Long‐period tidal factors at Antarctica Syowa Station determined from 10 years of superconducting gravimeter data

Abstract

[1] We determined long-period gravimetric tidal parameters from 10 years of superconducting gravimeter observations at Syowa Station in Antarctica. The obtained amplitude and phase lead for the Mm wave were 6.106 ± 0.030 mGal (mGal = 10 À8 m s À2 ), 0.32°± 0.28°, respectively, and those for the Mf wave were 11.657 ± 0.018 mGal, 0.78°± 0.09°, respectively. We also determined the parameters of other tidal constituents with periods of 6 to 32 days; Mqm, Msqm, Mtm, Mstm, Msf, Msm, and their frequency dependence was estimated by means of a weighted least squares method. The observed values, corrected by the four ocean tide models of Schwiderski, NAO.99L, FES99, and TPXO6.0, were compared with the theoretical values calculated from the elastic and inelastic solid Earth tide models by Dehant et al. Even though the values of the ocean tide corrections have relatively large discrepancies between the four models and it is still difficult to discuss the degree of inelasticity of the Earth for this frequency band, we can say that the observations favor the inelastic Earth model rather than the elastic model.

Assessment of the Algorithm for Single Frequency Precise Point Positioning at Different Latitudes and with Distinct Magnetic Storm Conditions

“…The hydrostatic tropospheric delay was corrected by the Saastamoinen model [30], and the tropospheric constraints were products released by IGS. Earth, pole, and ocean tides were corrected according to [31], and model corrections for the Sagnac [32] and the relativistic effect [33] have been used for model corrections. The Kalman filtering method was adopted to estimate the parameters, and finally the float solution was obtained.…”

Five years’ gravity observation with the superconducting gravimeter OSG#058 at Syowa Station, East Antarctica: gravitational effects of accumulated snow mass

“…The data provided many results related to the Earth's tides, free oscillations and variable rotations in addition to seasonal variations in the ocean, whose magnitudes ranged from 0.001 to 100 µGal (1 µGal = 10 −8 m s −2 ) (e.g. Sato et al 1997;Nawa et al 1998;Sato et al 2001;Iwano et al 2005;Kim et al 2011). However, there was uncertainty in these deduced long-period gravity variations due to the significant step-like perturbations that arose in this instrument as a result of regular maintenance, during which gas helium was liquefied by a separate liquefier system and the obtained liquid helium (LHe) was transferred into the dewar of the TT-70#016 when the LHe levels become depleted (for details, see Appendix).…”

“…Fig. 4(a) shows the filtered gravity data at 1 min intervals for the 5 yr period of 2010 January 7-2015 January 10, together with the predicted tides computed using the tidal parameters obtained from 10 yr's observations with TT-70#016 (Iwano et al 2005). The non-tidal gravity (grey line, Fig.…”

Earth Tides

“…The lowest noise and most stable calibration are provided by the superconducting gravimeter (Goodkind, 1999), in which a superconducting sphere is suspended in a magnetic field at liquid-helium temperatures. Because the noise is so low, small tidal signals can be measured with great precision; recent examples include the detection of loading from small nonlinear ocean tides Merriam, 1995) and the discrimination between the loads from equilibrium and dynamic models for the long-period ocean tides (Boy et al, 2006a;Iwano et al, 2005). At the periods of the semidiurnal tides, the noise on superconducting gravimeters ranges from À130 to À140 dB (relative to 1 m 2 s À4 ), with the noise being about 5 dB higher in the diurnal band (Rosat et al, 2004); these levels are about 5 dB below those of spring gravimeters (Cummins et al, 1991).…”