Retrieval of cloud optical and microphysical properties from multispectral radiances

This paper describes measurements made with a high spectral resolution radiometer (OVID) during the EUCREX mission 206, for the retrieval of optical and microphysical cloud properties. The retrieval algorithm is based on the calculation of the radiative transfer through a cloudy atmosphere with a numerical model based on the Matrix Operator method. The simulation of the spectral radiances at the night level in 942 spectral channels fits precisely the actual spectra measured with OVID, with a good description of the absorption and scattering features. A number of 1486 simulations, based on a plane parallel model of clouds with various combinations of cloud optical thickness and droplet effective radius, form the lookup table of reflectance values that are used to retrieve these parameters from the measured spectra. The OVID measurements performed along five legs flown by the DLR-F20 aircraft during the EUCREX mission 206 have been processed. The retrieved values of optical thickness and effective radius are compared in the EUCREX summary paper to estimates derived from in situ measurements and values retrieved from airborne lidar and radiometric measurements as well as from satellite radiometric measurements. (C) 2000 Elsevier Science B.V. All rights reserved.