Tracking of fresh-water plumes in Dutch coastal waters by means of
Presented at the IGARSS'99 Session: Eddies, Fronts and Currents
Klaus-Werner Gurgel ,
H.-H. ESSEN and
University of Hamburg, Institute of Oceanography,
Tropolwitzstrasse 7, D-22529 Hamburg, Germany.
Tel: +49-40-42838-5742, Fax: +49-40-42838-5713,
A full paper has been published in the conference
Since more than 20 years high-frequency (HF)-radars have been used for
measuring surface current fields and ocean-wave spectra. The physics behind
is backscattering from a moving rough sea surface. Radar systems, working at
frequencies between 25 and 30 MHz, are deployed along the coast and cover
an area of up to 50 km * 50 km, which can be observed continuously at
10 minute intervals.
Recent developments at the University of Hamburg led to a new HF radar system
called WERA (Wellen Radar). WERA is a frequency-modulated continuous-wave
(FMCW) radar which, when linked to a linear array of receice antennas,
simultanously measures surface currents and ocean waves. The highest spatial
resolution is 300 m. The area covered in this mode is about 35 km * 35 km.
Results from an experiment at the Dutch coast in fall 1997 are presented.
Fresh water plumes, travelling along the Dutch coast, could be observed.
The plumes are originated from the Rhine and Ijssel outflow into
the North Sea. The measurements were conducted at Petten, 25 km south of
the island Texel. The WERA high resolution mode showed much more details
of the plume structure than was possible with the resolution of 1.2 km of
the pulsed Coastal Radar (CODAR) of the University of Hamburg. Horizontal
shear of the surface current of up to 50 cm/s within 300 m has been
In addition to the surface currents, the spatial distribution of backscatter
strength will be investigated. In accordance with theory, some evidence has
been found that backscatter strength is related to sea-water conductivity.
This work has partly been funded by the European Commision DG XII within the
MAST-2 programme, project SCAWVEX, ct94-0103.
last update 06-Jul-1999