Effects of ice nucleation and crystal habits on the dynamics of Arctic mixed-phase clouds

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Description

Both climate and weather prediction models produce results that are inconsistent among them and that do not match the observations in the Arctic. Some prior studies suggest that ice nucleation parameterizations are a primary reason for the mismatch between the observed and modeled cloud water contents. Recent findings also show that the choice of ice crystal habit in models leads to large differences in the partitioning of phase between liquid water and ice. In order to improve model predictions in the Arctic, it is important to identify the processes responsible for mixed-phase cloud development and persistence. In our study we examine the complex interactions between microphysics and dynamics that lead to persistent mixed-phase clouds. We investigate and inter-compare the impacts of different ice nucleation mechanisms and ice crystal habits on mixed-phase cloud evolution. Our preliminary studies show that although different nucleation mechanisms lead to different water paths, the difference in water paths caused by the choice of habits is greater. The amount of radiative cooling at cloud top and ice precipitation at the surface changes as the strength of ice production changes for different nucleation mechanisms, or as the in-cloud lifetime of an ice crystal changes for different habits. As a result, the cloud dynamics and cloud evolution differ for each habit and nucleation mechanism.