These harmonic constants for tidal variations in rotation rate and polar motion are based on the TPXO.6.2 global ocean tide model, produced in 2003 by Gary Egbert and Lana Erofeeva of Oregon State University. The tidal model is an update to work published by Egbert et al. (1994). The Earth rotation parameters for an earlier version of Egbert's model (TPXO.2) were published by Chao et al. (1996), and the same computational procedures were used here to determine EOP.
The TPXO.6 model is an assimilation model. It uses both a numerical hydrodynamic model and tidal observations, the latter in the form of sea-surface height differences measured by the Topex/Poseidon satellite. The model is truly global: the finite-difference grid was rotated so that "poles" appeared only over land regions. This solution of the model is considerably more accurate than earlier versions, at least in terms of tidal elevations.
B F Chao, R D Ray, J M Gipson, G D Egbert, C Ma, Diurnal/semidiurnal polar motion excited by oceanic tidal angular momentum, J. Geophys. Res., 101, 20151-63, 1996.
G D Egbert, A F Bennett, M G G Foreman, Topex/Poseidon tides estimated using a global inverse model, J. Geophys. Res., 99, 24821-52, 1994.
Each pair of numbers below is an amplitude and a phase lag. Amplitude units for UT are microseconds. Amplitude units for polar motion are microarcseconds. Phase units are degrees.
TIDAL VARIATIONS IN UT1
Q1 O1 P1 K1
----- ----- ----- -----
Tidal currents 3.7 19 17.9 30 6.1 38 20.4 40
Tidal heights 1.5 50 4.5 82 0.8 295 2.4 287
TOTAL 5.1 28 20.9 39 6.0 31 19.6 33
N2 M2 S2 K2
----- ----- ----- -----
Tidal currents 4.3 239 22.3 230 10.6 258 2.8 249
Tidal heights 1.1 317 6.1 356 2.8 39 1.0 31
TOTAL 4.7 253 19.3 245 8.6 269 2.1 265
TIDAL VARIATIONS IN PROGRADE POLAR MOTION
Q1 O1 P1 K1
----- ----- ----- -----
Tidal currents 1.9 81 26.5 68 15.2 98 48.9 97
Tidal heights 28.8 78 115.3 60 43.3 46 136.4 44
TOTAL 30.7 79 141.5 62 54.0 59 170.7 57
N2 M2 S2 K2
----- ----- ----- -----
Tidal currents 11.1 106 78.9 107 41.6 79 11.4 88
Tidal heights 9.2 173 17.1 203 16.6 243 4.4 242
TOTAL 17.0 136 78.9 119 26.0 89 7.7 103
TIDAL VARIATIONS IN RETROGRADE POLAR MOTION
Q1 O1 P1 K1
----- ----- ----- -----
Tidal currents 26.1 312 150.5 297 73 282 193 284
Tidal heights 13.2 316 41.7 137 900 131 10041 132
TOTAL 39.2 314 112.4 289 837 134 9872 133
N2 M2 S2 K2
----- ----- ----- -----
Tidal currents 38.4 251 279.7 260 151/2 295 43.1 289
Tidal heights 15.6 346 72.7 19 32.3 83 8.9 83
TOTAL 40.1 274 252.9 275 125.0 303 35.3 296