Preprints
https://doi.org/10.5194/acpd-6-9545-2006
https://doi.org/10.5194/acpd-6-9545-2006
28 Sep 2006
 | 28 Sep 2006
Status: this preprint was under review for the journal ACP. A revision for further review has not been submitted.

Behavior of CCN to CN fraction during aging and mixing processes of atmospheric particles

S. Rojas, L. Gomes, and P. Villani

Abstract. During Spring 2003, field experiments were conducted at the summit of Puy de Dôme (1465 m a.s.l.), in Central France, mainly in the free troposphere and during cloudy conditions. During this experiment, cloud condensation nuclei (CCN) concentrations were measured with a thermal gradient CCN counter at applied supersaturations that ranged between 0.2 and 2%. Aerosol size distributions were obtained with a TSI scanning mobility particle sizer (SMPS) consisting of a DMA and a CPC, and aerosol number (CN) concentrations were derived by integrating the SMPS size spectra between 0.015 and 0.3 µm. The isentropic back trajectories were computed for the altitude of the observation site using the Hybrid Single Particle Lagrangian Integrated Trajectory (HY-SPLIT) code from NOAA. For each air mass type, the aerosol bulk chemical composition used was that previously determined from cascade impactor samples by Sellegri et al. (2003). The methodological approach of this study was, firstly, to determine the relationships between CN and CCN concentrations for various air mass types arriving on the observation site. According to their origin, air masses arriving on the observation site are classified into 4 types: continental, clean marine, modified marine and polar. The CN concentrations appear to clearly depend on the type of air mass with the highest concentrations for the continental event and the lowest ones for the marine events. Moreover, a typical range can be attributed for the CCN/CN ratio to each air mass type. Then, the objective was to observe the hygroscopic behavior of aerosol particles upon heating of the sample in a thermo-desorber. Since the heated sample can be considered as representative of the original state of the aerosol, it appears that the evolution of CN to CCN is much more affected when the air mass is modified by aging and mixing processes with the contact of various atmospheric species all along the transport pathway. This result shows indirectly but clearly the presence of an active chemical layer containing more hygroscopic properties on the aerosol particle surface that can favour the particle growth. However, the role played by organic species is not clear and more work is needed to know if organic compounds may act to increase the CCN concentration.

Publisher's note: Copernicus Publications remains neutral with regard to jurisdictional claims made in the text, published maps, institutional affiliations, or any other geographical representation in this preprint. The responsibility to include appropriate place names lies with the authors.
S. Rojas, L. Gomes, and P. Villani
 
Status: closed (peer review stopped)
Status: closed (peer review stopped)
AC: Author comment | RC: Referee comment | SC: Short comment | EC: Editor comment
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Status: closed (peer review stopped)
Status: closed (peer review stopped)
AC: Author comment | RC: Referee comment | SC: Short comment | EC: Editor comment
Printer-friendly Version - Printer-friendly version Supplement - Supplement
S. Rojas, L. Gomes, and P. Villani
S. Rojas, L. Gomes, and P. Villani

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