AAAR 32nd Annual Conference
September 30 - October 4, 2013
Oregon Convention Center
Portland, Oregon, USA
Abstract View
Black Carbon Mixing State in Paris during MEGAPOLI: Connecting Particle-Resolved Observations to Particle-Resolved Modeling
SWARNALI SANYAL, Nicole Riemer, Robert Healy, Valérie Gros, John Wenger, Greg J. Evans, Univerisity of Illinois at Urbana-Champaign
Abstract Number: 660 Working Group: Carbonaceous Aerosols in the Atmosphere
Abstract The composition and properties of black carbon aerosol particles change continuously after emission during transport in the atmosphere. Coagulation, condensation, and photochemistry are contributing processes, frequently called "aging". Understanding these processes is important for assessing the climate impacts of black carbon aerosol. The use of single particle mass spectrometers has allowed unprecedented insight into black carbon mixing state and associated aging processes, however it is difficult to fully exploit these measurements using traditional modal or sectional models. The particle-resolved aerosol PartMC-MOSAIC, on the other hand, is a suitable interface to connect to these observations from the modeling side. In this work, we present the first PartMC-MOSAIC case study that uses data from an aerosol time-of-flight mass spectrometer (ATOFMS) to constrain the model. The instrument was deployed during the 2010 MEGAPOLI winter campaign in Paris, France.
PartMC-MOSAIC is a Lagrangian box model that resolves the per-particle composition and hence provides a detailed representation of black carbon mixing state and aging processes. The model simulates a representative group of particles distributed in composition space, treating coagulation, condensation and other important processes on individual particle levels. For the initial conditions of the aerosol population and for the particle emissions we use quantitative chemical composition estimates from the ATOFMS measurements collected during MEGAPOLI. We then track the particle population for several hours as it evolves undergoing coagulation, dilution with the background air, and chemical transformations in the aerosol and gas phase. We quantify the contribution of coagulation and condensation to black carbon aging, discuss the implications of black carbon aging for cloud condensation nucleation activity, and present a comparison to ATOFMS mixing state observations.