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Rapid photochemical production of ozone at high concentrations in a rural site during winter


Ozone is an air pollutant that can cause severe respiratory health effects. Photochemical ozone production near the Earth’s surface is considered a summertime, urban phenomenon1,2,3, where hourly average ozone concentrations can exceed 150 p.p.b., compared with background values of about 50 p.p.b., and wintertime ozone concentrations in the US are usually in the range of 35–50 p.p.b. (refs 1, 2, 3). Here we report rapid, diurnal photochemical production of ozone during air temperatures as low as −17 C, in the rural Upper Green River Basin, Wyoming, in the vicinity of the Jonah–Pinedale Anticline natural gas field. We find that hourly average ozone concentrations rise from 10–30 p.p.b. at night to more than 140 p.p.b. shortly after solar noon, under the influence of a stagnant, high-pressure system that promotes cold temperatures, low wind speeds and limited cloudiness. Under these conditions, an intense, shallow temperature inversion develops in the lowest 100 m of the atmosphere, which traps high concentrations of ozone precursors at night. During daytime, photolytic ozone production then leads to the observed high concentrations. We suggest that similar ozone production during wintertime is probably occurring around the world under comparable industrial and meteorological conditions.

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Figure 1: Hourly average solar radiation, ozone, NOx and temperature data for the Jonah air-quality-monitoring site, 18–25 February 2008.
Figure 2: Ozonesonde profile 10 km north of the gas field showing ozone and temperature profiles, surface to 2,600 m, 21 February 2008.


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This research was supported by the NOAA, Earth System Research Laboratory, Boulder, Colorado. Data were provided by the Wyoming Department of Environmental Quality, Cheyenne, Wyoming. P. J. Crutzen, Max-Planck Institute, Mainz, Germany, and D. D. Parrish and J. A. deGouw, NOAA Earth System Research Laboratory, Boulder, Colorado, provided helpful suggestions on ozone formation chemistry.

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R.C.S., S.J.O., R.R.N., J.V.M. and A.B.W. conducted the data analysis; J.V.M. assisted in field data collection and ran the TUV model; M.S.E. brought the ozone-production phenomenon to our attention and facilitated access to the data. Conclusions expressed should be considered those of the NOAA authors.

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Correspondence to Russell C. Schnell.

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Schnell, R., Oltmans, S., Neely, R. et al. Rapid photochemical production of ozone at high concentrations in a rural site during winter. Nature Geosci 2, 120–122 (2009).

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