The delay, in degrees of the constituent's own cycle, between the peak of the equilibrium tide and the peak of the same constituent at the station. It is quoted either relative to the local meridian (kappa) or referred to Greenwich (often written G or g), the form used on cotidal charts and in global tide models. Together with amplitude, the phase lag of each constituent is one of the two harmonic constants that define the local tide.
M2 phase lag is 215 degrees here against 190 at the entrance, so high water arrives about 50 minutes later.
Also heard as
- kappa
- Greenwich phase lag
- epoch (harmonic)
- G
Related terms
Harmonic constituent
One of the regular cosine waves, each with a period fixed by astronomy, that together make up the tide.
Equilibrium tide
The theoretical tide an ocean covering the whole Earth would show if it responded instantly to the tidal forces.
Cotidal line
A map line through every place where high water of a tide or constituent arrives at the same moment.
Harmonic analysis
Breaking an observed water level or current record into its tidal constituents to find each one's amplitude and phase.