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The Association Between Cloud Droplet Number Over the Summer Southern Ocean and Air Mass History
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  • Gerald Mace,
  • Sally Benson,
  • Elizabeth Sterner,
  • Alain Protat,
  • Ruhi S Humphries,
  • Anna Gannet Hallar
Gerald Mace
University of Utah

Corresponding Author:[email protected]

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Sally Benson
University of Utah
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Elizabeth Sterner
University of Utah
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Alain Protat
Australian Bureau of Meteorology
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Ruhi S Humphries
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Anna Gannet Hallar
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The cloud properties and governing processes in Southern Ocean marine boundary layer clouds have emerged as a central issue in understanding the Earth's climate sensitivity. While the simulated cloud feedbacks in Southern Ocean clouds have evolved in the most recent climate model intercomparison, the background properties of simulated summertime clouds in the Southern Ocean are not consistent with measurements due to known biases in simulating cloud condensation nuclei concentrations. This paper presents several case studies collected during the Capricorn 2 and Marcus campaigns held aboard Australian research vessels in the Austral Summer of 2018. Combining the surface-observed cases with MODIS data along forward and backward air mass trajectories, we demonstrate the evolution of cloud properties with time. These cases are consistent with multi-year statistics showing that long trajectories of air masses over the Antarctic ice sheet are critical to creating high droplet number clouds in the high latitude summer Southern Ocean. We speculate that secondary aerosol production via the oxidation of biogenically derived aerosol precursor gasses over the high actinic flux region of the high latitude ice sheets is fundamental to maintaining relatively high droplet numbers in Southern Ocean clouds during Summer.
24 Dec 2023Submitted to ESS Open Archive
27 Dec 2023Published in ESS Open Archive