We explore the ability of a space-time model to decompose the 8-hour ozone concentration on a given day at a given site into the parts attributable to local emissions and regional transport, and ultimately to assess the efficacy of past and future emission control programs. We model ozone as created plus transported ozone plus an error term that has a seasonally varying spatial covariance. The created component uses atmospheric chemistry results to express ozone created on a given day at a given site as a function of the observed NOx concentration, the latent VOC concentration, and temperature. The ozone transported to a given day at a given site is expressed as a weighted average of the ozone observed at all sites on the previous day, where the weights are a function of wind speed and direction that appropriately distribute weight across redundant information. The latent VOC process model has a mean trend that includes emissions from various source types, temperature, a workday indicator variable, and an error term that has a seasonally varying spatial covariance. We fit the model using likelihood methods, and we compare our predictions to observations from a withheld dataset and to those predictions of CMAQ, the deterministic model used by EPA to assess emission control programs. We find that the model predictions based on the mean trend and the random deviations from this mean outperform CMAQ predictions according to multiple criteria, but predictions based on the mean trend alone underperform CMAQ predictions.
| Identifer | oai:union.ndltd.org:NCSU/oai:NCSU:etd-08092007-123658 |
| Date | 20 August 2007 |
| Creators | Nail, Amy Jeanette |
| Contributors | John F. Monahan, Jacqueline M. Hughes-Oliver |
| Publisher | NCSU |
| Source Sets | North Carolina State University |
| Language | English |
| Detected Language | English |
| Type | text |
| Format | application/pdf |
| Source | http://www.lib.ncsu.edu/theses/available/etd-08092007-123658/ |
| Rights | unrestricted, I hereby certify that, if appropriate, I have obtained and attached hereto a written permission statement from the owner(s) of each third party copyrighted matter to be included in my thesis, dis sertation, or project report, allowing distribution as specified below. I certify that the version I submitted is the same as that approved by my advisory committee. I hereby grant to NC State University or its agents the non-exclusive license to archive and make accessible, under the conditions specified below, my thesis, dissertation, or project report in whole or in part in all forms of media, now or hereafter known. I retain all other ownership rights to the copyright of the thesis, dissertation or project report. I also retain the right to use in future works (such as articles or books) all or part of this thesis, dissertation, or project report. |
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