Maximum Supersaturation in the Marine Boundary Layer Clouds Over the North Atlantic

Journal Article · 20 November 2023 · AGU Advances

DOI: https://doi.org/10.1029/2022AV000855 · OSTI ID:2217412

Gong, Xianda  ^[1]; Wang, Yang  ^[2]; Xie, Hua ^[3]; Zhang, Jiaoshi ^[2]; Lu, Zheng  ^[3]; Wood, Robert  ^[4]; Stratmann, Frank ^[5]; Wex, Heike  ^[5]; Liu, Xiaohong  ^[3]; Wang, Jian  ^[2]

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1. Center for Aerosol Science and Engineering Department of Energy, Environmental and Chemical Engineering Washington University in St. Louis St. Louis MO USA, Now at Research Center for Industries of the Future Westlake University Hangzhou China
2. Center for Aerosol Science and Engineering Department of Energy, Environmental and Chemical Engineering Washington University in St. Louis St. Louis MO USA
3. Department of Atmospheric Sciences Texas A&,M University College Station TX USA
4. Department of Atmospheric Sciences University of Washington Seattle WA USA
5. Leibniz Institute for Tropospheric Research Leipzig Germany

Abstract The maximum supersaturation ( S _x ) in clouds is a key parameter affecting the cloud's microphysical and radiative properties. We investigate the S _x of the marine boundary layer clouds by combining airborne and surface observations in the Eastern North Atlantic. The cloud droplet number concentration ( N _c ) in the least diluted cloud cores agrees well with the number concentration of particles larger than the Hoppel Minimum (HM) ( N _>HM ) below clouds, indicating that the HM represents the average size threshold above which particles are activated to form cloud droplets. The S _x values derived from surface observations vary from 0.10% to 0.50% from June 2017 to June 2018, with a clear seasonal variation exhibiting higher values during winter. Most of the S _x variance (∼60%) can be explained by the cloud condensation nuclei (CCN) concentration and updraft velocity ( w ), with the CCN concentration playing a more important role than w in explaining the variation of S _x . The influence of CCN concentration on S _x leads to a buffered response of N _c to aerosol perturbations. The response of N _c to low aerosol concentration during winter is further buffered by the high w . The global Community Earth System Model (CESM) simulated S _x values in the Azores have a positive bias compared to measured S _x , likely due to overestimated w and underestimated CCN concentration. The CESM simulated S _x exhibits higher values further north over the North Atlantic Ocean, which is attributed to stronger w . The suppression of S _x by aerosol is also evident in regions with high CCN concentrations.

• Research Organization: Oak Ridge National Laboratory (ORNL), Oak Ridge, TN (United States). Atmospheric Radiation Measurement (ARM) Archive; Univ. of Washington, Seattle, WA (United States)
• Sponsoring Organization: National Aeronautics and Space Administration (NASA); USDOE; USDOE Office of Science (SC), Biological and Environmental Research (BER)
• Contributing Organization: Argonne National Laboratory (ANL); Brookhaven National Laboratory (BNL); Oak Ridge National Laboratory (ORNL), Oak Ridge, TN (United States); Princeton Plasma Physics Laboratory (PPPL)
• Grant/Contract Number: SC0020259; SC0021017; SC0021103
• OSTI ID: 2217412
• Journal Information: AGU Advances, Journal Name: AGU Advances Journal Issue: 6 Vol. 4; ISSN 2576-604X
• Publisher: American Geophysical Union (AGU)Copyright Statement
• Country of Publication: United States
• Language: English