Cloud and Blowing Snow Impacts on Atmospheric Boundary Layer and Surface Radiation over Dome C, Antarctica

Blowing snow, which involves the lifting and redistribution of accumulated snow by winds, is a common occurrence over Antarctica, and affects the hydrological and surface mass balance of the ice sheet. Recent satellite-based measurements have shown that similar to clouds, blowing snow can increase the outgoing longwave radiation (OLR) during polar night when it is encapsulated within strong and persistent surface-based inversions (SBIs) that are significantly warmer than the underlying ice-sheet. Yet, little is known regarding the physical relationship between Antarctic sky condition (blowing snow, clouds) and atmospheric boundary layer properties (thermodynamic structure, winds) which is a crucial link for understanding and modeling their impacts. In this study, we use a novel method combining multi-year and multi-instrument Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observation (CALIPSO) and CloudSat products to identify the sky condition (blowing snow, cloud, clear) over Dome C, and contemporaneous in-situ atmospheric measurements (radiosondes) to determine its physical relationship with atmospheric boundary layer properties. Our results indicate that increased wind speed shear which is often observed during blowing snow events, leads to increased boundary layer turbulence which then contributes to reduced SBI intensity in all seasons except summer. Additionally, we investigate the impact of sky condition on the downwelling surface longwave radiation (DSLR) using contemporaneous high temporal resolution measurements from the Baseline Surface Radiation Network at Dome C, and confirm that a statistically significant increase in DSLR is indeed observed during cloud and blowing snow in winter months compared to clear-sky conditions. Longwave radiation emission from blowing snow appears to be enhanced when its optical depth is higher than a certain threshold, aided by the positive temperature gradient of the layer within which it occurs. Using innovative methodology to combine a suite of observations, this study improves process-level understanding of surface-atmosphere interactions which are important for accurate modeling of Antarctica's weather, climate, hydrology, and ice-sheet mass balance.