Study of ERS SAR Tandem Imagery of the Malin-Hebrides Shelf

AUTHORS: Stapleton, Scott, Small and Brownsword

ABSTRACT:

ERS-1 and ERS-2 SAR imagery was obtained in the period
August-December 1995 in support of measurements being made in the UK
Shelf-Edge Studies (SES) Programme at the European Continental Shelf
Break West of Scotland.  Thirty-nine images - including nine
ERS-1/ERS-2 tandem pairs - were obtained at the West Freugh
receiving station and were then processed in strip mode by DRA
Farnborough.  The images allow the identification of oceanic and
atmospheric phenomena in the region, and they aid our understanding
of the physical processes active at the shelf edge and includes
eighteen ERS-1 & 2 tandem pairs.  The imagery provide synoptic views
of oceanographic variability, although atmospheric effects
influencing the wind speed at the sea surface need to be taken into
account.  The strip mode SAR processor allows long image strips - as
long as 1500km - to be produced.  

Analysis of the tandem imagery has revealed that complex patterns of
oceanic internal waves produced by tidal flow over the shelf break
are generated in a deterministic manner.  Shallow-water regions in
the region have also been identified where internal wave activity is
particularly high.  The imagery indicates the wind direction can
often be determined in coastal regions as result of wind-wakes,
which can extend to 100 km offshore, caused by coastal terrain, and
also as a result of atmospheric boundary layer roll vortices.  Minor
ocean fronts, including that at the shelf break and the Islay Front,
are sometimes visible.  Internal waves are not seen after late
October due to mixing by storms and cold winds, which mix down the
summer mixed layer.  No strong dependence for generation of
internal-waves on the strength of the internal tide, whether neap or
spring has been found.  Shallow-water bathymetric features and
biogenic slicks, imaged at low wind speeds, can also be seen in the
images. 

Keywords: ESA European Space Agency - Agence spatiale europeenne, observation de la terre, earth observation, satellite remote sensing, teledetection, geophysique, altimetrie, radar, chimique atmospherique, geophysics, altimetry, radar, atmospheric chemistry