A Time-Varying 3-D Displacement Model of the ∼5.9-Year Westward Motion and its Applications for the Global Navigation Satellite System Positions and Velocities

To advance geodynamics and geophysical research, high precision Global Navigation Satellite System (GNSS) observations of velocity and position are needed. In this study, we construct a 3-D model of a similar to 5.9-year periodic signal for the Earth surface displacements. This model is mainly based on the determined time sequences and the Y-22 spatial pattern of this similar to 5.9-year periodic signal from the global Global Positioning System (GPS) observations. Based on the constructed model, we calculate synthetic temporal 3-D displacements on the Earth surface and the velocity changes, and we compare them to observed GPS displacements. Our results reveal that the similar to 5.9-year signal contributes to surface displacements and velocity fields. Maximum displacements for the N, E, and U components can reach up to 0.28, 0.55, and 1.69 mm, respectively; maximum velocity effects can up to 1.69 mm/year for the U component (depending on record length). For those studies which need millimeter or even submillimeter accuracy (e.g., tectonic deformations, glacial isostatic adjustment, and deformations caused by core motions), these effects cannot be simply ignored. Our results also confirm that the model we present here can heavily reduce the similar to 5.9-year signal in the original GPS time series. We suggest that our model should be used to pretreatment the GPS data at the observation level, which could improve signals used for geophysical or geodynamic interpretations.