Field experiment with an ocean surface current sensing microwave radar

There has long been a need for an automated, remote current mapping instrument for use in harbours, bays and estuaries. To meet this need, a dual frequency (Delta-K) X-band microwave radar is being developed by Quadrant Engineering for the National Ocean Service (NOS). It differs from other commercially available surface current sensing radars in that it offers a much finer current resolution cell (100 m/spl times/100 m) than HF/VHF radars, good velocity resolution (1-5 cm/sec) and can automatically transmit multiple frequencies (frequency agility) to adapt to varying surface wave conditions. This paper describes NOS needs, the basic principle and system parameters of Delta-K radar, and a field experiment conducted in January 8-9, 1997 at Newark Bay, New Jersey. The goal of the experiment was to demonstrate the feasibility of the radar system in measuring the surface currents in a harbor environment. Ocean surface conditions varied from rough to calm during the two-day period. The experiment showed that the Delta-K system provided good current signals in the harbor environment under two very different surface conditions. In-situ current measurements consisted of those from a Price current meter, surface drifters, and a bottom-mounted Acoustic Doppler Current Profiler (ADCP). The currents measured by Delta-K radar appear to be reasonable in both magnitude and its spatial distribution. However, because of the uncertainties of the in-situ observations, no quantitative comparison was attempted.