A new parameterization of ice cloud optical properties for applications in radiative transfer models and general circulation models

The accuracy in the parameterization of ice cloud optical properties largely determines the uncertainty range of ice cloud radiative forcing simulations in the single-column radiative transfer models (RTM) and general circulation models (GCM). In this study, we introduce a new parameterization of ice cloud optical properties for shortwave and longwave spectral bands in several RTMs (Fu-liou model and RRTMG model) and GCMs (CAM5 and WRF). A comprehensive database of single-scattering properties of atmospheric ice particles from the ultraviolet to the far IR that contains nine different ice particle shapes and three levels of ice surface roughness has been used. The ice cloud particle size distributions are derived from several field campaigns that were carried out in different locations. The bulk optical properties of ice clouds have been calculated and parameterized into the spectral bands of several RTMs and GCMs. The simulation results for ice cloud radiative forcing at the top of the atmosphere show larger differences in the shortwave part than the longwave. Compared with the previous parameterization schemes, larger net ice cloud radiative forcing is simulated with the new scheme.