Preprints
https://doi.org/10.5194/acp-2021-819
https://doi.org/10.5194/acp-2021-819

  11 Oct 2021

11 Oct 2021

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

New particle formation in coastal New Zealand with a focus on open ocean air masses

Maija Peltola1, Clémence Rose1, Jonathan V. Trueblood1, Sally Gray2, Mike Harvey2, and Karine Sellegri1 Maija Peltola et al.
  • 1Laboratoire de Météorologie Physique (LaMP-UMR 6016, CNRS, Université Clermont Auvergne), 63178, Aubière, France
  • 2National Institute of Water & Atmospheric Research Ltd (NIWA) Private Bag 14-901, Wellington, New Zealand

Abstract. Even though oceans cover the majority of the Earth, most aerosol measurements are from continental sites. We measured aerosol particle number size distribution at Baring Head, in coastal New Zealand, over a total period of 10 months to study aerosol properties and new particle formation, with a special focus on aerosol formation in open ocean air masses. Particle concentrations were higher in land-influenced air compared to clean marine air in all size classes from sub-10 nm to cloud condensation nuclei sizes. When classifying the particle number size distributions with traditional methods designed for continental sites, new particle formation was observed at the station throughout the year with an average event frequency of 23 %. While most of these traditional event days had some land-influence, we also observed particle growth starting from nucleation mode during 16 % of the data in clean marine air and at least part of this growth was connected to nucleation in the marine boundary layer. Sub-10 nm particles accounted for 29 % of the total aerosol number concentration of particles larger than 1 nm in marine air during the spring. This shows that nucleation in marine air is frequent enough to influence the total particle concentration. Particle formation in land-influenced air was more intense and had on average higher growth rates than what was found for marine air. Particle formation and primary emissions increased particle number concentrations as a function of time spent over land during the first 1–2 days spent over land. After this, nucleation seems to start getting suppressed by the pre-existing particle population, but accumulation mode particle concentration keeps increasing, likely due to primary particle emissions. Further work showed that traditional NPF events were favoured by sunny conditions with low relative humidity and wind speeds. In marine air, formation of sub-10 nm particles was favoured by low temperatures, relative humidity, and wind speeds and could happen even during the night. Our future work will study the mechanisms responsible for particle formation at Baring Head with a focus on different chemical precursor species. This study sheds light on both new particle formation in open ocean air masses coming from the Southern Ocean and local aerosol properties in New Zealand.

Maija Peltola et al.

Status: open (until 22 Nov 2021)

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse

Maija Peltola et al.

Maija Peltola et al.

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Short summary
Despite the importance of marine aerosol measurements for constraining climate models, these measurements are scarce. We measured the aerosol particle number size distribution in coastal New Zealand over a total period of 10 months. This paper analyses the aerosol properties at the site with a special focus on new particle formation and marine air masses. New particle formation was observed frequently, but in marine air masses it did not follow traditional event criteria.
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