Validation results of maximum S4 index in F-layer derived from GNOS on FY3C satellite

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

“…The accuracy of IRO products of FY3C/GNOS has been verified with ionosondes as follows, the bias and std of NmF2 relative errors between FY3C/GNOS GPS RO and ionosondes are 6.71% and 18.03%, respectively, and the bias and std of hmF2 are 4.68 and 25.96 km, respectively [3]. Besides, the bias and std of differences of maximum S4 index between FY3C/GNOS and COSMIC are 0.004 and 0.063, respectively [4]. The above results illustrate the decent precision of FY3C/GNOS GPS RO products, which offer the possibilities for its application in magnetic storm research [41,49], indicating its significant potential in studying the physical mechanism of the event-specific magnetic storm.…”

“…Therefore, FY3D/GNOS launched in 2017 was enhanced in number of occultation channels and antenna coverage, thus increasing the observed number of daily ionospheric occultation events to about 500 (just for GPS). With the enhancement of the observation capability of GNOS payload and the gradual implementation of the 3+1 constellation network established by FY3 series satellites (E, F, G and R) [4], the FY3 series occultation project will make more contributions to the international ionospheric climatology research.…”

“…After being compatible with the Global Navigation Satellite System (GNSS) led by Global Positioning System (GPS), Global Navigation Satellite System (GLONASS), GALILEO and Beidou Navigation Satellite System (BDS), RO technique has become one of the most promising space exploration technologies in the 21st century. It has many advantages over the traditional ionospheric observation method, such as low cost, self-calibration, wide coverage, all-time, all-weather, high precision, and high vertical resolution [3,4]. The ionospheric radio occultation (IRO) products provided by GNSS RO technique have great scientific significance in ionospheric climatology research, ionospheric model and data assimilation, ionospheric scintillation research, space environmental monitoring, numerical weather prediction, etc., thus have broad application values and development prospects in fields of meteorology, communication, astronomy, and national defense [2,5,6].…”

“…It is found that the Root-Mean-Square error (RMSE) of foF2 between COSMIC and ionosondes is around 0.5 MHz [29], the bias and std of NmF2 differences between COSMIC and ionosondes are 0.72% and 8.42%, respectively, and the bias and std of hmF2 are 2.80 and 11.46 km [30], respectively, which shows the great precision of COMSIC IRO data. Thanks to the large amount of timely and high-quality IRO products provided by COSMIC, the operationalization of occultation observation has been greatly promoted [20,31], and the IRO products of COSMIC have been widely used in ionospheric research, such as lower atmosphere-ionosphere coupling [32,33], ionospheric climatology study [1,[34][35][36][37], model assimilation [26,33,38,39], scintillation research [4,40,41], earthquake precursor study [42][43][44], and so on. It is worth mentioning that the globally distributed high-precision electron density profiles (EDPs) given by COSMIC provide unprecedented details for global ionospheric climatology study.…”

“…Considering the one-year LSA time scale of the IRO data adopted in other ionospheric climatological studies [45][46][47][48] and the particularity of the LSA year 2016 in the unique extremely low solar cycle 24 (2008-2018) [50,51], the IRO measurements of FY3C/GNOS and COSMIC during 2016.035 and 2017.035 were selected. In addition, as can be seen from the previous FY3C/GNOS verification studies [3,4,49], the accuracy of its NmF2/hmF2 is only obtained by comparison with ionosondes. COSMIC IRO data are widely used in ionospheric research, which set a high standard for the validation of other IRO products, therefore, we compared the NmF2/hmF2 of FY3C/GNOS with those of COSMIC to verify the profile-level accuracy of FY3C/GNOS IRO data.…”