The article discusses the results of theoretical and experimental studies of Doppler velocity on the sea surface. Doppler
velocity is measured by radar sensing at moderate and low grazing angles. The experiments were performed using
coherent X-band and Ka-band panoramic digital radars operating with the horizontal polarization for transmission and
reception. These radars have high spatial resolution. An algorithm for reconstructing Doppler velocities is proposed and
estimates of the fluctuation sensitivity of the method are carried out. The method is applied to the conditions of the fetch-limited
wind wave growth, which is typical for enclosed waters and the sea nearshore, where the dominant wavelength is
of the order of ten meters. Based on the two-scale model, the dependences of the Doppler velocity on the parameters of
the ocean-atmosphere interface are considered. The effect of shadowing by the crests of wind waves on the magnitude of
the Doppler velocity at low grazing angles is discussed. The manifestation of the orbital velocity of wind waves is
Surfactant films on the sea surface can appear due to pollutions, river and collector drains, as well as biological processes. Film slicks can indicate different processes in the upper ocean and in atmosphere. In particular, slick signatures in SAR-imagery of the sea surface at low and moderate wind speeds are often associated with marine currents. Other factors such as wind and physical characteristics of films can significantly influence the dynamics of slick structures. A perspective approach aimed at measuring surface currents is developed. Based on the approach an impact of wind on the kinematics of artificial slick bands is determined. Simulation of slick band propagation from the localized source of surfactant in the field of wind and eddy-shape current is performed. As a result of simulation the shape of surface slick structure, which is close to the observed on SAR image of water surface, is obtained. It is shown that the possibility of spiral bands formation due to presence of marine submesoscale eddies is determined by near-surface wind. Moreover, it is declared that a traditional estimation of scales of marine eddies based on the scales of spiral slick structures is not basically correct.
The work is devoted to the experimental study of Doppler velocity in artificial surfactant films on the sea surface. Such
films simulate the oil spills. The paper develops a method of remote detection of oil spill pollution on the water surface.
The method is based on a joint analysis of amplitude and velocity radar images of the water surface. It is shown that the
surfactant films lead to a significant change in the Doppler velocity, which can be used to increase the detection
probability of pollution on the sea surface. A statistical analysis of the two-dimensional distribution of RCS and Doppler
velocity in artificial surfactants films and pure water in a wide range of weather conditions is performed. It is
demonstrated that the difference between the measured Doppler velocity in the upwind direction and the phase velocity
of the Bragg waves corresponds with the slick drift velocity.