On Tidal Inference in the Diurnal Band

Abstract

Standard methods of tidal inference should be revised to account for a known resonance that occurs mostly within the K1 tidal group in the diurnal band. The resonance arises from a free rotational mode of Earth caused by the fluid core. In a set of 110 bottom-pressure tide stations, the amplitude of the P1 tidal constituent is shown to be suppressed relative to K1, which is in good agreement with the resonance theory. Standard formulas for the K1 nodal modulation remain essentially unaffected. Two examples are given of applications of the refined inference methodology: One with monthly tide gauge data and one with satellite altimetry. For some altimeter-constrained tide models, an inferred P1 constituent is found to be more accurate than a directly determined one.