Simulating gas-aerosol-cirrus interactions: Process-oriented microphysical model and applications B. Kärcher Deutsches Zentrum für Luft- und Raumfahrt (DLR), Institut für Physik der Atmosphäre (IPA), Oberpfaffenhofen, Germany
Abstract. This work describes a process-oriented,
microphysical-chemical model to simulate the formation and evolution of aerosols and ice crystals under the conditions prevailing in the upper troposphere and lower stratosphere. The model
can be run as a box model or along atmospheric trajectories, and considers mixing, gas phase chemistry of aerosol
precursors, binary homogeneous aerosol nucleation, homogeneous and heterogeneous ice nucleation, coagulation,
condensation and dissolution, gas retention during particle freezing, gas trapping in growing ice crystals, and
reverse processes. Chemical equations are solved iteratively using a second order implicit integration method. Gas-particle interactions and
coagulation are treated over various size structures, with fully mass conserving and non-iterative numerical solution
schemes. Particle types include quinternary aqueous solutions composed of
H2SO4, HNO3, HCl, and HBr with and without insoluble components, insoluble aerosol particles, and spherical or columnar
ice crystals deriving from each aerosol type separately. Three case studies are discussed in detail to demonstrate the
potential of the model to simulate real atmospheric processes and to highlight current research topics concerning
aerosol and cirrus formation near the tropopause. Emphasis is placed on how the formation of cirrus clouds
and the scavenging of nitric acid in cirrus depends on small-scale temperature fluctuations and the presence of
efficient ice nuclei in the tropopause region, corroborating and partly extending the findings of previous studies.
Citation: Kärcher, B.: Simulating gas-aerosol-cirrus interactions: Process-oriented microphysical model and applications, Atmos. Chem. Phys., 3, 1645-1664, doi:10.5194/acp-3-1645-2003, 2003.