Chemistry Reference
In-Depth Information
The waters bordering Taiwan look darker in stable atmospheric con-
ditions and decreasing of wind speed. The dark patches around Lutao indi-
cate that the wind speed was about 3 ms
-1
or less here. Contrary to Figure
1a, no radar signatures around Lutao or to the northwest of it were detected
indicating the presence of current shift zones associated with the topogra-
phy. However, filamentary slicks and bright narrow bands are probably the
expressions of surface circulation in a cold water area
8
.
In order to estimate the surface currents, line
5
was extended to the
south. It crossed the centre of eddy
9
and a dark patch (point
A
) near the
lower boundary of the SAR image. The length of the line between the
point
A
at the beginning of spill and point
B
, the location of ship
1
, is
about 84 km. An increased amount of oil in the cleaning waters was ob-
served in the middle part of the spill. The radar contrast of this part was
high. In the southern part, the amount of oil was significantly less and the
radar contrast of the spill decreased too. However, it was enough to deter-
mine its location reliably, and to observe the eastward displacement of pol-
luted waters under the current's action. The northern part was characterized
by a low radar contrast. Probably, the discharge of polluted waters had fin-
ished, and, therefore, the linear feature behind the ship represented a turbu-
lent wake.
The ship's course was in the immediate vicinity of the dynamic Ku-
roshio boundary
6
. Most likely, this was the main cause of perturbations in
a spill. There were several pronounced displacements of the spill relative
to line
AB
both to the west and the east. The maximum westward compo-
nent of the surface current was observed at a distance of 30 km behind the
ship, where the drift of the oil-polluted waters was 2.2 km (area
C
in Fig-
ure 4).
The small-scale eddies
7
-
9
were observed on the SAR image shown in
Figure 4 and also on the next SAR image covering the Kuroshio south of
the considered area (frame 3158). The large displacements in area
D
were,
most likely, caused by a small-scale vortex circulation
9
near the Kuroshio
boundary
6
. The low contrast lines spiralling towards the brighter centre of
the eddy provide a rough index of the current direction. The ship crossed
the centre of this cyclonic vortex. The oppositely directed surface currents
stretched the spill near the centre of the vortex so that it became almost
undistinguishable against the background, since the amount of oil was
small. The western and eastern parts of the spill separated at about 4.5 km.
On both sides of the centre the oil film was in the main shifted rather than
stretched. These parts of the spill are reliably distinguished against the
background. Further south (area
E
), the eastward component of the cur-
rent, caused by influence of the topography, predominated. The small-
