Abstract
The site displacement due to diurnal and semidiurnal atmospheric tides (S1/S2) is often neglected in the routine precise GPS data processing. We recall the S1/S2 modeling method and show the magnitude of the S1/S2 tides under the Center of Mass (CM) frame. The results show that the annual amplitudes caused by both S1 and S2 tides exceed 1 mm for stations near the equator. The impact of S1/S2 on the 24-h Global Positioning System (GPS) solution is typically at the sub-mm level, and the scatter of the S1/S2 caused displacement difference increases with the decreasing latitude for northern hemisphere stations, among which the maximum Standard Deviation (STD) reaches up to 1.5 mm, 1 mm and 0.7 mm for the Up, East and North components, respectively, at low-latitude stations. We also find that 65% of the stations’ vertical velocity change caused by S1/S2 is larger than 1%, among which the maximum velocity variation rate reaches more than 40% for some coastal/island stations, while stations with the weighted root mean square reduced account for 65%, 39%, and 38% for the up, east, and north components respectively, in particular for most coastal/island stations. Furthermore, the S1/S2 correction could partly reduce the annual and the semi-annual signals of the global stacked vertical component together with the semi-annual amplitude of the east component. The power of some anomalous harmonics of 1.04 cycle per year also decreased a lot. These results further prove the benefits of S1/S2 correction in the precise GPS data processing.
Highlights
The diurnal heating of the atmosphere causes the oscillation of the surface pressure at the diurnal (S1), semi-diurnal (S2) periods, as well as other higher frequency harmonics [1]
What is the effect of S1/S2 on the spectrum, especially the annual and semiannual variation of the global International GNSS Service (IGS) stations’ position time series? What is the magnitude of the S1/S2 on the 24-h Global Positioning System (GPS) solution, long-term velocity together with the non-linear variations of global IGS stations? without using the existing precise GPS data processing software, for example, GAMIT [13], how do we implement the S1/S2 correction during our own self-developed GPS data processing? These are the focuses of this paper
We first recall the S1/S2 modeling method and give the magnitude and spatial distribution of the global IGS station’s annual amplitude caused by S1/S2 itself under the Center of Mass (CM) frame. We find that both S1 and S2 tides could result in big vertical annual movements, in particular, for those near the equator, whose annual amplitudes are larger than 1 mm
Summary
The diurnal heating of the atmosphere causes the oscillation of the surface pressure at the diurnal (S1), semi-diurnal (S2) periods, as well as other higher frequency harmonics [1]. The amplitude of the vertical deformation caused by S1 and S2 atmospheric tides (hereafter, S1/S2) reached several millimeters, which is equal to the magnitude of some ocean tidal loading components, they must be precisely modeled for geodynamic studies, for example, sea level change or gravity [3,4,5].
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