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Climate Impact on Regional Air Quality (CIRAQ)
Research Programs
Climate & Air Quality
Air quality is determined both by emissions of air pollutants, including ozone and particulate matter precursors, and by meteorological conditions, including temperature, wind flow patterns, and the frequency of precipitation and stagnation events. For air quality management applications, regional-scale models are used to assess whether various emission control strategies will result in attainment of the National Ambient Air Quality Standards (NAAQS). These modeling applications typically assume present meteorological conditions, which means that potential changes in climate are not included in the assessment. With emission controls that are implemented over several decades, however, future climate trends could impact the effectiveness of these controls.
EPA's Atmospheric Modeling and Analysis program initiated the Climate Impact on Regional Air Quality (CIRAQ) project in 2002 to develop a pilot modeling study to incorporate regional-scale climate effects into air quality modeling. It involved collaboration across multiple federal agencies and with academic groups with global-scale modeling expertise, who were supported through the EPA Science To Achieve Results (STAR) grant program.
The Goddard Institute for Space Studies (GISS) global climate model (GCM) version 2' was used to simulate the period from 1950-2055 at 4° latitude × 5° longitude resolution. Historical values for greenhouse gases (as CO2 equivalents) were used for 1950-2000, with future greenhouse gas forcing following the Intergovernmental Panel on Climate Change's A1B scenario. Colleagues at the Pacific Northwest National Laboratory downscaled the GCM outputs using the Penn State/NCAR MM5 model to simulate meteorology over the continental U.S. at 36 km resolution for two 10-year periods centered on 2000 and 2050.
For the first phase of this project, the effect of climate change alone was considered, without attempting to account for changes in emissions of ozone and PM precursors. Hourly emissions were simulated using the SMOKE model. Anthropogenic emissions were based on the USEPA 2001 version ad (2001ad) modeling inventory, projected from the 1999 National Emission Inventory version 3. Biogenic emissions were calculated using the BEIS model and the simulated future meteorology. Air quality was simulated for two 5-year periods (1999-2003 and 2048-2052) using CMAQ v4.5.
Differences (5-year future − 5-year current) in mean (top) and 95th percentile (bottom)
maximum daily 8-h average (MDA8) ozone concentrations. Results show summertime increases of 2-5 ppb in mean MDA8 concentrations
in Texas and parts of the eastern U.S. and even larger increases in 95th percentile concentrations, suggesting increased severity
of ozone episodes. Still larger increases are predicted for the September-October time period, suggesting a lengthening of
the ozone season (Nolte et al., J. Geophy. Res., 2008).
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As the next step, we are investigating the combined effect of climate change together with emission changes on air quality. Emission projections for different scenarios of economic growth and technological utilization have been developed. Air quality simulations using these emissions projections and the climatological meteorology described above has been conducted using CMAQ v4.7.
Contacts: Chris Nolte
Related Publications:
C. P. Weaver, et al. (2009),
A preliminary synthesis of modeled climate change impacts on U.S. regional ozone concentrations,
Bulletin of the American Meteorological Society, 90.
U.S. EPA (2009), Assessment of the Impacts of Global Change on Regional U.S. Air Quality: A Synthesis of Climate Change Impacts on Ground-Level Ozone (An Interim Report of the U.S. EPA Global Change Research Program), U.S. Environmental Protection Agency, Washington, DC, EPA/600/R-07/094F.
C. G. Nolte, A. B. Gilliland, C. Hogrefe, and L. J. Mickley (2008),
Linking global to regional models to assess future climate impacts on surface ozone levels in the United States,
Journal of Geophysical Research, 113, D14307.
U.S. Climate Change Science Program (2008),
Climate Projections Based on Emissions Scenarios for Long-Lived and Short-Lived Radiatively Active Gases and Aerosols,
H. Levy II, D. Shindell, A. Gilliland, L.W. Horowitz, and M. D. Schwarzkopf, eds.,
U.S. Department of Commerce, National Climatic Data Center, Washington, DC.
C. Nolte, A. Gilliland, and C. Hogrefe (2008), Linking global and regional models to simulate U.S. air quality in the year 2050, Air Pollution Modeling and its Application XIX, C. Borrego and A. I. Miranda, eds., Elsevier, 559-567.
E. J. Cooter, R. Gilliam, W. Benjey, C. Nolte, J. Swall, and A. Gilliland (2007), Examining the impact of changing climate on regional air quality over the U.S., Air Pollution Modeling and its Application XVIII, C. Borrego and E. Renner, eds., Elsevier, 633-647.
Related Links of Interest:
Goddard Institute for Space Studies
IPCC Special Report on Emission Scenarios
Pacific Northwest National Laboratory
SMOKE emissions model