Remote sensing of surface currents and waves

By clicking on this link you will be able to check the tool we developed that facilitates the visualization of surface currents and waves...

The measuring system operates in the high-frequency domain 20-300 MHz, ie. at wavelengths 10-100 m. Total power of emitted radiation amounts up to 30 W. The system comprises of transmitting and receiving antennas. Transmitters emmit electromagnetic (EM) radio waves which scatter off the ocean surface and partly reflect back to receiving antennas. Properties of scattered radiation allow for a determination of surface currents and waves at the location of the scattering.

When radio waves scatter off the ever-moving ocean surface, their frequency changes slightly due to the Doppler effect. If the radial component of the ocean current (at the location of the scattering) is directed towards the receiving antennas, the frequency of the EM radiation reflected towards the receiving antennas increases slightly (with respect to the base frequency of the transmitter). If the radial component of the ocean current (at the location of the scattering) is directed away from the receiving antennas, the frequency of the radiation reflected towards the receiving antennas decreases slightly. This slight frequency shift can be used to determine the radial component of the ocean current velocity at the location of the scattering. A full reconstruction of the surface current field is possible as a combination of two independent measurements from two distant HF systems. The Gulf of Trieste is thus covered by the Piran system, maintained by the Marine Biology Station, and the Trieste station, maintained by the Italian Institute of Oceanography and Experimental Geophysics.

Written by: Matjaž Ličer