Satellite SAR oil spill detection using wind history information

Due to its large coverage, satellite based SAR (Synthetic Aperture Radar) has proven very useful in large scale oil spill detection and monitoring. However, radar backscatter values from oil spills are not unique. Other phenomena may dampen out the capillary and short gravity waves which are sensed by the radar, and cause dark areas (generally called slicks) in the SAR imagery. At present, operational satellite SAR oil spill detection systems are based on an operator's experience in slick classification. Discrimination between oil and look-alikes includes analysis of shape, size, dB-values, gradients, texture, instantaneous wind, currents, platform-, ship lane- and natural seepage locations. However, data showing the temporal evolvement of the wind (i.e. the wind history) during the day(s) before SAR imaging, may also contribute significantly in the interpretation process. The geometrical shape of the slick is matched against wind history to estimate slick age. A procedure for such use of wind history in SAR oil spill detection is described by simple flow charts, and some examples are discussed. The method is in practical use at Tromso Satellite Station.