What is triggering ice in mixed-phase clouds in ECHAM-HAM: the importance of ice nucleation

L. Ickes, D. Neubauer, U. Lohmann

We investigate the role of primary ice nucleation as a source of ice in mixed-phase clouds compared to other processes, such as sedimentation of ice crystals from an ice cloud above and vertical transport of ice crystals. For our sensitivity studies, we use the global climate model ECHAM-HAM with a detailed two-moment cloud microphysics scheme. We show how the different physical parameterizations of the processes introducing ice crystals into a mixed-phase cloud influence each other. We also study how changes in one physical parameterization scheme (ice nucleation parameterization) affect the importance of the other processes. In ECHAM-HAM, sedimentation of ice crystals from above-lying ice clouds is the main source of ice crystals.

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