AAAR 31st Annual Conference
October 8-12, 2012
Hyatt Regency Minneapolis
Minneapolis, Minnesota, USA
Abstract View
Using Simulated Particle Formation Events for Testing and Improving Event Analysis Tools
KARI LEHTINEN, Hannele Korhonen, Johannes Leppä, Veli-Matti Kerminen, Finnish Meteorological Institute, Kuopio, Finland
Abstract Number: 112 Working Group: Aerosol Nucleation: From Clusters to Nanoparticles
Abstract The analysis of new particle formation events may involve issues such as estimation of particle formation rates, nucleation rates, growth rates and fractions of ion induced and neutral nucleation, and, through application of the first nucleation thorem, an estimation of the critical cluster composition. These are typically done by analysing the initial particle (and ion, if possible) size distribution evolution right after particle formation, plus some assumptions. For example, the particle growth rate may be estimated by following the peak location of the nucleation mode, the formation rate by looking at the change in number concentration of some size range, say 3-6nm, and the critical cluster composition from the slope of log(formation rate) vs. log(vapor concentration).
In this work, we analyze some of the most widely used event analysis methods by first generating the particle formation events through computer simulation of all relevant aerosol microphysics and then analyzing them. Since we know ’the correct answers’, we can find out how the methods perform. In addition, with some tuning based on the simulation results as well as aerosol microphysics theory, we can improve some of the methods significantly. One such improvement is modifying the estimation of nucleation rate from the observed particle formation rate to include the effect of size dependent growth rate.