Ozone production in the rural troposphere and the implications for regional and global ozone distributions

Abstract

The relationship between O3 and NOx (NO + NO2) which was measured during summer and winter periods at Niwot Ridge, Colorado, has been analyzed and compared to model calculations. Both model calculations and observations show that the daily O3 production per unit of NOx is greater for lower NOx. Model calculations without nonmethane hydrocarbons (NMHC) tend to underestimate the O3 production rate at NOx higher than 1.5 parts per billion by volume and show the opposite dependence on NOx. The model calculations with NMHC are consistent with the observed data in this regime and demonstrate the importance of NMHC chemistry in the O3 production. In addition, at eight other rural stations with concurrent O3 and NOx measurements in the central and eastern United States the daily O3 increase in summer also agrees with the O3 and NOx relationship predicted by the model. The consistency of the observed and model‐calculated daily summer O3 increase implies that the average O3 production in rural areas can be predicted if NOx is known. The dependence of O3 production rate on NOx deduced in this study provides the basis for a crude estimate of the total O3 production. For the United States an average summer column O3 production of about 1×1012Cm−2S−1 from anthropogenically emitted NOx and NMHC is estimated. This photochemical production is roughly 20 times the average cross‐tropopause O3 flux. Production of O3 from NOx that is emitted from natural sources in the United States is estimated to range from 1.9×1011 to 12×1011 cm−2 s−1, which is somewhat smaller than ozone production from anthropogenic NOx sources. Extrapolation to the entire northern hemisphere shows that in the summer, 3 times as much O3 is generated from natural precursors as those of anthropogenic origin. The winter daily O3 production rate was found to be about 10% of the summer value at the same NOx level. However, because of longer NOx lifetime in the winter, the integrated O3 production over the lifetime of NOx may be comparable to the summer value. Moreover, because the natural NOx sources are substantially smaller in the winter, the wintertime O3 budget in the northern hemisphere should be dominated by ozone production from anthropogenic ozone precursors. The photochemical lifetime of O3 in the winter in the mid‐latitude is approximately 200 days. We propose that this long lifetime allows anthropogenically produced O3 to accumulate and contribute substantially to the observed spring maximum that is usually attributed to stratospheric intrusion. Furthermore, the anthropogenic O3 may be transported not only zonally but also to lower latitudes. Thus the long‐term interannual increase in O3, observed in the winter and spring seasons at Mauna Loa, may be due to the same anthropogenic influences as the similar winter trend observed at Hohenpeissenberg, Germany.

Stratosphere‐troposphere exchange: A review, and what we have learned from STACCATO

“…[21] Intrusions of stratospheric air into the troposphere are rich in O 3 [Danielsen, 1968] and, because of the long chemical lifetime (order of a month) of O 3 in the free troposphere [Liu et al, 1987], contribute substantially to the tropospheric O 3 budget [Fabian and Pruchniewicz, 1977]. During pre-industrial times, when tropospheric O 3 concentrations were lower than today [Volz and Kley, 1988], STT likely made the major contribution to surface O 3 [Levy et al, 1985].…”

Effects of 1997 Indonesian forest fires on tropospheric ozone enhancement, radiative forcing, and temperature change over the Hong Kong region

“…elevating Ha2 relative to OH via the cycle). The reaction of Ha2 with NO followed by photolysis of NO2 will produce atomic oxygen, which readily coinbines with molecular oxygen to form ozone [Liu et al 1987]. Also, note that suppression of OH by high CO will elevate or free up more NOx (NO+NO2) because of less available OH for converting NO2 into the more inert form HNO3.…”

Isoprene and monoterpene emission rate variability: Model evaluations and sensitivity analyses

“…Biogenic and anthropogenic hydrocarbons can influence the chemical composition of the atmosphere by controlling the oxidation capacity of the troposphere [Chameides et al, 1988]. In regions with sufficient levels of oxides of nitrogen and sunlight, this influence can include photochemical production of ozone and peroxides [Liu et al, 1987]. Highly reactive biogenic hydrocarbons play a major role in photochemical oxidant production even when they are present in the atmosphere at concentrations that are much lower than those of anthropogenic hydrocarbons [Chameides et al, 1992].…”