Effects of future US and global emissions on air quality in the US

Global change will clearly have a significant impact on the environment. Among the concerns for future air quality in the United States, intercontinental transport of pollution has become increasingly important. In this study, we examined the effect of the changes in chemical boundary conditions and the continental US emissions on US air quality using a multi-scale modeling framework. Meteorological fields were downscaled from the results of the ECHAM5 global climate model using WRF. Two nested domains were employed, one covering most of the Northern Hemisphere from eastern Asia to North America at 220-km horizontal resolution (hemispheric domain) and one covering the continental US at 36-km resolution (CONUS). Meteorological results from WRF were used to drive the MEGAN biogenic emissions model, the SMOKE emissions processing tool, and the CMAQ chemical transport model to predict ozone and aerosol concentrations for the current (1995-2004) and a future decade (2045-2054). The MEGAN model was used to calculate biogenic emissions for all simulations. For the current decade hemispheric domain simulation, year 2000 global emissions of gases (ozone precursors) from anthropogenic, natural, and biomass burning sources from the POET and EDGAR emission inventories were used. Global emissions inventories for black and organic carbon from Bond et al (2004) were applied. For the future decade hemispheric domain simulations, current decade emissions were projected to the year 2050 following the Intergovernmental Panel for Climate Change (IPCC) A1B emission scenario. WRF and CMAQ results from the hemispheric domain simulations provided the boundary conditions for CONUS simulations. For the CONUS simulations, US anthropogenic emissions including mercury emissions for the current decade were based on the 2002 National Emissions Inventory prepared by the Environmental Protection Agency. For the future decade simulation, these emissions were projected to 2050 using growth factors from the U.S. EPA MARKAL nine-region database and energy system model following a scenario that assumes baseline criteria pollutant policies, including the application of the Clean Air Interstate Rule (CAIR). We present the results showing the changes in US air quality due to changes in future global emissions and US anthropogenic emissions.