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Articles

1986: Vol. LXIII, No. 1

On the Conditions for Classification of Tides

Submitted
July 31, 2015
Published
2015-07-21

Abstract

This investigation is carried out to examine the conditions which are commonly used to classify a tidal regime as diurnal or semi-diurnal. It is observed that the application of Courtier's (1938) criterion in tidal predictions is not always appropriate. It is shown that during some neap tides most of the major tidal harmonics of the semi-diurnal band may conspire to oppose the M2 tide. Consequently, at some ports the semi-diurnal component may degenerate into a dodge tide. Under these circumstances, though a tide may be classified as semi-diurnal according to Courtier’s criterion, the tidal profile is determined by the constituents of the other species. A diurnal tide can occasionally become semidiurnal for similar reasons. A simple mathematical explanation of these conditions and when they are likely to occur is given. For practical purposes, new conditions that must be satisfied for a tide to be diurnal or semi-diurnal during the full spring-neap cycle are suggested.