Corsica and Sardinia
641 of 1114

Corsica and Sardinia

January 19, 2006
This ASAR image was acquired over a small low pressure structure passing between Corsica and the Italian peninsula. The center of the depression shows up as a dark area in the image due to the low wind speeds at the center of the system and the corresponding reduction in sea surface roughness. Between southern Corsica and the depression center, a distinct change in surface wind speed can be determined on the ASAR image due to the sudden variation in tone. This is the surface impact of an atmospheric front associated. The change in tone relates to the increase in surface roughness moving south through the image the cold air north of the front ensures greater atmospheric stability close to the sea surface and hence lower surface wind speeds while warmer air on the other side of the front generates lighter colors due to the higher wind speeds. The area covers several major shipping lanes including the main route to Genova as well as access to a major oil refinery near Cagliari in the south of Sardinia (where several ships can be seen as bright white points in the bay). The long thin dark structures are due to oil dumped illegally by shipping in the area. The presence of oil or natural films damps out the surface waves and reduces the observed backscatter levels. ASAR wide swath imagery will make a major contribution to improved monitoring of marine areas to prevent such dumping. The image was acquired at approximately 11:30 hence most of the dumping probably occurred during the hours of darkness. Due to the operating wavelength, ASAR is able to detect illegal dumping both day and night. Close analysis of the oil slicks enables detailed characterization of the wind circulation around the center of the depression. Between the center of the structure and Corsica, the oil slicks have been blown southwards, while the slicks to the south of the depression have been blown in an easterly direction and those to the north in a westerly direction.

Technical Information:
  • Satellite: Envisat
  • Instrument: ASAR
  • Acquisition: 26-Jun-2002
  • Orbit nr: 01679
  • Center coordinates: lat. 39.62, lon. 8.87

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