Detection and measurement of wave breaking - Breaking and Dissipation of Ocean Surface Waves - page 103

Mariupol

Odessa

Crimea

Oil rig

Sevastopol

Novorossiisk

Kotetvell

The Black Sea

Istanbul

Figure 3.14 Location of research platforms in the Black Sea (pluses). Figure is reproduced from
Babanin & Soloviev ( 1998a ) © American Meteorological Society. Reprinted with permission

The waves were recorded by an array of high-precision wire wave gauges, deployed
beyond the zone perturbed by the platform legs. The breaking events were labelled elec-
tronically by an observer (see also Section 3.2 ). The observer located 16m above the wave
probe array monitored one of the wave probes and triggered a signal whenever a white-
cap of any size occurred at the probe. The signal was recorded synchronously with the
wave data. An example of a wave record with breaking waves marked as vertical bars was
shown in Figure 2.2 . The waves propagate at a speed of 8m

s, and thus it is difficult for
the observer to place the marks precisely. So the marks, even though they are short, only
indicate the presence of breaking waves and not an exact position of whitecapping over the
wave phase.
Another set of wave breaking was recorded from a research vessel in the Black Sea
and the Mediterranean Sea by means of an accelerometer buoy. Wave measurements by
this buoy are described in Babanin et al. ( 1993 ) and environmental conditions during the
measurements are given in Table 5.1 (see also Section 5.2 ). Again, the observer watched
the buoy from the vessel and triggered the signal to register the passage of a whitecap over
the buoy. Both the ship and the buoy were drifting, the buoy being deployed far beyond the
zone perturbed by the ship and connected to the ship by a long loose cable. The observer
was about 10m above sea level, allowing a clear view of whitecaps with scales down to
the size of the buoy (less than a metre). This set of data was used to obtain the histograms
of maximal acceleration in the breaking wave ( Figure 3.15 ) and to support the breaking
criterion (2.60) in terms of the surface accelerations employed by the wavelet breaking-
detection procedure.

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