Tidal variations of Earth rotation

Abstract

We have rederived the periodic variations of the earth's rotation due to the tidal deformation of the earth by the sun and moon and included all terms with amplitudes ≥0.002 milliseconds (1 mm). This series applies to the mantle (plus crust) and oceans, which rotate together for characteristic tidal periods. The parameter which scales the rotational series is k/C, where k is that fraction of the Love number which causes the tidal variation in the moment of inertia of the coupled mantle and oceans while C is the dimensionless polar moment of inertia of the coupled units. If the whole earth (minus oceans) were coupled rotationally, then k = 0.30 and C = 0.33. Ocean tides increase k by 0.04. Decoupling of the fluid core from the mantle decreases k by 0.06 while C = Cmantle = 0.29, since neither pressure, viscous, nor hydromagnetic coupling locks the fluid to the mantle for periods less than 5 to 25 years. From the analysis of lunar laser ranging data we find that k/C at monthly and fortnightly frequencies equals 0.99 ±0.15 and 0.99 ± 0.20 as compared with a theoretical value of 0.94 ± 0.04. In addition, we have estimated theoretically the effects of ocean tides on earth rotation, nutation and polar motion using models based on the Laplace tidal equations.

The various contributions in Venus rotation rate and LOD

“…3. The zonal part of the potential on a nonrigid Venus thus has little influence on its very slow rotation, in contrast to the Earth, for which these variations with annual and semi-annual components are not negligible (on the order of 10 −3 s) with respect to the 1d rotation (Yoder et al 1981;Souchay & Folgueira 1998). The semi-annual components are particularly small for Venus because its eccentricity and obliquity are much lower than their respective value for the Earth.…”

Geodetic and Geophysical Applications of High Precision Astrometry

“…Tidal variations in LOD arise from changes in Earth's moment of inertia due to the solid body tides (Yoder et al, 1981), and PM and LOD e ects at tidal frequencies are also expected from the tri-axiality of the Earth (Chao et al, 1 9 9 1 ) . In addition to these solid Earth in uences, there are also ocean tide e ects on PM and LOD.…”

Commission 19: ROTATION OF THE EARTH

“…Of the oceanic tide models evaluated, models constrained by data are shown to perform better than those not constrained by data. The sum of the Yoder et al (1981) elastic body tide model, Wahr & Bergen (1986) inelastic body tide model, and Kantha et al (1998) . The residuals would be compatible with corrections of a few tens of μas to the 18.6-yr nutation, which would be absorbed in small corrections to the estimates for a couple of the BEP of the MHB model.…”