You are here

Ice nucleation

EUCAARI studied the formation of CCN and cloud activation both in field and in laboratory. Laboratory experiments were carried out on single component, binary and ternary particles in a controlled laboratory environment to investigate the effect of organic molecules with different properties on cloud droplet activation. EUCAARI research found that it is important to account correctly for partitioning of the surfactant molecules between the bulk and surface of the growing droplet to match measured critical supersaturations.

A synthesis study of parameterizations describing the activation of SOA was designed from EUCAARI data. This study combines CCN measurements in the laboratory obtained with those in the fields in other WPs. Herein, extensive and intensive CCN-parameters compiled from the exceptionally broad data set from CCN measurements that were carried out at locations all over the world, including long-term as well as intensive field studies, are statistically analyzed and reported as monthly, daily and/or hourly mean values to account for seasonal, weekly, and diurnal pattern.

Ice nucleation (IN) potential of particles were studied using wide variety of laboratory and field experiments. All modes of ice nucleation (deposition, condensation, immersion) were studied. The results suggest that in terms of heterogeneous ice nucleation, IN surfaces cannot be described appropriately by assuming all particles to have equal and uniform surface properties. These findings can be important for the initiation of precipitation in numerical models, as a small fraction of aerosol particles acting as IN is sufficient to initiate precipitation.
CCN activation is a function of the chemistry of aerosol particles. As there are well over 1000 different potential organic species a detailed and specific inclusion in GCM simulations is still unrealistic. The EUCAARI results show that efforts are needed to bulk - generalize the parameterization of the influence of organic chemistry on CCN formation.