Modelling of cirrus clouds – Part 1a: Model description and validation P. Spichtinger1 and K. M. Gierens2 1Institute for Atmospheric and Climate Science, ETH Zurich, 8092 Zurich, Switzerland 2Deutsches Zentrum für Luft- und Raumfahrt, Institut für Physik der Atmosphäre, Oberpfaffenhofen, Germany
Abstract. A double-moment bulk microphysics scheme for modelling
cirrus clouds including explicit impact of aerosols on different
types of nucleation mechanism is described. Process rates are
formulated in terms of generalised moments of the underlying a
priori size distributions in order to allow simple switching
between various distribution types. The scheme has been implemented
into a simple box model and into the anelastic non-hydrostatic model
EULAG. The new microphysics is validated against simulations with
detailed microphysics for idealised process studies and for a well
documented case of arctic cirrostratus. Additionally, the formation
of ice crystals with realistic background aerosol concentration is
modelled and the effect of ambient pressure on homogeneous
nucleation is investigated in the box model.
The model stands all tests and is thus suitable for
cloud-resolving simulations of cirrus clouds.
Citation: Spichtinger, P. and Gierens, K. M.: Modelling of cirrus clouds – Part 1a: Model description and validation, Atmos. Chem. Phys., 9, 685-706, doi:10.5194/acp-9-685-2009, 2009.