The evolution of clouds in Arctic marine cold air outbreaks

Marine cold air outbreaks (MCAOs) are important parts of the high-latitude climate system and are characterised by strong surface fluxes generated by the air-sea temperature gradient. These fluxes promote cloud formation, which can be identified in satellite imagery by the distinct transformation of stratiform cloud 'streets' into a broken field of cumuliform clouds downwind of the outbreak. This evolution of cloud morphology changes the radiative properties of the cloud and therefore is of importance to the surface energy budget.  

While the drivers of stratocumulus-to-cumulus transitions have been extensively studied for subtropical clouds, such as aerosols or the sea surface temperature gradient, the factors influencing transitions at higher latitudes are relatively poorly understood. This work uses reanalysis data to create a set of composite trajectories of cold air outbreaks moving off the Arctic ice edge and co-locates these trajectories with data from multiple satellites to generate a unique view of cloud development within cold air outbreaks. 

Clouds embedded in MCAOs have distinctive properties relative to clouds following other, more stable trajectories in the region. The initial instability and aerosol environments have distinct impacts on cloud development within outbreaks. The strength of the outbreak has a lasting effect on the magnitude of cloud properties along the trajectory. However, it does not strongly affect the timing of the transition to cumuliform clouds. In contrast, the initial aerosol concentration changes the timing of cloud break-up rather than the size of the cloud response.