CETN IV-21
December 1999
Table 1
Principal tidal constituents (Defant 1961)
Name
Symbol
Period, solar hr
Principal lunar
M2
12.42
Principal solar
S2
12.00
Larger lunar elliptic
N2
12.66
Luni-solar semidiurnal
K2
11.97
Larger solar elliptic
T2
12.01
Smaller solar elliptic
L2
12.19
Lunar elliptic second order
2N2
12.91
ν2
Larger lunar evectional
12.63
λ2
Smaller lunar evectional
12.22
2
Variational
12.87
Luni-solar diurnal
K1
23.93
Principal lunar diurnal
O1
25.82
Principal solar diurnal
P1
24.07
Larger lunar elliptic
Q1
26.87
Smaller lunar elliptic
M1
24.84
Small lunar elliptic
J1
23.10
Lunar fortnightly
Mf
327.86
Lunar monthly
Mm
661.30
Solar semiannual
Ssa
2191.43
Tidal boundary specification within the SMS requires that nodes residing on the open ocean
edges of a mesh be marked as tidal boundaries. The set of marked nodes is termed a nodestring
in SMS and represents adjacent nodes sharing a particular characteristic; in this case, they share
the property of being tidal-forcing nodes. Once the tidal boundary type is specified for the nodes,
the tidal constituent toolbox will read those nodes automatically.
Three items can be specified in the toolbox:
1. Tide potential on or off
2. Ramp function on or off
3. Tidal constituent selection and time
The tide potential selection depends on the grid size. Tidal potential forcing should be turned on
for large domains, such as regional grids, but is not necessary for small domains (Westerink et al.
1994).
The ramp function allows an ADCIRC simulation to be initiated without full forcing to eliminate
transient shocks as the model spins up from quiescent conditions. If the ramp function is
invoked, forcing will be initiated at small magnitude and a hyperbolic tangent function applied to
increase the forcing to full magnitude. The user specifies ramp duration. In typical applications,
the ramp duration is 1 to 2 days.
Selection of tidal constituents is demonstrated in the example application.
2
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