A comparison of GPS-TEC with IRI-TEC at low latitudes in China in 2006

A comparison between GPS derived total electron content (TEC) and IRI-2012 is studied at low latitudes in China in 2006. 4 GPS receivers form a small scale GPS network, and the spatial coverage starts at (26.1°N, 119.3°E) and ends at (22.8°N, 108.3°E), the corresponding magnetic coordinate is from (19.6°N, 191.6°E) to (16.2°N, 180.4°E). The network covers a region at or near the northern crest of the equatorial anomaly with ∼11° and ∼3° in longitude and latitude, respectively. The GPS-TEC is computed with the grid-based method. The ABT-2009 and NeQuick are selected for the bottomside and topside profile model for IRI-2012. There are similar monthly and seasonal variation trends between GPS-TEC and IRI-TEC in 2006, while the peak value of GPS-TEC and IRI-TEC appear at different times. The IRI-TEC is almost larger than GPS-TEC at day time, while the difference is small at night time. The largest difference between GPS-TEC and IRI-TEC can reach 16.5 TECU, and the ratio of the largest difference and GPS-TEC is about 65%. The largest latitudinal gradient of GPS-TEC at 22-24°N was 5 TECU/deg, while that of IRI-TEC was 2.5 TECU/deg. These above results indicate that the IRI-2012 can reproduce the TEC variation trends at low latitudes in China, but the IRI-2012 overestimates the GPS-TEC at day time in this region.