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A Comparison of Surface Current Fields derived by Beam Forming and Direction Finding Techniques as applied by the HF Radar WERA


Presented at the IGARSS'97, HF Radar Special Session, Paper 3


Klaus-Werner Gurgel , Georg Antonischki and Thomas Schlick
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 backscattering of electromagnetic waves of 10 m to 50 m wavelength from the rough sea surface. The backscattered signal can be analysed to derive surface current and ocean 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 adopting NOAA's CODAR (COastal raDAR), introduced in 1977 by D. E. Barrick. Many modifications have been applied to the CODAR since then and the system has been deployed during numerous experiments. In 1987, a shipborne version allowed for measuring 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 has been designed to offer as much flexibility as possible, both in hardware and the algorithms to process the backscattered sea echos. This flexibility allows for simultanous measurements with a 4 element squared CODAR array and a 12 element linear array. In Spring 1996, two WERA systems have been deployed north and south the Rhine mouth at the Dutch coast. In addition to WERA, two CODAR systems have been operated at the same sites, alternating the time slices with WERA. This setup of the HF radars allows for comparisons between CODAR and WERA as well as between the different algorithms for azimuthal resolution, like direction finding and beam forming. This paper decribes the systems and algorithms used, some differences identified in the surface current fields measured, and finally tries to show up the advantages and difficulties of the different algorithms.


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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