Whereas residual dispersion curves exhibit one minimum (Fig. 9.3), it was
selected for the subsequent analysis and corresponding oscillation was extracted
from the original data.
In the case of inertial with short periods, the rotation of the current vector has a
sense of cyclonic and the periods are tens of minutes (Fig. 9.4). For short periods
spectral method has been used, using sections of varying lengths of the initial data
series.
The short period motions represent a superposition (interference) of some
different waves types typical for the continental shelf area (Fig. 9.5).
Due to the transient nature of the processes, most of the series have to be
truncated. In order to avoid an arbitrary selection, the length of the final data sets
was chosen as to meet the FFT requirements (number of records equals a power of
2). This method also facilitates the comparison between series, as the spectra will
contain amplitude estimations at the same frequency values (Figs. 9.6 and 9.7).
For the high frequency waves, the calculated spectrums by the method of the
Fast Fourier transform (FFT) highlight waves with very close frequency (Figs. 9.6
and 9.7).
9.4 Conclusion
In this paper were analysed the characteristics of the inertial currents on the western
Black sea shelf. The analysed data consist of current speed and direction time series
recorded during 1977–1991 on two fixed oceanographic stations: in the middle of
Table 9.1 Sea currents characteristics, during 1976–1991, at water depth ¼ 52 m, 5 min
No. Code
Max. water
depth (m)
Time (h) Period (h)
Average
speed
(cm/s)
Resultant
direction
(degree)
Resultant
speed (cm/s)
1
77a
10
50.00
15.67
16.5
325
7.6
2
77b
30
50.00
15.83
7.7
345
3.0
3
78c
a
10
56.00
17.50
21.3
265
16.1
4
82a
30
59.83
15.83
7.6
70
4.6
5
83a
10
112.17
17.17
13.7
135
0.6
6
83b
30
43.33
16.92
13.9
240
5.7
7
84a
b
10
40.00
16.25
9.1
95
2.9
8
91a
20
21.83
19.08
10.4
330
3.6
9
78a
10
21.83
1
14.1
95
9.0
10
78b
25
21.67
1
17.7
295
1.4
11
79a
c
5
105.33
1
20.6
295
2.2
12
91b
30
21.67
1
14.8
360
1.5
Sampling were
a
10 min sampling;
b
15 min s ¸i
c
44
12
0 N–28
20
0 E, 12 m water depth
146
M.-E. Mihailov
selected for the subsequent analysis and corresponding oscillation was extracted
from the original data.
In the case of inertial with short periods, the rotation of the current vector has a
sense of cyclonic and the periods are tens of minutes (Fig. 9.4). For short periods
spectral method has been used, using sections of varying lengths of the initial data
series.
The short period motions represent a superposition (interference) of some
different waves types typical for the continental shelf area (Fig. 9.5).
Due to the transient nature of the processes, most of the series have to be
truncated. In order to avoid an arbitrary selection, the length of the final data sets
was chosen as to meet the FFT requirements (number of records equals a power of
2). This method also facilitates the comparison between series, as the spectra will
contain amplitude estimations at the same frequency values (Figs. 9.6 and 9.7).
For the high frequency waves, the calculated spectrums by the method of the
Fast Fourier transform (FFT) highlight waves with very close frequency (Figs. 9.6
and 9.7).
9.4 Conclusion
In this paper were analysed the characteristics of the inertial currents on the western
Black sea shelf. The analysed data consist of current speed and direction time series
recorded during 1977–1991 on two fixed oceanographic stations: in the middle of
Table 9.1 Sea currents characteristics, during 1976–1991, at water depth ¼ 52 m, 5 min
No. Code
Max. water
depth (m)
Time (h) Period (h)
Average
speed
(cm/s)
Resultant
direction
(degree)
Resultant
speed (cm/s)
1
77a
10
50.00
15.67
16.5
325
7.6
2
77b
30
50.00
15.83
7.7
345
3.0
3
78c
a
10
56.00
17.50
21.3
265
16.1
4
82a
30
59.83
15.83
7.6
70
4.6
5
83a
10
112.17
17.17
13.7
135
0.6
6
83b
30
43.33
16.92
13.9
240
5.7
7
84a
b
10
40.00
16.25
9.1
95
2.9
8
91a
20
21.83
19.08
10.4
330
3.6
9
78a
10
21.83
1
14.1
95
9.0
10
78b
25
21.67
1
17.7
295
1.4
11
79a
c
5
105.33
1
20.6
295
2.2
12
91b
30
21.67
1
14.8
360
1.5
Sampling were
a
10 min sampling;
b
15 min s ¸i
c
44
12
0 N–28
20
0 E, 12 m water depth
146
M.-E. Mihailov