Mixed-phase clouds consist of supercooled cloud droplets and ice  crystals. They can be found at temperatures between 0 and -40ºC. Their  formation is triggered by different processes forming or introducing ice  crystals into a supercooled cloud. Once ice crystals are present they  grow at the expense of the cloud droplets due to the  Wegener-Bergeron-Findeisen process. This causes a partial or complete  glaciation of the mixed-phase cloud. The phase of the mixed-phase cloud  is an important characteristics for its role in the radiation budget.

The aim of this master project will be to look at two different trigger  processes, which introduce initial ice crystals into a supercooled  cloud: heterogeneous ice nucleation and sedimentation of ice Crystals  from cirrus clouds (amongst others seeder-feeder process). The student  will analyze the importance of each process in the climate modell NorESM  by using an ensemble of simulations with each process switched on/off.  The outcome is analyzed using the factorial method with the supercooled  liquid fraction as a tracer for the microphysical structure of the  mixed-phase clouds.

This topic is ideal for a student interested in global climate modeling  and cloud microphysics.