Application of Doppler Radar for Measurement of Current Velocity at Small Incidence Angles: The First Experiments at the River

Measuring the global field of sea currents is an important task, therefore, several projects of orbital radars designed to solve the problem are developing in parallel. To measure sea currents, it is proposed to use Doppler radars that will operate at small or middle incidence angles. However, there are virtually no measurements of the Doppler spectrum (DS) at small incidence angles, thus the series of DS measurements carried out in the fall of 2019 in the range of incidence angles of 0°-25° is unique. The paper presents the results of measuring the DS of the backscattered microwave signal for a stationary river current. Doppler radar was mounted on a bridge over the Oka River (Nizhny Novgorod) at an altitude of about 30 m. The first results of the radar data processing show that the river current strongly affects the DS shape and leads to an additional shift of the DS compared to that in the absence of current. Comparison of the theoretical model of the DS with the measured DS has shown good results.