About some very small harmonics which are present in the tide of the Pacific

Abstract

Over 85% of the harmonic components of the tide along the west coast of Mexico have amplitudes smaller than 2 cm. Yet they are fully resolvable from the noise back-ground so that cotidal charts could be drawn for minor components such as Q1 and T2. A cotidal chart for S1 ist also presented; the presence of this component is attributed not to the tidal forces but to some irregularity in the shape of the Earth or in the distribution of its mass. Third order effects of a magnitude of 1 to 9 mm are evident in the semidiurnal band; they actually exceed the second order input at some stations. The presence of compound harmonics of nonlinear origin, such as 2MK2, MOK2 and NK3 is also detectable. © 1991 Deutsches Hydrographisches Institut.