A010-0002
Colliding Ice Crystals: a Key Process to Understand Ice Formation in Polar Clouds

Monday, 7 December 2020
Poster
Georgia Sotiropoulou1,2, Luisa Ickes3, Athanasios Nenes4 and Annica Ekman1, (1)Stockholm University, Department of Meteorology, Stockholm, Sweden, (2)EPFL Swiss Federal Institute of Technology Lausanne, LAPI, ENAC, Lausanne, Switzerland, (3)Chalmers University of Technology, Department of Space, Earth and Environment, Gothenburg, Sweden, (4)Swiss Federal Institute of Technology Lausanne, Laboratory of Atmospheric Processes and their Impacts, School of Architecture, Civil & Environmental Engineering, Lausanne, Switzerland
Abstract:
Atmospheric models often fail to correctly reproduce the microphysical structure of polar mixed-phase clouds and underpredict the ice water content, even when simulations are constrained by observed levels of ice-nucleating particles (INP). Secondary Ice Processes (SIP) have been suggested as a way to enhance ice crystal concentrations above INP levels. The most well-known SIP processes are rime-splintering (or the Hallet-Mossop process), ice-ice collisions and drop-shattering. Rime-splintering is not active outside the -8oC to -3oC temperature range. Drop-shattering is also inefficient due to a lack of relatively large drops. Using large-eddy simulation, we find that ice-ice collisions are likely important in polar clouds, but the efficiency decreases with increasing concentrations of INPs. Including a description for ice-ice collisions can improve the cloud microphysical representation, but the degree of influence depends on other poorly constrained microphysical parameters that include ice habit, rimed fraction and cloud ice-to-snow autoconversion rate.
<< Previous Abstract | Next Abstract >>