The closest wave buoy to WIS Station 218 is the National Data Buoy Center Buoy 44014 located at 36.58 deg N and
74.83 deg W in depth of 48 m. In addition to the nearshore save locations, WIS saves wave model results for all
active buoy locations for verification. For 1998, data from Buoy 44014 were available for the months of June
through December. Estimates of WIS errors, based on Buoy 44014, are given in Table 1. The bias and root-mean-
square (RMS) error are defined as:
∑ (P
- Psimulated )
measured
Bias =
(1)
n
∑
( Pmeasured - Psimulated ) 2
RMS Error =
(2)
n
where Pmeasured is the measured wave parameter (buoy), Psimulated is the modeled wave parameter (WIS), and n is the
number of values.
Table 1. WIS Errors based on Buoy 44014
Wave Height
Peak Wave Period
Directional Bias
(deg)
Bias (m)
RMS Error (m)
Bias (sec)
RMS Error (sec)
-0.04
0.33
-0.87
2.5
-7.9
2.2 STWAVE
The numerical model STWAVE (Resio 1987, 1988; Smith et al. 2001) was used to transformation the WIS hindcast
from the 25-m depth at Station 218 to 8-m depth for comparison to the FRF 8-m directional array. STWAVE
numerically solves the steady-state conservation of spectral wave action balance along backward-traced wave rays:
C C cos( - α ) E ( f ,α )
C C cos( - α ) E ( f ,α )
∂
∂
S
a ga
a ga
+ (C )
=∑
(C )
(3)
ga x ∂x
ga y ∂y
ω
ω
ω
r
r
r
where
Cga = absolute wave group celerity
Ca = absolute wave celerity
= current direction
α = propagation direction of spectral component
E = spectral energy density
S = energy source/sink terms
The source and sink terms include wind input, nonlinear wave-wave interactions, dissipation within the wave field,
and surf-zone breaking. The terms on the left-hand side of Equation 3 represent wave propagation (refraction and
shoaling), and the source/sink terms on the right-hand side of the equation represent energy growth or decay in the
spectrum.
The assumptions made in STWAVE are as follows:
Mild bottom slope and negligible wave reflection.
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