EM 1110-2-1100 (Part II)
30 Apr 02
(g) Reconstruction of the tide involves determining the equilibrium arguments, node factors, longitude
and time adjustment for each constituent, and using the published values for κ, Hn, and H0 in the NOS
harmonic analysis. Table II-5-6 summarizes all necessary quantities.
Harmonic Arguments for Sandy Hook NJ (1 January 1984 at 0000 hr)
(h) The NOS harmonic analysis indicates that a multiplier of 1.04 should be used for all short-period
constituents and that the value of H0 is 2.36 MSL. Also indicated on the analysis is the time meridian of 75E
west longitude for use in computing the time zone compensation term aS/15. The 15-day tidal envelope is
shown in Figure II-5-14. The open circles shown in the figure represent high- and low-water level predictions
extracted from the tide tables in Figure II-5-13. As stated, the comparison is not exact because only eight
constituents were used in the reconstruction. The match is, however, adequate for the majority of design
(i) The phase lag κ in Equation II-5-19 is called the local epoch in order to distinguish it from other
forms of epochs (see Schureman (1924)). Some harmonic analyses use a modified form of the epoch that
automatically accounts for the longitude and time meridian corrections. This modification is designated as
κ' and is defined as shown below
κ) ' κ % pL &
(j) This modified form is usually included on NOS harmonic analyses as indicated on Figure II-5-12.
Use of this form of epoch in the reconstruction of tides is as shown below
H (t)local ' H0 % j fn Hn cos [ant % Greenwich (V0 % u) & κ, n]
(4) Tidal envelope classification.
(a) Semidiurnal, diurnal, and mixed tidal classifications were described in Part II-5-3a. Equation II-5-22
is a more quantitative delineation of tide types.
Water Levels and Long Waves