Cloud Characteristics and Thermodynamic Conditions at McMurdo Station, Antarctica Based on DOE/ARM Remote Sensing, Radiosonde Observations and Climate Model Simulations

Abstract:

In this study, a year of remote sensing and radiosonde retrieved cloud characteristics and thermodynamic conditions from the McMurdo Station, Antarctica are examined in conjunction with a global climate model (GCM) simulation. The DOE ARM mobile facility deployed during the AWARE field campaign provided a series of ground-based remote sensing and radiosonde observations, which was the first comprehensive study on Antarctic clouds since 1957 International Geophysical Year. Ka-Band Zenith Radar (KAZR) and High Spectral Resolution Lidar (HSRL) retrievals are used to generate a cloud phase observation mask and cloud fraction. We used these data to analyze biases of cloud fraction and cloud phase in the NCAR Community Atmosphere Model version 6 (CAM6). Radiosondes are then compared with thermodynamic outputs (i.e., temperature, relative humidity, and water vapor mixing ratio) from the CAM6 model to diagnose driving thermodynamic characteristics behind cloud fraction and phase biases. The CAM6 model shows high (low) biases of cloud fraction below (above) 3 km at the research location. In addition, the model overestimates (underestimates) occurrence frequencies of liquid (ice) phase. These biases are associated primarily with biases in relative humidity, which in turn is driven by water vapor mixing ratio biases. These findings illustrate the need to improve the estimation of driving thermodynamic variables responsible for representing Antarctic clouds in a GCM.