Wintertime Synoptic Patterns of Midlatitude Boundary Layer Clouds Over the Western North Atlantic: Climatology and Insights From In Situ ACTIVATE Observations

• Published in: Journal of Geophysical Research: Atmospheres
• Main Authors: Painemal, David, Chellappan, Seethala, Smith, William L., Spangenberg, Douglas, Park, J. Minnie, Ackerman, Andrew, Chen, Jingyi, Crosbie, Ewan, Ferrare, Richard, Hair, Johnathan, Kirschler, Simon, Li, Xiang‐Yu, McComiskey, Allison, Moore, Richard H., Sanchez, Kevin, Sorooshian, Armin, Tornow, Florian, Voigt, Christiane, Wang, Hailong, Winstead, Edward, Zeng, Xubin, Ziemba, Luke, Zuidema, Paquita
• Format: Article in Journal/Newspaper
• Language: English
• Published: Wiley 2023
• Subjects: Wolkenphysik; North Atlantic
• Online Access: https://elib.dlr.de/195324/; https://elib.dlr.de/195324/2/JGR%20Atmospheres%20-%202023%20-%20Painemal%20-%20Wintertime%20Synoptic%20Patterns%20of%20Midlatitude%20Boundary%20Layer%20Clouds%20Over%20the%20Western.pdf; https://doi.org/10.1029/2022JD037725

The synoptic evolution of boundary layer clouds over the western North Atlantic is described by means of a regime classification based on Self-Organizing Maps. The analysis is able to capture events with low and high low-cloud coverage. High-cloud coverage days are associated with cold-air outbreaks (CAOs). The combination of cold and dry conditions gives rise to an enhancement of surface heat fluxes during CAO, consistent with an increase in cloud fraction. In addition, prevailing winds during CAO days explain the occurrence of a synoptic maximum in cloud droplet number concentration, linked to transport of continental aerosol over the ocean. Overall, the dynamics of midlatitude low clouds substantially differ from archetypal stratocumulus clouds regimes.