Applying a unified directional wave spectrum to the remote sensing of wind wave directional spreading

Abstract

Models for directional wind wave spectra can be used to assist in interpretation and analysis of Doppler sea echo spectra to determine wind direction over the oceans by remote sensing techniques. This paper compares and contrasts the data analysis required at different electromagnetic wavelengths. At large wavenumbers the observed spreading depends not only on the directional spreading at the Bragg wavenumber, but also on the weighted integrals over all shorter wavenumbers. This is discussed in terms of microwave and VHF Doppler spectra. At small wavenumbers (HF) the observed directional spreading should be directly predicted by the model. It is in this simple case that there is an inconsistency between the models and the observations, and this has a potential impact on the use of the models at all wavenumbers.