Retrieval of cloud optical and microphysical properties from multispectralradiances

This paper describes measurements made with a high spectral resolution radi ometer (OVID) during the EUCREX mission 206, for the retrieval of optical a nd microphysical cloud properties. The retrieval algorithm is based on the calculation of the radiative transfer through a cloudy atmosphere with a nu merical model based on the Matrix Operator method. The simulation of the sp ectral radiances at the night level in 942 spectral channels fits precisely the actual spectra measured with OVID, with a good description of the abso rption and scattering features. A number of 1486 simulations, based on a pl ane parallel model of clouds with various combinations of cloud optical thi ckness and droplet effective radius, form the lookup table of reflectance v alues that are used to retrieve these parameters from the measured spectra. The OVID measurements performed along five legs flown by the DLR-F20 aircr aft during the EUCREX mission 206 have been processed. The retrieved values of optical thickness and effective radius are compared in the EUCREX summa ry paper to estimates derived from in situ measurements and values retrieve d from airborne lidar and radiometric measurements as well as from satellit e radiometric measurements. (C) 2000 Elsevier Science B.V. All rights reser ved.