Short sea wave measurements by a drifting buoy system

Measurements of short sea waves are often conducted by resistance wire methods. Instruments installed in fixed positions provide frequencies which are Doppler-shifted by tidal and orbital currents, also by wind induced surface drifts. In the case of cm-waves these shifts go up to several hundred per cent. To study short wave dynamics in detail, e.g., the modulation by long waves, the shifts must be excluded by the measuring method. A buoy has been developed which follows the long wave amplitudes and the local currents. Short waves are measured at greatly reduced Doppler-shifts and the wind is measured in constant height above the long wave profile. Examples of wave and wind spectra and short wave-long wave correlations are presented. Short wave modulation depths are depicted, too