Ocean Surface Current Measurements Research Articles

Applications of dual-doppler HF radar measurements of ocean surface currents

HF Doppler radar measurements of near-shore sea-surface currents is a relatively new technique. It has the advantage of covering a wide area of the sea surface simultaneously while being shore-based. In this paper, we compute the M 2, K 1, and mean currents over an area of the easter Strait of Juan de Fuca from HF radar measurements made during the summer of 1979. From these components, we computed trajectories of simulated continuous leaks from a proposed oil pipeline in this area. By computing the trajectory over one day, we estimated the shoreline locations that would be impacted by the oil.

Synthetic aperture radar measurements of ocean surface currents

The data recorded by a synthetic aperture radar (SAR) can in principle be analyzed to obtain the radial velocity of moving objects in the scene relative to the flight path of the SAR platform. The application of this concept for measuring ocean surface currents has been evaluated using data from SAR systems mounted in aircraft and spacecraft platforms. This paper summarizes the results of these experiments and describes the system effects which can influence the measurement accuracy. Considerations involved in the design of optimum systems for this application are also discussed.

Ocean surface current measurements by an L band two‐frequency microwave scatterometer

Real time current measurements with an L band pulsed two‐frequency microwave scatterometer (2FS) were carried out from the German North Sea Research Platform (Forschungsplattform Nordsee) during the 1979 Marine Remote Sensing (Marsen) experiment. The principle of this remote sensing technique consists of measuring the phase velocity of a long ocean wave by resonant scattering of a beat wave produced by two microwave signals. The difference between the measured phase velocity and the phase velocity, as calculated from the dispersion relation for still water, represents a weighted average of the ocean current near the surface. Current measurements over full tidal cycles in various wind conditions (up to 18 m s−1) are presented. At high wind speeds, pronounced differences are found between the 2FS measurements and the in situ current measurements made at depths of 9 m and 23 m. These differences can be explained as the effect of the wind stress acting on the upper layer of the ocean. The measurements indicate that the interaction of the tide‐ and wind‐driven currents strongly depends on the parallel and antiparallel orientation of the currents. The accuracy of the measurements reported here is approximately ±0.12 m s−1, but this can, in principle, be improved.

Studies of the sea using HF radio scatter

Radio signals of decameter wavelength resonantly scattered from waves on the sea surface are used to measure precisely the wavelength, frequency, and direction of travel of those waves. These measurements are not only important in themselves, but are also used to deduce currents, winds, and perhaps wind stress at the sea surface. Techniques for obtaining these measurements, as well as experiments to evaluate these techniques are discussed. Finally, scatter has been used to produce the first high-resolution measurements of the directional distribution of large ocean waves, measurements of ocean surface currents at ranges of 20 km, and of surface winds at ranges of 3000 km.

Studies of the sea using HF radio scatter

Radio signals of decameter wavelength resonantly scattered from waves on the sea surface are used to measure precisely the wave. length, frequency, and direction of travel of those waves. These measurements are not only important in themselves, but are also used to deduce currents, winds, and perhaps wind stress at the sea surface. Techniques for obtaining these measurements, as well as experiments to evaluate these techniques are discussed. Finally, scatter has been used to produce the first high-resolution measurements of the directional distribution of large ocean waves, measurements of ocean surface currents at ranges of 20 km, and of surface winds at ranges of 3000 km.