An airborne microwave scatterometer-radiometer system operated in X band and Ka band was applied to the observations of microwave backscattering signatures of the ocean. The normalized radar cross sections &sgr;0 were measured as combined functions of microwave frequency (10.00 GHz and 34.43 GHz), polarization (HH and VV), incident angle (0¿--70¿), azimuth angle (0¿--360¿), and wind speed (3.2--17.2 m/s). The azimuth anisotropic signatures for Ka band are confirmed to be similar to those for X band, and the wind speed dependences are analyzed for each azimuth angle, polarization, and incident angle. For each parameter the behaviors of &sgr;0 for microwave frequencies is shown as compared with the results obtained by other experiments and theories. The effective reflection coefficient, the mean square surface slope, and the two-dimensional wave number spectrum of the short surface waves are estimated from the microwave scattering signatures.