Spatial and temporal analysis of the total electron content over China during 2011–2014

• 4-year observation of ionospheric TEC with dense GPS network over China.
• EOF analysis show dominant spatial and temporal variabilities over China.
• Thermospheric zonal wind/magnetic declination effect accounts for part of the features.

In the present work we investigate variations of ionospheric total electron content (TEC) with empirical orthogonal function (EOF) analysis, the four-year TEC data are derived from ∼250 GPS observations of the crustal movement observation network of China (CMONOC) over East Asian area (30–55°N, 70–140°E) during the period from 2011, January to 2014, December. The first two EOF components together account for ∼93.78% of total variance of the original TEC data set, and it is found that the first EOF component represents a spatial variability of semi-annual variation and the second EOF component exhibits pronounced east–west longitudinal difference with respect to zero valued geomagnetic declination line. In addition, climatology of the vertical plasma drift velocity vdz induced by HWM zonal wind field (∼300 km) are studied in the paper. Results shows vdz displays significant east–west longitudinal difference at 10:00 LT and 20:00 LT, and its daytime temporal variation is consistent with the second EOF principal component, which suggests that the east–west longitudinal variability is partly caused by the thermospheric zonal wind and geomagnetic declination. It is expected that with this dense GPS network, local ionospheric variability can be described more accurately and a more realistic ionospheric model can be constructed and used for the satellite navigation and radio propagation.