Parameterizing the competition between homogeneous and heterogeneous freezing in cirrus cloud formation – monodisperse ice nuclei D. Barahona1 and A. Nenes1,2 1School of Chemical and Biomolecular Engineering, Georgia Institute of Technology, USA 2School of Earth and Atmospheric Sciences, Georgia Institute of Technology, USA
Abstract. We present a parameterization of cirrus cloud formation that computes the ice
crystal number and size distribution under the presence of homogeneous and
heterogeneous freezing. The parameterization is very simple to apply and is
derived from the analytical solution of the cloud parcel equations, assuming
that the ice nuclei population is monodisperse and chemically homogeneous. In
addition to the ice distribution, an analytical expression is provided for
the limiting ice nuclei number concentration that suppresses ice formation
from homogeneous freezing. The parameterization is evaluated against a
detailed numerical parcel model, and reproduces numerical simulations over a
wide range of conditions with an average error of 6±33%. The
parameterization also compares favorably against other formulations that
require some form of numerical integration.
Citation: Barahona, D. and Nenes, A.: Parameterizing the competition between homogeneous and heterogeneous freezing in cirrus cloud formation – monodisperse ice nuclei, Atmos. Chem. Phys., 9, 369-381, doi:10.5194/acp-9-369-2009, 2009.