Deepwater Horizon oil slick characterization with UAVSAR: Continuing investigations

Abstract

In June 2010, the UAVSAR platform was deployed to the Gulf of Mexico in response to the Deepwater Horizon (DWH) oil spill. We have analyzed the quad-polarized L-band SAR data collected over the main oil slick to develop and validate algorithms for improved discrimination of oil slicks on water and identification of oil properties. Our results show that radar backscatter from both clean water and oil in the slick is predominantly from a single surface scatterer, consistent with the tilted Bragg scattering mechanism across the incidence angle range of 26-60°. We find that the change of backscatter over the main slick is due to both a damping of the ocean wave spectral components by the oil and an effective redn. of the dielec. const. resulting from a mixt. of 65-90% oil with water in the surface layer. These results support the use of synthetic aperture radar in quantifying oil volumetric concn. in a thick slick of emulsified oil. Our results are unique in that they quantify specific properties of thicker emulsified oil rather than simple slick extent, so are potentially useful for guiding spill clean-up. The improved sensitivity of UAVSAR compared to other aircraft and satellite SAR is due primarily to the low noise floor of ∼-50 dB, which is at least 20 dB below that of most radars in use over the DWH spill. With UAVSAR we can discriminate small variations in the radar signature within the oil slick, from which we have extd. bulk ests. of the volumetric concn. of the surface oil.This research was conducted in part at the Jet Propulsion Lab., California Institute of Technol., under contract with the National Aeronautics and Space Administration.

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