Several different instruments are necessary to extract a full set of cloud properties, such as cloud boundaries, cloud optical thickness, particle size and particle phase. The sensor synergy used in this study is a combination of active and passive instruments. Both radiative and intrinsic cloud properties are extracted, and the relation between the two is studied for liquid water clouds. The experimental method for extracting IR emissivity (epsilon) form IR radiometer and lidar measurements will be explained. Cloud Liquid Water Path (LWP) can be extracted from the microwave radiometer. Comparing the two leads to a clear relation between (epsilon) and LWP in the case of liquid water clouds. This can be understood if one considers a simple approximation to the extinction efficiency of liquid water droplets in the IR, leading to an RI emissivity that solely depends on LWP, and not on the particle size distribution. Similar methods can be applied to space-based observations, such as combining LITE and Meteosat measurements to derive IR emissivity. First results are shown.
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