Comparison and Validation of the Ionospheric Climatological Morphology of FY3C/GNOS with COSMIC during the Recent Low Solar Activity Period

Abstract

With the accumulation of the ionospheric radio occultation (IRO) data observed by Global Navigation Satellite System (GNSS) occultation sounder (GNOS) onboard FengYun-3C (FY3C) satellite, it is possible to use GNOS IRO data for ionospheric climatology research. Therefore, this work aims to validate the feasibility of FY3C/GNOS IRO products in climatology research by comparison with that of Constellation Observing System for Meteorology, Ionosphere, and Climate (COSMIC), laying the foundation for its application in climatology study. Since previous verification works of FY3C/GNOS were done by comparison with ionosondes, this work matched NmF2/hmF2 of FY3C/GNOS and COSMIC into data pairs to verify the profile-level accuracy of FY3C/GNOS IRO data. The statistical results show that the overall correlation coefficients of both NmF2 and hmF2 are above 0.9, the overall bias and std of NmF2 differences between FY3C/GNOS and COSMIC are −2.19% and 17.48%, respectively, and the bias and std of hmF2 differences are −3.29 and 18.01 km, respectively, indicating a high profile-level precision consistency between FY3C/GNOS and COSMIC. In ionospheric climatology comparison, we divided NmF2/hmF2 of FY3C/GNOS into four seasons, then presented the season median NmF2/hmF2 in 5° × 10° grids and compared them with that of COSMIC. The results show that the ionospheric climatological characteristics of FY3C/GNOS and COSMIC are highly matched, both showing the typical climatological features such as equatorial ionosphere anomaly (EIA), winter anomaly, semiannual anomaly, Weddell Sea anomaly (WSA) and so on, though minor discrepancies do exist like the differences in magnitude of longitude peak structures and WSA, which verifies the reliability of FY3C/GNOS IRO products in ionospheric climatology research.

Global Comparison of F2-Layer Peak Parameters Estimated by IRI-2016 With Ionospheric Radio Occultation Data During Solar Minimum

“…For example, Mao et al [29] found that the root-mean-square (RMS) values of the EDPs between FY3C-GNOS GPS IRO and COSMIC/ionosondes are 10%/7%, respectively, demonstrating the precision consistency of the EDP among FY3C-GNOS, COSMIC, and ionosondes. Bai et al [30] also found decent unbiasedness in the statistical difference and ionospheric climatology of NmF2/hmF2 between COSMIC and FY3C-GNOS, which showed an overall systematic offset of −2.19% for NmF2 and −3.29 km for hmF2. The large amount of FY3C-GNOS IRO data can be a great source of ionospheric climatology, radio communication, and vital precursor information for earthquakes and other hazards [31].…”

“…Based on these, the bias and STD of NmF2/hmF2 relative/absolute differences are calculated as the degree of deviation between IRO and IRI-2016. The detailed derivation method of the bias and STD can be found in the work by Bai et al [30].…”

“…It is capable of tracking signals of 6 GPS and 4 BDS satellites simultaneously and can receive up to 700 occultation events per day (500GPS + 200BDS) [28]. Many studies have evaluated the accuracy of FY3C-GNOS IRO products [15], [16], [29], [30]. For example, Mao et al [29] found that the root-mean-square (RMS) values of the EDPs between FY3C-GNOS GPS IRO and COSMIC/ionosondes are 10%/7%, respectively, demonstrating the precision consistency of the EDP among FY3C-GNOS, COSMIC, and ionosondes.…”

Evaluation of Forward Models for GNSS Radio Occultation Data Processing and Assimilation

“…According to [1], RO observation ranked fourth among data that affected NWP. With the rapid development of the RO technique, numerous missions have been planned, launched, and run steadily to serve the operational NWP, such as Constellation Observing System for Meteorology, Ionosphere, and Climate (COSMIC/COSMIC-2), the Meteorological Operational satellite Programme-A/B (MetOpA/B), FengYun-3C/D (FY-3C/D) [2], GRACE/GRACE-FO, Scientific Application Satellite-C/D (SAC-C/D), Korea Multi-Purpose Satellite-5 (KOMPSAT-5), and Spanish PAZ ('peace' in Spanish) [3][4][5]. By 2027, these missions will provide approximately 18,400 observations per day which theoretically is the number threshold of the positive effect that RO could bring to NWP [6,7].…”

Validation and Improvement of NeQuick Topside Ionospheric Formulation Using COSMIC/FORMOSAT‐3 Data

“…The radio occultation (RO) technique is based on precise dual‐frequency phase measurements (Schreiner et al., 1999) from global navigation satellite system (GNSS) receivers on board Low‐Earth Orbit (LEO) satellites that exploit radio signals transmitted from GNSS satellites. Many authors have worked on the validation of COSMIC data using colocated digisonde and Incoherent Scatter Radar (ISR) stations (Bai et al., 2019; Cherniak & Zakharenkova, 2014; Hu et al., 2014; Krankowski et al., 2011; Lei et al., 2007; Panda et al., 2018; Shaikh et al., 2018; Singh et al., 2021; Stankov & Jakowski, 2006; Yue et al., 2011).…”