Comparison of COSMIC ionospheric measurements with ground-based observations and model predictions: Preliminary results

Electron densities retrieved from the Constellation Observing System for Meteorology, Ionosphere, and Climate (COSMIC) radio occultation (RO) measurements are compared with those measured by incoherent scatter radars (ISR) and ionosondes in this paper. These results show that electron density profiles retrieved from COSMIC RO data are in agreement with the ISR and ionosonde measurements. The ionospheric characteristics (NmF2 and h(m)F(2)) derived from the COSMIC satellites are also compared with those calculated by the latest International Reference Ionosphere model (IRI-2001) and the National Center for Atmospheric Research Thermosphere-Ionosphere-Electrodynamics General Circulation Model (NCAR-TIEGCM). The comparison of the magnitude of the COSMIC NmF2 data with those calculated by the IRI model and the TIEGCM is good. However, features such as the north-south asymmetry and longitudinal variation of the equatorial anomaly that are seen in the COSMIC data and the TIEGCM simulations are not fully present in the IRI model. On the other hand, the TIEGCM produces a stronger winter anomaly than that seen in either the COSMIC data or the IRI model.