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Geoscientific Model Development An interactive open-access journal of the European Geosciences Union
https://doi.org/10.5194/gmd-2018-62
© Author(s) 2018. This work is distributed under
the Creative Commons Attribution 4.0 License.
Development and technical paper
13 Mar 2018
Review status
This discussion paper is a preprint. A revision of the manuscript is under review for the journal Geoscientific Model Development (GMD).
Implementation of a comprehensive ice crystal formation parameterization for cirrus and mixed-phase clouds into the EMAC model (based on MESSy 2.53)
Sara Bacer1, Sylvia C. Sullivan2, Vlassis A. Karydis1, Donifan Barahona3, Martina Krämer4, Athanasios Nenes2,5,6,7, Holger Tost8, Alexandra P. Tsimpidi1, Jos Lelieveld1,9, and Andrea Pozzer1 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, USA
4Institut für Energie und Klimaforschung, 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
8Institute for Atmospheric Physics, Johannes Gutenberg University Mainz, Mainz, Germany
9Energy, Environment and Water Research Center, The Cyprus Institute, Nicosia, Cyprus
Abstract. A comprehensive ice nucleation parameterization has been implemented in the global chemistry-climate model EMAC to realistically represent ice crystal number concentrations. The parameterization of Barahona and Nenes (2009, hereafter BN09) allows the treatment of ice nucleation, taking into account the competition for water vapour between homogeneous and heterogeneous nucleation and pre-existing ice crystals in cold clouds. Furthermore, the influence of chemically-heterogeneous, polydisperse aerosols is considered via multiple ice nucleating particle spectra, which are included in the parameterization to compute the heterogeneously formed ice crystals. BN09 has been implemented to operate both in the cirrus and in the mixed-phase regimes. Compared to the standard EMAC results, BN09 produces fewer ice crystals in the upper troposphere but higher ice crystal number concentrations in the middle troposphere, especially in the Northern Hemisphere where ice nucleating mineral dust particles are relatively abundant. The comparison with a climatological data set of aircraft measurements shows that BN09 used in the cirrus regime improves the model results and, therefore, is recommended for future EMAC simulations.
Citation: Bacer, S., Sullivan, S. C., Karydis, V. A., Barahona, D., Krämer, M., Nenes, A., Tost, H., Tsimpidi, A. P., Lelieveld, J., and Pozzer, A.: Implementation of a comprehensive ice crystal formation parameterization for cirrus and mixed-phase clouds into the EMAC model (based on MESSy 2.53), Geosci. Model Dev. Discuss., https://doi.org/10.5194/gmd-2018-62, in review, 2018.
Sara Bacer et al.
Sara Bacer et al.
Sara Bacer et al.

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Short summary
The complexity of ice nucleation mechanisms and aerosol-ice interactions makes their representation still challenging in the 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 (ICNCs). The newly implemented parameterization, in comparison with the standard EMAC results, produces ICNCs that are closer to the observations.
The complexity of ice nucleation mechanisms and aerosol-ice interactions makes their...
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