Long Period Tide Variation from Satellite Laser Ranging (SLR)

The satellite laser ranging (SLR) over four decades has recorded the global nature of the long-wavelength mass change within the Earth system, in particular, the Earth’s dynamical oblateness, characterized by the second degree gravitational zonal geopotential spherical harmonic J2.  The SLR tracking data is a unique space geodetic measurement capable of characterizing the 18.6-yr tide variations in the solid earth and ocean, which produce the variations in J2 with different amplitude and phase. Analysis of the most recent time series of 30-day SLR-based estimates of J₂ yield a nominal anelasticity Love number estimate of k₂ = 0.31107±0.0011 with the IERS model of the frequency dependent Love number at 18.6-yr period from the reference frequency= 200 seconds and a = 0.155 for mantle inelasticity. The effects of the mantle inelasticity of the solid earth must be considered in modeling of the response of the global ocean to the lunar attraction at the 18.6-yr period. Results show that the mantle effects produce a deviation by ~0.09 cm in amplitude and ~2.5° in phase from the equilibrium ocean with elastic response model.