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

Weihua Bai,Cheng Cheng,Guangyuan Tan,Yuerong Cai,Mi Liao,Yueqiang Sun,Junming Xia,Cong Yin,Congliang Liu,Yan Liu,Qifei Du,Danyang Zhao,Peng Hu,Xiangguang Meng,Guanglin Yang,Yingqiang Wang,Ziyan Liu,Dongwei Wang,Xianyi Wang

doi:10.3390/rs11222686

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.

Highlights

Traditional ionospheric observation methods, such as sounding rocket, ionosonde/digisonde and ISR (Incoherent Scatter Radar), are susceptible to natural conditions, unable to provide long-term stable ionospheric observations at a global scale [1]
FT2o oebnsseurvreedthbeynFuYm3Cb/eGrNoOf SdaatnadgCrOidSsM, iInCwarheicdheptihcetenduinmtubietirvoelfyN. mF2/hmF2 is greater than 5, occupies at least 60% of the whole grid within ±60◦ latitude regions, a 5◦ × 10◦ grid was adopted in our 3w. oRreks.ulTtshe season median value of NmF2/hmF2 in one grid represents its NmF2/hmF2 level [1], which can effectively reduce the deviations of NmF2/hmF2 caused by contingency factors that are not cons3id.1e. rVeadlidinatiSoencotfioNnm2F.21/.hImnFt2hoibsswervaeydtbhyeFiYo3nCo/sGpNhOerSicwcitlhimCaOtSoMloIgCical features of NmF2/hmF2 observed by F3Y.13.C1./EGrNroOr AS naanldysCisOofSNMmICF2abreetdweepenicFteYd3Cin/GtuNitOivSealyn.d COSMIC
We present the global distribution of season median NmF2 of FY3C/GNSS occultation sounder (GNOS) and COSMIC and their relative differences at daytime(0800–1100LT) and nighttime (2000LT–2300LT) during ME-month, JS-month, SE-month, and DS-month from Figures 6–9, respectively, the consistency and inconsistency of NmF2 morphology between FY3C/GNOS and COSMIC can be obtained intuitively

Summary

Introduction

Traditional ionospheric observation methods, such as sounding rocket, ionosonde/digisonde and ISR (Incoherent Scatter Radar), are susceptible to natural conditions, unable to provide long-term stable ionospheric observations at a global scale [1]. 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]. With the success of the COSMIC-I project, the United States and Taiwan actively planned another six-satellite occultation project COSMIC-II and successfully launched it in June 2019, which is expected to revolutionize the atmospheric/ionospheric occultation observation [26,27]

Objectives

Methods

Findings

Discussion

Conclusion