A study of the ozone formation by ensemble back trajectory-process analysis using the Eta–CMAQ forecast model over the northeastern U.S. during the 2004 ICARTT period |
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| Authors: | Shaocai Yu Rohit Mathur Daiwen Kang Kenneth Schere Daniel Tong |
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| Affiliation: | 1. Asia Center for Air Pollution Research, 1182 Sowa, Nishi-ku, Niigata 950-2144, Japan;2. Japan Weather Association, 3-1-1 Higashi-ikebukuro, Toshima-ku, Tokyo 170-6055, Japan;3. Osaka City Institute of Public Health and Environmental Sciences, 8-34 Tojo-cho, Tennoji-ku, Osaka 543-0026, Japan;1. ENVIRON International Corporation, 773 San Marin Drive, Suite 2115, Novato, CA 94998, USA;2. Electric Power Research Institute, 2000 L Street, NW, Suite 805, Washington, DC 20036, USA;1. State Key Laboratory of Earth Surface Processes and Resource Ecology, College of Water Sciences, Beijing Normal University, Beijing, 100875, China;2. Chinese Research Academy of Environmental Sciences, Beijing, 100012, China;3. State Key Laboratory of Earth Surface Processes and Resource Ecology, College of Global Change and Earth System Sciences, Beijing Normal University, Beijing, 100875, China;4. College of Earth, Ocean, and Atmospheric Sciences, Oregon State University, Oregon, USA;5. Institute of Urban Meteorology, China Meteorological Administration, Beijing, China;6. National Engineering Research Center for Information Technology in Agriculture, 11 Shuguang Huayuan Middle Road, Beijing, 100097, China;1. Institute of Environmental Studies, Pusan National University, Busan 46241, South Korea;2. Department of Earth and Atmospheric Sciences, University of Houston, Houston, TX 77204, USA;3. Division of Earth Environmental System, Pusan National University, Busan 46241, South Korea;4. Department of Earth Science Education, Pusan National University, Busan 46241, South Korea;5. Department of Physics and Earth Science, Korea Science Academy of KAIST, Busan 47162, South Korea;6. Department of Atmospheric Sciences, Pusan National University, Busan 46241, South Korea |
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| Abstract: | The integrated process rates (IPRs) estimated by the Eta–CMAQ model at grid cells along the trajectory of the air mass transport path were analyzed to quantitatively investigate the relative importance of physical and chemical processes for O3 formation and evolution over the northeastern U.S. during the 2004 International Consortium for Atmospheric Research on Transport and Transformation (ICARTT) period. The Hybrid Single Particle Lagrangian Integrated Trajectory (HYSPLIT) model is used to determine the back trajectory of air masses reaching the northeast by linking a downwind receptor to upwind source areas. The process analysis is applied to a high O3 episode occurring on July 22, 2004 at three selected sites in the northeastern U.S. The process analysis at the location of the site shows that during the daytime, the O3 concentrations in the surface layer are mainly enhanced by the vertical diffusion of O3-rich air from aloft, followed by horizontal advection (HADV) and chemical production (CHEM), whereas dry deposition (DDEP) and vertical advection (ZADV) mainly deplete O3 concentrations at the sites of Valley Central (VC), NY and Castle Spring (CS), NH. By integrating the effects of each process over the depth of the daytime planetary boundary layer (PBL), it was found that at the VC site, CHEM and HADV contributed about 53% and 41%, respectively, to O3 levels within the PBL. This confirms the significance of regional transport of O3 from the industrialized areas into the Northeast. On the other hand, the process analysis results for O3 formation in moving air masses indicate that on July 22, large chemical production of O3 along the transport path over the polluted urban regions leads to significant increase in O3 in the air mass reaching the VC site, whereas the low chemical production of O3 along the transport path over the low emission regions leads to the low O3 concentration at the site of Belleayre Mountain (BM), NY. The dramatic buildup of O3 concentration from 50 ppb to 102 ppb in the air masses before reaching the VC site after 12:00 EST on 7/22 indicates the significant impact of pollution from the northeastern urban corridor at this site. On the basis of the results at the CS site, it was found that high NOx emissions along the transport path led to large chemical production of O3 in the air mass reaching the CS site on July 22. In contrast, the low chemical production of O3 associated with low emission (relatively clean conditions) along the transport path over the northern portions of the domain is responsible for the low O3 concentration at the CS site on July 26. |
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