Cloud Macro-and Microphysical Properties as Coupled to Sea Ice Leads During the MOSAiC Expedition

This study presents the micro- and macrophysical cloud properties as a function of their surface coupling state with the sea ice during the wintertime of the MOSAiC field experiment. Cloud properties such as cloud base height, liquid- and ice water content have been previously found to have statistically distinguished features under the presence of sea ice leads (characterized by sea ice concentration, SIC) along downwind direction from the central observatory RV Polarstern. Those findings are mainly in an increase of liquid water content, and favored occurrence of low level clouds as contrasted to situations when the clouds are thermodynamically decoupled. The present contribution is an update considering two recent developments in the liquid detection in clouds and in the detection of sea ice leads. First, radar and lidar-based cloud droplet detection approaches like Cloudnet (Illingworth et al. 2007, Tukiainen et al. 2020) using Arctic wintertime observations and applied to measurements by the Atmospheric Radiation Measurement mobile facility (ARM) instrumental suite on-board the RV Polarstern during MOSAiC. Secondly, we explore a new sea ice lead fraction product based on sea ice divergence. Sea ice divergence is estimated from sequential images of space-borne synthetic aperture radar with a spatial resolution of 700 m. The lead divergence product, being independent of cloud coverage, offers the unique advantage to detect opening leads at high spatial resolution. Statistics for the wintertime cloud properties based on the coupling state with the sea ice concentration and sea ice lead fraction will be presented as an approach to study Arctic clouds and their interaction with sea ice.