AAAR 34th Annual Conference
October 12 - October 16, 2015
Hyatt Regency
Minneapolis, Minnesota, USA
Abstract View
Simulation of the Size-Composition Distribution of Atmospheric Nanoparticles over Europe
David Patoulias, Christos Fountoukis, Ilona Riipinen, SPYROS PANDIS, University of Patras, Greece
Abstract Number: 364 Working Group: Carbonaceous Aerosols in the Atmosphere
Abstract In this work, we continue the development of a three-dimensional chemical transport model, PMCAMx-UF, focusing on the simulation of the ultrafine particle size distribution and composition. The Volatility Basis Set (VBS) approach is used for the simulation of organic aerosol. PMCAMx-UF is applied to Europe to quantify the contribution of organic vapors to total number concentrations and fresh particles’ growth. PMCAMx-UF uses the new version of the Dynamic Model for Aerosol Nucleation and the Two-Moment Aerosol Sectional algorithm to track both aerosol number and mass concentration using a sectional approach. We evaluate the model predictions for the European domain against field observations collected in the PEGASOS campaigns during spring 2012 and 2013. The measurements include both ground stations across Europe and airborne measurements from a Zeppelin.
PMCAMx-UF reproduces reasonably well the N10 (number concentration of particles larger than 10 nm) hourly observations both aloft (over the Po Valley in Italy) as well as at the ground level. The ground level concentrations of N100 are well predicted (normalized mean error of -16%, normalized mean bias 27%) while there is tendency to overestimate N10 is overestimated by approximately 50%. The sensitivity of the model predictions to various processes and parameters is examined. The condensation of organics increases the N100 concentration mainly in central and northern Europe by 50-200% while, on the other hand, it decreases by 10-40% the N10 concentration. This counterintuitive result can be explained by an increase of the aerosol surface area leading to an increase of the rate of coagulation and then to a decrease of the nucleation rate. Sensitivity tests highlight the importance of chemical aging reactions of secondary organic aerosol for the ultrafine particle growth and total particle number concentration.