The effects of water temperature on radar scattering from the water surface: An X-band laboratory study

The surface tension is a restoring force, the viscosity is a dissipative resistance for microwave scattering gravity-capillary waves on the ocean surface. Both the surface tension and viscosity are water temperature dependent; therefore, it is reasonable to expect the surface wave spectral density in the centimeter range to be temperature dependent. Bragg scatter is wave intensity dependent; therefore, the radar cross section of the ocean surface should also be temperature dependent. In order to verify this inference, a laboratory experiment for X-band backscattering from a rough water surface with varied water temperature was conducted in the absence of wind. Our data show a monotonic increase of the radar cross section with the water temperature. Based on our data, a semi-analytic model is proposed to relate the water surface temperature and the Normalized Radar Cross Section (NRCS) of the water surface as follows: Δσ₀(T)(dB) = 0.24ΔT The semi-analytical model can be used to improve the scatterometer wind algorithm as well as SAR image interpretation, in general.