Enhanced new particle formation observed in the northern midlatitude tropopause region

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Read Full Article (file size: 3367882 bytes) Cited by 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. Read Full Article (file size: 3367882 bytes) Cited by 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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