Evaluation of regional ionospheric grid model over China from dense GPS observations

The current global or regional ionospheric models have been established for monitoring the ionospheric variations. However, the spatial and temporal resolutions are not enough to describe total electron content (TEC) variations in small scales for China. In this paper, a regional ionospheric grid model (RIGM) with high spatial-temporal resolution (0.5° × 0.5° and 10-min interval) in China and surrounding areas is established based on spherical harmonics expansion from dense GPS measurements provided by Crustal Movement Observation Network of China (CMONOC) and the International GNSS Service (IGS). The correlation coefficient between the estimated TEC from GPS and the ionosonde measurements is 0.97, and the root mean square (RMS) with respect to Center for Orbit Determination in Europe (CODE) Global Ionosphere Maps (GIMs) is 4.87 TECU. In addition, the impact of different spherical harmonics orders and degrees on TEC estimations are evaluated and the degree/order 6 is better. Moreover, effective ionospheric shell heights from 300 km to 700 km are further assessed and the result indicates that 550 km is the most suitable for regional ionospheric modeling in China at solar maximum.