Geoscience Reference
In-Depth Information
Table 5.1
Summary of Black Sea data used for the breaking-probability analysis.
Here,
f
p
is the spectral peak frequency,
H
s
is significant wave height,
U
10
is wind
speed at
10m
,
peak
is the significant steepness of the spectral peak,
shear
=
u
s
/
u
o
is the shear parameter defined by the ratio of the surface drift
u
s
to wave orbit
u
o
velocity,
U
10
f
p
g
f
p
=
1
2
U
10
c
p
is the non-dimensional peak frequency or the
parameter of the inverse wave age, and
b
T
is the spectral peak breaking
probability
(2.3)
.
=
π
f
p
Run
f
p
,Hz
H
s
,m
U
10
,m/s
peak
shear
b
T
6(1)
0.36
0.39
11.7
0.085
0.318
0.430
0.038
7(2)
0.34
0.49
12.7
0.099
0.280
0.441
0.065
9(3)
0.30
0.53
14.0
0.080
0.336
0.428
0.060
10(4)
0.31
0.54
14.4
0.084
0.341
0.455
0.052
11(5)
0.44
0.38
15.0
0.120
0.344
0.657
0.063
13(6)
0.39
0.45
14.6
0.114
0.320
0.581
0.067
14(7)
0.41
0.45
13.7
0.126
0.285
0.571
0.084
16
0.17
1.19
8.4
0.062
0.148
0.146
0
18
0.16
1.32
11.2
0.058
0.198
0.183
0
211
0.16
0.83
9.5
0.032
0.303
0.154
0
238
0.17
0.89
10.7
0.040
0.293
0.186
0
242(8)
0.27
0.99
10.0
0.124
0.139
0.274
0.034
244(9)
0.25
0.88
8.7
0.093
0.152
0.224
0.058
direction, measured by a standard Russian M63-MP anemometer on the ship's bow,
together with mean water- and air-temperature data.
The first ten records were obtained with the ship anchored about 3.2 to 6
4 km offshore
on the relatively flat west coast of the Crimea. Relatively young, strongly forced, fetch-
limited waves with
U
10
/
.
c
p
=
2
.
7-4
.
1 were observed. Their spectral peak frequencies
f
p
ranged from 0.3 to 0
s. Records
16 and 18 were gathered from the drifting vessel during the same PK cruise in the eastern
part of the Mediterranean Sea, during which older waves were observed approaching full
development, with
U
10
/
.
44 Hz. The wind speed
U
10
ranged from 11.7 to 15
.
0m
/
c
p
=
0
.
9 and 1.15. Their rather low peak frequencies of 0
.
16 Hz
and 0
s wind speeds respectively.
The last four wave records were recorded from an oil rig situated 60 km offshore in the
north-west region of the Black Sea in horizontally uniform water of 30m depth. These
are the deep-water records which have been used extensively in wavelet analysis of wave
breaking and were described in
Section 3.7
above. The complete environmental data set
included one-minute averaged wind speeds, five-minute averaged surface-current speed
and direction measurements at three-hour intervals as well as water and air temperatures
recorded every three hours (see
Babanin
,
1988
). To avoid possible air-flow distortion by
the platform, an M63-MP anemometer was deployed on a tower 42m above sea level, well
above the deck buildings. The drag-coefficient dependence of
Large & Pond
(
1981
)was
used to estimate the 10m wind speed from the observed data.
.
17 Hz corresponded to 8
.
4m
/
s and 11
.
2m
/
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