Cause Analysis of the Non‐Linear Variations of the IGS Reference Station Coordinate Time Series in China

Abstract

Abstract GPS position time series exhibit dramatic seasonal variations. It is generally considered that atmospheric pressure loading, nontidal ocean loading snow depth and soil moisture loading account for these seasonal changes. Focusing on the 11 IGS reference stations in China, this paper calculates station displacements caused by the above four kinds of surface mass loadings to correct the coordinate time series of these 11 stations during period of 1995–2010 under ITRF2005. We establish a preliminary numerical link among certain geophysical phenomena, seasonal variations and noise characteristics, finding that the calculated four kinds of surface mass loadings could produce variations in station's noise features, mainly exhibiting characteristics of band pass noise and random walk noise, and could reduce the annual amplitude of station's Up component. However, it could not well interpret station's semi‐annual and horizontal annual movement. We investigate the possible factors that could cause non‐linear variations of IGS stations, taking emphasis on the contributions of diurnal (S1) and semi‐diurnal (S2) atmospheric tides to the annual amplitude of the 11 stations, and propose that the S1–S2 atmospheric tides could be one of the main factors for annual motion of IGS stations in China, especially for the vertical annual motion of stations in central and southern regions.