TITLE:
Experimental Study on the Dependency of Ice Nucleation Active Surface Site Density on ATD Aerosol Size
AUTHORS:
Franco Belosi, Gianni Santachiara
KEYWORDS:
Ice Activated Fraction, Ice Nucleation Active Surface Site Density, Condensation Freezing
JOURNAL NAME:
Atmospheric and Climate Sciences,
Vol.11 No.3,
May
31,
2021
ABSTRACT: 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 (ns). It is usually assumed that ns 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 ns 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 ns increased by lowering the
nucleation temperature, and was also dependent on the particle size. The ns 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 ns dependence of same composition aerosol particles with a view to support weather
and climate predictions.