Adaptive Habit Microphysics Evolution in Arctic Stratus within the Single Column Model of Golaz (1997)

Arctic single-layer mixed-phase clouds were studied using a one-dimensional model that incorporated the adaptive habit growth model for ice microphysics. The base case was from the Indirect and Semi-Direct Aerosol Campaign, and it was perturbed over a range of cloud average temperatures, maximum (per model run) ice nuclei concentrations, and large-scale subsidence velocities. For each parameter combination the model was iterated out to 48 h, and the time, called the glaciation time, to complete disappearance of liquid recorded if this occurred within the 48 h. Dependence of glaciation times on cloud average temperatures from -30°C to -5°C, maximum ice nuclei concentrations from 0.10 L-1 to 30 L-1, and strong to no subsidence, with both isometric and habit-dependent ice crystal growth, were investigated. For isometric crystal growth, the relationship between the critical maximum ice nuclei concentration (INcrit), the maximum (per model run) ice nuclei concentration above which a mixed-phase cloud glaciated within a fixed model runtime, and cloud average temperature was monotonic. INcrit decreased with decreasing cloud average temperature. Strengthening of subsidence led to a further decrease in INcrit for every cloud average temperature. For habit-dependent ice crystal growth, the relationship with cloud average temperature was non-monotonic. Ice crystals develop dendritic and columnar habits near -15°C and -7°C, respectively, and at these two temperatures ice crystals grew and depleted supercooled liquid water faster than for isometric growth. This led to deep local minima in INcrit around these two temperatures in the model runs. Habit-dependent ice crystal growth, coupled with changes in cloud average temperature, INcrit, and subsidence strength, led to significant changes in Arctic single-layer mixed-phase cloud lifetimes.