AAAR 33rd Annual Conference
October 20 - October 24, 2014
Rosen Shingle Creek
Orlando, Florida, USA
Abstract View
Simulation of Particle Number and Cloud Droplet Concentrations in the Midwestern United States Using WRF-Chem
CAN DONG, Charles Stanier, Robert Bullard, Ashish Singh, University of Iowa
Abstract Number: 309 Working Group: Aerosols, Clouds, and Climate
Abstract New particle formation (NPF) and growth can influence the concentration of aerosols and cloud droplets, which have been acknowledged to play an important role in both global climate and human health. Several mechanisms have been proposed to explain secondary particle formation and growth. In this study, the NPF explicit version (Matsui et al, Journal of Geophysical Research, 116(D19208), 2011) of the Weather Research and Forecasting Chemistry (WRF-chem) model was used to simulate the particle number concentration in the Midwest.
The three-dimensional chemical transport model has a total of 20 size bins ranging 1-10000 nm in diameter. Particle number concentration, aerosol size distribution, and cloud droplet concentration were simulated in summer 2008 and evaluated versus aircraft and surface measurements in Bondville, Illinois. Bondville is characterized by frequent NPF and growth, and particle concentrations greater than 14 nm of 2,500 – 12,000 #/cm3 depending on season and time of day. Sensitivity of these model outputs to changes in SO2 and NH3 consistent with recent trends in these precursors will be evaluated and compared to measurements. Sensitivity of model prediction to selection of empirical nucleation schemes (activation and kinetic) and the binary homogeneous nucleation will be investigated in the boundary layer and the free troposphere, respectively.
Aspects to be discussed include the selection of activation and kinetic coefficients, and contribution of NPF to aerosol particle concentration estimated from differences between nucleation-on and nucleation-off simulations. Sensitivity analysis will also be performed to investigate aerosol number vertical profiles versus model parameter selection with comparison to observed profiles.