A033-0008
Controls of Condensation Nuclei, Cloud Condensation Nuclei over the Southern Ocean: Results from MARCUS

Tuesday, 8 December 2020
Poster
Qing Niu, University of Oklahoma Norman Campus, Norman, OK, United States, Greg M McFarquhar, Cooperative Institute for Mesoscale Meteorological Studies, University of Oklahoma, Norman, OK, United States, Roger Marchand, University of Washington, Department of Atmospheric Sciences, Seattle, WA, United States, Saisai Ding, Peking University, Beijing, China, Ruhi Humphries, CSIRO Marine and Atmospheric Research, Aspendale, Australia, Adam Theisen, Argonne National Laboratory, Lemont, United States and Martin Schnaiter, Karlsruhe Institute of Technology, Institute of Meteorology and Climate Research, Atmospheric Aerosol Research (IMK-AAF), Karlsruhe, Germany
Abstract:
Weather and climate models are challenged by uncertainties and biases in representing Southern Ocean (SO) aerosols and their impacts. Therefore, a better characterization of the production and removal of aerosols in the SO marine boundary layer (MBL) is required. The SO, dominated by high surface wind speeds associated with frequent cyclones, is the most pristine environment on earth, providing a natural laboratory to study the correlation of MBL aerosols and their biological components with meteorological conditions. The Atmospheric Radiation Measurement Program’s Mobile Facility-2 (AMF2) onboard the Australian icebreaker Aurora Australis (AA) provides ship-based cloud, precipitation and aerosol measurements during the 2017-18 Measurements of Aerosols, Radiation and CloUds over the SO (MARCUS) Experiment. After removing time periods contaminated by the ship stack during MARCUS, analysis of measurements of condensation nuclei (CN) from an Ultra High Sensitivity Aerosol Spectrometer (UHSAS) reveals that particles in the accumulation mode with particle diameters (D) between 100 and 1000 nm correlated well with the concentration of Cloud Condensation Nuclei (CCN) at 0.2% supersaturation (R2=0.691). HYbrid Single-Particle Lagrangian Integrated Trajectory (HYSPLIT) model 72-hour back trajectories show 83% of air masses sampled during MARCUS originated over the SO 1km above the water, implying that sources of SO MBL lack soot and other continental pollutants. While the integrated aerosol particle number (500 nm < D < 1000 nm) is weakly but significantly positively dependent on wind speed, aerosols with 300 nm < D < 500 nm do not show a significant dependence on wind speed (p value 0.315), whereas aerosols with 60 nm < D < 300 nm show a statistically significant negative dependence on wind speed. The influence of associated meteorological conditions including precipitation and subsidence, as well as the fraction of fluorescing aerosols measured by the Wideband Integrated Bioaerosol Sensor 4 (WIBS4), on these relations will be discussed in order to understand the physical processes responsible for these relationships.
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