Influence of parameterized ice habit on simulated mixed phase Arctic clouds

Abstract

The phase partitioning of cloud mass between liquid and ice in mixed phase clouds and its dependence on ambient ice nuclei (IN) concentrations and ice habit parameterizations is explored in this paper. Single‐layered and multilayered cloud systems observed during the Mixed‐Phase Arctic Cloud Experiment were simulated with a cloud‐resolving model. The model used a two‐moment (mass and number concentration) microphysical scheme with ice crystal habit parameterized by mass and fall speed relationships and IN prediction scheme that accounts for depletion of IN through nucleation scavenging. The mixed phase cloud simulations show a strong sensitivity to the ambient deposition/condensation freezing IN concentrations, which is similar to some prior studies. This sensitivity depends on the mass, fall speed, and capacitance relationships used to parameterize crystal habit and vapor growth: Mass and fall speed relationships associated with compact, high‐density crystals produce clouds with a weaker sensitivity to ambient IN concentrations, whereas more extreme crystal shapes (e.g., dendrites) produce clouds with strong IN concentration sensitivity. This sensitivity also affects the number of liquid layers (from 1 to 5) predicted for the multilayer case. The strength of the vapor growth rates and the crystal fall speeds appear to be of roughly equal importance for determining the strength of mixed phase cloud sensitivity to ice concentrations.