SLACK TIDE DEFINITION FULL

angular velocity of the Earth's rotation (Ω) Time rate of change of angular displacement relative to the fixed stars. analyzer, harmonic See harmonic analyzer. analysis, harmonic See harmonic analysis. analog A continuous measurement or a continuous graphic display of data. By analogy, it may be applied also to the maximum speed of a constituent current. amplitude (H) One-half the range of 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. amphidromic point A point of zero amplitude of the observed or a constituent tide. It is an extension of the Alaska Current. Alaskan Stream A North Pacific Ocean current setting westward along the south side of the Aleutian Islands. Alaska Current A North Pacific Ocean current setting counterclockwise along the coasts of Canada and Alaska in the Gulf of Alaska. Air temperature sensors are located in the protective well for the purpose of verifying uniformity of temperature for measurements taken by the air acoustic ranging sensor. A calibration point is set at a fixed distance from the acoustic transducer and is used to correct the measured distance using the calibrated sound velocity in the tube. The distance from a reference point to the water surface is derived from the travel time. The fundamental measurement is the time it takes for the acoustic signal to travel from a transmitter to the water surface and then back to the receiver. air acoustic ranging sensor A pulsed, acoustic ranging device using the air column in a tube as the acoustic sound path.

Agulhas Current An Indian Ocean current setting southwestward along the southeast coast of Africa. age of tide Same as age of phase inequality agger Same as double tide. This age may be computed from the harmonic constants by the formula:Īge of phase inequality = 0.984(S 2° - M 2°) hours.

SLACK TIDE DEFINITION FULL

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 the formula:Īge of parallax inequality = 1.837(M 2° - N 2°) hours. age of Moon The time elapsed since the preceding new Moon age of parallax inequality The time interval between perigee of the Moon and the maximum effect of parallax upon range of tide or speed of the tidal current. The age may be computed from the harmonic constants by the formula:Īge of diurnal inequality = 0.911(K 1° - O 1°) hours. 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 speedof the tidal current. A float or pressure-actuated water level gauge that records heights at regular time intervals in digital format. ADR gauge Analog to Digital Recording water level gauge. In the latter configuration, it is nonobtrusive in the water column and thus can be deployed in shipping channels.

The ADCP can be deployed from a moving vessel, tow, buoy, or bottom platform. The bin determinations allow development of a profile of current speed and direction over most of the water column.

Time gating circuitry is employed which uses differences in acoustic travel time to divide the water column into range intervals, called bins. The current is determined by a Doppler shift in the backscatter echo from plankton, suspended sediment, and bubbles, all assumed to be moving with the mean speed of the water. acoustic Doppler current profiler (ADCP) A current measuring instrument employing the transmission of high frequency acoustic signals in the water. 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 equivalent value that would be obtained with a 19-year series. Absolute mean sealevel 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.

Slack tide definition