Tidal analysis experiments with sun-synchronous satellite altimeter data

The ERS-1, ERS-2 and Envisat series of satellite altimeters provide the only extensive datasets that could conceivably be usedto constrain ocean tide models in high latitudes. Their sun-synchronous sampling, however, severely limits theobservations of solar tides, especially the principal semidiurnal S₂ constituent. The Munk–Cartwright response method is anatural choice when attempting to analyze sun-synchronous data. The present study examines various ways a response analysis might be implemented to extract tides from ERS data. Admittances expressed as simple linear or constant functions of frequency cansometimes improve estimates over standard parameterizations, especially if done in conjunction with a reasonably accurate priorsolution. Some form of regularization, such as ridge regression, is also shown to improve the estimates. The approach provesbeneficial in a test for the southern Indian Ocean tides. It offers some promise for regions otherwise void of usefulobservations.