Integration of a Size-Resolved Aerosol Microphysics Model with CMAQ: Toward Enhanced Representation of Particle Number Concentrations over the U.S.

JINGBO MAO, Fangqun Yu, Benjamin Murphy, Jingyu An, Yan Zhang, Gan Luo, Shao Lin, Anna Gannet Hallar, State University of New York at Albany

     Abstract Number: 270
     Working Group: Aerosol Physics

Abstract
Accurate representation of aerosol size distributions and total number concentrations is critical for evaluating particle impacts on climate, clouds, and public health. An advanced particle microphysics model (APM), which has previously been incorporated into global and regional chemistry transport models (e.g., GEOS-Chem, WRF-Chem), has been successfully coupled into the USEPA’s Community Multiscale Air Quality Modeling System (CMAQ). CMAQ is a state-of-the-science air quality model simulating the emission, transport, formation, evolution, and deposition of criteria and toxic air pollutants, and the default version uses the modal approach to treat aerosol processes and properties. The sectional APM model distinguishes secondary and primary particles and keeps track of the amount of secondary species coated on each type of primary particle (black carbon, primary organic carbon, dust, and sea salt). Further, APM is designed to capture key particle properties important for their health and climatic effects. One hundred and sixteen additional APM-related tracers have been included in CMAQ-APM. The chemical mechanisms Carbon-Bond version 6 (CB6), the Community Regional Atmospheric Chemistry Multiphase Mechanism (CRACMM) version 1 (CRACMM1), and version 2 (CRACMM2) are supported in the CMAQ-APM model. The formation and growth of particles over the United States is studied using an up-to-date version of the H2SO4-H2O-NH3 ternary ion-mediated nucleation (TIMN) scheme, along with the organics-mediated (OrgT) scheme, both implemented in CMAQ-APM and driven by offline meteorology from the Weather Research and Forecasting (WRF) model. Comparisons of WRF-CMAQ-APM simulated particle size distributions and other particle properties with recent measurements at selected sites (e.g. Southern Great Plains, Bankhead National Forest, and Coast-Urban-Rural Atmospheric Gradient Experiment) in the US will be presented. The simulated spatial distributions of key parameters controlling new particle formation, nucleation rates, and number concentrations over the United States in different seasons will be discussed.