Thermal IR emissivity of oil films on sea surfaces at moderate winds

Oil slick detection, identification, and even quantization are of great interest in the context of oil spill countermeasures. As a first approximation, it can be assumed that at radar wavelengths, as the oil film thickness is much lower than the wavelength, the electromagnetic wave cannot “see” the thickness H [?]; consequently, it could be concluded that the radar response is not significantly sensitive to H. By contrast, at infrared (IR) wavelengths, as the wavelength λ is in the same order as the oil film thickness H, the electromagnetic response sensitivity with respect to H can be hoped for. Then, the thermal IR emissivity of clean and contaminated seas is studied for this purpose. The phenomenon of multiple scattering at the same interface is not taken into account here, making the model applicable for moderate winds (corresponding to gentle surface slopes). By contrast, the phenomenon of multiple scattering inside the inner oil layer between the upper and lower interfaces is taken into account. Hereafter, the hydrodynamic modelling describing the surfaces is summed up in section 2, and the numerical results of the electromagnetic model based on the Geometric Optics (GO) approximation are presented in section 3.