The airborne identification of oil films at the Caspian sea surface using CO2 lidar

Abstract Contrast in the reflectivity between pure and contaminated sea surfaces is the result of two effects, namely: (1) the different reflectivity of sea water and oil films on sea water, and (2) the damping effect by the oil film on the sea waves. The problem is to estimate the contribution of these two effects on the total contrast, so that the substance effect can be calculated. Magnitude is related to the oil film thickness. The spectral behaviour of the contrast and its relationship with the film thickness were calculated for an undisturbed sea surface. The estimate of the damping effect was made using the Cox and Munk's slope distributions for pure and contaminated surfaces. The method chosen was verified by a series of tests conducted over the Caspian Sea from an aircraft carrying a CO2 laser sensor operating at 10.6 μm.