S. D. Desai, and J. M. Wahr, Monthly and fortnightly tidal variations of the Earth's rotation rate predicted by a TOPEX/POSEIDON empirical ocean tide model, Geophys. Res. Lett., 26(8), 1035-1038, 1999.

S. D. Desai, and J. M. Wahr, Empirical ocean tide models estimated from TOPEX/POSEIDON altimetry, J. Geophys. Res., 100(C12), 25205-25228, 1995.

E. W. Schwiderski, Ocean tides: a hydrodynamic interpolation model, Marine Geodesy, 3, 219-255, 1980.

The two principal tidal constituents in the long-period tidal band are the monthly (Mm) and fortnightly (Mf) tidal constituents. Desai and Wahr (1999) presented harmonic constants for the Mm and Mf ocean tide contribution to tidal variations of the Earth's rotation rate. These were predicted from an extended empirical ocean tide model that was estimated from approximately 5.4 years of TOPEX/POSEIDON altimetric data. It should be noted that the Mm and Mf empirical ocean tide models are actually limited to those latitudes within ±66 degrees, and are extended to global models using the Mm and Mf hydrodynamic ocean tide height models of Schwiderski (1980) poleward of ±66 degrees latitude.

The empirical models used by Desai and Wahr (1999) are described in a preliminary analysis performed by Desai and Wahr (1995), where only 1.8 years of TOPEX/POSEIDON altimetric data were used to derive the empirical ocean tide height models for Mm and Mf.

Desai and Wahr (1999) caution the use of the currents term for Mm which appears to be anomalously large, because in theory it is expected to be smaller than the currents term for Mf. Comparisons with geophysical phenomena (e.g. mantle anelasticity) support the suggestion that the Mm currents term from Desai and Wahr (1999) is too large.

Each pair of numbers below is an amplitude and a phase lag. Values in brackets are derived from the 1 sigma scatter in these predictions (see Desai and Wahr (1999) for explanation). Amplitude units for UT are microseconds. Phase units are degrees.

                                       TIDAL VARIATIONS IN UT1

                                    Mm                            Mf    
                         ------------------------      -----------------------
Ocean Tidal currents      48.3 (6.4)  354.4 (7.6)       16.9 (2.2)  359.0 (5.9)
Ocean Tidal heights      119.1 (2.0)  273.1 (0.8)      102.4 (0.4)  287.5 (0.3)
Ocean Tide  TOTAL        135.1 (7.6)  293.8 (4.3)      109.1 (2.0)  295.9 (1.6)