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This contribution to the EUCREX mission 206 series aims at evaluating the performances of three methods considered for the retrieval of cloud microphysical properties (optical depth, droplet effective radius and liquid water path (LWP)) from Advanced Very High Resolution Radiometer (AVHRR) satellite images. These procedures, namely a set of empirical parameterizations, a physically based inversion code, and a neuronal approach, are tested with the mission 206 case study. The influence of horizontal averaging on the retrieved cloud properties is also investigated to assess the limitations of the comparison between satellite observations and aircraft measurements performed at a smaller scale.

Postlaunch calibration of the Meteosat visible (VIS) channel has been performed with Meteosat-1, Meteosat-2, and Meteosat-4. The radiance at the satellite radiometer aperture has been determined by independent means and has been related to the simultaneous satellite radiometer count. This technique has been named vicarious calibration. Airborne radiance measurements over homogeneous targets (two land surfaces, clear ocean, and stratiform clouds) have been performed. The derived calibration factors are scene dependent because of the nonrectangular shape of the Meteosat VIS channel spectral responsivity curve. The latter and, hence, the scene dependence, slightly differs between the three satellites. Therefore, the calibration factors also differ within ±15%. Average values of the calibration factors are about 11 W m−2 sr−1 per count for land surfaces and clouds and about 1.5 W m−2 sr−1 per count for ocean.