Study of bending angle residual ionosphric error in real RO data

With the development of global navigation satellite system (GNSS) remote sensing, radio occultation (RO) has become an important atmospheric observation technique that mainly be used for numerical weather prediction (NWP) and global climate monitoring (GCM). However, residual ionopheric error (RIE) can still be significant after an ionospheric error elimination by linear combination of dual-frequency RO bending angles. Lots of quantification and analysis of RO bending angle RIEs has been conducted by using quasi-realistic end-to-end simulations. In this study, the RIEs in RO observations have been investigated by comparative analysis of COSMIC RO measurements and ECMWF model data. The results illustrate that the RIE is a major source of the bending angle in lower mesosphere and upper stratosphere, and its bias has a clear negative tendency that in line with our empirical studies based on simulation RO data. This study helps to inform future RIE mitigation schemes for ensuring benchmark quality stratospheric RO data.