Atmospheric effect on microwave polarimetric passive remote sensing of ocean surfaces

A theoretical emission model of combined ocean surface and atmosphere is pr esented to predict the microwave emissivity of the ocean. The modeled ocean surface is one-dimensional with a random rough profile. The electromagneti c scattering from the surface is calculated based on the extended boundary condition method. Realizations of rough surfaces are created using Monte Ca rlo simulations. The bistatic scattering coefficients are computed from the ensemble average. The millimeter-wave propagation model is used to evaluat e the absorption of microwave radiation at all height levels in the atmosph ere. An expression for the observed brightness temperatures is derived by s olving the radiative transfer equations. The radiative transfer model resul ts show a good agreement with the measured data from the 1995 NASA Jet Prop ulsion Laboratory WIND radiometer (WINDRAD) campaign. An approximate model is provided to estimate the atmospheric effect on the ocean brightness temp eratures based on the overall atmospheric attenuation. The approximate mode l also compares well with the WINDRAD data. Further comparisons are made be tween the approximate formula and the radiative transfer results on the rat io of the third Stokes parameter in the atmosphere to the one in free space by varying the atmospheric conditions, surface roughness, and radiation fr equencies. The approximate formula shows its usefulness for the prediction of the ocean brightness temperatures.