Representing the Effects of Long- Range Transport and Lateral Boundary Conditions in Regional Air Pollution Models

The Community Multiscale Air Quality (CMAQ) modeling system was applied to a domain covering the northern hemisphere; meteorological information was derived from the Weather Research and Forecasting (WRF) model run on identical grid and projection configuration, while the emission inputs were derived from global inventories. The ability of the model to represent long-range transport of pollutants is analyzed through comparisons with aircraft measurements from the 2006 INTEX-B field campaign, ozonesonde profiles, and remotely sensed observations of aerosol optical depth. Time varying lateral boundary conditions from these hemispheric scale calculations were used to drive regional-scale air quality simulations over a finer resolution domain covering the continental United States. Comparison of model predictions with surface O-3 and PM(2.)5 measurements indicate comparable or better performance relative to other approaches (e.g., other global models, static profiles). The successful expansion of CMAQ to the hemispheric scales now provides a conceptual framework to examine interactions between atmospheric processes occurring at various spatial and temporal scales in a consistent manner.