06 Sep 2021

06 Sep 2021

Review status: this preprint is currently under review for the journal ACP.

Circum-Antarctic abundance and properties of CCN and INP

Christian Tatzelt1, Silvia Henning1, André Welti2, Andrea Baccarini3,4, Markus Hartmann1, Martin Gysel-Beer3, Manuela van Pinxteren1, Robin L. Modini3, Julia Schmale3,4, and Frank Stratmann1 Christian Tatzelt et al.
  • 1Leibniz Institute for Tropospheric Research, Permoserstrasse 15, 04318 Leipzig, Germany
  • 2Finnish Meteorological Institute, Erik Palménin aukio 1, FI-00560 Helsinki, Finland
  • 3Laboratory of Atmospheric Chemistry, Paul Scherrer Institute, 5232 Villigen PSI, Switzerland
  • 4Extreme Environments Research Laboratory, École Polytechnique Fédérale de Lausanne, School of Architecture, Civil and Environmental Engineering, Lausanne, Switzerland

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 types of particles are sparse, especially for remote areas of the world, such as the Southern Ocean (SO). In this work, we present unique results from ship-borne aerosol-particle-related in situ measurements and filter sampling in the SO region, carried out during the Antarctic Circumnavigation Expedition (ACE) in the Austral summer of 2016/17. An overview of CCN and INP concentrations on the Southern Ocean is provided and using additional quantities, insights regarding possible CCN and INP sources and origins are presented. 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 showed variable contributions of organic and inorganic material (inter-quartile range of hygroscopicity parameter κ from 0.2 to 0.9). No distinct size-dependence of κ was apparent, indicating homogeneous composition across sizes (critical dry diameter on average between 37 and 123 nm). The contribution of sea spray aerosol (SSA) to the CCN number concentration was on average small. Ambient INP number concentrations were measured in the temperature range from −5 to −27°C. 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, with lower and more constant concentrations when at sea. This hints towards terrestrial and/or coastal INP sources being dominant close to land. In pristine marine areas INP may originate from both oceanic sources and/or long range transport. Sampled aerosol particles (PM10) were analysed for sodium and methanesulfonic acid (MSA). Resulting mass concentrations were used as tracers for primary marine and secondary aerosol particles, respectively. Sodium, with an average concentration around 2.8 μg m⁻³, was found to dominate the sampled particle mass. MSA was highly variable over the SO, with concentrations up to 0.5 μg m⁻³ near the sea ice edge. A correlation analysis yielded strong correlations between sodium mass concentration and particle number concentration in the coarse mode, unsurprisingly indicating a significant contribution of SSA to that mode. CCN number concentration was highly correlated with the number concentration of Aitken and accumulation mode particles. 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. INP number concentrations did not significantly correlate with any other measured aerosol physico-chemical parameter.

Christian Tatzelt et al.

Status: open (until 18 Oct 2021)

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Christian Tatzelt et al.

Data sets

Ionic composition of particulate matter (PM10) from high-volume sampling over the Southern Ocean during the austral summer of 2016/2017 on board the Antarctic Circumnavigation Expedition (ACE) Tatzelt, Christian; Henning, Silvia; Tummon, Fiona; Hartmann, Markus; Baccarini, Andrea; Welti, André; Lehtipalo, Katrianne; Schmale, Julia; Van Pinxteren, Manuela

Christian Tatzelt et al.


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Short summary
We present the abundance and origin of cloud-relevant aerosol particles in the preindustral-like conditions of the Southern Ocean (SO) during Austral summer. Cloud condensation nuclei (CCN) and ice nucleating particles (INP) were measured during a circum-Antarctic scientific cruise with in situ instrumentation and offline filter measurements, respectively. Transport processes were found to play an equally important role as local sources for both the CCN and INP population of the SO.