Using ERS-2 SAR images for routine observation of marine pollution in European coastal waters

More than 660 synthetic aperture radar (SAR) images acquired over the south ern Baltic Sea, the North Sea, and the Gulf of Lion in the Mediterranean Se a by the Second European Remote Sensing Satellite (ERS-2) have been analyze d since December 1996 with respect to radar signatures of marine pollution and other phenomena causing similar signatures. First results of our analys is reveal that the seas are most polluted along the main shipping routes. T he sizes of the detected oil spills vary between < 0.1 km(2) and > 56 km(2) . SAR images acquired during descending (morning) and ascending (evening) s atellite passes show different percentages of oil pollution, because most o f this pollution occurs during night time and is still visible on the SAR i mages acquired in the morning time. Moreover, we found a higher amount of o il spills on SAR images acquired during summer (April-September) than on SA R images acquired during winter (October-March). We attribute this finding to the higher mean wind speed encountered in all three test areas during wi nter. By using an ERS-2 SAR image of the North Sea test area we show how th e reduction of the normalized radar backscattering cross section (NRCS) by an oil spill depends on wind speed. (C) 1999 Elsevier Science B.V. All righ ts reserved.