Effects Of Ocean Current On Electromagnetic Backscattering From One Dimensional Drifting Fractal Sea Surface

Currents have significant effects on the environment, whether in nearshore areas, or in the deep sea ocean, because currents can diffuse pollutants such as crude oil spills, drifting marine debris, red tide outbreaks and related variables.To study the electromagnetic backscattering from a one-dimensional drifting fractal sea surface and a fractal sea surface wave-current model is derived, based on the mechanism of wave-current interactions. The numerical results show the effects of the ocean currents on the waves. Wave amplitudes decrease, wavelengths and kurtosis of wave heights increase, spectra intensity decreases and shift to lower frequencies when currents occur parallel to the direction of the ocean waves. By comparison, wave amplitudes increase, wavelengths and kurtosis of wave heights decrease, spectra intensity increase and shift to higher frequencies if currents are in the opposite direction to the direction of ocean waves. The wave-current interaction effects of ocean currents are much stronger than those of the nonlinear wave-wave interactions. The kurtosis of the nonlinear fractal ocean surface is larger than that of linear fractal ocean surface. Effects of currents on skewness of the probabilities the distribution function are negligible. Therefore, the ocean wave spectra are notably changed by the surface currents and the changes should be detectible in electromagnetic backscattering signals.Further more, sea surface current also has a significant impact on electromagnetic (EM) backscattering signals and may constitute a dominant SAR imaging mechanism. An effective EM backscattering model for a one dimensional drifting fractal sea surface is presented in this paper. This model is used to simulate EM backscattering signals from the drifting sea surface. Numerical results show that ocean currents have a significant impact on EM backscattering signals from the sea surface. The NRCS discrepancies between models for a coupled wave-current fractal sea surface and an uncoupled fractal sea surface increase with the increasing incidence angle, as well as with increasing ocean currents. Ocean currents that are parallel to the direction of the waves can weaken the EM backscattering signal intensity while the EM backscattering signal is intensified by ocean currents propagating opposite to the waves direction. The model presented in this thesis can be used to study the SAR imaging mechanism for a drifting sea surface.