The effect of cloud top cooling on the evolution of the Arctic boundary layer observed by balloon-borne measurements

The presence of clouds significantly affects Arctic boundary layer dynamics. However, the accessibility of clouds over the Arctic sea ice for in-situ observations is challenging. Measurements from tethered balloon platforms are one option to provide high-resolution data needed for model evaluation.

The tethered balloon system BELUGA (Balloon-bornE moduLar Utility for profilinG the lower Atmosphere) was deployed to profile the boundary layer at the Multidisciplinary drifting Observatory for the Study of Arctic Climate (MOSAiC), and in Ny-Alesund. A set of scientific payloads for the observation of broadband radiation, turbulence, aerosol particles, and cloud microphysics properties were operated to study the interactions in the cloudy and cloud-free boundary layer.

Measurements obtained under various cloud conditions, including single-layer and multi-layer clouds, are analyzed. Heating rates profiles are calculated to validate radiative transfer simulations and to study the temporal development of the cloud layers. 

The in-situ observations display the importance of radiation-induced cloud top cooling in maintaining stratocumulus clouds over the Arctic sea ice. Case studies also indicate how the subsequent turbulent mixing can lead to the entrainment of aerosol particles into the cloud layer.