Significant wave height estimation using azimuth cutoff of C-band RADARSAT-2 single-polarization SAR images

This paper proposes two simple models, look-up table (LUT) model and empirical model, to directly retrieve significant wave height (H_s) using synthetic aperture radar (SAR) azimuth cutoff (λ_c). Both models aim at C-band VV, HH, VH, and HV single-polarization SAR images. The LUT model relates H_s to λ_c, while the empirical model relates H_s to both λ_c and SAR range-to-velocity (β). The LUT model coefficients are derived by simulation under different sea states and observation conditions, which depend on incidence angle (θ), wave direction (d_w), and β but are independent of polarization. The empirical model coefficients are obtained by fitting the collocated data, which only depend on polarization. To fit empirical model coefficients and validate the two models, C-band RADARSAT-2 fine quad-polarization (VV+HH+VH+HV) single-look complex (SLC) SAR images and collocated buoy data are collected. Retrieved H_s, using Yang model and the two models proposed in this paper from four kinds of polarization SAR data, are compared with buoy H_s. Results show that both LUT and empirical models have the capacity of retrieving H_s from C-band RADARSAT-2 co-polarization SAR data, while Yang model is not suitable for these kinds of SAR data. Moreover, the empirical model is also valid for cross-polarization SAR data showing clear ocean wave stripes.