Characteristics of second-order residual ionospheric error in GNSS radio occultation and its impact on inversion of neutral atmospheric parameters

Qu, Xiaochuan; Zhenghang, LI; An, Jiachun; Ding, Wenwu

doi:10.1016/j.jastp.2015.05.016

Cited by 8 publications

(8 citation statements)

References 24 publications

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“…The RIEs' characteristics and impact on the RO atmospheric profile retrievals have been investigated thoroughly [10,11,13,[16][17][18][19][20][21][22][23][24], and several approaches of higher-order correction in GNSS RO bending angles have been developed so far [16,17,21,25].…”

Section: Introductionmentioning

confidence: 99%

New Higher-Order Correction of GNSS RO Bending Angles Accounting for Ionospheric Asymmetry: Evaluation of Performance and Added Value

et al. 2020

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The residual ionospheric error (RIE) from higher-order terms in the refractive index is not negligible when using global navigation satellite system (GNSS) radio occultation (RO) data for climate and meteorology applications in the stratosphere. In this study, a new higher-order bending angle RIE correction named “Bi-local correction approach” has been implemented and evaluated, which accounts for the ray path splitting of the dual-frequency GNSS signals, the altitude of the low Earth orbit (LEO) satellite, the ionospheric inbound (GNSS to tangent point) vs. outbound (tangent point to LEO) asymmetry, and the geomagnetic field. Statistical results based on test-day ensembles of RO events show that, over the upper stratosphere and mesosphere, the order of magnitude of the mean total RIE in the bi-local correction approach is 0.01 μrad. Related to this, the so-called electron-density-squared (Ne2) and geomagnetic (BNe) terms appear to be dominant and comparable in magnitude. The BNe term takes negative or positive values, depending on the angle between the geomagnetic field vector and the direction of RO ray paths, while the Ne2 term is generally negative. We evaluated the new approach against the existing “Kappa approach” and the standard linear dual-frequency correction of bending angles and found it to perform well and in many average conditions similar to the simpler Kappa approach. On top of this, the bi-local approach can provide added value for RO missions with low LEO altitudes and for regional-scale applications, where its capacity to account for the ionospheric inbound-outbound asymmetry as well as for the geomagnetic term plays out.

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Section: Introductionmentioning

confidence: 99%

New Higher-Order Correction of GNSS RO Bending Angles Accounting for Ionospheric Asymmetry: Evaluation of Performance and Added Value

et al. 2020

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“…(2) During the RO data processing, the refractive index at the LEO satellite orbit is considered as unity. (3) Except the inverse quadratic term, the high‐order terms in the Appleton‐Hartree equation also result in the RIE (Qu et al, 2015). Of these three RIE sources, the raypaths separation effect plays the main role (Mannucci et al, 2011).…”

Section: Introductionmentioning

confidence: 99%

Characterizing Ionospheric Effect on GNSS Radio Occultation Atmospheric Bending Angle

Yue

Wan

et al. 2020

JGR Space Physics

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Global Navigation Satellite System (GNSS) atmospheric radio occultation (RO) has been an active remote sensing method to explore the Earth's atmosphere recently. The RO products especially atmospheric bending angles have been widely used for climate study. However, the residual ionospheric error (RIE) still exists to a certain extent after the widely used linear combination in bending angle calculation. In this study, we analyzed both CHAMP and COSMIC data and did full 3‐D ray tracing to characterize RIE. It is found that the order of RIE is around ±0.1 μrad and has an obvious dependency on a variety of factors including altitude, latitude, local time, season, and solar activity level. The amplitude and complexity of RIE generally increase with altitude. It is closely related to the strength of the E layer and the asymmetry between LEO side and GNSS side. Along magnetic latitude direction, the RIE shows a pronounced feature of two peaks and three troughs. From both the simulated and observed RIE, we can identify clearly the ionospheric seasonal variation features, such as the semiannual variation, the equinox asymmetry and the annual anomaly. A spherical asymmetry factor was also defined to quantify the correlation between ionospheric spherical asymmetry degree and RIE. The study provides a comprehensive understanding of RIE, which could contribute to the correction of RIE in the future.

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“…In this paper, the RO azimuth is the angle between the signal propagation direction in the occultation plane and the true north at the occultation point (Qu et al, 2015). When the signal propagates from the north to the south, the azimuth is 180 • (see α in Fig.…”

Section: High-order Ionospheric Effects With the Ro Azimuthmentioning

confidence: 99%

High-order ionospheric effects on electron density estimation from Fengyun-3C GPS radio occultation

Jin

2017

Ann. Geophys.

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Abstract. GPS radio occultation can estimate ionospheric electron density and total electron content (TEC) with high spatial resolution, e.g., China's recent Fengyun-3C GPS radio occultation. However, high-order ionospheric delays are normally ignored. In this paper, the high-order ionospheric effects on electron density estimation from the Fengyun-3C GPS radio occultation data are estimated and investigated using the NeQuick2 ionosphere model and the IGRF12 (International Geomagnetic Reference Field, 12th generation) geomagnetic model. Results show that the high-order ionospheric delays have large effects on electron density estimation with up to 800 el cm −3 , which should be corrected in high-precision ionospheric density estimation and applications. The second-order ionospheric effects are more significant, particularly at 250-300 km, while third-order ionospheric effects are much smaller. Furthermore, the high-order ionospheric effects are related to the location, the local time, the radio occultation azimuth and the solar activity. The large high-order ionospheric effects are found in the low-latitude area and in the daytime as well as during strong solar activities. The second-order ionospheric effects have a maximum positive value when the radio occultation azimuth is around 0-20 • , and a maximum negative value when the radio occultation azimuth is around −180 to −160 • . Moreover, the geomagnetic storm also affects the high-order ionospheric delay, which should be carefully corrected.

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Characteristics of second-order residual ionospheric error in GNSS radio occultation and its impact on inversion of neutral atmospheric parameters

Cited by 8 publications

References 24 publications

New Higher-Order Correction of GNSS RO Bending Angles Accounting for Ionospheric Asymmetry: Evaluation of Performance and Added Value

New Higher-Order Correction of GNSS RO Bending Angles Accounting for Ionospheric Asymmetry: Evaluation of Performance and Added Value

Characterizing Ionospheric Effect on GNSS Radio Occultation Atmospheric Bending Angle

High-order ionospheric effects on electron density estimation from Fengyun-3C GPS radio occultation

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