Retrieval and Validation of FY-3C Radio Occultation Refractivities

  Objectives  In 2013, the first meteorological satellite of China with global navigation satellite system (GNSS) radio occultation (RO) observation capability, FY-3C, was launched, and FY-3C RO products have been released by the National Satellite Meteorological Center (NSMC).

  Methods  In the present study, the RO refractivity profiles are retrieved from FY-3C excess phase data during the whole year of 2017 by combing the geometric optical inversion and the full spectrum inversion (FSI) algorithms, and the quality of the retrieved refractivity profiles are evaluated with NSMC products and ERA-Interim reanalysis data.

  Results  The success rate of our retrieval process is 82%, which is basically consistent with that of NSMC's 83.5%. With ERA-Interim reanalysis data as references, the relative biases (RBs) of the inverted refractivities are smaller than 1.5% below 25 km, which are slightly better than those of the NSMC refractivity products. While the standard deviations of the relative biases (SDRBs) of the inverted refractivities reach 3.6%, which are larger than those of the NSMC refractivity products.

  Conclusions  Compared with ERA-Interim reanalysis data, the RBs and the SDRBs of the inverted refractivities and NSMC products are significantly lower at high latitudes than those at middle and low latitudes, and the RBs of the inverted refractivities are generally larger in summer than in winter.