In-depth evaluation of OTAG modeling
- MCNC-North Carolina Supercomputing Center, Research Triangle Park, NC (United States)
The Ozone Transport and Assessment Group (OTAG) photochemical grid modeling analysis was an unprecedented effort, in terms of scope of work and active participants, to quantify the transport of ozone and ozone precursors across the eastern United States. It is expected that the findings of this study will shape the policy of regional pollutant transport for many years. This paper will evaluate the ability of the OTAG modeling system to replicate the pertinent features of the four historical episodes and the attendant examinations of future year control strategies. This paper briefly summarizes the many existing reports investigating OTAG model performance. Based on this thorough review of previous OTAG model evaluation products, the authors focused on two evaluation issues: 1. The need for an evaluation against meteorological and eight-hour ozone data. An assessment of OTAG model mixing heights revealed that the system was improperly compressing mixing depths for most regions for all four episodes. This resulted in part from an inappropriately coarse vertical grid. Also, an evaluation of 8-hour ozone performance in OTAG concluded that model performance was poorer for the longer-term averaging period than for the previously considered 1-hour standard. 2. The need for detailed evaluation against regional ozone transport concepts. By evaluating the OTAG UAM-V modeling against particular concepts of regional ozone formation, the authors uncovered a major concern in the model treatment of ozone precursors. Several key species appear to be improperly conserved in the base case results. This resulted in an increasingly positive surface ozone bias with time. More importantly, the erroneous species accumulations resulted in an overabundance of hydroxyl radicals available for reaction in the latter parts of the OTAG episodes.
- OSTI ID:
- 361981
- Report Number(s):
- CONF-980632--
- Country of Publication:
- United States
- Language:
- English
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