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reduced by comparison with simultaneous observations
thermosteric anomaly( , , or ) The specific
T s,t
from a control current station. See current station, control
volume anomaly (steric anomaly) that would be attained if
current station, and reference station. (2) A station listed
the water were changed isothermally to a standard pressure
in the Tidal Current Tables for which predictions are to be
of one atmosphere. The specific volume anomaly with
obtained by means of differences and ratios applied to the
pressure terms omitted. See isanostere.
full predictions at a reference station. See reference
tidal bench mark See bench mark.
station.
tidal bench mark description A published, concise
subordinate tide station (1) A tide station from
description of the location, stamped number or des-
which a relatively short series of observations is reduced
ignation, date established, and elevation (referred to a tidal
by comparison with simultaneous observations from a tide
datum) of a specific bench mark.
station with a relatively long series of observations. See
tidal bench mark state index map A state map
tide station, primary control tide station, secondary control
which indicates the locations for which tidal datums and
tide station, and tertiary tide station. (2) A station listed in
tidal bench mark descriptions are available.
the Tide Tables from which predictions are to be obtained
tidal bore A tidal wave that propagates up a rela-
by means of differences and ratios applied to the full
tively shallow and sloping estuary or river with a steep
predictions at a reference station. See reference station.
wave front. The leading edge presents an abrupt rise in
summer time British name for daylight saving time.
level, frequently with continuous breaking and often
synodical month The average period of the revolu- immediately followed by several large undulations. An
tion of the Moon around the Earth with respect to the Sun,
uncommon phenomenon, the tidal bore is usually asso-
or the average interval between corresponding phases of
ciated with very large ranges in tide as well as wedge
the Moon. The synodical month is approximately
shaped and rapidly shoaling entrances. Also called eagre,
29.530,588 days in length.
eager (for Tsientan, China bore), mascaret (French),
syzygy With respect to tides, whenever the Moon is
pororoca (Brazilian), and bore.
lined up with the Earth and Sun in a straight Sun-Moon-
tidal characteristics Principally, those features re-
Earth or Sun-Earth-Moon configuration. At these times the
lating to the time, range, and type of tide.
range of tide is greater than average. See spring tides or
tidal constants Tidal relations that remain prac-
tidal currents.
tically constant for any particular locality. Tidal constants
are classified as harmonic and nonharmonic. The harmonic
T
constants consist of the amplitudes and epochs of the
T Rate of change of hour angle of mean Sun at place
harmonic constituents, and the nonharmonic constants
of observation.
include the ranges and intervals derived directly from the
T = 15° per mean solar hour.
high and low water observations.
T2 Larger solar elliptic constituent. See R2.
tidal constituent See constituent.
Speed = 2T h + p1 = 29.958,933,3° per solar hour.
tidal current A horizontal movement of the water
tape gauge See electric tape gauge.
caused by gravitational interactions between the Sun,
telemetry The capability of transmitting or retriev- Moon, and Earth. The horizontal component of the
particulate motion of a tidal wave. Part of the same general
ing data over long distance communication links, such as
movement of the sea that is manifested in the vertical rise
satellite, VHF radio, or telephone.
and fall called tide. The United States equivalent of the
terdiurnal Having three periods in a constituent
British tidal stream. See tidal wave, tide, and current.
day. The symbol of a terdiurnal constituent is the subscript
Tidal Current Chart Diagrams A series of
3.
monthly diagrams to be used with the Tidal Current Charts.
tertiary tide station A tide station at which con-
Each diagram contains lines that indicate the specific tidal
tinuous observations have been made over a minimum
current chart to use for a given date and time, and the speed
period of 30 days but less than 1 year. The series is
factor to apply to that chart.
reduced by comparison with simultaneous observations
Tidal Current Charts Charts on which tidal current
from a secondary control tide station. This station provides
data are depicted. Tidal Current Charts for a number of
for a 29-day harmonic analysis. See tide station, primary
important waterways are published by the National Ocean
control tide station, secondary control tide station, and
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