Observations of scatterometer asymmetry over sand seas and derivation of wind ripple orientation

Over sand seas the ERS scatterometer has observed asymmetries similar to those found over open water. In this paper this asymmetric backscatter response is investigated using C-band VV data from the ERS scatterometer and the data are analysed using a simple empirical model combined with quick-look Synthetic Aperture Radar (SAR) data to provide information on dune type and orientation. The results suggest that the azimuthal response is sensitive to the orientation of small-scale (millimetres to metres) wind-induced sand ripples, rather than the larger scale dune orientation. Additionally, the study investigates the feasibility of using such observations to determine ripple orientation over areas of active sand.