Performance Summary of the 2006 Community Multiscale Air Quality (CMAQ) Simulation for the AQMEII Project: North American Application

The CMAQ modeling system has been used to simulate the CONUS using 12-km by 12-km horizontal grid spacing for the entire year of 2006 as part of the Air Quality Model Evaluation International Initiative (AQMEII). The operational model performance for O3 and PM2.5 for the simulation was assessed. The model underestimates O3 mixing ratios in the winter, which is likely due to low O3 mixing ratios in the middle and lower troposphere from the lateral boundary conditions. PM2.5 performance varies seasonally and geographically, with PM2.5 overestimated in the winter and fall, while performance in the spring and summer is generally good, especially in the summer. PM2.5 concentrations are systematically higher in the AQMEII CMAQ simulation than in previous CMAQ simulations, primarily due to higher concentrations of TC and unspeciated PM2.5 mass, which may also be due to differences in the lateral boundary conditions.