Open AccessEnhanced new particle formation observed in the northern midlatitude tropopause region
Author(s) -
Young LiHao,
Benson David R.,
Montanaro William M.,
Lee ShanHu,
Pan Laura L.,
Rogers David C.,
Jensen Jorgen,
Stith Jeffrey L.,
Davis Christopher A.,
Campos Teresa L.,
Bowman Kenneth P.,
Cooper William A.,
Lait Leslie R.
Publication year - 2007
Publication title -
journal of geophysical research: atmospheres
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.67
H-Index - 298
eISSN - 2156-2202
pISSN - 0148-0227
DOI - 10.1029/2006jd008109
Subject(s) - tropopause , troposphere , stratosphere , atmospheric sciences , nucleation , middle latitudes , relative humidity , particle (ecology) , aerosol , water vapor , environmental science , geology , meteorology , physics , thermodynamics , oceanography
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.