The intercomparison of selected cloud retrieval algorithms

The paper is devoted to the comparison of selected cloud retrieval algorithms. In particular, the authors compare cloud optical thickness, liquid water path and effective droplet size as obtained from the algorithms developed at the Japan Aerospace Exploration Agency (JAXA) and US National Aeronautics and Space Administration (NASA) and a new simplified cloud retrieval algorithm that is based on the analytical solutions of the radiative transfer equations valid for optically thick weakly absorbing cloud layers. Over ocean all three retrievals show very close results but differences increase for a scene over land. This is mainly caused by uncertainties due to the unknown surface albedo, especially for the semi-analytical approach that is based on measurements at 0.86 μm, where the contribution from ground is particularly large. Still, the simplified analytical retrieval technique gives results comparable with much more advanced codes.