The Dynamics of Freshwater Plumes at the Dutch Coast as observed by
high-resolution HF Radar
K.-W. GURGEL, H.-H. ESSEN and T. SCHLICK
OCEANS'98 Conference, Proceedings Vol I, pp. 467...471, 1998.
Abstract - -
Ground-based HF (High Frequency) radars are able to measure ocean
surface currents (by means of first-order Bragg scattering) and wave spectra
(by means of second-order scattering). A carrier frequency of some 30 MHz
allows the mapping of currents within an area of up to 50 * 50 km.
Recently, the University of Hamburg developed a new HF radar system, called
WERA (WEllen RAdar), replacing the CODAR (COastal raDAR). One advantage of
WERA is the flexiblity in range resolution between 0.3 and 1.2 km,
instead of the fixed resolution of some 2 km of CODAR. This is achieved
by making use of FMCW (Frequency-Modulated Continuous Wave) techniques.
When operated with a linear array of receive antennas, WERA allows the
mapping of surface-wave spectra within a reduced area of about 35 * 35 km.
This paper reports on current measurements off the Dutch coast in
fall 1996. Fresh water lenses could be tracked, which originate from the
Rhine and Ijssel outflow and propagate along the coast. The WERA high
resolution mode reveals much more details of the plume structure than
attainable with CODAR. Surface current shear of up to 50 cm/s within
300 m has been observed.
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