HR: 1340h
AN: A13A-0876    [Abstracts]
TI: When Does New Particle Formation Not Occur in the Upper Troposphere?
AU: * Lee, S
EM: slee19@kent.edu
AF: Kent State University, Dept Chemistry, Kent, OH 44240,
AU: Benson, D
EM: dbenson2@kent.edu
AF: Kent State University, Dept Chemistry, Kent, OH 44240,
AU: Young, L
EM: lyoung8@kent.edu
AF: Kent State University, Dept Chemistry, Kent, OH 44240,
AB: Recent aircraft studies showed that new particle formation is very active in the free troposphere and lower stratosphere. And, these observations lead to a new question: when does new particle formation not occur? Here, we provide case studies to show how convection and surface area affect new particle formation in the upper troposphere, using the measured aerosol size distributions during the NSF/NCAR GV Progressive Science Missions in December 2005. There were ten research flights, including three days of nighttime experiments, at latitudes from 18 °N to 52 °N and altitudes up to 14 km. About 78 % of the total samples showed the new particle formation feature with number concentrations of particles with the diameter from 4 to 9 nm, 670 ± 1270 per cc, and the total particle number concentrations in the diameter range from 4 to 2000 nm, 920 ± 1470 per cc. Our case studies show that new particle formation was closely associated with convection and low surface areas of preexisting aerosol particles. On the other hand, for the cases where no new particle formation events were observed, air masses did not experience a vertical motion and there were also high surface area densities. These observations were consistent other observations during the Progressive Science Missions. Our results indicate that low temperatures, low surface areas, and convection together are responsible for frequent new particle formation events observed in this region. Latitude dependence of new particles also shows higher particle concentrations in the midlatitude tropopause region than in the subtropics, consistent with Hermann et al. [2003].
DE: 0300 ATMOSPHERIC COMPOSITION AND STRUCTURE
DE: 0305 Aerosols and particles (0345, 4801, 4906)
DE: 0365 Troposphere: composition and chemistry
DE: 0368 Troposphere: constituent transport and chemistry
SC: Atmospheric Sciences [A]
MN: 2007 Fall Meeting