Is aerosol formation in cirrus clouds possible? J. Kazil1,2, E. R. Lovejoy1, E. J. Jensen3, and D. R. Hanson4 1NOAA Earth System Research Laboratory, Boulder, CO, USA 2NRC Research Associateship Programs, Washington, D.C., USA 3NASA Ames Research Center, Moffett Field, CA, USA 4Augsburg College, Minneapolis, MN, USA
Abstract. The recent observation of ultrafine aerosol particles in cirrus clouds has
raised the question whether aerosol formation within cirrus clouds is possible,
and if so, what mechanisms are involved.
We have developed an aerosol parcel model of neutral and charged
H2SO4/H2O aerosol processes, including nucleation from the gas
phase and loss onto cirrus ice particles.
Laboratory thermodynamic data for sulfuric acid uptake and loss by small neutral
and charged clusters are used, allowing for a reliable description of both
neutral and charged nucleation down to the very low temperatures occurring in
the upper troposphere and lower stratosphere.
The model implements a first order scheme for resolving the aerosol size
distribution within its geometric size sections, which efficiently suppresses
We operate the model offline on trajectories generated with a detailed 1D cirrus
model which describes ice crystal nucleation, deposition growth, vertical
advection of ice crystals and water vapor, and ice crystal sedimentation.
In this paper we explore the possibility of aerosol formation within
non-convective cirrus clouds and draw conclusions for aerosol formation in anvil
We find that sulfate aerosol formation within cirrus clouds can proceed even at
high ice surface area concentrations, and depends strongly on the size of the
cirrus ice crystals and on the surface area concentration of preexisting aerosol
Citation: Kazil, J., Lovejoy, E. R., Jensen, E. J., and Hanson, D. R.: Is aerosol formation in cirrus clouds possible?, Atmos. Chem. Phys., 7, 1407-1413, doi:10.5194/acp-7-1407-2007, 2007.