Dynamical and Microphysical Evolution during Mixed-Phase Cloud Glaciation Simulated Using the Bulk Adaptive Habit Prediction Model

Abstract

bulk microphysics scheme predicting ice particle habit evolution has been implemented in the Weather Research and Forecasting Model. Large-eddy simulations are analyzed to study the effects of ice habit and number concentration on the bulk ice and liquid masses, dynamics, and lifetime of Arctic mixed-phase boundary layer clouds. The microphysical and dynamical evolution simulated using the adaptive habit scheme is compared with that assuming spherical particles with a density of bulk ice or a reduced density and with mass?dimensional parameterizations. It is found that the adaptive habit method returns an increased (decreased) ice (liquid) mass as compared to spheres and provides a more accurate simulation as compared to dendrite mass?size relations.Using the adaptive habit method, simulations are then completed to understand the microphysical and dynamical interactions within a single-layer mixed-phase stratocumulus cloud observed during flight 31 of the Indirect and Semi-Direct Aerosol Campaign. With cloud-top longwave radiative cooling as a function of liquid mass acting as the primary dynamic driver of turbulent eddies within these clouds, the consumption of liquid at the expense of ice growth and subsequent sedimentation holds a strong control on the cloud lifetime. Ice concentrations ≥ 4 L?1 collapse the liquid layer without any external maintaining sources. Layer maintenance is possible at 4 L?1 when a constant cloud-top cooling rate or the water mass lost due to sedimentation is supplied. Larger concentrations require a more substantial source of latent or sensible heat for mixed-phase persistence.