AAAR 33rd Annual Conference
October 20 - October 24, 2014
Rosen Shingle Creek
Orlando, Florida, USA
Abstract View
The Contribution of Sub-Grid, Plume-Scale Nucleation to Global CCN Concentrations
ROBIN STEVENS, Jeffrey Pierce, Dalhousie University
Abstract Number: 65 Working Group: Advances in the Physics and Chemistry of New Particle Formation and Growth
Abstract New-particle formation in the plumes of coal-fired power plants and other anthropogenic sulfur sources may be an important source of particles in the atmosphere. It has been unclear, however, how best to reproduce this formation in global and regional aerosol models with grid-box lengths that are 10s of kilometers and larger. The predictive power of these models has thus been limited by the resultant uncertainties in aerosol size distributions.
Based on the results of the System for Atmospheric Modelling (SAM), a Large-Eddy Simulation/Cloud-Resolving Model (LES/CRM) with online TwO Moment Aerosol Sectional (TOMAS) microphysics, we developed the Predicting Particles Produced in Power-Plant Plumes (P6) parameterization: a computationally-efficient, but physically-based, parameterization that predicts the characteristics of aerosol formed within sulfur-rich plumes based on large-scale mean meteorological parameters, emissions of SO$_2 and NO$_x from the source, and mean background pollutant concentrations.
We implement the P6 parameterization in the GEOS-Chem global chemical-transport model in order to evaluate the contribution of coal-fired power plants globally to particle number and CCN concentrations. We find that sub-grid scale new particle formation is sensitive to preexisting aerosol condensation sink. For constant SO$_2 emissions, fewer new particles are formed in more polluted regions. Additionally, we see a seasonal cycle in sub-grid scale new-particle formation rates due to changes in SO$_2 oxidation rates from changes in OH production from photolysis.