Laboratory studies on the potential of tropospheric insoluble aerosol components for heterogeneous ice nucleation

The large coolable and evacuable aerosol chamber AIDA is used as a cloud chamber to study processes of ice formation in tropospheric clouds. Intensity and depolarisation of forward- and back-scattered laser radiation is measured, caused by particles in a small scattering volume far from the walls. Number size distribution of interstitial aerosol and activated ice particles are measured with an optical particle counter. Droplet freezing and growth of the ice particles can thus be detected unambiguously. Particle freezing and growth is initiated by adiabatic expansion which leads to volume cooling and thus ice- and water supersaturation at constant wall temperature. Various insoluble aerosol components can be generated and added to the chamber in order to investigate their influence on ice formation processes at controlled temperatures and supersaturations.