Impacts of Climate-responsive Controls and Land Usage on Regional Climate and Air Quality Marcus A. Trail 201 pages Directed by Dr. Armistead G. Russell Regional air quality impacts public health, visibility and ecosystem health, and is significantly affected by changes in climate, land use and pollutant emissions. Predictions of regional air quality responses to such changes can help inform policy makers in the development of effective approaches to both reduce greenhouse gases and improve air quality. However, major sources of uncertainty exist in predicting future air quality including limitations in the tools used to project future emissions, land use changes and uncertainties associated with predicting future climate. Recently, technical advances in downscaling global climate simulations to regional scales, and, the development of bottom-up operational tools used to forecast emissions have enhanced our ability to account for the complex interactions between population, socio-economic development, technological change, and federal and regional environmental policies. The results show that emissions reductions strategies will continue to play a vital role in improving air quality over the U.S. while CO2 emission reduction policies can have mixed positive and negative impacts on air quality. However, additional costs will be necessary to reach air quality goals due to climate change because deeper emission reductions will be required to compensate for a warmer climate, even if current efforts are predicted to show improvement. The results of this study also show that regional climate and O3 and aerosol concentrations are highly sensitive to reforestation and cropland conversion in the Southeast and these land use changes should be considered in air quality management plans.

The Models-3/Community Multi-scale Air Quality modeling system (CMAQ), coupled with Goddard Institute for Space Studies (GISS) atmospheric General Circulation Model (GCM), fifth Generation Mesoscale Model system (MM5), and Goddard Earth Observing System-CHEMistry (GEOS-Chem), was used to simulate atmospheric concentration of ozone and particulate matter over the continental United States 12-km and 36-km (CONUS) domains at year 2000 and year 2050. In the study, GISS GCM model outputs interfaced with MM5 were utilized to supply the current and future meteorological conditions for CMAQ. The conventional CMAQ profile initial and boundary conditions were replaced by time-varied and layer-varied GEOS-Chem outputs. The future emission concentrations were estimated using year 2000 based emissions with emission projections suggested by the IPCC A1B scenario. Multi-scenario statistical analyses were performed to investigate the effects of climate change and change of anthropogenic emissions toward 2050. The composite effects of these changes were broken down into individual effects and analyzed on three distinct regions (i.e., Midwest, Northeast and Southeast). The results of CMAQ hourly and 8-hour average concentrations indicate the maximum ozone concentration in the Midwest is increased slightly from year 2000 to year 2050, as a result of increasing average and maximum temperatures by 2 to 3 degrees Kelvin. In converse, there is an observed reduction of surface ozone concentration in the Southeast caused by the decrease in solar radiation. For the emission reduction scenario, the decline of anthropogenic emissions causes reductions of both ozone and PM2.5 for all regions. The emission reduction has compensated the effect of increasing temperature. The overall change on the maximum daily 8-hr ozone and average PM2.5 concentrations in year 2050 were estimated to be 10% and 40% less than the values in year 2000, respectively. The modeling results indicates the effect of emissions reduction has greater impact than the effect of climate change.