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HF Radar Systems for Wave and Current Measurement


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 Oceanology'98 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 both in technology and algorithms has been acheaved since the discovery of the basic physics in 1955 by D. D. Crombie.

The main requirements for successful measurement of ocean waves are:

  1. Access to the second order reflections from the sea surface and
  2. an increased signal-to-noise ratio of the measured Dopper spectrum, because the second order returns are much weaker compared to the strong first order reflections, which are used to derive surface current information.

Based on these requirements, a new system called WERA (WEllen RAdar) has been designed within the European project SCAWVEX (Surface Current And Wave Variability Experiments), which brings together the potential of 8 partners from 4 European countries. The second order returns are resolved by using a linear antenna array and forming beams to different azimuthal directions. Side lobes have to be suppressed carefully to avoid strong first order returns from other directions to be misinterpreted as second order returns. A high signal-to-noise ratio has been acheaved by parallel processing of the receiving antenna signals and using an advanced FMCW technique for range resolution, which can be set to 1.2 km, 600 m and 300 m. WERA has been operated in the 27 MHz and 30 MHz band, giving working ranges of up to 55 km for mapping current fields. With slight modifications, operation on other frequency bands is possible.

Ocean surface current fields are derived from the radar data using the University of Hamburg algorithms, the spatial distribution of wave hight directional spectra are calculated using the University of Sheffield wave algorithm. Both informations can be gained from the same data set, so simultanous measurements of currents and waves are possible. This opens new possibilities to environmental monitoring, coastal engineering and increasing ship safety.


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
last update 21-Jan-1998
 
 
 
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