Articles | Volume 9, issue 2
https://doi.org/10.5194/amt-9-335-2016
https://doi.org/10.5194/amt-9-335-2016
Research article
 | 
03 Feb 2016
Research article |  | 03 Feb 2016

Ionospheric correction of GPS radio occultation data in the troposphere

Z. Zeng, S. Sokolovskiy, W. Schreiner, D. Hunt, J. Lin, and Y.-H. Kuo

Abstract. For inversions of the GPS radio occultation (RO) data in the neutral atmosphere, this study investigates an optimal transition height for replacing the standard ionospheric correction using the linear combination of the L1 and L2 bending angles with the correction of the L1 bending angle by the L1–L2 bending angle extrapolated from above. The optimal transition height depends on the RO mission (i.e., the receiver and firmware) and is different between rising and setting occultations and between L2P and L2C GPS signals. This height is within the range of approximately 10–20 km. One fixed transition height, which can be used for the processing of currently available GPS RO data, can be set to 20 km. Analysis of the L1CA and the L2C bending angles shows that in some occultations the errors of standard ionospheric correction substantially increase around the strong inversion layers (such as the top of the boundary layer). This error increase is modeled and explained by the horizontal inhomogeneity of the ionosphere.

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Short summary
This study discusses the ionospheric correction problem of RO data in the troposphere and investigates an optimal transition height (OTH) for replacing the standard linear combination method by the L1–L2 bending angle extrapolated from above. By comparing the RO ionosphere-free bending angles with the ECMWF global forecast ones, the OTH is found when it gives the minimal standard deviations. The results show the OTH depends mainly on the L2 signal and is ~20 km for COSMIC L2P and ~10 km for L2C.