excellent agreement with meteorological analysis. Almost no refractivity bias is observed between 5 and 30km, the standard deviation is between 1 and 2% within this altitude interval. The GRACE satellite clock stability is significantly improved in comparison with CHAMP. This allows for the application of a zero difference technique for precise analysis of the GRACE occultation data.
Highlights
Atmospheric scientists are looking forward to the promises that a GPS radio occultation multi-satellite constellation can offer
This deviation is a measure for the water vapor content, itself shows good agreement with European Centre for Medium-Range Weather Forecasts (ECMWF), where larger deviations are observed below 4 km
The Full Spectrum Inversion (FSI) algorithm provides a criterion to cut-off the data at 2.4 km altitude without using auxiliary data for quality control
Summary
Atmospheric scientists are looking forward to the promises that a GPS radio occultation multi-satellite constellation can offer. Schmidt et al, 2004) or to generate global climatologies (Foelsche et al, 2005) Up to now these studies are limited to data of only one single satellite, except for selected periods with SAC-C measurements. Future GPS occultation missions, as COSMIC (Constellation Observing System for Meteorology, Ionosphere and Climate) (Rocken et al, 2000), MetOp-GRAS (Meteorology Operational, Global Navigation Satellite Systems Radio Occultation Receiver for Atmospheric Sounding) (Larsen et al, 2005) or EQUARS (EQUatorial Atmosphere Research Satellite) (Takahashi et al, 2004) will not provide data before 2006. The activation of the GPS radio occultation experiment of the U.S American/German GRACE mission (Tapley and Reigber, 2004; Dunn et al, 2003) opens the possibility to double the continuously and operational available globally distributed occultation measurements in relation to CHAMP before the upcoming missions.
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