Chemistry Reference
In-Depth Information
Thus, one can conclude that different SAR systems and their viewing ge-
ometry can result in highly different damping ratios of the same spill.
On two occasions (August 22
nd
and 25
th
) both satellites imaged the spills
within a close time span. A comparison of the damping ratios for these two
days shows that, among other factors, they highly depend on the viewing
geometry, wind speed and sea state.
Fig. 4.
Almaz-1 and ERS-1 SAR images of August 25
th
, 1991, at 10:44 and 10:48
UTC showing the first oil spill released on August 21
st
and the second oil spill of
August 24
th
(incidence angles 52.6q and 23q, wind speed 2-3 m s
-1
, spill age 88 hrs
and 18 hrs, respectively) (
left
). Variations of the radar backscatter along the scan
lines are shown on the Almaz-1 and ERS-1 SAR images by white thin arrows
(
right
), flight/look directions by thin black arrows, and wind direction by a double
black arrow (image courtesy NPO Mashinostroenia and ESA)
The last Almaz-1 SAR image of the second oil spill taken on August
27
th
at 15:29 UTC (Figure 5) shows an oil spill affected by wind and
waves for about 3 days. The image was acquired when the wind speed was
about 12 m s
-1
and the significant waveheight about 3 m, wavelength about
200 m with a period of 12.5 s. This spill was positioned at 10:15 by an air-
craft between 64q 38c N, 08q 01c E and 64q 36c N, 07q 57c E and was ob-
served from RV
Svanaug Elise
at 16:45 as a pure blue shine (Bern et al.
1992b). It can be inferred from the image section that the NRSC contrast
with respect to the background has alternate sign along the spill: some ar-
eas within it are even brighter than the oil-free surface. It probably shows
that this oil spill was in a destruction stage.
