Study of cloud condensation nuclei and ice nucleating particles during the Antarctic Circumnavigation Expedition (ACE)
Final Report Abstract
Aerosol particles acting as cloud condensation nuclei (CCN) or ice nucleating particles (INP) play a major role in the formation and glaciation of clouds. Thereby they exert a strong impact on the radiation budget of the Earth. Data on abundance and properties of both particle types are still sparse for remote areas of the world, such as the Southern Ocean (SO). Within this project, unique results from ship-borne aerosol-particle-related in situ measurements and filter sampling in the SO-region during austral summer are presented. An overview of CCN and INP number concentrations on the Southern Ocean region is provided. Furthermore, using additional analyses concerning particle chemical composition and airmass origin, insights regarding possible CCN and INP sources and origins are presented, accompanied by a correlation analysis. CCN number concentrations spanned 2 orders of magnitude, e.g. for a supersaturation of 0.3 % values ranged roughly from 3 to 590 cm^−3. CCN featured variable contributions of organic and inorganic material. No distinct size-dependence of CCN hygroscopicity was apparent, indicating homogeneous chemical composition across sizes (critical dry diameter on average between 30 nm and 110 nm). The relative contribution of sea spray aerosol (SSA) to the CCN number concentration was on average small (below 35 %). Ambient INP number concentrations were measured in the temperature range from −4 to −27 °C using an immersion freezing method. Concentrations spanned up to 3 orders of magnitude, e.g. at −16 °C from 0.2 to 100 m^−3. Elevated values (above 10 m^−3 at −16 °C) were measured when the research vessel was in the vicinity of land (excluding Antarctica). Lower, less variable concentrations (about 2 orders of magnitude) were measured on the open ocean. This, along with results of backward-trajectory analyses, hints towards terrestrial and/or coastal INP sources being dominant close to ice-free (non-Antarctic) land. In pristine marine areas INP may originate from both oceanic sources and/or long-range transport. A correlation analysis yielded strong correlations between sodium mass concentration and particle number concentration in the coarse mode (larger 1 μm), unsurprisingly indicating a significant contribution of SSA to that mode. CCN number concentration was highly correlated with the number concentrations of Aitken (10 to 100 nm) and accumulation mode particles (100 to 1000 nm). This, together with a lack of correlation between sodium mass and Aitken and accumulation mode number concentrations, underlines the important contribution of non-SSA, probably secondarily formed particles, to the CCN population.
Publications
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Overview of the Antarctic Circumnavigation Expedition: Study of Preindustrial-like Aerosols and Their Climate Effects (ACE-SPACE). Bulletin of the American Meteorological Society, 100(11), 2260-2283.
Schmale, Julia; Baccarini, Andrea; Thurnherr, Iris; Henning, Silvia; Efraim, Avichay; Regayre, Leighton; Bolas, Conor; Hartmann, Markus; Welti, André; Lehtipalo, Katrianne; Aemisegger, Franziska; Tatzelt, Christian; Landwehr, Sebastian; Modini, Robin L.; Tummon, Fiona; Johnson, Jill S.; Harris, Neil; Schnaiter, Martin; Toffoli, Alessandro; ... & Carslaw, Ken S.
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The value of remote marine aerosol measurements for constraining radiative forcing uncertainty. Atmospheric Chemistry and Physics, 20(16), 10063-10072.
Regayre, Leighton A.; Schmale, Julia; Johnson, Jill S.; Tatzelt, Christian; Baccarini, Andrea; Henning, Silvia; Yoshioka, Masaru; Stratmann, Frank; Gysel-Beer, Martin; Grosvenor, Daniel P. & Carslaw, Ken S.
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Exploring the coupled ocean and atmosphere system with a data science approach applied to observations from the Antarctic Circumnavigation Expedition. Earth System Dynamics, 12(4), 1295-1369.
Landwehr, Sebastian; Volpi, Michele; Haumann, F. Alexander; Robinson, Charlotte M.; Thurnherr, Iris; Ferracci, Valerio; Baccarini, Andrea; Thomas, Jenny; Gorodetskaya, Irina; Tatzelt, Christian; Henning, Silvia; Modini, Rob L.; Forrer, Heather J.; Lin, Yajuan; Cassar, Nicolas; Simó, Rafel; Hassler, Christel; Moallemi, Alireza; Fawcett, Sarah E.; ... & Schmale, Julia
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Low‐Volatility Vapors and New Particle Formation Over the Southern Ocean During the Antarctic Circumnavigation Expedition. Journal of Geophysical Research: Atmospheres, 126(22).
Baccarini, Andrea; Dommen, Josef; Lehtipalo, Katrianne; Henning, Silvia; Modini, Robin L.; Gysel‐Beer, Martin; Baltensperger, Urs & Schmale, Julia
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Sources, Occurrence and Characteristics of Fluorescent Biological Aerosol Particles Measured Over the Pristine Southern Ocean. Journal of Geophysical Research: Atmospheres, 126(11).
Moallemi, Alireza; Landwehr, Sebastian; Robinson, Charlotte; Simó, Rafel; Zamanillo, Marina; Chen, Gang; Baccarini, Andrea; Schnaiter, Martin; Henning, Silvia; Modini, Robin L.; Gysel‐Beer, Martin & Schmale, Julia
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Circum-Antarctic abundance and properties of CCN and INPs. Atmospheric Chemistry and Physics, 22(14), 9721-9745.
Tatzelt, Christian; Henning, Silvia; Welti, André; Baccarini, Andrea; Hartmann, Markus; Gysel-Beer, Martin; van Pinxteren, Manuela; Modini, Robin L.; Schmale, Julia & Stratmann, Frank
