Beschreibung:
<jats:p>Abstract. The Chinese radio occultation sounder GNOS (Global Navigation Occultation
Sounder) is on the FY-3C satellite, which was launched on 23 September 2013.
Currently, GNOS data are transmitted via the Global Telecommunications
System (GTS), providing 450–500 profiles per day for numerical weather
prediction applications. This paper describes the processing of the GNOS
profiles with large biases related to L2 signal degradation. A new
extrapolation procedure in bending angle space corrects the L2 bending
angles using a thin ionosphere model and the fitting relationship
between L1 and L2. We apply the approach to improve the L2 extrapolation of GNOS.
The new method can effectively eliminate about 90 % of large
departures. In addition to the procedure for the L2 degradation, this paper
also describes our quality control (QC) for FY-3C GNOS. A noise estimate for
the new L2 extrapolation can be used as a QC parameter to evaluate the
performance of the extrapolation. A statistical comparison between GNOS
bending angles and short-range ECMWF (European Centre for Medium-Range
Weather Forecasts) forecast bending angles demonstrates that GNOS performs
almost as well as the Global Navigation Satellite System (GNSS) Receiver for
Atmospheric Sounding (GRAS), especially in the core region from around 10 to
35 km. The GNOS data with the new L2 extrapolation are suitable for assimilation
into numerical weather prediction systems.
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