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Measurement of Surface Current Fields with High Spatial Resolution by the HF Radar WERA


Presented at the IGARSS'97, HF Radar Special Session, Paper 8


Klaus-Werner Gurgel and Georg Antonischki
University of Hamburg, Institute of Oceanography, Tropolwitzstrasse 7, D-22529 Hamburg, Germany.
Tel: +49-40-42838-5742, Fax: +49-40-42838-5713,
email: klaus-werner.gurgel@uni-hamburg.de
WWW: http://wera.cen.uni-hamburg.de/index.shtml

A full paper has been published in the conference proceedings


Abstract

HF radar in oceanography make use of backscatter of electromagnetic waves of 10 m to 50 m wavelength from the rough sea surface. The backscattered signal can be analysed to derive ocean surface current and wave parameters. Several HF radars have been developed all over the world and significant progress has been acheaved since the discovery of the basic physics in 1955 by D. D. Crombie.

In Germany, the work on ground wave HF radar started in 1980. NOAA's CODAR (COstal raDAR), introduced in 1977 by D. E. Barrick, has been adopted, modified and deployed during numerous experiments. In 1987, the system has been extended to a shipborne version to allow for measurement of the circulation at the Arctic Front and near the ice edge in the North Atlantic. Recent developments within the European project SCAWVEX (Surface Current And Wave Variability Experiment) lead to a new design called WERA (WEllen RAdar).

WERA can be operated in many different modes, depending on the requirements of the oceanographic experiments. Due to an advanced FMCW technique, a range resolution between 1.2 km and 300 m can be selected. A flexible receiving antenna configuration allows for beam forming and direction finding techniques, giving high azimuthal resolution and access to second order sea echos, which can be used for deriving wave parameters. WERA has been operated in the 27 MHz and 30 MHz band, giving working ranges of up to 55 km. With slight modifications, operation on other frequency bands is possible.

Within the recent SCAWVEX measurement campaign at the Dutch coast near Petten, surface current fields at 300 m range resolution have been measured every 20 minutes for the last two days of the experiment. As only 128 range cells have been stored, a working range of 38.4 km has been covered, although sufficient signal to noise ratio was expected up to 50 km. The current fields show strong correlation to the topography, and a zone of current shear due to a coastal jet could be observed much more detailed compared to the low resolution measurements during the other days of the experiment.


This work has been funded by the European Commision DG XII within the MAST-2 programme, project SCAWVEX, ct94-0103.
klaus-werner.gurgel@uni-hamburg.de
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