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Volume 9, issue 4 | Copyright

Special issue: CHemistry and AeRosols Mediterranean EXperiments (ChArMEx)...

Atmos. Meas. Tech., 9, 1721-1742, 2016
https://doi.org/10.5194/amt-9-1721-2016
© Author(s) 2016. This work is distributed under
the Creative Commons Attribution 3.0 License.

Research article 20 Apr 2016

Research article | 20 Apr 2016

LOAC: a small aerosol optical counter/sizer for ground-based and balloon measurements of the size distribution and nature of atmospheric particles – Part 1: Principle of measurements and instrument evaluation

Jean-Baptiste Renard1, François Dulac2, Gwenaël Berthet1, Thibaut Lurton1, Damien Vignelles1, Fabrice Jégou1, Thierry Tonnelier3, Matthieu Jeannot1,4, Benoit Couté1, Rony Akiki3, Nicolas Verdier5, Marc Mallet6, François Gensdarmes7, Patrick Charpentier8, Samuel Mesmin8, Vincent Duverger1, Jean-Charles Dupont9, Thierry Elias10, Vincent Crenn2, Jean Sciare2, Paul Zieger11, Matthew Salter11, Tjarda Roberts1, Jérôme Giacomoni4, Matthieu Gobbi4, Eric Hamonou2, Haraldur Olafsson12, Pavla Dagsson-Waldhauserova12,13, Claude Camy-Peyret14, Christophe Mazel15, Thierry Décamps15, Martin Piringer16, Jérémy Surcin1, and Daniel Daugeron17 Jean-Baptiste Renard et al.
  • 1LPC2E-CNRS, Université d'Orléans, 3A Avenue de la Recherche Scientifique, 45071 Orléans, France
  • 2LSCE-CEA, Institut Pierre Simon Laplace, CEA Saclay 701, 91191 Gif-sur-Yvette, France
  • 3Environnement-SA, 111 Boulevard Robespierre, BP 4513, 78304, Poissy, France
  • 4Groupe Aerophile, 106 Avenue Felix Faure, 75015 Paris, France
  • 5Centre National d'Etudes Spatiales (CNES), DCT/BL/NB, 18 Avenue Edouard Belin, 31401 Toulouse CEDEX 9, France
  • 6Laboratoire d'Aérologie, Université Paul Sabatier, 14 Avenue Edouard Belin, 31400 Toulouse, France
  • 7Institut de Radioprotection et de Sûreté Nucléaire (IRSN), PSN-RES, SCA, Gif-sur-Yvette, 91192, France
  • 8MeteoModem, Rue de Bessonville, 77760 Ury, France
  • 9LMD/IPSL, Ecole Polytechnique, Route de Saclay, 91128 Palaiseau CEDEX, France
  • 10HYGEOS/LMD/IPSL,Ecole Polytechnique, Route de Saclay, 91128 Palaiseau CEDEX, France
  • 11Stockholm University Department of Environmental Science and Analytical Chemistry, Svante Arrhenius väg 8, 11418 Stockholm, Stockholm, Sweden
  • 12University of Iceland and Icelandic Meteorological Office, Reykjavik, Iceland
  • 13Agricultural University of Iceland, Keldnaholt, Reykjavik, Iceland
  • 14Institut Pierre Simon Laplace (UPMC/UVSQ), 4 place Jussieu, Boîte 101, 75252 Paris CEDEX 05, France
  • 15Fly-n-Sense, 25 rue Marcel Issartier, 33700 Mérignac, France
  • 16Zentralanstalt für Meteorologie und Geodynamik, Fachabteilung Umwelt, Vienna, Austria
  • 17Université d'Auvergne, LPC2E, Paul Constans, Rue Christophe Thivrier, BP 415, 03107 Montluçon CEDEX, France

Abstract. The study of aerosols in the troposphere and in the stratosphere is of major importance both for climate and air quality studies. Among the numerous instruments available, optical aerosol particles counters (OPCs) provide the size distribution in diameter range from about 100nm to a few tens of µm. Most of them are very sensitive to the nature of aerosols, and this can result in significant biases in the retrieved size distribution. We describe here a new versatile optical particle/sizer counter named LOAC (Light Optical Aerosol Counter), which is light and compact enough to perform measurements not only at the surface but under all kinds of balloons in the troposphere and in the stratosphere. LOAC is an original OPC performing observations at two scattering angles. The first one is around 12°, and is almost insensitive to the refractive index of the particles; the second one is around 60° and is strongly sensitive to the refractive index of the particles. By combining measurement at the two angles, it is possible to retrieve the size distribution between 0.2 and 100µm and to estimate the nature of the dominant particles (droplets, carbonaceous, salts and mineral particles) when the aerosol is relatively homogeneous. This typology is based on calibration charts obtained in the laboratory. The uncertainty for total concentrations measurements is ±20% when concentrations are higher than 1particlecm−3 (for a 10min integration time). For lower concentrations, the uncertainty is up to about ±60% for concentrations smaller than 10−2particlecm−3. Also, the uncertainties in size calibration are ±0.025µm for particles smaller than 0.6µm, 5% for particles in the 0.7–2µm range, and 10% for particles greater than 2µm. The measurement accuracy of submicronic particles could be reduced in a strongly turbid case when concentration of particles >3µm exceeds a few particles cm−3. Several campaigns of cross-comparison of LOAC with other particle counting instruments and remote sensing photometers have been conducted to validate both the size distribution derived by LOAC and the retrieved particle number density. The typology of the aerosols has been validated in well-defined conditions including urban pollution, desert dust episodes, sea spray, fog, and cloud. Comparison with reference aerosol mass monitoring instruments also shows that the LOAC measurements can be successfully converted to mass concentrations.

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LOAC is a light aerosols counter for performing measurements at the surface and under all kinds of atmospheric balloons. LOAC performs observations at two scattering angles. The first one at 12° is insensitive to the refractive index of the particles; the second one at 60° is strongly sensitive to the refractive index. By combining the measurements, it is possible to retrieve the size distribution between 0.2 and 100 micrometeres and to estimate the nature of the dominant particles.
LOAC is a light aerosols counter for performing measurements at the surface and under all kinds...
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