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[1] New measurements of the permittivity of saline water at millimeter wavelengths have the potential to improve the accuracy of ocean surface emissivity models for use with microwave and millimeter-wave imaging and sounding instruments. Recent radiative transfer models employing a range of different treatments of surface ocean emissivity are compared with observations from the following microwave radiometers: Advanced Microwave Sounding Unit, Special Sensor Microwave Imager, TRMM Microwave Imager, Microwave Airborne Radiometer Scanning System, and Deimos. Emissivity models using the new permittivity model fit these observations more closely than those models which use the Klein and Swift extrapolation model. INDEX TERMS: 3337

The Envisat microwave radiometer is designed to correct the satellite altimeter data for the excess path delay resulting from tropospheric humidity. Neural networks have been used to formulate the inversion algorithm to retrieve this quantity from the measured brightness temperatures. The learning database has been built with European Centre for Medium-Range Weather Forecasts (ECMWF) analyses and simulated brightness temperatures by a radiative transfer model. The in-flight calibration has been performed in a consistent way by adjusting measurements on simulated brightness temperatures. Finally, coincident radiosonde measurements are used to validate the Envisat wet-tropospheric correction, and this comparison shows the good performances of the method.

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