EGU21-3369, updated on 12 May 2021
EGU General Assembly 2021
© Author(s) 2021. This work is distributed under
the Creative Commons Attribution 4.0 License.

The impact of Secondary Ice Processes on a stratocumulus-to-cumulus transition during a Cold-Air Outbreak

Michail Karalis1, Georgia Sotiropoulou2,3, Steven J. Abel4, Elissavet Bossioli1, Paraskevi Georgakaki3, Georgia Methymaki1, Athanasios Nenes3,5, and Maria Tombrou1
Michail Karalis et al.
  • 1Divis. of Environmental Physics and Meteorology, Dept. of Physics, University of Athens, Athens, Greece
  • 2Department of Meteorology, Stockholm University, Stockholm, Sweden
  • 3Laboratory of Atmospheric Processes and their Impacts, ENAC, Ecole Polytechnique Fédérale de Lausanne, Lausanne, Switzerland
  • 4Met Office, Exeter, United Kingdom
  • 5Institute of Chemical Engineering Sciences, Foundation for Research and Technology Hellas, Patras, Greece

The representation of boundary layer clouds during marine Cold-Air Outbreaks (CAO) remains a great challenge for weather prediction models. Recent studies have shown that the representation of the transition from stratocumulus clouds to convective cumulus open cells largely depends on microphysical and precipitation processes, while Abel et al. (2017) further suggested that Secondary Ice Processes (SIP) may play a crucial role in the evolution of the cloud fields. In this study we use the Weather Research Forecasting model to investigate the impact of the most well-known SIP mechanisms (rime-splintering or Hallet-Mossop, mechanical break-up upon collisions between ice particles and drop-shattering) on a CAO case observed north of UK in 2013. While Hallet-Mossop is the only SIP process extensively implemented in atmospheric models, our results indicate that collisional break-up is also important in these conditions.


Abel, S. J., Boutle, I. A., Waite, K., Fox, S., Brown, P. R. A., Cotton, R., Lloyd, G., Choularton, T. W., & Bower, K. N. (2017). The Role of Precipitation in Controlling the Transition from Stratocumulus to Cumulus Clouds in a Northern Hemisphere Cold-Air Outbreak, Journal of the Atmospheric Sciences, 74(7), 2293-2314. Retrieved Jan 9, 2021, from

How to cite: Karalis, M., Sotiropoulou, G., Abel, S. J., Bossioli, E., Georgakaki, P., Methymaki, G., Nenes, A., and Tombrou, M.: The impact of Secondary Ice Processes on a stratocumulus-to-cumulus transition during a Cold-Air Outbreak, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-3369,, 2021.


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