2006 | OriginalPaper | Buchkapitel
Refractivity Biases in GNSS Occultation Data
verfasst von : G. Beyerle, S. Heise, J. Kaschenz, G. König-Langlo, C. Reigber, T. Schmidt, J. Wickert
Erschienen in: Atmosphere and Climate
Verlag: Springer Berlin Heidelberg
Aktivieren Sie unsere intelligente Suche, um passende Fachinhalte oder Patente zu finden.
Wählen Sie Textabschnitte aus um mit Künstlicher Intelligenz passenden Patente zu finden. powered by
Markieren Sie Textabschnitte, um KI-gestützt weitere passende Inhalte zu finden. powered by
An analysis of atmospheric refractivity profiles observed by the georesearch satellite CHAMP between May 2001 and October 2004 reveals a negative bias compared to ECMWF meteorological fields at altitudes below 5 km. In order to separate bias contributions caused by critical refraction from contributions induced by the receiver tracking process a comprehensive end-to-end simulation study was performed. The simulations are based on radiosonde profiles obtained aboard research vessel “POLARSTERN”. Within a subset of 3039 profiles recorded on the Atlantic Ocean between 60°N and 60°S, 1202 profiles (39.6%) are found with vertical refractivity gradients below the threshold value of −157 km−1. Critical refraction layers occur mainly between 1 km and 2.5 km altitude, above 3 km the occurrence of critical refraction can be disregarded. End-to-end simulations using these 3039 refractivity profiles confirm that four quadrant carrier phase extraction outperforms the two quadrant method currently implemented on CHAMP. Within regions of low signal-to-noise ratios “open-loop” tracking methods yield improvements with respect to the current “fly-wheeling” method.