Articles | Volume 9, issue 2
https://doi.org/10.5194/amt-9-781-2016
https://doi.org/10.5194/amt-9-781-2016
Research article
 | 
02 Mar 2016
Research article |  | 02 Mar 2016

Preliminary validation of the refractivity from the new radio occultation sounder GNOS/FY-3C

Mi Liao, Peng Zhang, Guang-Lin Yang, Yan-Meng Bi, Yan Liu, Wei-Hua Bai, Xiang-Guang Meng, Qi-Fei Du, and Yue-Qiang Sun

Abstract. As a new member of the space-based radio occultation sounders, the GNOS (Global Navigation Satellite System Occultation Sounder) mounted on Fengyun-3C (FY-3C) has been carrying out atmospheric sounding since 23 September 2013. GNOS takes approximately 800 daily measurements using GPS (Global Positioning System) and Chinese BDS (BeiDou navigation satellite) signals. In this work, the atmospheric refractivity profiles from GNOS were compared with the ones obtained from the co-located ECMWF (European Centre for Medium-Range Weather Forecasts) reanalysis. The mean bias of the refractivity obtained through GNOS GPS (BDS) was found to be approximately −0.09 % (−0.04 %) from the near surface to up to 46 km. While the average standard deviation was approximately 1.81 % (1.26  %), it was as low as 0.75 % (0.53 %) in the range of 5–25 km, where best sounding results are usually achieved. Further, COSMIC (Constellation Observing System for Meteorology, Ionosphere and Climate) and MetOp/ GRAS (GNSS Receiver for Atmospheric Sounding) radio occultation data were compared with the ECMWF reanalysis; the results thus obtained could be used as reference data for GNOS. Our results showed that GNOS/FY-3C meets the design requirements in terms of accuracy and precision of the sounder. It possesses a sounding capability similar to COSMIC and MetOp/GRAS in the vertical range of 0–30 km, though it needs further improvement above 30 km. Overall, it provides a new data source for the global numerical weather prediction (NWP) community.

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Short summary
This paper provides a preliminary validation for the refractivity of GNOS, a new addition to the space-based radio occultation sounder on FY-3C. It possesses a similar sounding capability that COSMIC and GRAS did in the vertical range of 0-30 km, with a precision below 1 %.