Comparison of global TEC between IRI TEC and GPS TEC in the spring of 2006

Comparison of the global Total Electron Content (TEC) derived from dual-frequency Global Positioning System (GPS) data and International Reference Ionosphere (IRI) used tomographic models, it has very important significance for IRI upgrading [1]. We investigate the trend of global TEC between IRI TEC and GPS TEC in the spring of 2006. IRI TEC is derived from the IRI-2012 model and GPS TEC is obtained from the International GNSS service (IGS) [1, 2]. By comparing the results, IRI TEC agrees with GPS TEC very well at high latitudes. They are generally in agreement even at low latitudes for the period from evening to morning. However, differences are found from 11:00-17:00 LT at low latitudes. It can be seen that the north-south asymmetry has remarkable effect on both IRI TEC and GPS TEC, especially in the equatorial ionization anomaly (EIA). The strength of EIA crest is obviously higher in north than in south about IRI TEC, it reaches ~11 TECU around 15° E longitude at 13:00 LT. Meanwhile, EIA crest in daytime is generally exaggerated and the noon-bite out is deep in the IRI TEC than GPS TEC, the difference of noon-bite is about 12 TECU around 105° E longitude at 13:00 LT.