Measurement of ocean waveheight and direction by means of HF radar: an
H.-H. ESSEN, K.-W. GURGEL and T. SCHLICK
German Hydrographic Journal, Volume 51 (1999), No. 4, pp. 369...383, 1999.
Abstract - -
High-frequency (HF) radars have been used since 20 years for remotely
sensing ocean surface currents and ocean waves. Backscattered Doppler
spectra contain two discrete lines, the frequencies of which (Bragg
frequency) determine the current speed, and four continuous side bands,
which allow to apply inversion techniques for retrieving ocean wave spectra.
Recently, a new HF radar has been developed at the University of Hamburg
(Germany). Data of a 34-days experiment reveal a high correlation between
the standard deviation of the Bragg frequencies and the significant
waveheight weighted by an azimuthal function. Applying empirical regression
curves it is possible to determine the significant waveheight and the mean
wave direction from intersecting beams of two radar stations. Compared with
inversion techniques the new method is applicable to data with lower
signal-to-noise ratio, i.e. allows larger ranges. For current measurements,
two radar sites are necessary. The optimum distance between two 30 MHz radars
is about 20 km and, with the new method, needs not to be reduced for the
purpose of simultaneous wave measurements.
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