Ice Multiplication - Solving the longest standing puzzle in cloud physics

Ice formation in clouds plays an important role both for precipitation formation and climate. It is generally assumed that most ice in clouds warmer than about -36°C forms heterogeneously, i. e. at the surface of an aerosol particle acting as ice nucleus. It has been known for long that in many clouds the concentration of ice particles exceeds the concentration of suitable aerosols by several orders of magnitude. This apparent contradiction may be explained by secondary ice processes (see figure), which may cause an avalanche process of ice formation, the so-called ice multiplication. Up to date, in situ observations and laboratory experiments have been inconclusive in identifying the importance and effectiveness of each of these processes under real cloud conditions. Therefore, ice multiplication is only very crudely included in cloud and weather models.

Recent progress in material science, fluid dynamics, laboratory experiments, cloud modelling, in-situ observations and remote sensing allows now to assess ice multiplication processes in much better detail. Within an interdisciplinary project, 6 PIs from these research areas come together to start solving the ice multiplication puzzle:

Prof. Dr. Corinna Hoose – cloud modelling

Prof. Dr. Thomas Leisner – laboratory experiments

Prof. Dr. Britta Nestler – material sciences

Prof. Dr. Markus Uhlmann – fluid mechanics

Prof. Dr. Jan Cermak – satellite remote sensing

Dr. Emma Järvinen – aircraft observations