Effects of global change on air quality in the US

As part of an ongoing analysis of the effects of global change upon US air quality, we report results for current and future simulations based upon the WRF/CMAQ modeling framework in terms of the sensitivity of future air quality to changes in meteorology, in global emissions (chemical boundary conditions), in US land use and biogenic emissions, and in US anthropogenic emissions. Meteorological fields, downscaled from the results of the ECHAM5 global climate model using 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 representative years within the current (1995-2004) and a future decade (2045-2054). CMAQ simulations employed two nested domains covering most of the Northern Hemisphere from eastern Asia to North America at 220-km horizontal resolution (hemispheric domain) and covering the continental US at 36-km resolution (CONUS); CMAQ results from the hemispheric domain simulations provided the chemical boundary conditions for CONUS 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. For the CONUS simulations, US anthropogenic 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).