Effect of the variance of the polarimetric brightness temperature on azimuth resolution and wind stress sensing

Coincident measurements with a 37 GHz polarimetric radiometer and a 10 GHz scatterometer during the Coastal Ocean Probing Experiment (COPE) in September and October of 1995 offered a unique opportunity to compare their relative sensitivity and performance in observing sea surface winds. The scatterometer cross section, σ₀, and the radiometer´s second and third Stokes parameters, Q and U were measured. This is a study of the variance of the microwave brightness temperature (both “Q” and “U” quantities) as a function of wind speed and incidence angle, with a simultaneous comparison of the variance of the scatterometer radar cross section under identical air-sea conditions, and general system parameters. The sensitivity of the radar and radiometer to the wind direction were then compared by computing the ratio of the angular signal to the inherent variability of the measurements for both instruments, that is, their signal-to-noise ratios (SNR) for the angular signals. SNRs were comparable for the radar and radiometer and both increased with wind speed. However, the SNR of the radiometer decreased with increasing incidence angle while that of the radar increased