Relative importance and interactions of primary and secondary ice production in the Arctic mixed-phase clouds

• Main Authors: Zhao, Xi, Liu, Xiaohong
• Format: Text
• Language: English
• Published: 2021
• Subjects: Arctic; Rime
• Online Access: https://doi.org/10.5194/acp-2021-686; https://acp.copernicus.org/preprints/acp-2021-686/

A discrepancy of up to 5 orders of magnitude between ice crystal and ice nucleating particle (INP) number concentrations was found in the measurements, indicating the potential important role of secondary ice production (SIP) in the clouds. However, the relative importance and interactions between primary and SIP processes remain unexplored. In this study, we implement five different ice nucleation schemes as well as physical representations of SIP processes (i.e., droplet shattering during rain freezing, ice-ice collisional break-up, and rime splintering) in the Community Earth System Model version 2 (CESM2). We run CESM2 in the single column mode for model comparisons with the DOE Atmospheric Radiation Measurement (ARM) Mixed-Phase Arctic Cloud Experiment (M-PACE) observations. We find that the model experiments with aerosol-aware ice nucleation schemes and SIP processes yield the best simulation results for the M-PACE single-layer mixed-phase clouds. We further investigate the relative importance of ice nucleation and SIP to ice number and cloud phase as well as interactions between ice nucleation and SIP in the M-PACE single-layer mixed-phase clouds. Our results show that SIP contributes 80 % to the total ice formation and transforms ~ 30 % of pure liquid-phase clouds simulated in the model experiments without considering SIP into mixed-phase clouds. We find that SIP is not only a result of ice crystals produced from ice nucleation, but also competes with the ice nucleation. Conversely, strong ice nucleation also suppresses SIP by glaciating mixed-phase clouds.