Predicting Cloud Liquid Water and Cloud Ice for Pristine Coastal Antarctica

Supercooled liquid water is common in the clouds near coastal Antarctica and occasionally occurs at temperatures near -30°C. Yet the ice physics in most regional and global numerical models will glaciate out clouds in these cases. This presents a challenge for the simulation of cold supercooled clouds that were observed at McMurdo, Antarctica during the Atmospheric Radiation Measurement (ARM) West Antarctic Radiation Experiment (AWARE) project during 2015-2017. The simulations were conducted with the polar-optimized version of the Weather Research and Forecasting model (Polar WRF) with the recently developed two-moment P3 microphysics scheme. Simulations are conducted of two observed supercooled liquid water cases of a few days duration during March and August 2016. Nudging of the simulations to observed rawinsonde profiles at McMurdo, Antarctica and observed Antarctic automatic weather stations provided increased realism and much greater, more realistic cloud water amounts. Adjusting the ice physics for extremely low ice nucleating particle (INP) concentrations decreases cloud ice and increases the cloud liquid water toward more realistic amounts. Accurate representation of INP appears to be critical for simulation of Antarctic clouds.