Atmos. Chem. Phys. Discuss., 10, 27777-27823, 2010
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This discussion paper has been under review for the journal Atmospheric Chemistry and Physics (ACP). Please refer to the corresponding final paper in ACP.
Multi-scale modeling study of the source contributions to near-surface ozone and sulfur oxides levels over California during the ARCTAS-CARB period
M. Huang1, G. R. Carmichael1, S. N. Spak1, B. Adhikary1,2, S. Kulkarni1, Y. F. Cheng1, C. Wei1, Y. Tang3, A. D'Allura4, P. O. Wennberg5, G. L. Huey6, J. E. Dibb7, J. L. Jimenez8, M. J. Cubison8, A. J. Weinheimer9, A. Kaduwela10, C. Cai10, M. Wong11, R. B. Pierce12, J. A. Al-Saadi13, D. G. Streets14, and Q. Zhang14
1Center for Global and Regional Environmental Research, the University of Iowa, Iowa City, IA, USA
2Kathmandu University, Dhulikhel, Nepal
3Meso-scale modeling, NOAA/NCEP/EMC, W/NP2, NOAA, Camp Springs, MD, USA
4ARIANET Srl, Milano, Italy
5California Institute of Technology, Pasadena, CA, USA
6Geogia Institute of Technology, Atlanta, GA, USA
7University of New Hampshire, Durham, NH, USA
8University of Colorado, Boulder, CO, USA
9NCAR, Boulder, CO, USA
10California Air Resource Board, Sacramento, CA, USA
11The University of Maryland, MD, USA
13NASA Langley Research Center, Hampton, VA, USA
14Argonne National Laboratory, Argonne, IL, USA

Abstract. Chronic ozone (O3) problems and the increasing sulfur oxides (SOx=SO2+SO4) ambient concentrations over South Coast (SC) and other areas of California (CA) are affected by both local emissions and long-range transport. In this paper, multi-scale tracer and full-chemistry simulations with the STEM atmospheric chemistry model are used to assess the contribution of local emission sources to SC O3 and evaluate the impacts of transported sulfur and local emissions on the SC sulfur budget during the ARCTAS-CARB experiment period in 2008. Sensitivity simulations quantify contributions of biogenic and fire emissions to SC O3 levels. California biogenic and fire emissions contribute 3–4 ppb to near-surface O3 over SC, with larger contributions to other regions in CA. Long-range transport from Asia is estimated to enhance surface SO4 over SC by ~0.5 μg/sm3, and the higher SOx levels (up to ~0.7 ppb of SO2 and ~6 μg/sm3 of SO4) observed above ~6 km did not affect surface air quality in the study region. Enhanced near-surface SOx levels over SC during the flight week were attributed mostly to local emissions. Two anthropogenic SOx emission inventories (EIs) from the California Air Resources Board (CARB) and the US Environmental Protection Agency (EPA) are compared and applied in 60 km and 12 km chemical transport simulations, and the results are compared with observations. The CARB EI shows improvements over the National Emission Inventory (NEI) by EPA, but generally underestimates surface SC SOx by about a factor of two. Maritime (mostly shipping) emissions contribute to the high SO2 levels over the ocean and on-shore, and fine SO4 over the downwind areas is impacted by maritime sources. Maritime emissions also modify the NOx-VOC limitations over coastal areas. These suggest an important role for shipping emission controls in reducing fine particle and O3 concentrations in SC.

Citation: Huang, M., Carmichael, G. R., Spak, S. N., Adhikary, B., Kulkarni, S., Cheng, Y. F., Wei, C., Tang, Y., D'Allura, A., Wennberg, P. O., Huey, G. L., Dibb, J. E., Jimenez, J. L., Cubison, M. J., Weinheimer, A. J., Kaduwela, A., Cai, C., Wong, M., Pierce, R. B., Al-Saadi, J. A., Streets, D. G., and Zhang, Q.: Multi-scale modeling study of the source contributions to near-surface ozone and sulfur oxides levels over California during the ARCTAS-CARB period, Atmos. Chem. Phys. Discuss., 10, 27777-27823, doi:10.5194/acpd-10-27777-2010, 2010.
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