Thesis
Evaluating the AIRPACT-4 air quality model for wintertime conditions in the Yakima Valley, and refining the treatment of residential wood combustion emissions
Washington State University
Master of Science (MS), Washington State University
2015
Handle:
https://hdl.handle.net/2376/104987
Abstract
In January 2013, researchers at Washington State University and Central Washington University performed the Yakima Air Wintertime Nitrate Study (YAWNS) in order to obtain a better understanding of the elevated PM2.5 and nitrate levels in the Yakima Valley. The YAWNS measurements provided an extensive data base that was used to evaluate the AIRPACT-4 air quality forecast system during stagnant, wintertime conditions. The data show significant differences in the daily pollutant concentration patterns for clear sky stagnant conditions vs. cloudy stagnant conditions, when it appears low clouds promote significant vertical mixing and secondary aerosol production. Results from several different model configurations are compared to the available observations. These comparisons focus on the ability of the modeling system to capture the very distinct concentration patterns that occur in clear sky vs. cloudy conditions. The emission inventory for Yakima is then evaluated using source attribution for mobile sources and residential woodstove emissions. Based upon both observed source contributions and model results, residential wood combustion (RWC) is shown to be a prominent source of wintertime PM2.5 in the Yakima Valley. However, the numerous uncertainties in compiling wood stove emissions limit the accuracy of wintertime air quality forecasts in the region. The latter portion of this study expands the scope to the entire Pacific Northwest for testing a forecast-mode temperature adjustment to RWC emissions within the AIRPACT-4 model. The temperature-adjustment experiment failed to significantly improve AIRPACT-4 PM2.5 forecasting, but highlighted the more fundamental limitation of precise spatial allocation of RWC emissions. Accordingly, a variety of RWC spatial surrogates are tested throughout the AIRPACT domain. Results indicate the best approach to improving RWC emissions processing, and subsequent wintertime PM2.5 modeling, is the application of an aggregate spatial surrogate for woodstove emissions. In the Pacific Northwest, a RWC spatial surrogate blending maps of forest coverage and rural population helped ease the tendency to over-predict wintertime PM2.5 in many populated urban areas, while the census data for population using primary wood heating, though outdated, continued to be most representative of wood burning emissions in most of the rural and agricultural sectors of the domain.
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Details
- Title
- Evaluating the AIRPACT-4 air quality model for wintertime conditions in the Yakima Valley, and refining the treatment of residential wood combustion emissions
- Creators
- Drew Ansel Polley
- Contributors
- Brian Lamb (Degree Supervisor)
- Awarding Institution
- Washington State University
- Academic Unit
- Civil and Environmental Engineering, Department of
- Theses and Dissertations
- Master of Science (MS), Washington State University
- Publisher
- Washington State University; [Pullman, Washington] :
- Identifiers
- 99900525371401842
- Language
- English
- Resource Type
- Thesis