5. Glossary
- Aliasing
spurious tidal frequency appearing in an analysis due to inadequate temporal sampling
- Amphidrome
point of zero tidal amplitude in a tidal wave due to a canceling of tidal waves
- Amplitude
one half of the range of a tidal constituent
- Anomaly
angular distance between the perihelion and the position of a celestial body
- Apogee
point of an orbit where a celestial body is furthest to Earth
see Perigee
- Aphelion
point of an orbit where a celestial body is furthest from the sun
see Perihelion
- Apsides
points of an orbit where a celestial body is closest and furthest from the center of attraction
see Perihelion, Aphelion, Perigee and Apogee
- Ascending Node
point of an orbit where a celestial body intersects the ecliptic, and the latitude coordinate is increasing
- Barycenter
center of mass of a system of bodies, such as the solar system or the Earth-Moon system
- Body Tide
see Solid Earth Tide
- Chandler Wobble
small, semi-periodic deviations in the motion of the pole of rotation
- Compound Tide
harmonic constituent with a speed equal to the sum or difference of the speeds of two or more elementary constituents
- Constituent
- Declination
angular distance of an astronomical body north or south of the celestial equator, with north being positive and south negative
- Descending Node
point of an orbit where a celestial body intersects the ecliptic, and the latitude coordinate is decreasing
- Diurnal Tide
tidal oscillations with a near-daily period
- Earth Tide
tidal variations of the surface of the solid Earth, frequently split into the Body Tide and the Load Tide
- Ecliptic
mean plane of the orbit of the Earth around the sun
- Ephemerides
plural of Ephemeris
- Ephemeris
table of positions and velocities of a celestial body at given instances in time
- Epoch
fixed point in time used as a reference value
- Equilibrium Theory
model under which the ocean of a uniformly covered Earth responds instantaneously to lunisolar gravitational forces and forms an equilibrium under these forces, in the absence of inertia, currents and the irregular distribution of land
- Equilibrium Tide
hypothetical tide produced solely by lunisolar gravitational forces under Equilibrium Theory, in the absence of ocean dynamics or terrestrial constraints
- Equinox
the ascending node of the Earth’s orbit about the sun, and the point on the equatorial plane where it meets the ecliptic plane
- Flattening
ratio of the difference between the semi-major and semi-minor axes of an ellipsoid to the semi-major axis
- Free Core Nutation
Nearly diurnal deviations in the motion of the pole of rotation due to the resonant motion of the Earth’s core relative to the mantle
see Nutation
- Frequency
number of cycles in a unit time
- Geocentric Tide
tidal variation relative to the Earth’s center of figure, which is equal to the sum of the Ocean Tide and Earth Tide
- Geopotential
the Earth’s gravitational potential
- Geoid
equipotential surface coinciding with the ocean surface in the absence of astronomical or dynamical effects
- Harmonic Analysis
mathematical process by which the tides are separated into Harmonic Constituents
- Harmonic Constants
amplitude and phase of the Harmonic Constituents
- Harmonic Constituents
harmonic elements of the tide-producing force corresponding with a periodic change of relative position of the Earth, Sun and Moon
- Harmonic Prediction
method of estimating tidal elevations and currents through a combination of the Harmonic Constituents
- High Water Height
height of the maximum vertical elevation of the tide relative to a fixed datum
see Low Water Height
- King Tide
see Spring Tide
- Load Tide
elastic deformation of the solid Earth due to ocean and atmospheric tides
- Long Period Tide
tidal oscillations with periods much greater than one day (typically 9.1 days to 18.6 years)
- Love and Shida Numbers
dimensionless parameters relating the vertical (h), horizontal (l) and gravitational (k) elastic responses to tidal loading
- Low Water Height
height of the minimum vertical elevation of the tide relative to a fixed datum
- Lunisolar Tide
tidal constituent induced from a combination of lunar and solar gravitational forces
- Mean Tide
model with both direct and indirect permanent tidal effects retained
- Neap Tide
tides of the least amplitude within a 15-day cycle
see Spring Tide
- Nodal Corrections
adjustments to the amplitudes and phases of harmonic constituents to allow for periodic modulations over the 18.6-year nodal period
- Nutation
short-period oscillations in the motion of the pole of rotation of a freely rotating body
- Obliquity
angle between the equatorial and orbital planes
- Ocean Tide
periodic movement in the level of sea surface due to gravitational and rotational forces
- Perigee
point of an orbit where a celestial body is closest to Earth
see Apogee
- Perihelion
point of an orbit where a celestial body is closest to the sun
see Aphelion
- Period
time it takes to make one complete revolution
- Permanent Tide
permanent deformation of the Earth caused by the presence of the Sun and the Moon
- Polar Motion
irregular motion of the Earth’s pole of rotation relative to the Earth’s crust
- Pole Tide
apparent tide due to variations in the Earth’s axis of rotation about its mean
- Precession
regular conical motion of the pole of rotation of a freely rotating body
- Radiational Tide
tidal constituents or components induced by the absorption and re-emission of solar radiation
- Range
height difference between the High Water Height and the Low Water Height
- Residuals
differences between the observed sea level and the tidal predictions for a given location
- Semi-diurnal Tide
tidal oscillations with an approximate half-day period
- Shallow-water Tide
additional tidal constituents necessary for shallow seas that are heavily dependent on ocean bathymetry and coastline geometry
- Sidereal day
time it takes for a celestial body to make one complete rotation relative to the stars
- Solid Earth Tide
deformation of the solid Earth due to gravitational forces
- Species
classification of tidal constituents based on approximate period
see Semi-diurnal Tide, Diurnal Tide, and Long Period Tide
- Spring Tide
tides of the greatest amplitude within a 15-day cycle, sometimes called a King Tide
see Neap Tide
- Tidal Current
horizontal movement of water due to periodic forces
- Tidal Datum
reference level to which a phase of the tides are measured
see High Water Height and Low Water Height
- Tidal Species
see Species
- Tidal Stream
see Tidal Current
- Tide-Free
model with direct and indirect permanent tidal effects removed
- Vernal Equinox
intersection of the Earth’s equatorial plane and the Earth’s Ecliptic
see Equinox
- Vertical Datum
reference coordinate surface used for vertical positions
- Zero Tide
model with permanent direct tidal effects removed, but indirect loading effects retained