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Volume 15, issue 24
Atmos. Chem. Phys., 15, 13993–14003, 2015
https://doi.org/10.5194/acp-15-13993-2015
© Author(s) 2015. This work is distributed under
the Creative Commons Attribution 3.0 License.
Atmos. Chem. Phys., 15, 13993–14003, 2015
https://doi.org/10.5194/acp-15-13993-2015
© Author(s) 2015. This work is distributed under
the Creative Commons Attribution 3.0 License.

Research article 18 Dec 2015

Research article | 18 Dec 2015

Spring and summer contrast in new particle formation over nine forest areas in North America

F. Yu1, G. Luo1, S. C. Pryor2, P. R. Pillai3, S. H. Lee4, J. Ortega5, J. J. Schwab1, A. G. Hallar6, W. R. Leaitch7, V. P. Aneja3, J. N. Smith5,8, J. T. Walker3,9, O. Hogrefe1,a, and K. L. Demerjian1 F. Yu et al.
  • 1Atmospheric Sciences Research Center, State University of New York, 251 Fuller Road, Albany, NY 12203, USA
  • 2Department of Earth and Atmospheric Sciences, Cornell University, Ithaca, NY 14853, USA
  • 3Department of Marine, Earth, and Atmospheric Sciences, North Carolina State University, Raleigh, NC 27695, USA
  • 4College of Public Health, Kent State University, Kent, OH, USA
  • 5National Center for Atmospheric Research, P.O. Box 3000, Boulder, CO 80307, USA
  • 6Desert Research Institute, Storm Peak Laboratory, Steamboat Springs, CO 80488, USA
  • 7Environment Canada, Science and Technology Branch, Toronto, ON, Canada
  • 8Applied Physics Dept., University of Eastern Finland, P.O. Box 1627, Kuopio 70211, Finland
  • 9US Environmental Protection Agency, Office of Research and Development, Durham, NC 27711, USA
  • acurrently at: Durham Technical Community College, Durham, NC 27703, USA

Abstract. Recent laboratory chamber studies indicate a significant role for highly oxidized low-volatility organics in new particle formation (NPF), but the actual role of these highly oxidized low-volatility organics in atmospheric NPF remains uncertain. Here, particle size distributions (PSDs) measured in nine forest areas in North America are used to characterize the occurrence and intensity of NPF and to evaluate model simulations using an empirical formulation in which formation rate is a function of the concentrations of sulfuric acid and low-volatility organics from alpha-pinene oxidation (Nucl-Org), and using an ion-mediated nucleation mechanism (excluding organics) (Nucl-IMN). On average, NPF occurred on ~ 70 % of days during March for the four forest sites with springtime PSD measurements, while NPF occurred on only ~ 10 % of days in July for all nine forest sites. Both Nucl-Org and Nucl-IMN schemes capture the observed high frequency of NPF in spring, but the Nucl-Org scheme significantly overpredicts while the Nucl-IMN scheme slightly underpredicts NPF and particle number concentrations in summer. Statistical analyses of observed and simulated ultrafine particle number concentrations and frequency of NPF events indicate that the scheme without organics agrees better overall with observations. The two schemes predict quite different nucleation rates (including their spatial patterns), concentrations of cloud condensation nuclei, and aerosol first indirect radiative forcing in North America, highlighting the need to reduce NPF uncertainties in regional and global earth system models.

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The role of low-volatility organics in new particle formation (NPF) in the atmosphere is assessed. An empirical formulation in which formation rate is a function of the concentrations of sulfuric acid and low-volatility organics significantly overpredicts NPF in the summer. Two different schemes predict quite different nucleation rates (including their spatial patterns), concentrations of cloud condensation nuclei, and aerosol first indirect radiative forcing in North America.
The role of low-volatility organics in new particle formation (NPF) in the atmosphere is...
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