LAUSR

Abstract Electron density profiles observed using Constellation Observing System for Meteorology, Ionosphere, and Climate (COSMIC) and Feng-Yun 3C (FY3C) radio occultation (RO) missions from 2014 to 2018 were quality inspected and analysed. After eliminating observations that did not meet the quality requirements, we compared the critical frequency of the F2 layer (foF2) and total electron content (TEC) with data retrieved from ionosondes and global ionospheric maps (GIM). Results showed that the quality of the COSMIC and FY3C RO electron density profiles was higher during the daytime compared to that overnight and was better in summer and autumn compared to spring and winter. Furthermore, the electron density profile qualification rate was higher for FY3C RO than that for COSMIC RO in low latitude regions. The foF2 RO data correlated well with ionosonde data (0.94 and 0.90 for FY3C and COSMIC, respectively). Similarly, TEC RO data correlated well with data from GIM (0.95 and 0.92 for FY3C and COSMIC, respectively). The observation accuracy of the RO data was affected by both solar and geomagnetic activity, and the influence of solar activity was greater than that of geomagnetic activity. During periods of reduced solar and geomagnetic activity, the accuracy of foF2 and TEC retrieved from RO was dependent on the local time, season, and latitude.