driving force (e.g. wind speed, wind-driven circulation, instability of flows), the
inertial currents are developed, due to inertia and the Coriolis force.
In the Black Sea, average diameters of inertial circulations range from 200 m at
depths exceeding 1000 m to 1.8 km in the 0–200 m layer (Filippov 1968; Belyakov
1979; Blatov et al. 1984; Boguslavsky et al. 1996; Ivanov 1996; Ivanov and
Belokopatov 2011). According to previous research, the average duration of inertial
vortexes is 2–3 days (up to 8 days) and the average orbital velocity and amplitude of
components u and v in the surface layer is 10 cm/s (up to 40 cm/s) down to 1 cm/s at
a depth of 1500 m. Some oscillations with a period greater than the inertial ones,
were observed (Morozov 2001; Zhurbas et al. 2002, 2003) and explained by
amplitude modulation of high frequency motions with low-frequency processes
(Zhurbas et al. 2002).
Recently, for the area of Main Black Sea Current (MBSC or RIM current) off the
southern coast of Crimea, hodographs of inertial currents were determined with
amplitudes of fluctuations from 5 to 24 cm/s. (Dzhiganshin and Polonsky 2011).
The aim of the paper is to furnish relevant arguments on the inertial currents
using the Fast Fourier Transform evolution (FFT) and progressive vector diagrams
(or integrated hodograph) together with the vector component using in-situ sea
currents measurements on the north-western Black Sea shelf.
9.2 Data and Method
The analysed data consist of current speed and direction time series recorded by
mechanical, paper printing, Alexaev type instruments and currentmeters, during
1977–1991. The values of the sea currents using the Alexaev type instrument are
the average speed (measured by a four plane blades, vertically mounted rotor) and
the instantaneous direction (indicated by a magnetic compass) at the end of the
averaging period (the last 100 s of the sampling interval).
The selected time series were recorded in the middle of the Romanian shelf
(44 10
0 N, 29 22
0 E) and at the southern end of the Mamaia bight (44
12
0 N–28
20
0 E).
The measurement method consists with the one or two instruments suspended from
a ship anchored in 52 m or 12 m of water for several days (2–6 days) and sampling
interval was 5, 10 and 15 min, continuously during the period.
The progressive vector diagrams with the vector component evolution that
indicates the presence of various wave events of different nature, periods, intensities, and durations are used. Due to the short length of the records, and taking into
account the time scale of the identified motions, different processing approaches
were used.
144
M.-E. Mihailov
inertial currents are developed, due to inertia and the Coriolis force.
In the Black Sea, average diameters of inertial circulations range from 200 m at
depths exceeding 1000 m to 1.8 km in the 0–200 m layer (Filippov 1968; Belyakov
1979; Blatov et al. 1984; Boguslavsky et al. 1996; Ivanov 1996; Ivanov and
Belokopatov 2011). According to previous research, the average duration of inertial
vortexes is 2–3 days (up to 8 days) and the average orbital velocity and amplitude of
components u and v in the surface layer is 10 cm/s (up to 40 cm/s) down to 1 cm/s at
a depth of 1500 m. Some oscillations with a period greater than the inertial ones,
were observed (Morozov 2001; Zhurbas et al. 2002, 2003) and explained by
amplitude modulation of high frequency motions with low-frequency processes
(Zhurbas et al. 2002).
Recently, for the area of Main Black Sea Current (MBSC or RIM current) off the
southern coast of Crimea, hodographs of inertial currents were determined with
amplitudes of fluctuations from 5 to 24 cm/s. (Dzhiganshin and Polonsky 2011).
The aim of the paper is to furnish relevant arguments on the inertial currents
using the Fast Fourier Transform evolution (FFT) and progressive vector diagrams
(or integrated hodograph) together with the vector component using in-situ sea
currents measurements on the north-western Black Sea shelf.
9.2 Data and Method
The analysed data consist of current speed and direction time series recorded by
mechanical, paper printing, Alexaev type instruments and currentmeters, during
1977–1991. The values of the sea currents using the Alexaev type instrument are
the average speed (measured by a four plane blades, vertically mounted rotor) and
the instantaneous direction (indicated by a magnetic compass) at the end of the
averaging period (the last 100 s of the sampling interval).
The selected time series were recorded in the middle of the Romanian shelf
(44 10
0 N, 29 22
0 E) and at the southern end of the Mamaia bight (44
12
0 N–28
20
0 E).
The measurement method consists with the one or two instruments suspended from
a ship anchored in 52 m or 12 m of water for several days (2–6 days) and sampling
interval was 5, 10 and 15 min, continuously during the period.
The progressive vector diagrams with the vector component evolution that
indicates the presence of various wave events of different nature, periods, intensities, and durations are used. Due to the short length of the records, and taking into
account the time scale of the identified motions, different processing approaches
were used.
144
M.-E. Mihailov