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  • Oceanographic Studies Oceanographic Studies
  • Natural Hydrocarbon Seepage Natural Hydrocarbon Seepage



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  • Data integration Data integration

The images on the following time composite page are sequential composites of up to three separate satellite collections. They were all made from synthetic aperture radar (SAR). Dates of the collections are shown in the same color. This analysis is intended to show rafts of oil as they separate from the much larger main spill that is centered around the BP well site. These oil rafts make landfall progressively as winds and tides push them along the coast.

It is important to understand some of the limits of SAR as one looks at these composite time-series. (Detailed discussion of SAR and floating oil can be found on elsewhere on SAR is not blinded by clouds, so we always get a good image of the water and coast for every collection. However, SAR "sees" the oil because the floating oil flattens the tiny ripples on the water so the oil layers appear dark in the radar. This technique is sensitive to windspeed. Too much wind (> 20 kt) and the oil layers are reduced or, for even stronger winds, disappear altogether. Under conditions of low wind (<6 kt), areas of calm water can be mistaken for oil. On 13 June, for example, the slick appears large, probably due to a period of calm weather that proceeded the satellite collection.

Another limit of SAR is the area covered by the satellite image is not exactly the same for every collection. So it can appear that the amount of oil is reduced simply because the satellite image is cut off at some point within a larger region of oil. Banding that sometimes appears within the SAR images due to glitches in the imager can have the same effect. In the composite images, boundaries or artifacts are indicated with white lines.

With these caveats, the SAR composites should show the public how the oil rafts are moving toward landfall along the Gulf coast.


Coastwatch Oil Spill Monitoring

Oil Sheen Tracking Time Composites

TCNNA Raster Data

Wings of Care

Images for Chris

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