Articles | Volume 18, issue 22
Atmos. Chem. Phys., 18, 16461–16480, 2018
Atmos. Chem. Phys., 18, 16461–16480, 2018

Research article 21 Nov 2018

Research article | 21 Nov 2018

The effect of secondary ice production parameterization on the simulation of a cold frontal rainband

Sylvia C. Sullivan1,2, Christian Barthlott1, Jonathan Crosier3, Ilya Zhukov4, Athanasios Nenes2,5,6,7, and Corinna Hoose1 Sylvia C. Sullivan et al.
  • 1Institute of Meteorology and Climate Research, Karlsruhe Institute of Technology, Karlsruhe, Germany
  • 2Department of Chemical and Biomolecular Engineering, Georgia Institute of Technology, Atlanta, GA 30332, USA
  • 3School of Earth, Atmospheric, and Environmental Studies, University of Manchester, Manchester, UK
  • 4Jülich Supercomputing Center, Forschungszentrum Jülich, Jülich, Germany
  • 5ICE-HT, Foundation for Research and Technology, Hellas, 26504 Patras, Greece
  • 6Institute of Environmental Research and Sustainable Development, National Observatory of Athens, 15236 Palea Penteli, Greece
  • 7Laboratory of Atmospheric Processes and their Impacts, School of Architecture, Civil and Environmental Engineering, École Polytechnique Fédérale de Lausanne, CH 1015, Lausanne, Switzerland

Abstract. Secondary ice production via processes like rime splintering, frozen droplet shattering, and breakup upon ice hydrometeor collision have been proposed to explain discrepancies between in-cloud ice crystal and ice-nucleating particle numbers. To understand the impact of this additional ice crystal generation on surface precipitation, we present one of the first studies to implement frozen droplet shattering and ice–ice collisional breakup parameterizations in a mesoscale model. We simulate a cold frontal rainband from the Aerosol Properties, PRocesses, And InfluenceS on the Earth's Climate campaign and investigate the impact of the new parameterizations on the simulated ice crystal number concentrations (ICNC) and precipitation. Near the convective regions of the rainband, contributions to ICNC can be as large from secondary production as from primary nucleation, but ICNCs greater than 50 L−1 remain underestimated by the model. The addition of the secondary production parameterizations also clearly intensifies the differences in both accumulated precipitation and precipitation rate between the convective towers and non-convective gap regions. We suggest, then, that secondary ice production parameterizations be included in large-scale models on the basis of large hydrometeor concentration and convective activity criteria.

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Short summary
Ice crystal formation in clouds can occur via thermodynamic nucleation, but also via mechanical collisions between pre-existing crystals or co-existing droplets. When descriptions of this mechanical ice generation are implemented into the COSMO weather model, we find that the contributions to crystal number from thermodynamic and mechanical processes are of the same order. Mechanical ice generation also intensifies differences in precipitation intensity between dynamic and quiescent regions.
Final-revised paper