Chemistry Reference
In-Depth Information
ing a five-frequency multi-polarization radar scatterometer, the so-called
HELISCAT of the University of Hamburg. During the same flight, we also
overflew biogenic sea slicks, which had been forming sufficiently close to
this sea area, under the same meteorological and oceanographic conditions.
It turned out that both the magnitudes of the damping ratios as well as the
characteristics of the damping ratio/wave number curves determined for
the PME slick spread from ethanol (Fig. 8) and for the biogenic slicks (Fig.
9) were very comparable, while in the presence of the PME slick spread
from
n-
hexane lower damping ratios were determined.
Fig. 8.
Damping ratio, i.e., reduction of
the backscattered radar power (in dB)
induced by a PME slick, which was
spread from ethanol, as a function of
the Bragg wave-number. The meas-
urements were performed at
L-
,
S-
,
C-
,
X-
, and
K
u
-
band using both
VV-
and
HH-
polarisations (up- >tri-angles@ and
downwind >squares@ look directions)
Fig. 9.
Damping ratio, i.e., reduction
of the backscattered radar power (in
dB) induced by natural sea slicks, as a
function of the Bragg wave number.
The measurements were performed at
L-
,
S-
,
C-
,
X-
, and
K
u
-
band using both
VV-
>triangles@ and
HH-
polarisations
>squares@
Obviously, we were able to simulate the water wave damping character-
istics of the biogenic sea slicks, in this case largely secreted from
phaeo-
cystis globosa
, as well as their influence on backscattered radar signals
very exactly by spreading PME from ethanol. This result is conceivable,
because biogenic slicks are being formed from microdroplets that are se-
creted by plankton, i.e., many tiny point sources will appear at the sea sur-
face, if the wind speed and thus the turbulence of the upper water layer
will be sufficiently reduced, say below about 7 m/s wind velocity. Further-
more, many alkanoic acid esters have been found in biogenic sea slicks,
