Microphysical processes involving the vapour phase dominate in simulated low-level Arctic clouds

• Main Authors: Kiszler, Theresa, Ori, Davide, Schemann, Vera
• Format: Article in Journal/Newspaper
• Language: English
• Published: Copernicus Publications 2023
• Subjects: article; Verlagsveröffentlichung; Arctic; polar night
• Online Access: https://doi.org/10.5194/egusphere-2023-2986; https://noa.gwlb.de/receive/cop_mods_00070632; https://noa.gwlb.de/servlets/MCRFileNodeServlet/cop_derivate_00068975/egusphere-2023-2986.pdf; https://egusphere.copernicus.org/preprints/2023/egusphere-2023-2986/egusphere-2023-2986.pdf

Current general circulation models struggle to capture the phase-partitioning of clouds accurately, either overestimating or underestimating the supercooled liquid substantially. This impacts the radiative properties of clouds. Therefore, it is of interest to understand which processes determine the phase-partitioning. In this study, microphysical process rates are analyzed to study what role each phase-changing process plays in low-level Arctic clouds. Several months of cloud-resolving ICON simulations using a two-moment cloud microphysics scheme, are evaluated. The microphysical process rates are extracted using a diagnostic tool introduced here, which runs only the microphysical parameterisation using previously simulated days. It was found that the importance of a process varies for the polar night and polar day, although phase changes that involve the vapour phase dominate. Additionally, the dependence of each process on the temperature, vertical wind and saturation was evaluated. Going a step further, we used the combined evaporation and deposition rates to demonstrate the Wegener-Bergeron-Findeisen process occurrence. This study helps to better understand how microphysical processes act in different regimes. It additionally shows which processes play an important role and contribute to the phase-partitioning in low-level Arctic clouds. Therefore, these processes can be better targeted for improvements in the model that aim to better represent the phase-partitioning of Arctic low-level mixed-phase clouds.