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Atmospheric Chemistry and Physics An interactive open-access journal of the European Geosciences Union
https://doi.org/10.5194/acp-2017-825
© Author(s) 2017. This work is distributed under
the Creative Commons Attribution 4.0 License.
Research article
27 Sep 2017
Review status
This discussion paper is a preprint. It is a manuscript under review for the journal Atmospheric Chemistry and Physics (ACP).
High occurrence of new particle formation events at the Maïdo high altitude observatory (2150 m), Reunion Island (Indian Ocean)
Brice Foucart1,2, Karine Sellegri2, Pierre Tulet1, Clémence Rose2, Jean-Marc Metzger3, and David Picard2 1Laboratoire de l'Atmosphère et des Cyclones (LACy-UMR 8015, CNRS, Université de La Réunion, Météo-France), 97744 Saint Denis de La Réunion, France
2Laboratoire de Météorologie Physique (LaMP-UMR 6016, CNRS, Université Blaise Pascal), 63178, Aubière, France
3Observatoire des Sciences de l'Univers de La Réunion, UMS 3365 (CNRS, Université de La Réunion), 97744 Saint Denis de La Réunion, France
Abstract. This study aims to report and characterize the frequent new particle formation (NPF) events observed at the Maïdo observatory, Reunion Island, a Southern Hemisphere site located at 2200 m and surrounded by the Indian Ocean. In 2014 and 2015, continuous aerosol measurements were made using both a Differential Mobility Particle Sizer (DMPS) and an Air Ion Spectrometer (AIS) to characterize the NPF events down to the lowest particle size scale. Carbon monoxide (CO) and sulfur dioxide (SO2) concentrations were monitored, as well as meteorological parameters, in order to identify the conditions that were favourable to the occurrence of nucleation in this specific environment. We point out that the annual NPF frequency average (65 %) is one of the highest reported so far. Monthly averages show a bimodal variation of the NPF frequency, with a maximum observed during off-season periods (March to May and September to December). A high yearly median particle Growth Rate (GR) of 15.16 nm.h−1 is also measured, occasionally peaking at values of the order of 100 nm.h−1 and showing a bimodal seasonal variation with maxima observed in July and November. Yearly medians of 2 and 12 nm particle formation rates (J2 and J12) are 0.858 and 0.508 cm−3.s−1 respectively, with a seasonal variation similar to that of the GR. The seasonal variations of GR and J correspond to the seasonal variation of radiation, which may be responsible for more efficient photochemistry and also for a higher influence of the boundary layer, as shown by the CO seasonal variation. Multiple sources can contribute to the NPF frequency and intensity, including marine, biogenic from vegetation, and anthropogenic sources.

Citation: Foucart, B., Sellegri, K., Tulet, P., Rose, C., Metzger, J.-M., and Picard, D.: High occurrence of new particle formation events at the Maïdo high altitude observatory (2150 m), Reunion Island (Indian Ocean), Atmos. Chem. Phys. Discuss., https://doi.org/10.5194/acp-2017-825, in review, 2017.
Brice Foucart et al.
Brice Foucart et al.
Brice Foucart et al.

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Short summary
The main objective of this study is to reinforce the observations of New Particle Formation (NPF) events in the Southern Hemisphere and more particularly for a site that is both marine and at altitude, the Maïdo Observatory (2150 m), on La Reunion Island. We recorded a high annual NPF frequency of 65 % and we note that monthly averages show a bimodal variation. We estimate the intensity and the characteristics of the events and describe their seasonality by comparing them to other parameters.
The main objective of this study is to reinforce the observations of New Particle Formation...
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