Parameterization of ice and water clouds and their radiation transport characteristics for large scale atmospheric models

A cloud and radiation transport model, for large-scale atmospheric models, which takes into account the ice as well as the water phase of clouds, is presented. An existing radiation model was extended for the parameterization of radiation transport in ice clouds. Calculations of the cloud coverage are in agreement with METEOSAT pictures. A sensitivity study shows a strong dependence of the coverage degree on changes in the relative humidity. The radiation transport model reacts sensitively to variations of coverage degree and ice content. Taking into account ice clouds it leads, on the average, to an increase of the lower cloudiness and to a decrease of the medium, high and convective cloudiness, as well as to a temperature rise.