Abstract
GPS radio occultation (GPS-RO) data, especially the parameters of signal-to-noise ratio normalized standard deviation (SNRnstd) and S4, are widely used to measure the ionospheric sporadic E (Es) layer. However, the Es occurrence rates vary with the applied GPS-RO parameters. In view of this fact, we investigate the performances of the GPS-RO SNRnstd and S4 in the detection of Es occurrence rates by comparing them with ionosonde measurements around the globe during a five-year period from 2009 to 2013. The relation between SNRnstd maximum and S4 maximum is constructed firstly to set suitable thresholds. Then the previous thresholds (0.1 for SNRnstd and 0.3 for S4) and new threshold 0.2 for S4 are processed. The statistical results show Es occurrence rates by SNRnstd with threshold 0.1 and S4 with threshold 0.2 are comparable to that of ionosonde for foEs greater than or equal 3 MHz, while the corresponding result by S4 with threshold 0.3 is significantly underestimated. This suggests the established relation between SNRnstd maximum and S4 maximum is reliable and the difference between SNRnstd and S4 could be significantly reduced by selecting a suitable threshold.
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Data availability
GPS-RO data are available from the public website: https://data.cosmic.ucar.edu/. Ionosonde data are available from the public website: https://giro.uml.edu/didbase/.
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Acknowledgements
The authors acknowledge the COSMIC data analysis and archive center and the digital ionogram database for providing GPS-RO and ionosonde data. This study was supported by the National Natural Science Foundation of China (Grant No. 42274017 and Grant No. No.42204012), Guangdong Basic and Applied Basic Research Foundation (Grant No. 2023A1515030184) and Guangzhou Science and Technology Plan Project (Grant No. 202201010129).
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L.T. contributed to research design and led manuscript writing. J.L. and F.Z. contributed to data processing and manuscript editing. F.Z. gave helpful suggestions.
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Tang, L., Li, J., Zhang, F. et al. Comparative study of ionospheric sporadic E occurrence rates using SNRnstd and S4 derived from GPS radio occultation. GPS Solut 27, 120 (2023). https://doi.org/10.1007/s10291-023-01464-y
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DOI: https://doi.org/10.1007/s10291-023-01464-y