Ionospheric Peak Parameters Retrieved from FY-3C Radio Occultation: A Statistical Comparison with Measurements from COSMIC RO and Digisondes Over the Globe

Abstract

In this study, two ionospheric peak parameters (ICPs), NmF2 and hmF2, derived from the global navigation satellite system (GNSS) radio occultation (RO) ionospheric electron density profiles (EDPs) obtained by Feng-Yun 3C (FY-3C) mission are compared with those derived from the observations of the Constellation Observing System for the Meteorology, Ionosphere, and Climate (COSMIC) mission and the measurements from 24 digisonde stations distributed around the world during the year from 2014 to 2017. The FY-3C derived ICPs and the COSMIC-derived ICPs are provided by the National Satellite Meteorological Centre (NSMC) and the COSMIC Data Analysis and Archive Center (CDAAC), respectively. The correlation and bias analyses are carried out in the comparison under the collocation criterion with the time interval of 1 h and the space interval of 3° in latitude and 5° in longitude. When comparing the ICPs derived from the two RO missions, the difference in the azimuth of occultation planes (DAOPs) between the matched pairs is limited to be within 20°. The comparison results are analyzed for different solar activity periods, and solar elevation angle (SEA) is taken for the first time as a factor that represents the comprehensive impacts of latitude zones, seasons, and local time of the observations. The results are shown as follows: (1) Both the COSMIC RO-derived and the digisonde-observed ICPs are in good agreement with the FY-3C RO-derived ones. The correlation coefficient (CC) between the NmF2 and hmF2 derived by COSMIC RO and FY-3C RO is 0.965 and 0.916, respectively, while the correlation coefficient between the NmF2 and hmF2 derived by digisonde and FY-3C RO is 0.924 and 0.832, respectively. The quality of FY-3C RO-derived ICPs are reliable enough for further applications. (2) The CC of NmF2 is, in general, higher than that of hmF2 when comparing FY-3C RO with other observations, and the overall MAB and MRB of FY-3C RO-derived ICPs during the higher solar activity period are higher than the ones during the lower solar activity period. The difference between the two RO missions is much smaller than that one between FY-3C RO and digisonde. (3) For a certain solar activity period, the standard deviations of the absolute bias (SDAB) and the standard deviations of the relative bias (SDRB) of FY-3C RO-derived ICPs compared with digisonde-derived ones generally increases with the increase of SEA, while the SDAB and SDRB of FY-3C RO-derived ICPs both get the minimum values for the AOP interval near to 90°.

Deriving Ionospheric Sporadic E Intensity From FORMOSAT‐3/COSMIC and FY‐3C Radio Occultation Measurements

“…Similar to the "ionPhs" data and the "ionPrf" data provided by the CDAAC, the NSMC of China also provides the ionospheric RO data and products of FY-3C mission, including the 1 Hz SNR and phase data ("IE" files) and the corresponding electron density and TEC profiles derived based on them ("EDP" files). It has been demonstrated that the FY-3C RO-derived ionospheric peak parameters, which are obtained from the electron density profiles of the EDP files, are in good agreement with both the COSMIC RO-derived and the ionosonde-observed ones (Wang et al, 2019). While till now, these FY-3C RO EDP files haven't been used in Es layer-related studies.…”

Algorithm Research Using GNSS-TEC Data to Calibrate TEC Calculated by the IRI-2016 Model over China

“…Evaluation scheme for the integrated interpolation of IG-up in time and space: Using high-precision TEC data extracted from 12 GNSS stations at different latitudes as a reference, the IG-up values obtained using the integrated interpolation scheme are substituted back into the IRI-2016 model to drive the output TEC. Then, the accuracy indices MAE, RMSE, and PI are calculated using Expression (4), Expression ( 5) and Expression (6), respectively, and the linear regression correlations of the TEC values are analyzed:…”

“…The ionosphere is a part of the atmosphere that exists in an ionized state within a range of tens of kilometers to thousands of kilometers from the ground. It is an important part of the geospatial environment and has a significant impact on radio information systems such as global navigation satellite systems (GNSS), communication systems, and radar [1][2][3][4][5][6]. The International Reference Ionosphere (IRI) is a widely used empirical ionospheric model.…”

“…into the IRI-2016 model to drive the output TEC. On this basis, we calculate the mean absolute error (MAE), root mean square error (RMSE), and precision improvement (PI) of the TEC estimates obtained with different time-interval schemes using Expression (4), Expression (5), and Expression(6), respectively, to evaluate the interpolation effects of the different time-interval schemes for IG-up.2. Evaluation scheme for the spatial interpolation of IG-up: High-precision TEC data extracted from 46 GNSS stations at different latitudes are used to drive the IRI-2016 model to calculate the IG-up values at different integer hours, and Expression (2) is used to calculate an IG-up map with a spatial resolution of 2.5 • in latitude and 5 • in longitude within the latitudinal range of 20 • N-55 • N and the longitudinal range of 70 • E-135 • E. On this basis, the IG-up values at integer hours corresponding to 12other GNSS stations at different latitudes are then calculated via interpolation using Expression(3).…”

An analysis of global ionospheric disturbances and scintillations during the strong magnetic storm in September 2017

“…A detailed description of the COSMIC mission can be found in Anthes et al [15]. COSMIC could provide up 1500-2500 decent soundings of the ionosphere and atmosphere per day at the early stages of its operation, but due to the aging and loss of the satellites, the number of profiles declined severely after 2014 [16]. As a result, in September 2017, we only have about 150 profiles per day.…”