Chapter 4: FINE STRUCTURE AND MICROSTRUCTURE
assumption of constant salinity. No rain was observed on the day of these
measurements. No signs of previous rains were found in the upper 10 m of
the ocean from a salinity profile measured 3 hours in advance of the data set
shown in X Figure 4-21X .
In addition to the temperature profiles calculated from conductivity
profiles, there are profiles of the vertical temperature gradient and velocity
fluctuation. Fluctuation velocity profiles are high-pass filtered with a 12 Hz
cut off frequency. Because free-rising profiler motions and surface wave
orbital velocities are insignificant for frequencies above 12 Hz, velocity
fluctuations shown in X Figure 4-21 are ascribed to small-scale turbulence.
The diurnal mixed layer and diurnal thermocline can be clearly seen in
the temperature profiles (X Figure 4-21). The mean velocity of the diurnal
mixed layer deepening calculated from the least squares method is e
w | 0.1
cm sP
-1
P.
Due to large amplitude internal waves developing in the deepening
diurnal thermocline (presumably because of the Kelvin-Helmholtz
instability), the depth of the diurnal mixed layer and diurnal thermocline
oscillate. This depth may also vary due to horizontal variability of the
studied phenomenon, since the ship drifted between the individual casts.
Table 4-3. Pertinent information for the field observations of near-surface microstructure.
Fig.
#
Date
Time
LST
Position
U 10
m s
-1
(1-A) I 6
W m
-2
Q 0
W m
-2
4-11
27 Aug 79 09:00
09
o N, 23
o W
0.5 to 2 630
70 to
120
4-17, 4-18 6 Oct 78
10:18
28
o N, 21
o W
2
840
150
4-17, 4-19 6 Oct 78
14:52
28
o N, 21
o W
3
620
190
4-17
6 Oct 78
16:22
28
o N, 21
o W
3
210
170
4-17
6 Oct 78
21:21
28
o N, 21
o W
4
0
190
4-17
7 Oct 78
04:18
28
o N, 21
o W
5
0
240
4-20
3 Sep 78
08:38
59
o N, 13
o W
4.5
510
220
4-20
3 Sep 78
10:38 to 11:00 59
o N, 13
o W
2
270 to
380
30
4-20
3 Sep 78
12:32
59
o N, 13
o W
2.5
260
40
4-20
3 Sep 78
12:47
59
o N, 13
o W
2.5
270
40
4-20
3 Sep 78
12:58
59
o N, 13
o W
2.5
260
40
4-20
3 Sep 78
13:20
59
o N, 13
o W
2.5
250
40
4-20
3 Sep 78
14:47
59
o N, 13
o W
1.0
400
20
4-20
3 Sep 78
15:10
59
o N, 13
o W
1.0
280
20
4-20
3 Sep 78
15:18
59
o N, 13
o W
1.0
240
20
4-20
3 Sep 78
19:30 to 20:27 59
o N, 13
o W
4
0
50
253
assumption of constant salinity. No rain was observed on the day of these
measurements. No signs of previous rains were found in the upper 10 m of
the ocean from a salinity profile measured 3 hours in advance of the data set
shown in X Figure 4-21X .
In addition to the temperature profiles calculated from conductivity
profiles, there are profiles of the vertical temperature gradient and velocity
fluctuation. Fluctuation velocity profiles are high-pass filtered with a 12 Hz
cut off frequency. Because free-rising profiler motions and surface wave
orbital velocities are insignificant for frequencies above 12 Hz, velocity
fluctuations shown in X Figure 4-21 are ascribed to small-scale turbulence.
The diurnal mixed layer and diurnal thermocline can be clearly seen in
the temperature profiles (X Figure 4-21). The mean velocity of the diurnal
mixed layer deepening calculated from the least squares method is e
w | 0.1
cm sP
-1
P.
Due to large amplitude internal waves developing in the deepening
diurnal thermocline (presumably because of the Kelvin-Helmholtz
instability), the depth of the diurnal mixed layer and diurnal thermocline
oscillate. This depth may also vary due to horizontal variability of the
studied phenomenon, since the ship drifted between the individual casts.
Table 4-3. Pertinent information for the field observations of near-surface microstructure.
Fig.
#
Date
Time
LST
Position
U 10
m s
-1
(1-A) I 6
W m
-2
Q 0
W m
-2
4-11
27 Aug 79 09:00
09
o N, 23
o W
0.5 to 2 630
70 to
120
4-17, 4-18 6 Oct 78
10:18
28
o N, 21
o W
2
840
150
4-17, 4-19 6 Oct 78
14:52
28
o N, 21
o W
3
620
190
4-17
6 Oct 78
16:22
28
o N, 21
o W
3
210
170
4-17
6 Oct 78
21:21
28
o N, 21
o W
4
0
190
4-17
7 Oct 78
04:18
28
o N, 21
o W
5
0
240
4-20
3 Sep 78
08:38
59
o N, 13
o W
4.5
510
220
4-20
3 Sep 78
10:38 to 11:00 59
o N, 13
o W
2
270 to
380
30
4-20
3 Sep 78
12:32
59
o N, 13
o W
2.5
260
40
4-20
3 Sep 78
12:47
59
o N, 13
o W
2.5
270
40
4-20
3 Sep 78
12:58
59
o N, 13
o W
2.5
260
40
4-20
3 Sep 78
13:20
59
o N, 13
o W
2.5
250
40
4-20
3 Sep 78
14:47
59
o N, 13
o W
1.0
400
20
4-20
3 Sep 78
15:10
59
o N, 13
o W
1.0
280
20
4-20
3 Sep 78
15:18
59
o N, 13
o W
1.0
240
20
4-20
3 Sep 78
19:30 to 20:27 59
o N, 13
o W
4
0
50
253