Validation of Ionospheric Parameters From Electron Density Profiles of FY-3E Satellite Using Ionosonde, GIMs, Satellite Altimetry and Other Occultations

Abstract

The FengYun-3E satellite (FY-3E) is the first to feature the GNSS Occultation Sounder II (GNOS-II). Occultation is effective for ionosphere detection, but data variations between FY-3E and other techniques are inevitable due to differing instruments and methodologies. Evaluating the GNOS-II performance against other techniques is imperative. We extract ionospheric parameters—the F2 layer peak height (hmF2), F2 layer critical frequency (foF2), and Vertical Total Electron Content (VTEC)—from FY-3E's electron density profile. We use ionosonde, Global Ionospheric Maps (GIMs), and Satellite Altimetry (SA), along with FY-3D and COSMIC-2 to analyze FY-3E's performance. Additionally, we use the International Reference Ionosphere (IRI-2020) to normalize VTEC, eliminating systematic biases due to altitude differences. Results show that FY-3E's foF2 has high consistency with ionosonde, while hmF2 shows larger differences. However, both foF2 and hmF2 from FY-3E, FY-3D, and COSMIC-2 have comparable data quality. TEC differences between FY-3E and GIMs are greater during equinoxes and in the daytime. Significant TEC deviations are observed, particularly in low-latitude region affected by the Equatorial Ionization Anomaly (EIA) during the daytime, with underestimation at EIA crests and overestimation at EIA troughs and around ±40° geomagnetic latitude, a phenomenon also observed when compared to SA. FY-3D and COSMIC-2 exhibit similar patterns, but FY-3E shows better consistency with GIMs and SA compared to FY-3D. Compared to FY-3D and FY-3E, COSMIC-2 has fewer overestimated profiles. Furthermore, FY-3E performs poorly in observing ionospheric structure in the EIA region but performs well in the Weddell Sea Anomaly (WSA) region, similar to FY-3E.