Chemistry Reference
In-Depth Information
75°, so-called Bragg waves). Figure 1 shows subsections of three SAR im-
ages of the Atlantic Ocean, north of the Azores, acquired on April 12
th
,
1994, at 0721 UTC by the Spaceborne Imaging Radar C/X Band SAR
(SIR-C/X-SAR) at L-, C-, and X-band (from left to right), VV polarisation.
The diagonal dark narrow line visible on the three images is caused by
freshly spilled mineral oil, and the irregular bright spot in the image centre
is caused by strong rain. This example shows the different imaging of the
two counteracting phenomena (surface film and strong rain) at the differ-
ent radar bands: the contrast is highest at X-band, and it is lowest at L-
band. A more detailed analysis of the described phenomena can be found
in Melsheimer et al. (1998) and Braun (1998), respectively.
Fig. 1
. Subsections of three synthetic aperture radar (SAR) images of the Atlantic
Ocean, north of the Azores, acquired on April 12
th
, 1994, at 0721 UTC by the
Spaceborne Imaging Radar C-/X-Band SAR (SIR-C/X-SAR) at L-, C-, and X-
band (from left to right), VV polarisation. The diagonal dark narrow line is caused
by freshly spilled mineral oil, whereas the irregular bright spot in the image centre
is caused by strong rain
Braun et al. (2002) presented results from laboratory studies of the in-
fluence of artificial rain on the measured water surface elevation and slope,
and, moreover, on the radar backscattering from a rain- and wind-
roughened slick-free water surface. In order to complement their findings,
we performed a second measurement series, where we investigated the in-
fluence of artificial rain on a slick-covered water surface. The aim of these
studies was to improve the classification of signatures visible on SAR im-
ages. In particular, for an effective surface film detection the influence of
rain on the visibility of oceanic surface films has to be known.
Vice versa
,
if spaceborne radar data is used for the estimation of rain rates (as pro-
posed by Melsheimer et al. (1998)), one has to know how surface films af-
fect the radar signal of (strong) rain events over the ocean surface. First re-
sults of our studies are presented herein.
