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4 Physical Mechanisms Forming the Wave Spectrum in Deep Water
E,m 1
0.5
0.4
0.3
0.2
0
0
15
30
45 1, minutes
E,m 2
0.8
0.6
0.4
0.2
0
0
5
10
15
20
t,minutes
Fig. 4.22. Wave dispersion E(t) obtained by the running averaging 77 2 (t):
(a) for the 60s averaging interval (Zaslavskii & Krasitskii, 1993); (b) for the 150 s
averaging interval (Andreev, 1988)
wave development with 3.5 min wave records (Andreev, 1988) is shown in
Fig. 4.23.
The obtained spectra reveal the following features:
- the measured wave values are characterized by various spectral densities
and wave dispersions;
- the most conservative parameter is the spectral maximum frequency Wmax,
which is approximately of the same value in different wave records;
- the greatest fluctuations manifest themselves in the vicinity of the spectral
maximum density.
The sea surface is assumed to respond to low-frequency wind gusts and
squall. This phenomenon can be considered as "quasi-oscillations", clearly
revealed in the changes of the frequency spectrum and wave dispersion even
under the stable conditions of wave development (Andreev, 1988; Zaslavskii
& Krasitskii, 1993).
It is possible to simulate these wave fluctuations of wind wave spectrum
parameters with the help of a source function of the wave energy balance
equation, including wind wave energy input. The role of gusts in the wind
wave generation is described above.
There exists a micro-meteorological spectral maximum possessing a minute period of the atmospheric turbulence spectra (Monin & Yaglom, 1992).
Thus, the fluctuations of wind wave parameters appear at these temporal
scales. The mechanism of wind dispersion generation by atmospheric turbu-