This is the cause of another phenomenon in the Indian Ocean: the eastern equatorial
undercurrent (Tareev Current) exists only during a part of the year, usually in
February–June, when the winds have an eastern component, and only when
anomalous east winds arise this undercurrent may appear in the other seasons.
According to the observations made over the cross-equatorial sections in the
region of 55° E in 1975 and 1976 [2], the existence of an equatorial counterflow
(Tareev Current) was confirmed during the boreal spring. Significant meandering of
the flow with a deviation of more than 100 km to the south from the equator has
been recorded.
The measurements made with the ADCP over several equatorial sections in the
50–60° E longitude band [6] and moored ADCP in the equatorial zone [5] also
revealed significant temporal and spatial variability of the equatorial undercurrent.
The Data and Measurements
In this contribution, we analyze the results of measurements over two meridional
sections using two DVS-750 Doppler current meters. All measurements were
carried out in the lowering and lifting mode from the ship maintaining stable
position using the GPS control system. Taking into account the specific properties
of these devices, the measurements were carried out according to the following
procedure. Both meters were installed on the SBE-32 water sampling system, one
with down-looking sonic transmitter and another with the up-looking one. The time
sampling of the current speed measurement was 1 s, the depth of lowering was
700 m. The SBE-32 system was stopped for one minute at specific depths (700,
500, 300, 250, 200, 150, 100, and 50 m) to accumulate statistically valid signal.
This allowed us to collect the data from each device with a high resolution in the
range of up to 5 m. The measurements at the 68° E section were carried out on
February 15–18, 2017, from 3° N to 3° S. Thirty three stations were occupied here.
Thirty two additional stations more were occupied over the section along 65° E on
February 18–23, 2017, from 3° S to 3.75° N. The distances between the stations
were 10–15 miles. The stations were occupied under the northeastern wind with a
wind speed not exceeding 12 m/s.
Thus, 65 vertical profiles of the current speed to a depth of 700 m were collected
at the sections. The data of measurements for the analysis in this paper were used up
to a depth of 300 m.
Analysis
According to the data of measurements, two sections of the distribution of the zonal
component of velocity were plotted. They are shown in the Fig. 1.
496
A. K. Ambrosimov et al.
undercurrent (Tareev Current) exists only during a part of the year, usually in
February–June, when the winds have an eastern component, and only when
anomalous east winds arise this undercurrent may appear in the other seasons.
According to the observations made over the cross-equatorial sections in the
region of 55° E in 1975 and 1976 [2], the existence of an equatorial counterflow
(Tareev Current) was confirmed during the boreal spring. Significant meandering of
the flow with a deviation of more than 100 km to the south from the equator has
been recorded.
The measurements made with the ADCP over several equatorial sections in the
50–60° E longitude band [6] and moored ADCP in the equatorial zone [5] also
revealed significant temporal and spatial variability of the equatorial undercurrent.
The Data and Measurements
In this contribution, we analyze the results of measurements over two meridional
sections using two DVS-750 Doppler current meters. All measurements were
carried out in the lowering and lifting mode from the ship maintaining stable
position using the GPS control system. Taking into account the specific properties
of these devices, the measurements were carried out according to the following
procedure. Both meters were installed on the SBE-32 water sampling system, one
with down-looking sonic transmitter and another with the up-looking one. The time
sampling of the current speed measurement was 1 s, the depth of lowering was
700 m. The SBE-32 system was stopped for one minute at specific depths (700,
500, 300, 250, 200, 150, 100, and 50 m) to accumulate statistically valid signal.
This allowed us to collect the data from each device with a high resolution in the
range of up to 5 m. The measurements at the 68° E section were carried out on
February 15–18, 2017, from 3° N to 3° S. Thirty three stations were occupied here.
Thirty two additional stations more were occupied over the section along 65° E on
February 18–23, 2017, from 3° S to 3.75° N. The distances between the stations
were 10–15 miles. The stations were occupied under the northeastern wind with a
wind speed not exceeding 12 m/s.
Thus, 65 vertical profiles of the current speed to a depth of 700 m were collected
at the sections. The data of measurements for the analysis in this paper were used up
to a depth of 300 m.
Analysis
According to the data of measurements, two sections of the distribution of the zonal
component of velocity were plotted. They are shown in the Fig. 1.
496
A. K. Ambrosimov et al.