PASSIVE POLARIMETRIC REMOTE SENSING OF THE OCEAN SURFACE: THE EFFECTS OF SURFACE ROUGHNESS AND WHITECAPS*

Foam on the ocean surface significantly increases the brightness temperatures measured by microwave radiometers. Previous results have shown that the microwave emissivity of foam on a calm water surface is significantly less than one and depends upon polarization and incidence angle. Recent radiometric and video observations of large-scale breaking waves from the R/P FLIP during the FAIRS experiment show that the emissivity of whitecaps evolves temporally and is not constant in time. Predicted changes in brightness temperatures measured by spaceborne radiometers due solely to the presence of foam are sufficiently large to significantly affect wind direction retrievals from polarimetric radiometers