Effects of Ice Nucleation and Crystal Habits on the Dynamics of Arctic Mixed Phase Clouds

Arctic mixed-phase clouds are particularly important for a number of reasons including their effects on Arctic climate. Yet numerical models poorly simulate observed Arctic mixed phase clouds with considerable deviations from observations. Reasons for the deviation of the simulated ice and liquid water paths from observations are due to a number of factors including the way ice crystal habits are parameterized in models and the way ice is nucleated. Predicting these physical processes controls the partitioning between liquid and ice, and hence the impact of mixed-phase clouds on the surface energy budget. Hence, there is a need to improve model cloud predictions in Arctic. However, the microphysical uncertainties mentioned above are tied directly to the cloud dynamics that help maintain persistent mixed-phase clouds. Therefore, we analyze and inter-compare the impacts of different ice nucleation mechanisms and ice crystal habits on mixed-phase cloud dynamics. We analyze the relative importance of the processes that influence the dynamics of the cloud, such as the radiative cooling at cloud top, and the cloud base stabilization and their connections to crystal habit and ice nucleation. To separate the influences of the various processes affecting the dynamics we use sensitivity studies by fixing the radiative heating, and the diabatic influences of ice precipitation on the cloud layers. We also use a trajectory ensemble model, in which we analyze output derived from Lagrangian to provide us with more information on the cloud physics and dynamics.