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© Author(s) 2020. This work is distributed under
the Creative Commons Attribution 4.0 License.
© Author(s) 2020. This work is distributed under
the Creative Commons Attribution 4.0 License.

  25 May 2020

25 May 2020

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A revised version of this preprint is currently under review for the journal ACP.

Secondary ice production in summer clouds over the Antarctic coast: an underappreciated process in atmospheric models

Georgia Sotiropoulou1,2, Etienne Vignon3, Gillian Young4, Hugh Morrison5,6, Sebastian J. O'Shea7, Thomas Lachlan-Cope8, Alexis Berne3, and Athanasios Nenes1,9 Georgia Sotiropoulou et al.
  • 1Laboratory of Atmospheric Processes and their Impacts (LAPI), Ecole Polytechnique Fédérale de Lausanne (EPFL), Lausanne, Switzerland
  • 2Department of Meteorology, Stockholm University & Bolin Center for Climate Research, Sweden
  • 3Environmental Remote Sensing Laboratory (LTE), EPFL, Lausanne, Switzerland
  • 4School of Earth and Environment, University of Leeds, UK
  • 5National Center for Atmospheric Research, Boulder, CO, USA
  • 6ARC Centre for Excellence in Climate System Science, University of New South Wales, Sydney, Australia
  • 7Centre for Atmospheric Science, University of Manchester, UK
  • 8British Antarctic Survey, Cambridge, UK
  • 9ICE-HT, Foundation for Research and Technology Hellas (FORTH), Patras, Greece

Abstract. The correct representation of Antarctic clouds in atmospheric models is crucial for accurate projections of the future Antarctic climate. This is particularly true for summer clouds which play a critical role in the surface melting of the ice-shelf in the vicinity of Weddell Sea. However these clouds are often poorly represented, as ice crystal number concentrations (ICNCs) are undepredicted by atmospheric models, even when primary ice formation is constrained with aerosol measurements. Rime-splintering, thought to be the dominant secondary ice production (SIP) mechanism at temperatures between −8 and −3 °C, is also very weak in summer Antarctic conditions. Including a parameterization for SIP due to break-up (BR) from collisions between ice particles in the Weather and Research Forecasting model bridges the gap between observations and simulations, suggesting that BR could account for the enhanced ICNCs in the pristine Antarctic atmosphere. These results are insensitive to uncertainties in primary ice production. The BR mechanism is currently not represented in most weather prediction and climate models; including this process can have a significant impact on the Antarctic radiation budget and thus in projections of the future regional climate.

Georgia Sotiropoulou et al.

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Georgia Sotiropoulou et al.

Georgia Sotiropoulou et al.


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Latest update: 24 Sep 2020
Publications Copernicus
Short summary
Summer clouds have a significant impact on the radiation budget of the Antarctic surface and thus on ice-shelf melting. However these are poorly represented in climate models due to errors in their microphysical structure, including the number of ice crystals that they contain. We show that break-up from ice-particle collisions can substantially magnify the ice crystal number concentration with significant implications for surface radiation. This process is currently missing in climate models.
Summer clouds have a significant impact on the radiation budget of the Antarctic surface and...