Fig. 4. Regional wave model grid with nested finer grids in areas of complex bathymetry.
STWAVE model runs were made with both measured Buoy 44025 bulk parameters
(Hmo, Tp, and vector mean wave direction) and WIS-hindcast wave spectra serving as input.
Because only bulk parameters were available from the buoy, spectra were synthesized with
a JONSWAP shape and cosine-4th Mitsuyasu spreading. The JONSWAP peak
enhancement factor was 3.3 in all cases. The two-dimensional spectra in both cases have
30 frequency bins and 35 direction bins. Because the nearshore wave transformation model
STWAVE is a half-plane model, only the portion of the directionally spread spectrum that
is traveling onshore (that is, with a wave angle of less than +/- 85 deg from shore-normal) is
transformed through the model domain. In those cases, the input significant wave height to
the model will be truncated as compared to the measured buoy wave height and the input
mean wave direction will be the mean of the onshore-directed wave components.
The hindcast wave spectra were also truncated to retain only the onshore-directed
portion of the directional wave spectrum. In this case only that part of the spectrum within
67.5 deg of shore-normal is retained because the directional spectra contain 20 frequency
and 16 directional bins. Again, because only a portion of the spectrum is input to the model
grid, the wave height, period, and mean direction can differ from values that are obtained
from integrating the total hindcast spectrum.
Offshore Boundary Conditions. For the entire validation period, the hindcast wave
spectra are compared to measurements at Buoy 44025. Hindcast waves from a point in
53-m water depth, located at 40.25 N, 72.5 served to develop input spectra for STWAVE
as were data from the buoy located in 40-m water depth at 40.25 N, 73.17 W. Figures 5
and 6 illustrate the quality of agreement between the two sources of offshore boundary data.