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Observation-based modeling of ozone chemistry in the Seoul metropolitan area during the Korea-United States Air Quality Study (KORUS-AQ)

Schroeder, Jason R. and Crawford, James H. and Ahn, Joon-Young and Chang, Limseok and Fried, Alan and Walega, James and Weinheimer, Andrew and Montzka, Denise D. and Hall, Samuel R. and Ullmann, Kirk and Wisthaler, Armin and Mikoviny, Tomas and Chen, Gao and Blake, Donald R. and Blake, Nicola J. and Hughes, Stacey C. and Meinardi, Simone and Diskin, Glenn and DiGangi, Joshua P. and Choi, Yonghoon and Pusede, Sally E. and Huey, Greg L. and Tanner, David J. and Kim, Michelle and Wennberg, Paul (2020) Observation-based modeling of ozone chemistry in the Seoul metropolitan area during the Korea-United States Air Quality Study (KORUS-AQ). Elementa: Science of the Anthropocene, 8 (1). ISSN 2325-1026. doi:10.1525/elementa.400.

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The Seoul Metropolitan Area (SMA) has a population of 24 million and frequently experiences unhealthy levels of ozone (O₃). In this work, measurements taken during the Korea-United States Air Quality Study (KORUS-AQ, 2016) are used to explore regional gradients in O₃ and its chemical precursors, and an observationally-constrained 0-D photochemical box model is used to quantify key aspects of O₃ production including its sensitivity to precursor gases. Box model performance was evaluated by comparing modeled concentrations of select secondary species to airborne measurements. These comparisons indicate that the steady state assumption used in 0-D box models cannot describe select intermediate species, highlighting the importance of having a broad suite of trace gases as model constraints. When fully constrained, aggregated statistics of modeled O₃ production rates agreed with observed changes in O₃, indicating that the box model was able to represent the majority of O₃ chemistry. Comparison of airborne observations between urban Seoul and a downwind receptor site reveal a positive gradient in O₃ coinciding with a negative gradient in NO_x, no gradient in CH₂O, and a slight positive gradient in modeled rates of O₃ production. Together, these observations indicate a radical-limited (VOC-limited) O₃ production environment in the SMA. Zero-out simulations identified C₇₊ aromatics as the dominant VOC contributors to O₃ production, with isoprene and anthropogenic alkenes making smaller but appreciable contributions. Simulations of model sensitivity to decreases in NO_x produced results that were not spatially uniform, with large increases in O₃ production predicted for urban Seoul and decreases in O₃ production predicted for far-outlying areas. The policy implications of this work are clear: Effective O₃ mitigation strategies in the SMA must focus on reducing local emissions of C₇₊ aromatics, while reductions in NO_x emissions may increase O₃ in some areas but generally decrease the regional extent of O₃ exposure.

Item Type:Article
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URLURL TypeDescription ItemData
Weinheimer, Andrew0000-0001-6175-8286
Hall, Samuel R.0000-0002-2060-7112
Ullmann, Kirk0000-0002-4724-9634
Diskin, Glenn0000-0002-3617-0269
DiGangi, Joshua P.0000-0002-6764-8624
Choi, Yonghoon0000-0001-6529-4722
Kim, Michelle0000-0002-4922-4334
Wennberg, Paul0000-0002-6126-3854
Additional Information:© 2020 The Author(s). This is an open-access article distributed under the terms of the Creative Commons Attribution 4.0 International License (CC-BY 4.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited. See Submitted: 03 May 2019; Accepted: 16 November 2019; Published: 13 January 2020. The KORUS-AQ study was jointly funded by NASA and the Korean National Institute of Environmental Research (NIER). Special thanks goes to all who made the DC-8 flights over Seoul and in Korean airspace possible. This includes civil and military air traffic coordinators, DC-8 pilots and crew, and the scientists who negotiated the flight paths and permissions needed to collect these observations. The members of the PTR-MS instrument team (P. Eichler, L. Kaser, M. Müller) are acknowledged for their support with instrument preparation and field work. Data Accessibility Statement: Outputs from all box model simulations used in this work are available on the KORUS-AQ archive: PTR-ToF-MS measurements aboard the NASA DC-8 during KORUS-AQ were supported by the Austrian Federal Ministry for Transport, Innovation and Technology (bmvit) through the Austrian Space Applications Programme (ASAP) of the Austrian Research Promotion Agency (FFG). The authors have no competing interests to declare. Author contributions: Contributed to conception and design: JRS and JHC. Contributed to acquisition of data: all authors. Contributed to analysis and interpretation of data: JRS and JHC. Drafted, revised, and approved of manuscript for submission: JRS and JHC.
Funding AgencyGrant Number
Korean National Institute of Environmental ResearchUNSPECIFIED
Bundesministerium für Verkehr, Innovation und Technologie (BMVIT)UNSPECIFIED
Austrian Research Promotion Agency (FFG)UNSPECIFIED
Subject Keywords:Ozone, Air quality, Photochemistry, Korea, Seoul
Issue or Number:1
Record Number:CaltechAUTHORS:20200213-104217327
Persistent URL:
Official Citation:Schroeder, J.R., Crawford, J.H., Ahn, J.-Y., Chang, L., Fried, A., Walega, J., Weinheimer, A., Montzka, D.D., Hall, S.R., Ullmann, K., Wisthaler, A., Mikoviny, T., Chen, G., Blake, D.R., Blake, N.J., Hughes, S.C., Meinardi, S., Diskin, G., Digangi, J.P., Choi, Y., Pusede, S.E., Huey, G.L., Tanner, D.J., Kim, M. and Wennberg, P., 2020. Observation-based modeling of ozone chemistry in the Seoul metropolitan area during the Korea-United States Air Quality Study (KORUS-AQ). Elem Sci Anth, 8(1), p.3. DOI:
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:101270
Deposited By: Tony Diaz
Deposited On:13 Feb 2020 19:24
Last Modified:16 Nov 2021 18:01

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