INVITED ABSTRACT
First Measurements of Atmospheric Cluster and 1-2 nm Particle Number Distribution Functions During Nucleation Events

PETER MCMURRY (1), Jingkun Jiang (1), Jun Zhao (2), Modi Chen (1), Jacob Scheckman (1), Brent Williams (1), Fred Eisele (2)

(1) University of Minnesota, Minneapolis, (2) National Center for Atmopsheric Research, Boulder

     Abstract Number: 363
     Last modified: May 10, 2010

Abstract
Atmospheric nucleation leads to the formation of new particles that influence concentrations of cloud condensation nuclei, thereby affecting human’s impact on climate. Size-resolved measurements extending down to molecular dimensions can provide information on chemical and physical processes that lead to nucleation. We report the first atmospheric measurements of cluster and nanoparticle number distribution functions over the complete range of sizes, extending down to single sulfuric acid molecules. Two new instrument systems were deployed during the 2009 Nucleation and Cloud Condensation Nuclei campaign (NCCN) in Atlanta, Georgia. The Cluster CIMS, a mass spectrometer, detected sulfuric acid vapor and neutral molecular clusters that contained three and four sulfuric acid molecules. The DEG SMPS, an aerosol mobility spectrometer equipped with a diethylene glycol condensation particle counter, extended measurements of nano condensation nuclei (nano CN) down to sizes close to 1 nm. A pair of conventional aerosol mobility spectrometers was used to measure the number distribution functions of particles larger than 3 nm. The smallest nano CN that were detected by the DEG SMPS are comparable in size to the size 3 and 4 clusters detected by the Cluster CIMS, and the distribution functions measured by the Cluster CIMS and DEG typically agree to within the estimated measurement uncertainty. The DEG SMPS and the conventional nano SMPS typically agree to within a factor of two in the overlapping 3 to 10 nm range.