Observations of Clouds, Aerosols, Precipitation, and Surface Radiation over the Southern Ocean An Overview of CAPRICORN, MARCUS, MICRE, and SOCRATES

• Published in: Bulletin of the American Meteorological Society Vol. 102; no. 4; pp. E894 - E928
• Main Authors: McFarquhar, Greg M., Bretherton, Christopher S., Marchand, Roger, Protat, Alain, DeMott, Paul J., Alexander, Simon P., Roberts, Greg C., Twohy, Cynthia H., Toohey, Darin, Siems, Steve, Huang, Yi, Wood, Robert, Rauber, Robert M., Lasher-Trapp, Sonia, Jensen, Jorgen, Stith, Jeffrey L., Mace, Jay, Um, Junshik, Järvinen, Emma, Schnaiter, Martin, Gettelman, Andrew, Sanchez, Kevin J., McCluskey, Christina S., Russell, Lynn M., McCoy, Isabel L., Atlas, Rachel L., Bardeen, Charles G., Moore, Kathryn A., Hill, Thomas C. J., Humphries, Ruhi S., Keywood, Melita D., Ristovski, Zoran, Cravigan, Luke, Schofield, Robyn, Fairall, Chris, Mallet, Marc D., Kreidenweis, Sonia M., Rainwater, Bryan, D’Alessandro, John, Wang, Yang, Wu, Wei, Saliba, Georges, Levin, Ezra J. T., Ding, Saisai, Lang, Francisco, Truong, Son C. H., Wolff, Cory, Haggerty, Julie, Harvey, Mike J., Klekociuk, Andrew R., McDonald, Adrian
• Format: Journal Article
• Language: English
• Published: Boston American Meteorological Society 01.04.2021
• Subjects: Aerosol-cloud interaction; Aerosols; Antarctic front; Atmospheric models; Auroras; Boundary layers; Climate change; Climate models; Cloud condensation nuclei; Cloud droplet concentration; Cloud droplets; Cloud formation; Cloud microphysics; Cloud properties; Cloud radiative effects; Cloud water/phase; Clouds; Cold; Cold water; Collaboration; Condensation nuclei; Cyclones; Energy budget; ENVIRONMENTAL SCIENCES; General circulation models; Heterogeneity; Instruments; Lidar; Long-range transport; Low clouds; Meteorology; Ocean models; Ocean, Atmosphere; Oceans; Particle formation; Polar fronts; Precipitation; Properties; Radar; Radiation; Radiation budgets; Radiation-cloud interactions; Remote sensing; Satellites; Sciences of the Universe; Soundings; Southern Ocean; Supercooled water; Thermodynamics; Troposphere; Turbulence; Workshops; Australia; United States > US; Macquarie Island; Southern Ocean
• ISSN: 0003-0007; 1520-0477
• DOI: 10.1175/bams-d-20-0132.1

Weather and climate models are challenged by uncertainties and biases in simulating Southern Ocean (SO) radiative fluxes that trace to a poor understanding of cloud, aerosol, precipitation, and radiative processes, and their interactions. Projects between 2016 and 2018 used in situ probes, radar, lidar, and other instruments to make comprehensive measurements of thermodynamics, surface radiation, cloud, precipitation, aerosol, cloud condensation nuclei (CCN), and ice nucleating particles over the SO cold waters, and in ubiquitous liquid and mixed-phase clouds common to this pristine environment. Data including soundings were collected from the NSF–NCAR G-V aircraft flying north–south gradients south of Tasmania, at Macquarie Island, and on the R/V Investigator and RSV Aurora Australis. Synergistically these data characterize boundary layer and free troposphere environmental properties, and represent the most comprehensive data of this type available south of the oceanic polar front, in the cold sector of SO cyclones, and across seasons. Results show largely pristine environments with numerous small and few large aerosols above cloud, suggesting new particle formation and limited long-range transport from continents, high variability in CCN and cloud droplet concentrations, and ubiquitous supercooled water in thin, multilayered clouds, often with small-scale generating cells near cloud top. These observations demonstrate how cloud properties depend on aerosols while highlighting the importance of dynamics and turbulence that likely drive heterogeneity of cloud phase. Satellite retrievals confirmed low clouds were responsible for radiation biases. The combination of models and observations is examining how aerosols and meteorology couple to control SO water and energy budgets.