A Comparison Between Oil-to-Water Volumetric Fractions Derived from L-Band Synthetic Aperture Radar Imagery and in Situ Samples

We compare in-situ water volume measurements of mineral oil emulsion sampled from an oil slick in Santa Barbara, California, to acquisitions of airborne UAVSAR data acquired in June 2022. Estimating the water-to-oil fraction using the UAVSAR imagery, we find that low SNR in the co- and cross-polarimetric channels limits this capability above a certain oil-to-water volumetric threshold. Higher SNR regions of the slick had water volume fractions below 20%, while lower SNR regions had water volume fractions above 20%. Calculated damping ratio values align with the noise analysis, indicating that a lower SNR corresponds to higher damping values, while a higher SNR corresponds to lower damping ratio values. For the high SNR case, water fractions calculated using the co-polarimetric ratio (VV/HH) and a theoretical backscattering model were slightly underestimated when compared with in-situ measurements. This observation could be due to potential sampling bias during the collection of in-situ samples, favoring thicker oil with a higher water cut.