Microwave radiation from a weakly non-Gaussian sea surface

The small deviation from Gaussian statistics of the sea surface is introduced to describe the up and downwind difference in microwave brightness temperature. The effect of long wave asymmetry is estimated using small-slope expansion and model slope distribution. Numerical analysis shows that the long-wave asymmetry cannot explain the observed values of the first harmonic in azimuthal dependencies of microwave radiation. The distribution of ripples over the long waves is considered using small-slope approximation and hydrodynamic modulation transfer function. The comparison with experimental radiometric observations allows the authors to derive the imaginary part of the modulation transfer function, which is in reasonably good agreement with independent radar measurements.