Monomolecular Slicks Research Articles

Polarimetric Doppler spectrum of backscattered echoes from nonlinear sea surface damped by natural slicks

Based on the Lombardini et al. model that can predict the hydrodynamic damping of rough sea surfaces in the presence of monomolecular slicks and the “choppy wave” model (CWM) that can describe the nonlinear interactions between ocean waves, the modeling of time-varying nonlinear sea surfaces damped by natural or organic sea slicks is presented in this paper. The polarimetric scattering model of second-order small-slope approximation (SSA-II) with tapered wave incidence is utilized for evaluating co- and cross-polarized backscattered echoes from clean and contaminated CWM nonlinear sea surfaces. The influence of natural sea slicks on Doppler shift and spectral bandwidth of radar sea echoes is investigated in detail by comparing the polarimetric Doppler spectra of contaminated sea surfaces with those of clean sea surfaces. A narrowing of Doppler spectra in the presence of oil slicks is observed for both co- and cross-polarization, which is qualitatively consistent with wave-tank measurements. Simulation results also show that the Doppler shifts in slicks can increase or decrease, depending on incidence angles and polarizations.

Oscillatory response of a monomolecular slick to progressive waves

The fluctuating velocity field of monomolecular slicks is investigated, by means of boundary-layer theory, whengravity waves propagate on the air-water interface. It is assumed that the surface-active material has visco-elastic properties and is insoluble. Graphical results are given, which illustrate the velocity (a) at the centre ofelastic slicks and (b) for inextensible slicks, of arbitrary width. In the latter case, the orbits of the surfactant elements are calculated, and shown diagrammatically.

Drift Response of Monomolecular Slicks to Wave and Wind Action

Abstract The drift responses of monomolecular slicks to wind and wave action have been investigated in a laboratory wind-wave tunnel and in the field. The wind-wave tunnel was fitted with a mechanical wave generator which produced uniform long-crested gravity waves. The field studies were performed off the island of Sylt (German Bight) in the North Sea. Laboratory results for the slick drift response to deep water gravity waves only were in excellent agreement with the Stokes irrotational mass transport drift velocity theory. The purely wind-induced slick drift was in good agreement with the results obtained by previous investigators using a variety of other floats. A number of laboratory and field investigations have been compared which show that the surface drift to wind speed ratio lies between 2.6–5.5%. A difference between the average ratios for the collected laboratory and field results indicates that the pure gravity wave drift component probably comprises 25–30% of the total surface drift. A quali...