Toward enhanced retrievals of supercooled droplet properties in Antarctic clouds

Clouds containing supercooled liquid are common over the Southern Ocean and coastal Antarctica. The liquid phase not only has strong influence on the surface energy budget, but also cloud microphysics and precipitation formation. Often, the droplets occur in thin layers stacked on top of each other and/or coexisting with ice particles. Both of these aspects pose a significant challenge for observations. Cloud radar Doppler spectra can contain this information in the form of individual peaks for different particle populations, but extracting useful data is challenging for automated retrievals.

Combining advanced Doppler spectra analysis techniques with established retrieval methods, such as ACTRIS-Cloudnet, can provide cloud microphysical properties even under complex conditions. This approach has been applied to observations from Neumayer Station III, Antarctica (70.67°S, 8.27°W), where synergistic remote sensing instruments are operated since 2023. During the 2024/25 austral summer, tethered-balloon in-situ observations provided complementary information on cloud droplet properties.

Two aspects will be presented: Firstly, properties of liquid layers in geometrically thick snowfall clouds. Spatiotemporal coinciding balloon-borne observations provide independent verification. Secondly, observations of seeder-feeder situations, in which ice crystals sediment into a supercooled – potentially drizzling – layer. It is envisaged that the Doppler spectral analysis will be implemented as a new method in ACTRIS-Cloudnet in the future.