Non-linear variation analysis of height time series of north China GNSS reference stations

The non-linear variation analysis of height time series of GNSS reference Stations in North China is studied by using power spectral analysis and least-squares method based on the GNSS observations of the CMONOC network, and the effects of different environmental loads are also analyzed. The results show that there are obvious annual and semi-annual cycle features in the height time series of the GNSS reference station in North China, and the annual feature is more significant than the semi-annual feature. There are differences in the periodic amplitudes and phases of the reference stations located in different regions, and the annual amplitudes are larger in the southern part of the North China than in the northern part. The overall annual variation in North China reached its maximum in the autumn season. The effect of different environmental loading effects on the GNSS height displacement of the North China is inconsistent. Results of correcting the GNSS time series using three environmental loads, So that, the hydrological loads have the best corrections, followed by the non-tidal atmospheric loads, and non-tidal ocean loads have poor corrections.