Cloud Condensation Nuclei and Ice-Nucleating Particles over the Southern Ocean: Abundance and Properties during the Antarctic Circum-navigation Expedition

• Main Author: Tatzelt, Christian
• Other Authors: Kalesse-Los, Heike, Pöhlker, Mira, Wu, Zhijun, Stratmann, Frank, Henning, Silvia, Universität Leipzig
• Format: Doctoral or Postdoctoral Thesis
• Language: English
• Published: 2022
• Subjects: Souther Ocean; clouds; aerosol particles; CCN; INP; Südlicher Ozean; Wolken; Aerosolpartikel; Wolkenkondensationskeime; Eiskeime; info:eu-repo/classification/ddc/551; ddc:551; Antarctic; Southern Ocean; The Antarctic; Antarc*; Antarctica
• Online Access: https://nbn-resolving.org/urn:nbn:de:bsz:15-qucosa2-859492; https://ul.qucosa.de/id/qucosa%3A85949; https://ul.qucosa.de/api/qucosa%3A85949/attachment/ATT-0/

Aerosol particles acting as cloud condensation nuclei (CCN) or ice nucleating parti- cles (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 sparse, especially for remote areas of the world, such as the Southern Ocean (SO). In this work, unique results from ship-borne aerosol-particle-related in situ measurements and filter sampling in the summertime SO region are presented. An overview of CCN and INP number concentrations on the Southern Ocean is provided and, using additional analyses on particle chemical composition and air-mass origin, insights regarding possible CCN and INP sources and origins are presented, with the help of 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 showed variable contributions of organic and inorganic material. No distinct size-dependence of the CCN hygroscopicity parameter was apparent, indicating homogeneous 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, more constant concentrations 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 ...