Comparison of FORMOSAT-3/COSMIC radio occultation measurements with radio tomography

The paper reports a comparison between the continuous tomographic observations of the ionosphere during July-August 2008 and radio occultation (RO) measurements made by the Formosa Satellite 3/Constellation Observing System for Meteorology, Ionosphere, and Climate (FORMOSAT-3/COSMIC or F3/C). The two sets of observations agree well qualitatively and bring out the main features of the low-latitude to midlatitude ionosphere: (1) The electron density enhancements observed at ∼26°N-31°N geographic (∼16°N- 21°N magnetic) latitudes during daytime are related to the equatorial ionization anomaly (EIA), and (2) the enhancements observed at night at latitudes poleward of ∼35°N geographic are related to the midlatitude summer nighttime anomaly. The comparison shows that the EIA crest densities are highly underestimated in the RO inversions that use F3/C data. It is also seen that the agreement is better in the midlatitude region, with overall features represented quite well in the RO data, highlighting its usefulness as the two techniques capture similar electron density structure, although there are some magnitude differences.