Advanced directional sea spectrum studies with the Bribie Island MF/lower HF surface-wave radar


  • M. L. Parkinson


The directional factor of sea spectra is an important oceanographic quantity which has been measured infrequently by a limited number of techniques. Here I report the use of a large-phased antenna array transmitting at 1.98, 3.84, and 5.80 MHz for measuring the directional factor from the observed first-order surface-wave sea echoes (i.e., those due to Bragg resonance) measured simultaneously at many azimuths through rapid, digital control of beam direction. This measurement process compares with the extraction of directional factors from second-order radar cross sections in that both techniques rely on the statistical quality of observations and the stability of integral inversion algorithms employed. Preliminary observations show that, in principle, this new technique can be used to measure the directional factor automatically, including dominant sea direction and angular spread with high resolution (±2°) in near-real time. The strategy required to achieve high accuracy is outlined.