Author(s)

Franco Belosi, Gianni Santachiara

National Research Council of Italy, Institute of Atmospheric Sciences and Climate (CNR-ISAC), Bologna, Italy.

In light of the percentage of Earth’s cloud coverage, heterogeneous ice nucleation in clouds is the most important global-scale pathway. More recent parameterizations of ice nucleation processes in the atmosphere are based on the concept of ice nucleation active surface site density (n_s). It is usually assumed that n_s is independent of time and aerosol size distribution, i.e. that the surface properties of aerosols of the same species do not vary with size. However, the independence of n_s on aerosol size for every species has been questioned. This study presents the results of ice nucleation processes of ATD laboratory-generated aerosol (particle diameters of 0 - 3 μm). Ice nucleation in the condensation mode was performed in a Dynamic Filter Processing Cham- ber at temperatures of -18°C and -22°C, with a saturation ratio with respect to water of 1.02. Results show that n_s increased by lowering the nucleation temperature, and was also dependent on the particle size. The n_s of particles collected on the filters, after a 0.5 μm D₅₀ cut-off cyclone, resulted statistically higher with respect to the values obtained from the particles collected on total filters. The results obtained suggest the need for further investigation of n_s dependence of same composition aerosol particles with a view to support weather and climate predictions.

Ice Activated Fraction, Ice Nucleation Active Surface Site Density, Condensation Freezing

Belosi, F. and Santachiara, G. (2021) Experimental Study on the Dependency of Ice Nucleation Active Surface Site Density on ATD Aerosol Size. Atmospheric and Climate Sciences, 11, 426-440. doi: 10.4236/acs.2021.113025.