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JOURNAL OF GEOPHYSICAL RESEARCH,
VOL. 112,
D10218,
doi:10.1029/2006JD008109,
2007
Enhanced new particle formation observed in the northern midlatitude tropopause region
Li-Hao Young
Department of Chemistry, Kent State University, Kent, Ohio, USA
David R. Benson
Department of Chemistry, Kent State University, Kent, Ohio, USA
William M. Montanaro
Department of Chemistry, Kent State University, Kent, Ohio, USA
Shan-Hu Lee
Department of Chemistry, Kent State University, Kent, Ohio, USA
Laura L. Pan
Atmospheric Chemistry Division, National Center for Atmospheric Research, Boulder, Colorado, USA
David C. Rogers
Research Aviation Facility, National Center for Atmospheric Research, Broomfield, Colorado, USA
Jorgen Jensen
Research Aviation Facility, National Center for Atmospheric Research, Broomfield, Colorado, USA
Jeffrey L. Stith
Research Aviation Facility, National Center for Atmospheric Research, Broomfield, Colorado, USA
Christopher A. Davis
Atmospheric Chemistry Division, National Center for Atmospheric Research, Boulder, Colorado, USA
Teresa L. Campos
Research Aviation Facility, National Center for Atmospheric Research, Broomfield, Colorado, USA
Kenneth P. Bowman
Department of Atmospheric Sciences, Texas A&M University, College Station, Texas, USA
William A. Cooper
Research Aviation Facility, National Center for Atmospheric Research, Broomfield, Colorado, USA
Leslie R. Lait
Goddard Space Flight Center, National Aeronautics and Space Administration, Greenbelt, Maryland, USA
Abstract
The free troposphere and lower stratosphere is a source region for new particle formation. In particular, nucleation can be
active near the tropopause because of low temperatures. Here we show enhanced new particle formation observed during midlatitude
tropopause folds. Number concentrations and size distributions of particles with diameters from 4 to 2000 nm were measured
in the midlatitude tropopause region on 1 and 7 December 2005 during the NSF/NCAR GV Progressive Science Missions. High number
concentrations of ultrafine particles with diameters from 4 to 9 nm, ranging from ∼700 to 3960 cm−3, were measured during tropopause folds. Our observations show that stratospheric and tropospheric air exchange during tropopause
folding events, with a large gradient of temperature and relative humidity, may have enhanced new particle formation. Our
results are consistent with other modeling predictions showing that nucleation rates are increased with mixing of two air
masses with different temperatures and relative humidities. In addition, new particle formation events were also associated
with vertical motion that may also have brought higher concentrations of water vapor and aerosol precursors (that originate
at the ground level) from lower altitudes to higher altitudes where temperatures and surface areas are lower. The average
ultrafine particle concentrations for the regions that were not affected by tropopause folds were also high (>100 cm−3), indicating that nucleation is active in the tropopause region, in general. Our results suggest that atmospheric dynamics,
such as stratosphere and troposphere exchange and vertical motion, affect new particle formation in this region.
Received 5
October
2006;
accepted 16
February
2007;
published 25
May
2007.
Keywords: New particle formation;
tropopause;
upper troposphere and lower stratosphere.
Index Terms: 0320 Atmospheric Composition and Structure: Cloud physics and chemistry; 0322 Atmospheric Composition and Structure: Constituent sources and sinks; 0368 Atmospheric Composition and Structure: Troposphere: constituent transport and chemistry; 0370 Atmospheric Composition and Structure: Volcanic effects (8409); 0310 Atmospheric Composition and Structure: Airglow and aurora.
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Citation: Young, L.-H., et al.
(2007),
Enhanced new particle formation observed in the northern midlatitude tropopause region,
J. Geophys. Res.,
112,
D10218,
doi:10.1029/2006JD008109.
Copyright 2007 by the American Geophysical Union.
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