The potential effects of aerosol particles on ice formation processes are critical unknowns in understanding cloud and climate forcing by aerosols. It is not possible to quantify present and future indirect effects of aerosols on cirrus cloud radiative properties without better knowledge of the effectiveness of various types of natural and anthropogenic aerosol particles acting as ice forming nuclei and of the ice nucleation mechanisms involved.

This poster reports on laboratory measurements to investigate homogeneous and heterogeneous ice nucleation by various aerosol particle types in the environmental regime of cirrus clouds. Ice nucleation ability is determined using a continuous flow ice-thermal diffusion chamber, which identifies the conditions of relative humidity and temperature required to initiate ice formation. Studies have examined ice nucleation by particles composed of pure sulfates, pure organic components (e.g., dicarboxylic acids), black carbon, mineral oxide and mineral dust surrogates, and mixtures of inorganic and organic chemical components. Key findings will be elucidated.