Wave-breaking probability - Breaking and Dissipation of Ocean Surface Waves - page 188

Figure 5.27 Breaking probabilities versus wave frequency f normalised by the peak frequency f p .
(a) b T ( f ) (5.28) ;(b) b T normalised by the spectral density P ( f ) . Squares: 12 . 8m / s; *: 12 . 9m / s;
∇ :13 . 2m / s; diamonds: 13 . 7m / s; × :15 . 0m / s; circles: 19 . 8m / s. The records are from Table 5.2 .
Figure is reproduced from Manasseh et al. ( 2006 )

© American Meteorological Society. Reprinted

with permission

the breaking-probability frequency distributions which had hardly been examined before
experimentally.
In this figure, distributions of b T ( f p

for records 5 through 11 of Table 5.2 , which correspond to different wave spectra devel-
oped under different wind speeds. In Lake George's bottom-limited environment, well-
developed and even fully developed waves can still be strongly forced ( Young & Babanin ,
2006b ) and therefore are expected to break at the spectral peak.
Out of the six wave records analysed, only the first one (19

f ) (5.28) are plotted versus relative frequency f /

s mean wind speed),
corresponds to full development for the given water depth ( Young & Babanin , 2006b ).
Therefore, although the waves are strongly forced, the wave spectrum will not develop
further: the total wave energy will not grow and the spectral peak will not shift to lower
frequencies. Since both the wind and the nonlinear interactions keep pumping energy into
these lower frequencies, it must be rapidly dissipated at these scales due to interaction of
the longer waves with the bottom and subsequent breaking. This is seen in the upper curve
of the top panel of Figure 5.27 : nearly 100% breaking is measured for frequencies below
the spectral peak.

. 8m /