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Internal waves in the Gibraltar Strait

Mesoscale oceanic phenomena become visible on SAR images because they are associated with variable surface currents which modulate the surface roughness. The figure shows an ERS-1 SAR image of the strait of Gibraltar on which roughness patterns associated with nonlinear internal waves propagating eastwards can be delineated.

If slicks are floating on the sea surface (like in the right part of the image), they are forced to follow the underlying water movement, and mesoscale oceanic phenomena become also visible by the spatial distribution of the slick material on the sea surface.

Another ERS-1 SAR image showing sea surface manifestation of internal wave forms has been acquired over the same area. It shows in the center sea surface manifestations of an oceanic internal wave packet generated in the Strait of Gibraltar. In the lower right part of the image is possible to recognize surface manifestation of atmospheric internal waves (lee waves) generated by an eastward blowing wind over the 600 m high mountain range Sierra de Hauz in Morocco.
Further images of the same area that show the same effects are provided by ERS-1:
22-03-1992 at 11:03
17-12-1993 at 22:39
02-01-1994 at 11:03
08-01-1994 at 11:03
13-02-1994 at 11:03
30-03-1994 at 11:03
03-05-1994 at 22:42
12-06-1994 at 22:37
28-04-1995 at 22:42

(From Measurements of mesoscale oceanic and atmosphere phenomena by ERS-1 SAR - Werner Alpers)

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