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JOURNAL OF GEOPHYSICAL RESEARCH, VOL. 108, NO. D19, 4604, doi:10.1029/2002JD003054, 2003

Nonmethane hydrocarbons and ozone in three rural southeast United States national parks: A model sensitivity analysis and comparison to measurements

Daiwen Kang

Department of Marine, Earth, and Atmospheric Sciences, North Carolina State University, Raleigh, North Carolina, USA

Viney P. Aneja

Department of Marine, Earth, and Atmospheric Sciences, North Carolina State University, Raleigh, North Carolina, USA

Rohit Mathur

Carolina Environmental Program, University of North Carolina, Chapel Hill, North Carolina, USA

John D. Ray

Air Resources Division, National Park Service, Denver, Colorado, USA

Abstract

A detailed modeling analysis is conducted focusing on nonmethane hydrocarbons and ozone in three southeast United States national parks for a 15-day time period (14–29 July 1995) characterized by high O₃ surface concentrations. The three national parks are Smoky Mountains National Park (GRSM), Mammoth Cave National Park (MACA), and Shenandoah National Park (SHEN), Big Meadows. A base emission scenario and eight variant predictions are analyzed, and predictions are compared with data observed at the three locations for the same time period. Model-predicted concentrations are higher than observed values for O₃ (with a cutoff of 40 ppbv) by 3.0% at GRSM, 19.1% at MACA, and 9.0% at SHEN (mean normalized bias error). They are very similar to observations for overall mean ozone concentrations at GRSM and SHEN. They generally agree (the same order of magnitude) with observed values for lumped paraffin compounds but are an order of magnitude lower for other species (isoprene, ethene, surrogate olefin, surrogate toluene, and surrogate xylene). Model sensitivity analyses here indicate that each location differs in terms of volatile organic compound (VOC) capacity to produce O₃, but a maximum VOC capacity point (MVCP) exists at all locations that changes the influence of VOCs on O₃ from net production to production suppression. Analysis of individual model processes shows that more than 50% of daytime O₃ concentrations at the high-elevation rural locations (GRSM and SHEN) are transported from other areas; local chemistry is the second largest O₃ contributor. At the low-elevation location (MACA), about 80% of daytime O₃ is produced by local chemistry and 20% is transported from other areas. Local emissions (67–95%) are predominantly responsible for VOCs at all locations, the rest coming from transport. Chemistry processes are responsible for about 50% removal of VOCs for all locations; less than 10% are lost to surface deposition and the rest are exported to other areas. Metrics, such as VOC potential for O₃ production (VPOP), which links the chemistry processes of both O₃ and VOCs and MVCP, are devised to measure the different characteristics of O₃ production and VOCs. The values of the defined metrics are mapped for the entire modeling domain. Implications of this model exercise in understanding O₃ production are analyzed and discussed. Even though this study was focused on three United States national parks, the research results and conclusions may be applicable to other or to similar rural environments in the southeast United States.

Received 18 October 2002; accepted 24 July 2003; published 8 October 2003.

Index Terms: 0345 Atmospheric Composition and Structure: Pollution—urban and regional (0305); 0368 Atmospheric Composition and Structure: Troposphere—constituent transport and chemistry; 0365 Atmospheric Composition and Structure: Troposphere—composition and chemistry.

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Citation: Kang, D., V. P. Aneja, R. Mathur, and J. D. Ray (2003), Nonmethane hydrocarbons and ozone in three rural southeast United States national parks: A model sensitivity analysis and comparison to measurements, J. Geophys. Res., 108(D19), 4604, doi:10.1029/2002JD003054.

Copyright 2003 by the American Geophysical Union.