The effect of bimodal sea spectra on HF radar wind analysis

HF radar spectra have been shown to be able to produce wind direction information from the first-order peaks. The main error in this analysis is the spreading function which one adopts for the directional wave spectrum. There is increasing evidence in recent literature that the directional spectrum for gravity waves above the peak is bimodal in form. The bimodal shape has been recently modified to merge with the observations of omnidirectionality at wavelengths around 1.0 - 0.3 m. The analysis of HF radar data for wind direction determination is discussed in terms of the modified bimodal form for the wind wave spectrum