Influence of parameterized ice habit on simulated mixed phaseArctic clouds

摘要

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