We investigate aerosol-cloud-processes, in particular primary ice formation in atmospheric clouds using the AIDA facility, and develops parameterisations of these processes for use in atmospheric cloud, weather and climate models. We also develop new methods and instruments to measure and characterise ice nucleating particles both in laboratory and field projects.

Aerosol Cloud Interactions

In clouds of the lower and middle troposphere, the formation of ice often triggers a cascade of secondary processes which are of importance for the formation, distribution and intensity of precipitation events. In the upper troposphere, the different pathways of ice formation influence the radiative properties of cirrus clouds and by that their important role in the climate system. We are using the AIDA (Aerosol Interaction and Dynamics in the Atmosphere) facilities to investigate the role of various atmospheric aerosol types in cloud ice formation under simulated cloud formation conditions. The experiments cover the full range of tropospheric temperature and humidity, and provide a unique data set to develop and improve formulations like the ice nucleation active site (INAS) concept, which can be used to quantify primary ice formation in cloud, weather and climate models.

Ice Nucleating Particles

Ice Nucleating Particles (INPs) are a very minor fraction of atmospheric aerosol particles, which are needed to form ice crystals at high temperatures or low ice supersaturation, and by that have important impact on the formation of precipitation and the net radiative effect of cirrus clouds in the Earth’s climate system. The atmospheric abundance and distribution of INPs strongly depends on the temperature as well as the concentration and type of aerosol particles. We are using the aerosol filter based method INSEKT (Ice Nucleation Spectrometer of the Karlsruhe Institute of Technology) and the newly developed PINE (Portable Ice Nucleation Experiment) instrument for INP measurements at about 10 different locations in Europe and in China. We are in particular interested in long-term observations at field sited influences by aerosol from different natural and anthropogenic sources.