Physics of the Earth - II The Figure of the Earth Bulletin of the National Research Council (1931) / Chapter Skim
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Chapter III. Tidal Computations and Predictions
Chapter III. Tidal Computations and Predictions
Pages 40-49
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From page 40... ...
IEN T OF TIDE :ElECORDS Since the advent of the automatic tide ¢,au~e, the records of tide observations usually consist of continuous curves graphically representing, the rise and fall of the tide, or of height reaclin~,s recorded mechanically at regular intervals such as at eatery quarter of an hour or at any other interval that may be clesired. These records are usually tabulated in two forms.
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From page 41... ...
Instructions f'or Analysis, Tidal Observations, published in 1928 by order of' the Lords Commissioners of the Admiraltv, London, En~lancl, include instructions for computing non-harmonic constants. Lists of' the principal non-harmonic constants for different parts of' the world as derived from reductions of' high and low waters are included in the tide tables published by the principal maritime nations.
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From page 42... ...
The period of the principal lunar component ^~ is the semilunar day, which is about 12.42 solar hours, and the period of the principal solar component So is the half of the solar day, or 12 hours. The number of components which theoretically compose the tide is unlimited, but the number o:t .
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From page 43... ...
The epochs are referred to certain astronomical events, and corrections are applied to both amplitudes and epochs in order to eliminate the effects of other components and to reduce to mean values. The following are the principal publications giving in detail the methods of harmonic reduction as carried on by different authorities: Report of a Committee for the Harmonic Analysis of Tidal Observations, prepared by G
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From page 44... ...
the lunar tropical diurnal and semidiurnal inequalities depending, upon changes in the moon's declination and having, periods of one tropical month, and one-half tropical month, respectively; 3) the lunar anomalistic semidiurnal illequa,lity depending upon changes ill the moods parallax and having a period of one anomalistic month; 4)
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From page 45... ...
This machine, in addition to evaluating the formula given above, also evaluates the first derivative of the equation and thereby indicates the exact times of the maxima and minima or high and low waters. This machine not only traces a tide curve similar to the curves traced by other machines, but it also indicates the times and heights on dials from which the curves may be tabulated directly.
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From page 46... ...
Mullen a tide -me created by- astronomical conditions runs into shallow water, tl~e trou~,l: of the wave is retarded snore than its crest and there results considerable departure from a simple harmo-nic-iorn~. In order to represent this modified form of the tide wave, it is necessary to introduce a series of components of short periocls.
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From page 47... ...
. On the harmonic analysis of tidal observations of high and low water, Proc.
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From page 48... ...
Proudman, J Report on harmonic analysis of tidal observations in the British Empire Brit.
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From page 49... ...
Investigation of harmonic constants, prediction of tides and currents and their description by means of constants, supplemented by an extended list of harmonic constants for the world. International Hydrographic Bureau, Monaco, Special Publication No.
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