Quality Analysis of the Neutral Atmospheric Products from FY-3C Radio Occultation Based on IGRA2 Radiosonde Data and COSMIC Radio Occulation Products

Based on the IGRA2 radiosonde data and the COSMIC(Constellation Observing System for Meteorology Ionosphere and Climate) radio occulation(RO) products, the quality analysis of the neutral atmospheric products from FY-3C RO observations, including the refractivity, the temperature and the specific humidity profiles, during 2015 to 2017 is carried out. The results show that below 25 km, there are no systematic negative deviations in FY-3C RO temperature profiles and the standard deviation of the relative deviation is smaller than 5.0%. Systematic negative deviations in temperature profiles exist, and the standard deviation is more than 1.5 K. The quality of specific humidity profiles is poorer when the height approaches the ground more closely, and the standard deviation is smaller than 1.2 g/kg. Although the FY-3C RO data is generally of high quality and the quality is higher and higher from 2015 to 2017, it needs to be further improved near the ground and above 25 km. The further analysis based on the products during 2017 shows that the qualities of the FY-3C RO refractivity profiles and temperature profiles are the worst in winter, while the qualities of the FY-3C RO specific humidity profiles are the worst in summer. The qualities of the FY-3C RO refractivity profiles are the worst in the low latitudes, while the altitudinal dependencies of the qualities of FY-3C RO temperature profiles are not the same at different altitude ranges, and the FY-3C specific humidity profiles are significantly worse in the low latitudes than in the middle latitudes. In addition, day and night differences and land and sea differences also exist in the qualities of FY-3C RO products.