AAAR 32nd Annual Conference
September 30 - October 4, 2013
Oregon Convention Center
Portland, Oregon, USA
Abstract View
Sub-grid Aging: When is the Internal Mixture Assumption Good Enough?
LAURA FIERCE, Nicole Riemer, Tami Bond, University of Illinois at Urbana-Champaign
Abstract Number: 528 Working Group: Aerosols, Clouds, and Climate
Abstract The characteristics of emitted particles change by condensation of secondary aerosol and coagulation with other particles, processes known collectively as aging. In many cases, aerosol properties evolve rapidly near the emission source, at spatial scales much smaller than global model boxes. This is largely due to conditions near emission being very different compared to the average over a global grid cell. Therefore, sub-grid processes must be included in global simulations to adequately represent the evolution of particle characteristics.
In this work, we introduce an aging routine that accounts for sub-grid aerosol dynamics in emission inventories, based on results from the particle-resolved model PartMC-MOSAIC. To obtain this aging routine, we simulated the evolution of black carbon emissions in a set of nearly 300 plume scenarios and identified the environmental parameters that most influence aging rates. Condensational aging depends on the flux and hygroscopicity of secondary aerosol, and coagulation aging depends on the number concentration and size-distribution of pre-existing particles. These parameters are used as inputs to the aging routine, along with the size distribution and composition of fresh aerosol emissions. The aging routine returns the size distribution and composition of modified emissions, accounting for sub-grid changes in particle hygroscopic properties by condensation and loss in particle number by coagulation.