Tides and Currents Glossary
Science / Tides and Currents Glossary
2N2: Lunar elliptic semi diurnal second-order constituent. Speed = 2T– 4s + 2h + 2p = 27.895,354,8° per solar hour.
2Q1: Lunar elliptic diurnal, second order, constituent. Speed = T – 4s + h + 2p = 12.854,286,2° per solar hour.
Absolute Mean Sea Level Change: An eustatic change in mean sea level relative to a conventional terrestrial coordinate system with the origin at the center of mass of the Earth.
Accepted Values: Tidal datums and Greenwich high and low water intervals obtained through primary de-termination or comparison of simultaneous observations with a control tide station in order to derive the . . . View Full Definition
Acoustic Doppler Current Profiler (ADCP): Current measuring instrument employing the transmission of high frequency acoustic signals in the water. The current is determined by a Doppler shift in the backscatter echo from plankton, s . . . View Full Definition
ADR Gauge: Analog to Digital Recording water level gauge. A float or pressure-actuated water level gauge that records heights at regular time intervals in digital format.
Age Of Diurnal Inequality: The time interval between the maximum semimonthly north or south declination of the Moon and the maximum effect of declination upon range of tide or speed of the tidal current. The age may b . . . View Full Definition
Age Of Moon: The time elapsed since the preceding new Moon
Age Of Parallax Inequality: The time interval be tween perigee of the Moon and the maximum effect of parallax upon range of tide or speed of the tidal current. This age may be computed from the harmonic constants by th . . . View Full Definition
Age Of Phase Inequality: The time interval between new or full Moon and the maximum effect of these phases upon range of tide or speed of the tidal current. This age may be computed from the harmonic constants by th . . . View Full Definition
Agulhas Current: An Indian Ocean current setting southwestward along the southeast coast of Africa.
Air Acoustic Ranging Sensor: A pulsed, acoustic ranging device using the air column in a tube as the acoustic sound path. The fundamental measurement is the time it takes for the acoustic signal to travel from a transmi . . . View Full Definition
Alaska Current: A North Pacific Ocean current setting counterclockwise along the coasts of Canada and Alaska in the Gulf of Alaska.
Alaskan Stream: A North Pacific Ocean current setting westward along the south side of the Aleutian Islands. It is an extension of the Alaska Current.
Amphidromic Point: A point of zero amplitude of the observed or a constituent tide.
Amphidromic Region: An area surrounding an am phidromic point from which the radiating cotidal lines progress through all hours of the tidal cycle.
Amplitude (H): One-half the range of a constituent tide. By analogy, it may be applied also to the maximum speed of a constituent current.
Analog: A continuous measurement or a continuous graphic display of data. See ADR gauge and marigram.
Angular Velocity Of The Earths Rotation: Time rate of change of angular displacement relative to the fixed stars. It is equal to 0.729,211 x 10-4 radian/second.
Annual Inequality: Seasonal variation in water level or current, more or less periodic, due chiefly to me teorological causes.
Anomalistic: Pertaining to the periodic return of the Moon to its perigee or the Earth to its perihelion. The anomalistic month is the average period of the revolution of the Moon around the Earth with r . . . View Full Definition
Anomaly: As applied to astronomy, the anomaly is the angle made at any time by the radius vector of a planet or moon with its line of apsides, the angle being reckoned from perihelion or perigee in t . . . View Full Definition
Antarctic Circumpolar Current: The largest permanent current in the world, setting eastward around the Antarctic Continent south of Cape Horn, Cape of Good Hope, Tasmania, and New Zealand. Through Drake Passage, it transp . . . View Full Definition
Anticyclonic Ring: A meander breaking off from the main oceanic current and spinning in a clockwise direction in the northern hemisphere (counter-clockwise in southern).
Antilles Current: A North Atlantic Ocean current setting northwestward along the northeast coasts of the Bahama Islands.
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