A regional ionospheric TEC mapping technique over China and adjacent areas on the basis of data assimilation

Abstract

In this paper, a regional total electron content (TEC) mapping technique over China and adjacent areas (70°E–140°E and 15°N–55°N) is developed on the basis of a Kalman filter data assimilation scheme driven by Global Navigation Satellite Systems (GNSS) data from the Crustal Movement Observation Network of China and International GNSS Service. The regional TEC maps can be generated accordingly with the spatial and temporal resolution being 1°×1° and 5 min, respectively. The accuracy and quality of the TEC mapping technique have been validated through the comparison with GNSS observations, the International Reference Ionosphere model values, the global ionosphere maps from Center for Orbit Determination of Europe, and the Massachusetts Institute of Technology Automated Processing of GPS TEC data from Madrigal database. The verification results indicate that great systematic improvements can be obtained when data are assimilated into the background model, which demonstrates the effectiveness of this technique in providing accurate regional specification of the ionospheric TEC over China and adjacent areas.

Regional 3‐D ionospheric electron density specification on the basis of data assimilation of ground‐based GNSS and radio occultation data

“… where L θ , L ϕ , and L z represent the ionospheric correlation lengths along the latitudinal, longitudinal, and altitudinal directions, respectively. However, specification of ionospheric correlation length is not fully well known so far, and the formulations used in the current study are the same as those used in Yue et al [, ] and Aa et al []. The altitudinal correlation length varies from 20 km in the E and F regions to 500 km in the plasmasphere height; both the latitudinal and longitudinal correlation lengths are given in great circle degrees, which varies with respect to the local time and geomagnetic latitude.…”

“…Moreover, the current work can be viewed as an in‐depth research‐to‐operation study on the basis of the previous work given by Aa et al []. First of all, the products provided by the previous study are 2‐D TEC RIMs, but slant TEC derived from 3‐D electron density specification is more desirable in providing application‐oriented ionospheric refraction correction.…”

“…The GNSS measurements from the CMONOC and part of the IGS networks are used in the current study. The CMONOC is comprised of 260 GNSS stations covering Chinese mainland for continuous observation with earthquake monitoring being the dominant scientific objective [ Aa et al , ]. An additional 38 sites from IGS stations located within China or adjacent regions are also used.…”

“…In this study, we will present a regional ionospheric three‐dimensional electron density specification over China and adjacent areas (70°E–140°E and 15°N–55°N) using a data assimilation technique similar to that proposed by Aa et al []. The assimilation is driven both by ground‐based GNSS measurements from Crustal Movement Observation Network of China (CMONOC) and International GNSS Service (IGS), and by LEO radio occultation data from FORMOSAT‐3/COSMIC (F3/C).…”

An Ionosphere Specification Technique Based on Data Ingestion Algorithm and Empirical Orthogonal Function Analysis Method

“…The Jet Propulsion Laboratory and University of Southern California have cooperatively constructed another Global Assimilation Ionospheric Model (JPL/USC Global Assimilation Ionospheric Model), which uses a traditional Kalman filter method to estimate the three‐dimensional density state and a four‐dimensional variational approach to estimate ionospheric drivers such as neutral winds and the equatorial E×B drift (Mandrake et al, ; Pi et al, ; Wang et al, ). Some studies use sophisticated empirical models to define the a priori state in order to implement data assimilation, such as Ionospheric Data Assimilation Three‐Dimensional (Bust et al, , ), Electron Density Assimilative Model (Angling & Cannon, ; Angling & Khattatov, ), North American/United States TEC (Fuller‐Rowell et al, ), and China assimilation TEC Model (Aa et al, , ). Moreover, there are extensive studies that described the development of ionospheric and thermospheric data assimilation models/procedures (e.g., Komjathy et al, ; Lee et al, ; Matsuo et al, ; Pi et al, ; Schunk et al, ; Yue et al, , ; Zhu et al, ).…”