Dependence of the normalized radar cross section of water waves on Bragg wavelength-wind speed sensitivity

Measurements of the normalized radar cross section (sigma degrees) made by the YSCAT ultrawide band scatterometer during an extended deployment on the Canada Centre for Inland Waters (CCIW) Research Tower located at Lake Ontario are analyzed and compared with anemometer wind measurements to study the sensitivity of sigma degrees to the wind speed as a function of the Bragg wavelength. This paper concentrates on upwind and downwind azimuth angles in the wind speed range of 4.5-12 m/s. While YSCAT collected measurements of sigma degrees at a variety of frequencies and incidence angles, this paper focuses on frequencies of 2.0, 3.05, 5.30, 10.02, and 14.0 GHz and incidence angles within the Bragg regime, 30-50 degrees. Adopting a power law model to describe the relationship between sigma degrees and wind speed, bath wind speed exponents and upwind/downwind (u/d) ratios of sigma degrees are found using least squares linear regression. The analysis of the wind speed exponents and u/d ratios show that shorter Bragg wavelengths (Lambda < 4 cm) are the most sensitive to wind speed and direction. Additionally, vertical polarization (V-pol) sigma degrees is shown to be ore sensitive to wind speed than horizontal polarization (H-pol) sigma, while the H-pol u/d ratio is larger than the V-pol u/d ratio.