Chemistry Reference
In-Depth Information
enough
in situ
data, the perturbations in a spill's shape can be used to esti-
mate mesoscale variations in surface currents or wind.
Several others features, which are important for the interpretation of the
spill shape disturbances, are depicted in Figure 1b. The appearance of a
part of them was associated with interaction of the Kuroshio Current with
Lutao and the underwater relief (see the location of the SAR image on a
bathymetry in Figure 3). The most distinctive bright features are: the Ku-
roshio fronts
1
and
2
and a broad band
3
located over a northward under-
water ridge between Lutao and Taiwan (Figure 3). The wave-like features
and darker patches within the band
3
are, likely, wakes, generated by un-
derwater mountains. The depth of the sea over these mountains is between
20 and 120 m. Mariners have observed intensive wave breaking over this
ridge and downstream from Lutao, and the corresponding marks are shown
on the navigation maps. These features have been found on many SAR im-
ages of the region.
Lutao is an obstacle within the boundaries of the Kuroshio. The flow of
Kuroshio waters around Lutao is accompanied by the formation of zones
of current shift,
4-6
(Figure 1b), the origin of which are the downstream
headlands of Lutao (Pattiaratchi et al. 1987). The zones are characterized
by increased sea surface roughness (radar backscattering) and are well dis-
tinguished on the SAR image (Figure 1a). The location, length and shape
of the current shift zones are determined by the characteristics of the Ku-
roshio flow and the complicated topography around Lutao. Since the to-
pography does not change, variations in the radar signatures can be used to
study the temporal variability of the Kuroshio in the considered area.
The Kuroshio and its fronts,
1
and
2,
are clearly observable on the SAR
image due to their high radar contrast against the darker background. It is
suggested that the increased Vq values in the frontal areas were due to short
gravity-wave/current interaction along the shear and/or convergence zones
within the front. The Kuroshio front near the coast
2
was characterized by
a somewhat lower radar contrast compared to frontal boundary
1,
located
at a distance of about 20-25 km from the coast.
Near Taiwan, variations in the Kuroshio characteristics, such as the lo-
cation of the axis, velocity, along-track width, flow separation, etc. are
pronounced (Hwang 1996). The analysis of the SAR image strips of the
Kuroshio, obtained during different seasons, has revealed a high variability
in the location, shape and radar contrasts (both magnitude and sign) of the
Kuroshio front (Mitnik et al. 1996, Hsu et al. 1997). The position of the
Kuroshio boundaries
1
and
2
was consistent with available data on the be-
haviour of the Kuroshio during the spring.
Several low contrast features were also related to the disturbances of
spill. The narrow light lines
7
and
8
are probably the boundaries of an east-
