An updated modeling framework to simulate Los Angeles air quality – Part 1: Model development, evaluation, and source apportionment
Creators
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1.
California Institute of Technology
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2.
Stanford University
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3.
Environmental Protection Agency
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4.
State Key Joint Laboratory of Environment Simulation and Pollution Control
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5.
Tsinghua University
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6.
Institute of Atmospheric Physics
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7.
California Air Resources Board
Abstract
This study describes a modeling framework, model evaluation, and source apportionment to understand the causes of Los Angeles (LA) air pollution. A few major updates are applied to the Community Multiscale Air Quality (CMAQ) model with a high spatial resolution (1 km × 1 km). The updates include dynamic traffic emissions based on real-time, on-road information and recent emission factors and secondary organic aerosol (SOA) schemes to represent volatile chemical products (VCPs). Meteorology is well predicted compared to ground-based observations, and the emission rates from multiple sources (i.e., on-road, volatile chemical products, area, point, biogenic, and sea spray) are quantified. Evaluation of the CMAQ model shows that ozone is well predicted despite inaccuracies in nitrogen oxide (NOx) predictions. Particle matter (PM) is underpredicted compared to concurrent measurements made with an aerosol mass spectrometer (AMS) in Pasadena. Inorganic aerosol is well predicted, while SOA is underpredicted. Modeled SOA consists of mostly organic nitrates and products from oxidation of alkane-like intermediate volatility organic compounds (IVOCs) and has missing components that behave like less-oxidized oxygenated organic aerosol (LO-OOA). Source apportionment demonstrates that the urban areas of the LA Basin and vicinity are NOx-saturated (VOC-sensitive), with the largest sensitivity of O3 to changes in VOCs in the urban core. Differing oxidative capacities in different regions impact the nonlinear chemistry leading to PM and SOA formation, which is quantified in this study.
Copyright and License
© Author(s) 2024. This work is distributed under the Creative Commons Attribution 4.0 License. Published by Copernicus Publications on behalf of the European Geosciences Union.
Acknowledgement
The authors would like to thank Leonardo Ramirez, for his guidance on the CARB emission inventories, and Han Kim, for introducing and explaining useful Python analysis tools. We are also grateful to John Crounse and Harrison Parker for managing the CITAQS station and collecting the CITAQS data used in this study. Elyse A. Pennington and John H. Seinfeld acknowledge funding support from the Samsung Global Research Outreach Program. Yuan Wang and John H. Seinfeld acknowledge funding support from the National Science Foundation (grant no. AGS-2103714). We also acknowledge high-performance computing support from NASA Pleiades.
Funding
This research has been supported by the Samsung Global Research Outreach Program and the National Science Foundation (grant no. AGS-2103714).
Data Availability
The following data used in this article have been deposited on Stanford Digital Repository (DOI: https://doi.org/10.25740/qc346hv0119, Wang et al., 2024):
CMAQ source code; WRF namelist files; CMAQ processing scripts.
Supplemental Material
The supplement related to this article is available online at: https://doi.org/10.5194/acp-24-2345-2024-supplement.
Contributions
EAP, YW, and JHS designed and led the research project. EAP performed all model simulations and drafted the paper. EAP, YW, and JHS analyzed the data. BCS collected AMS data and performed PMF analysis. KMS provided VCP emissions. JY provided VMT data. ZJ and BZ provided emissions for the California 4 km × 4 km domain. MV provided the CARB emissions inventory and all SMOKE input files. DC provided the EMFAC emissions inventory. BNM and HOTP participated in useful research discussions and mentored EAP. CMK and RXW collected AMS data. All authors participated in useful research discussions and revised the paper.
Conflict of Interest
At least one of the (co-)authors is a member of the editorial board of Atmospheric Chemistry and Physics. The peer-review process was guided by an independent editor, and the authors also have no other competing interests to declare.
Additional Information
This paper was edited by Manabu Shiraiwa and reviewed by two anonymous referees.
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acp-24-2345-2024.pdf
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Additional details
Related works
- Is new version of
- Discussion Paper: 10.5194/egusphere-2023-749 (DOI)
- Is supplemented by
- Supplemental Material: 10.5194/acp-24-2345-2024-supplement (DOI)
- Dataset: 10.25740/qc346hv0119 (DOI)
Funding
- National Science Foundation
- AGS-2103714
Dates
- Submitted
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2023-04-16
- Accepted
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2023-10-13