Monthly and fortnightly tidal variations of the Earth's rotation rate predicted by a TOPEX/POSEIDON empirical ocean tide model

Empirical models of the two largest constituents of the long-period ocean t ides, the monthly and the fortnightly constituents, are estimated from repe at cycles 10 to 210 of the TOPEX/POSEIDON (T/P) mission. These models are f irst validated with tide gauge observations which show residual variances w ith the T/P-derived models that are of the order of 2-3 mm(2) for both the monthly and fortnightly constituents, and which are smaller than residual v ariances from respective equilibrium models of these long-period ocean tide s. These empirical models are used to predict the contribution that they ea ch have on tidal variations of the Earth's rotation rate. For tidal variati ons in UT1 these contributions are predicted to be of the order of 0.1 ms w ith a scatter of the order of 8 and 3 mu s for the monthly and fortnightly ocean tides, respectively.