The Association Between Cloud Droplet Number over the Summer Southern Ocean and Air Mass History

Journal Article · 10 June 2024 · Journal of Geophysical Research. Atmospheres

DOI: https://doi.org/10.1029/2023jd040673 · OSTI ID:2373175

Mace, Gerald G.  ^[1]; Benson, Sally  ^[1]; Sterner, Elizabeth  ^[1]; Protat, Alain  ^[2]; Humphries, Ruhi  ^[3]; Hallar, A. Gannet  ^[1]

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1. Univ. of Utah, Salt Lake City, UT (United States)
2. Bureau of Meteorology, Melbourne, VIC (Australia)
3. Australian Antarctic Program Partnership, Hobart, TAS (Australia); Commonwealth Scientific and Industrial Research Organisation (CSIRO), Melbourne, VIC (Australia)

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 our understanding of Southern Ocean cloud feedbacks 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.

• Research Organization: Oak Ridge National Laboratory (ORNL), Oak Ridge, TN (United States). Atmospheric Radiation Measurement (ARM) Data Center
• Sponsoring Organization: USDOE Office of Science (SC), Biological and Environmental Research (BER); National Aeronautics and Space Administration (NASA); National Science Foundation (NSF)
• Contributing Organization: Pacific Northwest National Laboratory (PNNL); Brookhaven National Laboratory (BNL); Argonne National Laboratory (ANL); Oak Ridge National Laboratory (ORNL)
• Grant/Contract Number: SC0022001
• OSTI ID: 2373175
• Alternate ID(s): OSTI ID: 2376914
• Journal Information: Journal of Geophysical Research. Atmospheres, Journal Name: Journal of Geophysical Research. Atmospheres Journal Issue: 12 Vol. 129; ISSN 2169-897X
• Publisher: American Geophysical UnionCopyright Statement
• Country of Publication: United States
• Language: English