We have used the altimetric tides as derived by University of Texas group for assimilation. The coamplitude-cophase plots are shown for M2, S2, K1 and O1 from the global model along with the results from UT analyses. It is not surprising that the results constitute only a marginal improvement over UT product in the deeper parts of the basin. However in shallow parts and in semi-enclosed seas, the results are expected to be far more accurate. We have purposely avoided assimilating pelagic gages so that the results can be compared to those data.
Table shows the rms differences between pelagic gages and various models.
It is not surprising that the rms differences are within mms of the rest of the models although M2 shows large differences, especially in the South Pacific. We are examining the causes. In the deep, tides are close to altimetry- derived tides, but it is worth noting that they have been subjected to dynamical constrints by the fully nonlinear model. Shown also are global distribution of differences between this model and the UT model. The differences are mostly in the 2 cm level except near regions such as New Zealand, where UT tides are suspected to be inaccurate.