Sea surface probing with L-band Doppler radar: experiment and theory

In a first part, this paper describes radar experiments aimed at probing the sea surface from the coast. To capture small-scale changes in a coastal environment, a flexible high resolution, Doppler L-band radar with high resolution in range has been used. The data exhibit significant sensitivity to current and wind, which justifies the development of a model for inversion. The second part of the paper is thus devoted to our first attempt to model radar echoes, in order to accurately describe the influence of the geophysical parameters of interest. Here, the focus is put on waves generated by a local wind. The key point consists in taking properly into account non-linear hydrodynamic interactions between waves to generate a realistic moving sea surface. From the electromagnetic point of view, since standard low-frequency approximations no longer hold at L-band, a small-slope approximation has been implemented to compute the backscattered field. Numerical results show that for light winds (less than 5 m s −1 ) the model correctly predicts the behaviour of the data with respect to wind speed and direction.