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Volume 11, issue 10 | Copyright

Special issue: The Modular Earth Submodel System (MESSy) (ACP/GMD inter-journal...

Geosci. Model Dev., 11, 4021-4041, 2018
https://doi.org/10.5194/gmd-11-4021-2018
© Author(s) 2018. This work is distributed under
the Creative Commons Attribution 4.0 License.

Development and technical paper 05 Oct 2018

Development and technical paper | 05 Oct 2018

Implementation of a comprehensive ice crystal formation parameterization for cirrus and mixed-phase clouds in the EMAC model (based on MESSy 2.53)

Sara Bacer1, Sylvia C. Sullivan2, Vlassis A. Karydis1,a, Donifan Barahona3, Martina Krämer4, Athanasios Nenes2,5,6,7,8, Holger Tost9, Alexandra P. Tsimpidi1, Jos Lelieveld1,10, and Andrea Pozzer1 Sara Bacer et al.
  • 1Atmospheric Chemistry Department, Max Planck Institute for Chemistry, Mainz, Germany
  • 2School of Chemical and Biomolecular Engineering, Georgia Institute of Technology, Atlanta, USA
  • 3NASA Goddard Space Flight Center, Greenbelt, Maryland, USA
  • 4Institute for Energy and Climate Research – 7, Forschungszentrum Jülich, Jülich, Germany
  • 5School of Earth and Atmospheric Sciences, Georgia Institute of Technology, Atlanta, USA
  • 6ICE-HT, Foundation for Research and Technology, Hellas, Greece
  • 7IERSD, National Observatory of Athens, Athens, Greece
  • 8Laboratory of Atmospheric Processes and Their Impacts, École Polytechnique Fédérale de Lausanne, Lausanne, Switzerland
  • 9Institute for Atmospheric Physics, Johannes Gutenberg University Mainz, Mainz, Germany
  • 10Energy, Environment and Water Research Center, The Cyprus Institute, Nicosia, Cyprus
  • anow at: Institute for Energy and Climate Research – 8, Forschungszentrum Jülich, Jülich, Germany

Abstract. A comprehensive ice nucleation parameterization has been implemented in the global chemistry-climate model EMAC to improve the representation of ice crystal number concentrations (ICNCs). The parameterization of Barahona and Nenes (2009, hereafter BN09) allows for the treatment of ice nucleation taking into account the competition for water vapour between homogeneous and heterogeneous nucleation in cirrus clouds. Furthermore, the influence of chemically heterogeneous, polydisperse aerosols is considered by applying one of the multiple ice nucleating particle parameterizations which are included in BN09 to compute the heterogeneously formed ice crystals. BN09 has been modified in order to consider the pre-existing ice crystal effect and implemented to operate both in the cirrus and in the mixed-phase regimes. Compared to the standard EMAC parameterizations, BN09 produces fewer ice crystals in the upper troposphere but higher ICNCs in the middle troposphere, especially in the Northern Hemisphere where ice nucleating mineral dust particles are relatively abundant. Overall, ICNCs agree well with the observations, especially in cold cirrus clouds (at temperatures below 205K), although they are underestimated between 200 and 220K. As BN09 takes into account processes which were previously neglected by the standard version of the model, it is recommended for future EMAC simulations.

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The complexity of ice nucleation mechanisms and aerosol--ice interactions makes their representation still challenging in atmospheric models. We have implemented a comprehensive ice crystal formation parameterization in the global chemistry-climate model EMAC to improve the representation of ice crystal number concentrations. The newly implemented parameterization takes into account processes which were previously neglected by the standard version of the model.
The complexity of ice nucleation mechanisms and aerosol--ice interactions makes their...
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