New particle formation and its effect on cloud condensation nuclei abundance in the summer Arctic: a case study in the Fram Strait and Barents Sea

• Published in: Atmospheric chemistry and physics Vol. 19; no. 22; pp. 14339 - 14364
• Main Authors: Kecorius, Simonas, Vogl, Teresa, Paasonen, Pauli, Lampilahti, Janne, Rothenberg, Daniel, Wex, Heike, Zeppenfeld, Sebastian, van Pinxteren, Manuela, Hartmann, Markus, Henning, Silvia, Gong, Xianda, Welti, Andre, Kulmala, Markku, Stratmann, Frank, Herrmann, Hartmut, Wiedensohler, Alfred
• Format: Journal Article
• Language: English
• Published: Katlenburg-Lindau Copernicus GmbH 27-11-2019; Copernicus Publications
• Subjects: Abundance; Adiabatic; Aerosol-cloud interactions; Analysis; Anions; Arctic climates; Arctic clouds; Arctic expeditions; Arctic research; Budgets; Case studies; Chemical properties; Chemicophysical properties; Climate; Cloud condensation nuclei; Cloud formation; Clouds; Clouds (Meteorology); Condensation; Condensation nuclei; Diameters; Expeditions; Gases; Growth rate; Hygroscopic particles; Hygroscopicity; Ice cover; Ice environments; Negative ions; Nucleation; Nucleation processes; Nucleus; Organic chemistry; Particle formation; Particle size distribution; Physicochemical properties; Polar environments; Precursors; Research vessels; Size distribution; Sulfuric acid; Sulphuric acid; Summer; Vapors; Arctic; Arctic region
• ISSN: 1680-7324; 1680-7316; 1680-7324
• DOI: 10.5194/acp-19-14339-2019

In a warming Arctic the increased occurrence of new
particle formation (NPF) is believed to originate from the declining ice
coverage during summertime. Understanding the physico-chemical properties of
newly formed particles, as well as mechanisms that control both particle
formation and growth in this pristine environment, is important for
interpreting aerosol–cloud interactions, to which the Arctic climate can be
highly sensitive. In this investigation, we present the analysis of NPF and
growth in the high summer Arctic. The measurements were made on-board
research vessel Polarstern during the PS106 Arctic expedition. Four
distinctive NPF and subsequent particle growth events were observed, during
which particle (diameter in a range 10–50 nm) number concentrations
increased from background values of approx. 40 up to 4000 cm−3. Based
on particle formation and growth rates, as well as hygroscopicity of
nucleation and the Aitken mode particles, we distinguished two different
types of NPF events. First, some NPF events were favored by negative ions,
resulting in more-hygroscopic nucleation mode particles and suggesting
sulfuric acid as a precursor gas. Second, other NPF events resulted in
less-hygroscopic particles, indicating the influence of organic vapors on
particle formation and growth. To test the climatic relevance of NPF and its
influence on the cloud condensation nuclei (CCN) budget in the Arctic, we
applied a zero-dimensional, adiabatic cloud parcel model. At an updraft
velocity of 0.1 m s−1, the particle number size distribution (PNSD)
generated during nucleation processes resulted in an increase in the CCN
number concentration by a factor of 2 to 5 compared to the background CCN
concentrations. This result was confirmed by the directly measured CCN
number concentrations. Although particles did not grow beyond 50 nm in
diameter and the activated fraction of 15–50 nm particles was on average
below 10 %, it could be shown that the sheer number of particles produced
by the nucleation process is enough to significantly influence the
background CCN number concentration. This implies that NPF can be an important
source of CCN in the Arctic. However, more studies should be conducted in
the future to understand mechanisms of NPF, sources of precursor gases and
condensable vapors, as well as the role of the aged nucleation mode
particles in Arctic cloud formation.