|EARTH ROTATION VARIATIONS DUE TO ZONAL TIDES
UT1, hence the duration of the day Δ
and the Earth's rotation rate Ω are subject to variations
under the effect of zonal tides. We report here below the model of the IERS
96 conventions. It includes 62 periodic components, with periods ranging from
5.6 days to 18.6 years. They are 41 components with period under 35 days (Table
A) and 27 above (Table B).
UT1 - UT1R = Σ A i sin ξi
UT1R, R, ωR represent the corrected values of UT1, of the
duration of the day Δ and of the angular velocity
of the Earth Ω. The units are 10-4 s
for UT, 10-5 s for Δ , and 10-14
rad/s for Ω.
- R = Σ A'i cos ξi
ω - ωR = Σ A"i cos ξi
where ξi is integer linear combination
of Delaunay arguments : ξi
= a1 l + a2 l' + a3 D + a4 F + a5 Ω
Table A - WITH PERIODS UP TO 35 DAYS
(1981),with K/C = 0.94).
following approximate expressions are sufficient for computing zonal tides effects :