Chemistry Reference
In-Depth Information
Fig. 9.
A raw thermal image. These images cover ~10 x 10m of sea surface but are
geometrically distorted. The bottom of the image is closest to the viewing point,
and the image is foreshortened in the vertical due to the oblique (45
o
) view. The
breaking wave was propagating from left to right. (Images similar to this one have
been described by Jessup et al
.
(1997a). The highest temperatures are associated
with the high emissivity crest of the breaking wave, while warm water behind the
crest is indicative of a turbulent wake)
Images are then low-pass filtered to remove high wave number noise
while retaining low wave number information (low-pass images). One
low-pass image is shown in Figure 2 (right); the features in this particular
image are typical in form, but relatively intense. Since ancillary measure-
ments were only recorded at 5-minute or 10-minute intervals, we do not
know if there were large changes in wind forcing or atmospheric heat
fluxes coincident to the excursions in thermal signal. However, it is diffi-
cult to see how the features apparent in the low-pass images can be a direct
response to meteorological forcing. Variations in emissivity of the sea sur-
face and reflected features in the sky are also candidate explanations. The
variability in emissivity associated with the slope of waves would be the
most likely of these, but the orientation of the features seen in the proc-
essed images is contradictory to this explanation, and the strength and the
variability are also rather too high to be explained in this way.
