Dynamic evaluation of a regional air quality model: Assessing the emissions-induced weekly ozone cycle |
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| Authors: | Thomas Pierce Christian Hogrefe S Trivikrama Rao P Steven Porter Jia-Yeong Ku |
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| Institution: | 1. Atmospheric Modeling and Analysis Division, NERL, USEPA (MD-E243-04), Research Triangle Park, NC 27711, USA;2. Atmospheric Sciences Research Center, University at Albany, Albany, NY, USA;3. Department of Civil Engineering, University of Idaho, Idaho Falls, ID, USA;4. New York State Department of Environmental Conservation, Albany, NY, USA;1. Department of Marine, Earth, and Atmospheric Sciences, NCSU, Raleigh, NC 27695, USA;2. ORD, U.S. EPA, Research Triangle Park, NC 27711, USA;3. Atmospheric Chemistry Division, NCAR Earth System Laboratory, NCAR, Boulder, CO 80301, USA;4. Computer Science School, Technical University of Madrid, Campus de Montegancedo, Boadilla del Monte, 28660 Madrid, Spain;5. Department of Physics, University of Murcia, Ed. CIOyN, Campus de Espinardo, University of Murcia, 30100 Murcia, Spain;6. Air Quality Research Division, Environment Canada, Toronto, Ontario M3H 5T4, Canada;1. Atmospheric Chemistry Department, Max-Planck Institute of Chemistry, P.O. Box 3060, 55020 Mainz, Germany;2. The Cyprus Institute, P.O. Box 27456, 1645 Nicosia, Cyprus;3. King Saud University, Riyadh 11451, Saudi Arabia;4. Department of Atmosphere Sciences/IEAA BK 21 Plus, Yonsei University, Seoul, Republic of Korea;5. Research Institute of Basic Sciences, Chungnam National University, Daejeon, Republic of Korea;6. Department of Physics, University of Toronto, Toronto, Ontario, Canada;7. Earth System Science Interdisciplinary Center, University of Maryland, College Park, MD, USA;8. NASA Goddard Space Flight Center, Greenbelt, MD, USA;9. National Institute of Environmental Research (NIER), Incheon, South Korea;1. School of Earth and Environmental Sciences, Seoul National University, Seoul, Republic of Korea;2. Research Institute of Basic Sciences, Chungnam National University, Daejeon, Republic of Korea;3. Division of Polar Climate Research, Korea Polar Research Institute, Incheon, Republic of Korea;4. Department of Atmospheric Sciences, Yonsei University, Seoul, Republic of Korea;1. Department of Statistics, Colorado State University, 1877 Campus Delivery, Fort Collins, CO 80523-1877, USA;2. National Center for Atmospheric Research, Boulder, CO, USA;3. Department of Mathematical Sciences, Clemson University, Clemson, SC, USA;4. Department of Environmental Sciences, University of California, Riverside, CA, USA;1. State Environmental Protection Key Laboratory of the Cause and Prevention of Urban Air Pollution Complex, Shanghai, 200233, China;2. Shanghai Academy of Environmental Sciences, Shanghai, 200233, China;3. College of Geography and Environment, Shandong Normal University, Jinan, 250014, China;4. Ramboll Environ China, Shanghai, 200020, China |
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| Abstract: | Air quality models are used to predict changes in pollutant concentrations resulting from envisioned emission control policies. Recognizing the need to assess the credibility of air quality models in a policy-relevant context, we perform a dynamic evaluation of the Community Multiscale Air Quality (CMAQ) modeling system for the “weekend ozone effect” to determine if observed changes in ozone due to weekday-to-weekend (WDWE) reductions in precursor emissions can be accurately simulated. The weekend ozone effect offers a unique opportunity for dynamic evaluation, as it is a widely documented phenomenon that has persisted since the 1970s. In many urban areas of the Unites States, higher ozone has been observed on weekends than weekdays, despite dramatically reduced emissions of ozone precursors (nitrogen oxides NOx] and volatile organic compounds VOCs]) on weekends. More recent measurements, however, suggest shifts in the spatial extent or reductions in WDWE ozone differences. Using 18 years (1988–2005) of observed and modeled ozone and temperature data across the northeastern United States, we re-examine the long-term trends in the weekend effect and confounding factors that may be complicating the interpretation of this trend and explore whether CMAQ can replicate the temporal features of the observed weekend effect. The amplitudes of the weekly ozone cycle have decreased during the 18-year period in our study domain, but the year-to-year variability in weekend minus weekday (WEWD) ozone amplitudes is quite large. Inter-annual variability in meteorology appears to influence WEWD differences in ozone, as well as WEWD differences in VOC and NOx emissions. Because of the large inter-annual variability, modeling strategies using a single episode lasting a few days or a few episodes in a given year may not capture the WEWD signal that exists over longer time periods. The CMAQ model showed skill in predicting the absolute values of ozone concentrations during the daytime. However, early morning NOx concentrations were underestimated and ozone levels were overestimated. Also, the modeled response of ozone to WEWD differences in emissions was somewhat less than that observed. This study reveals that model performance may be improved by (1) properly estimating mobile source NOx emissions and their temporal distributions, especially for diesel vehicles; (2) reducing the grid cell size in the lowest layer of CMAQ; and, (3) using time-dependent and more realistic boundary conditions for the CMAQ simulations. |
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