Dissertation
Testing ozone sensitivities using process analysis, chemical indicators, and very fine scale modeling with CMAQ in the Pacific Northwest
Washington State University
Doctor of Philosophy (PhD), Washington State University
12/2008
DOI:
https://doi.org/10.7273/000005964
Abstract
This research employed the MM5/SMOKE/CMAQ modeling system to investigate ozone formation and fate in the Pacific Northwest region through three separate studies. In the first study, chemical features of instantaneous ozone production and the behavior of local photochemical indicators were examined with process analysis in CMAQ. Maximum ozone production (P(O3)) rate was 30-40 ppb hr-1 downwind of the Portland urban center, with NOx concentrations of 5-20 ppb and total VOC reactivity above 8 s-1. Five indicators (fOH+HC, fHO2+NO, P(H2O2)/P(HNO3), O3/NOx, and LN/Q) were found to be useful tools for distinguishing VOC/NOx sensitive conditions, and the results indicated that the greatest P(O3) (>30 ppb hr-1) occurred at transitional or NOx-limited conditions for the Portland area. In the second study, the CMAQ model was evaluated for predicted O3-NOx-VOC chemistry by comparing to aircraft measurements collected during a field experiment in western Washington. Results showed that anthropogenic VOC and CO were the major contributors to odd oxygen photochemistry in the morning urban profile, while CO and oxygenated compounds accounted for two thirds of the measured reactivity in the afternoon aged plume. Peak O3 was associated with VOC-sensitive conditions, but close to the transitional regime. The standard modeling scenario over-predicted the peak O3 and O3/NOy slope; these results suggested that the VOC in the current emission inventory might be too high. Modeled CO/NOy and VOC/NOy ratios obtained with the current emission inventory were also significantly higher than those observed from morning urban flights, with CO concentrations over-predicted by 80% and the total VOC reactivity over-predicted by 30%. Reducing the VOC emissions by 30% improved model performance for these parameters. In the last study, the effects of using high resolution (1 km) meteorological and emissions inputs to photochemical simulations of O3 were investigated. Results showed that using high resolution meteorological input alone had a larger impact on the position and peak levels of the O3 plume, with substantial increases in O3 concentrations at places where complex terrain plays an important role. Using high resolution emissions tended to affect small-scale features in O3 concentration patterns mainly within the urban area.
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Details
- Title
- Testing ozone sensitivities using process analysis, chemical indicators, and very fine scale modeling with CMAQ in the Pacific Northwest
- Creators
- Ying Xie
- Contributors
- Brian Lamb (Chair)B Thomas Jobson (Committee Member) - Washington State University, Department of Civil and Environmental EngineeringJeff Arnold (Committee Member)Halvor H Westberg (Committee Member)
- Awarding Institution
- Washington State University
- Academic Unit
- Department of Civil and Environmental Engineering
- Theses and Dissertations
- Doctor of Philosophy (PhD), Washington State University
- Publisher
- Washington State University
- Number of pages
- 155
- Identifiers
- 99901055031401842
- Language
- English
- Resource Type
- Dissertation