Improved Simulation of Arctic Mixed-Phase Clouds with Modified Ice Microphysics in the WDM6 Scheme

In this study, we evaluated the simulation performance of Arctic mixed-phase clouds using the Weather Research and Forecasting (WRF) Double-Moment 6-class (WDM6) scheme and its improved version (WDM6_ICE). WDM6_ICE prognoses the cloud ice number concentrations and incorporates the enhanced cloud ice shape parameters and cloud ice formation processes. Sensitivity experiments were conducted during the Mixed-Phase Arctic Cloud Experiment (M-PACE) period of October 9–10, 2004.

WDM6_ICE significantly improved cloud simulation, showing the enhanced low-level cloud fraction and more realistic radiation effects compared to WDM6. The vertical structure analysis revealed that WDM6_ICE more effectively maintained supercooled cloud liquid by reducing ice deposition and enhancing condensation processes and reduced efficiency of Wegener-Bergeron-Findeisen (WBF) process. Through the sensitivity experiments involving changes in cloud ice shape (SP) and ice nucleation processes (IN) (WDM6_SP and WDM6_SP_IN), we demonstrated how these changes contributed to the improved phase partitioning in mixed-phase clouds. However, our analysis also revealed limitations in the representation of total water content and boundary layer structure, suggesting the need for further improvements in surface-atmosphere interactions under stable Arctic conditions. Our findings provide insights for improving the representation of cloud microphysics and their interaction with boundary layer processes in Arctic mixed-phase clouds.