Measurements of the Aerosol Size Distribution Down to 1 Nanometer to Investigate Aerosol Nucleation and Initial Growth During the GoAmazon Campaign

Tuesday, 16 December 2014
Chongai Kuang1, Paulo Artaxo2, John Backman3, Saewung Kim4, Markku Tapio Kulmala3, Scot T Martin5, Tuukka Petäjä3, Roger Seco6, James N Smith7 and Rodrigo Augusto Ferreira de Souza8, (1)Brookhaven National Laboratory, Upton, NY, United States, (2)USP University of Sao Paulo, São Paulo, Brazil, (3)University of Helsinki, Helsinki, Finland, (4)University of California Irvine, Irvine, CA, United States, (5)Harvard University, Cambridge, MA, United States, (6)University of California Irvine, Department of Earth System Science, Irvine, CA, United States, (7)NCAR, Boulder, CO, United States, (8)Organization Not Listed, Washington, DC, United States
Atmospheric particle nucleation is an important environmental nano-scale process, with field measurements and modeling studies indicating that freshly nucleated particles are a significant source of global cloud condensation nuclei. However, our understanding of atmospheric nucleation and its influence on climate is limited as few ambient measurements have been made of either the nucleation rate (at 1 nm) or the initial growth rate of newly formed clusters (from 1 to 3 nm), both of which are necessary to constrain and investigate the nucleation mechanism and to develop process-level models. Aerosol nucleation and initial growth were investigated during the Green Ocean Amazon (GoAmazon) campaign spanning the wet and dry seasons of 2014 downwind of the city of Manaus, Brazil. Aerosol measurement was accomplished through the deployment of a condensation particle counter-based electrical mobility spectrometer, optimized for the detection of aerosol down to 1 nm in diameter. An electrometer-based neutral air ion spectrometer was also deployed at the same location to measure the neutral and charged fraction of aerosol down to 1.5 nm in diameter. From these size distribution measurements, periods of nucleation will be identified, and the resulting nucleation rates and initial growth rates will be presented. Concurrent and co-located measurements of gas-phase sulfuric acid will provide the opportunity to investigate the functional contribution of sulfuric acid to the observed nucleation rate and initial growth rate.