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- Title
One‐Dimensional Variational Ionospheric Retrieval Using Radio Occultation Bending Angles: 2. Validation.
- Authors
Elvidge, S.; Healy, S. B.; Culverwell, I. D.
- Abstract
Culverwell et al. (2023, https://doi.org/10.1029/2023SW003572) described a new one‐dimensional variational (1D‐Var) retrieval approach for ionospheric GNSS radio occultation (GNSS‐RO) measurements. The approach maps a one‐dimensional ionospheric electron density profile, modeled with multiple "Vary‐Chap" layers, to bending angle space. This paper improves the computational performance of the 1D‐Var retrieval using an improved background model and validates the approach by comparing with the COSMIC‐2 profile retrievals, based on an Abel Transform inversion, and co‐located (within 200 km) ionosonde observations using all suitable data from 2020. A three or four layer Vary‐Chap in the 1D‐Var retrieval shows improved performance compared to COSMIC‐2 retrievals in terms of percentage error for the F2 peak parameters (NmF2 and hmF2). Furthermore, skill in retrieval (compared to COSMIC‐2 profiles) throughout the bottomside (∼90–300 km) has been demonstrated. With a single Vary‐Chap layer the performance is similar, but this improves by approximately 40% when using four‐layers. Plain Language Summary: Culverwell et al. (2023, https://doi.org/10.22541/essoar.168614409.98641332) presented a new way of estimating ionospheric electron density using the amount of bending experienced by GNSS signals in the upper atmosphere. In this paper, as well as providing extensive validation of the technique, the computational performance is improved by using better initial conditions. The validation is done by comparing the newly described approach with the method used by the COSMIC‐2 satellite constellation using additional data from ground‐based sensors known as ionosondes. The newly described technique is found to provide improvements of approximately 40% compared to a complementary approach using by COSMIC‐2. Key Points: Improved computational performance of the 1D‐Var bending angle retrieval is demonstrated with a better background modelExtensive validation of the 1D‐Var retrieval approach compared to ionosonde and Abel‐inversion‐based COSMIC‐2 retrievals has been undertakenThe 1D‐Var retrieval, using four‐layers, is shown to have an 40% reduction in root mean square error compared to COSMIC‐2 retrievals
- Subjects
IONOSPHERIC electron density; ELECTRON distribution; STANDARD deviations; UPPER atmosphere; GLOBAL Positioning System
- Publication
Space Weather: The International Journal of Research & Applications, 2024, Vol 22, Issue 1, p1
- ISSN
1539-4956
- Publication type
Article
- DOI
10.1029/2023SW003571