Wind velocity and cross polarization radar backscatter

Several papers highlighting the monotonic increase (with respect to wind speed) of the cross polarization radar backscatter (σ_0VH or VH for shorthand in the text) from the ocean surface have been published recently (Hwang et al, 2010a, b; Vachon and Wolfe, 2011; Zhang et al., 2011). The result has generated some interest in exploring hurricane wind retrieval using VH and to incorporate VH in the next generation scatterometer designs. In the subsequent development of algorithms (e.g., Zhang el al, 2011, 2012, 2014 Zhang and Perrie, 2012; van Zadelhoff et al. 2013 Belmonte Rivas et al, 2014), it is assumed that VH varies mainly with wind speed (U₁₀) and independent on the azimuthal angle (φ). Its dependence on incidence angle (θ) is either ignored [Zhang et al, 2011, 2012, 2014 Zhang and Perrie, 2012] or accounted for only in low to strong wind range (U₁₀<;21 m/s) [van Zadelhoff et al., 2013, 1014].