Parameterization of single scattering properties of mid-latitude cirrus clouds for fast radiative transfer models using particle mixtures

A new parameterization of single scattering properties has been developed for mid latitude cirrus clouds, to be used in weather prediction and global circulation models. Ice clouds are treated as a mixture of ice crystals of different habits. Bulk optical properties of ice crystals are parametrized as function of the effective dimension (De) of measured particle size distributions that are representative of mid latitude cirrus clouds. De is itself parametrized as function of temperature and ice water content. The paper describes the results obtained with a stand-alone version of the radiation routine of the COSMO model and an initial test with the full forecast model on a complex meteorological situation over Europe.