Polarimetric Analysis of Backscatter From the Deepwater Horizon Oil Spill Using L-Band Synthetic Aperture Radar

Creators: Minchew, Brent; Jones, Cathleen E.; Holt, Benjamin

Abstract

We analyze the fully-polarimetric Uninhabited Aerial Vehicle Synthetic Aperture Radar (UAVSAR) data acquired on June 23, 2010, from two adjacent, overlapping flight tracks that imaged the main oil slick near the Deepwater Horizon (DWH) rig site in the Gulf of Mexico. 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 range of incidence angles from 26º to 60º. We show that the change of backscatter over the main slick is due both to a damping of the ocean wave spectral components by the oil and an effective reduction of the dielectric constant resulting from a mixture of 65–90% oil with water in the surface layer. This shows that synthetic aperture radar can be used to measure the oil volumetric concentration in a thick slick. Using the H/A/α parameters, we show that surface scattering is dominant for oil and water whenever the data are above the noise floor and that the entropy (H) and α parameters for the DWH slick are comparable to those from the clean water. The anisotropy, A, parameter shows substantial variation across the oil slick and a significant range-dependent signal whenever the backscatter in all channels is above the instrument noise floor. For slick detection, we find the most reliable indicator to be the major eigenvalue of the coherency matrix, which is approximately equal to the total backscatter power for both oil in the slick and clean sea water.

Additional Information

© 2012 IEEE. Open Access. Manuscript received January 25, 2011; revised September 9, 2011 and December 19, 2011; accepted January 13, 2012. Date of publication March 8, 2012; date of current version September 21, 2012. The research described in this paper was carried out at the Jet Propulsion Laboratory (JPL), California Institute of Technology, under a contract with the National Aeronautics and Space Administration. The UAVSAR data are processed by the UAVSAR team at JPL and archived for open distribution at the Alaska Satellite Facility. The authors would like to acknowledge C. Dobson, NASA Headquarters, for endorsing the UAVSAR flights; and S. Hensley, JPL, I. Leifer, University of Santa Barbara, and I. MacDonald and O. Garcia-Pineda, Florida State University, for valuable discussions. Thanks are also extended to B. Hawkins, Y. Zheng, and B. Chapman, JPL. The third author would also like to acknowledge the DESDynl Pre-mission Task for support. This paper is Caltech Seismo Lab contribution 10055.

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