Evaluation of seawater permittivity models at 150 GHz using satellite observations

Multisensor satellite measurements from the special sensor microwave water vapor sounder (SSM/T-2), special sensor microwave imager (SSM/I), and operational linescan system (OLS) are used to retrieve sea surface emissivity at 150 GHz with the goal of assessing selected permittivity models. Retrievals were limited to clear-sky SSM/T-2 field-of-views under arctic winter conditions to minimize atmospheric attenuation. Results show there is sometimes wide disagreement between the models and the observations even when considering measurement and model errors with differences as high as 2.4% (or equivalently ≈5 K). Models consisting of two relaxation time constants rather than one are found to be in closer agreement with the observations. The largest permittivity model errors have substantial effects on physically based atmospheric parameter retrievals with systematic errors of -65% and -20% for a column water vapor amount of 2 kg m^-2 and cloud liquid water path of 0.1 kg m^-2 respectively