Ozone Trends Across the United States over a Period of Decreasing NOx and VOC Emissions

Simon, Heather; Reff, Adam; Wells, Benjamin B.; Xing, Jia; Frank, N. H.

doi:10.1021/es504514z

Cited by 360 publications

(376 citation statements)

References 24 publications

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“…Of these six sites only three showed an earlier seasonal ozone peak; therefore the seasonal shift in the ozone cycle is not universal for time periods of 21 years or less. Similar shifts in the ozone seasonal cycle have been observed in the continental USA Simon et al, 2015;Bloomer et al, 2010).…”

Section: Changing Ozone -A Brief Historysupporting

confidence: 78%

Tropospheric ozone and its precursors from the urban to the global scale from air quality to short-lived climate forcer

et al. 2015

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Abstract. Ozone holds a certain fascination in atmospheric science. It is ubiquitous in the atmosphere, central to tropospheric oxidation chemistry, yet harmful to human and ecosystem health as well as being an important greenhouse gas. It is not emitted into the atmosphere but is a byproduct of the very oxidation chemistry it largely initiates. Much effort is focused on the reduction of surface levels of ozone owing to its health and vegetation impacts, but recent efforts to achieve reductions in exposure at a country scale have proved difficult to achieve owing to increases in background ozone at the zonal hemispheric scale. There is also a growing realisation that the role of ozone as a short-lived climate pollutant could be important in integrated air quality climate change mitigation. This review examines current understanding of the processes regulating tropospheric ozone at global to local scales from both measurements and models. It takes the view that knowledge across the scales is important for dealing with air quality and climate change in a synergistic manner. The review shows that there remain a number of clear challenges for ozone such as explaining surface trends, incorporating new chemical understanding, ozone-climate coupling, and a better assessment of impacts. There is a clear and present need to treat ozone across the range of scales, a transboundary issue, but with an emphasis on the hemispheric scales. New observational opportunities are offered both by satellites and small sensors that bridge the scales.

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Section: Changing Ozone -A Brief Historysupporting

confidence: 78%

Tropospheric ozone and its precursors from the urban to the global scale from air quality to short-lived climate forcer

et al. 2015

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“…As a result of the decrease in high and increase in low percentiles, there was a narrowing of the range of the near-surface O 3 concentrations over the period. This was also observed in the UK by Jenkin (2008) for 1990 until the early 2000s and in the US by Simon et al (2015) for 1998-2013, both studying urban and regional background measurements across the respective countries. Jenkin (2008) interpreted it as caused by three major influences: (i) increasing hemispheric background, (ii) decreasing severity in high-ozone events arising from the European continent and (iii) decreasing local-scale removal of ozone due the control of NO x emissions.…”

Section: Trend Over the Periodmentioning

confidence: 54%

“…Jenkin (2008) interpreted it as caused by three major influences: (i) increasing hemispheric background, (ii) decreasing severity in high-ozone events arising from the European continent and (iii) decreasing local-scale removal of ozone due the control of NO x emissions. Simon et al (2015) interpreted the US evolution as a response to the substantial decrease in O 3 precursor emissions in the US over the time period. Decreased primary NO emissions results in decreased O 3 titration close to combustion sources, but also reduces local O 3 further away from the emissions sources when there is little photolysis (especially in the winter and during nighttime).…”

Section: Trend Over the Periodmentioning

confidence: 99%

Reanalysis of and attribution to near-surface ozone concentrations in Sweden during 1990–2013

et al. 2017

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Abstract. We have constructed two data sets of hourly resolution reanalyzed near-surface ozone (O 3 ) concentrations for the period 1990-2013 for Sweden. Long-term simulations from a chemistry-transport model (CTM) covering Europe were combined with hourly ozone concentration observations at Swedish and Norwegian background measurement sites using retrospective variational data analysis. The reanalysis data sets show improved performance over the original CTM when compared to independent observations. In one of the reanalyses, we included all available hourly near-surface O 3 observations, whilst in the other we carefully selected time-consistent observations. Based on the second reanalysis we investigated statistical aspects of the distribution of the near-surface O 3 concentrations, focusing on the linear trend over the 24-year period. We show that high nearsurface O 3 concentrations are decreasing and low O 3 concentrations are increasing, which is reflected in observed improvement of many health and vegetation indices (apart from those with a low threshold).Using the CTM we also conducted sensitivity simulations to quantify the causes of the observed change, focusing on three factors: change in hemispheric background concentrations, meteorology and anthropogenic emissions. The rising low concentrations of near-surface O 3 in Sweden are caused by a combination of all three factors, whilst the decrease in the highest O 3 concentrations is caused by European O 3 precursor emissions reductions.While studying the impact of anthropogenic emissions changes, we identified systematic differences in the modeled trend compared to observations that must be caused by incorrect trends in the utilized emissions inventory or by too high sensitivity of our model to emissions changes.

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“…Since the 1990s, a large number of tropospheric ozone (O 3 ) trend analyses have been reported (e.g., Fiore et al, 1998;Chan, 2009;Lefohn et al, 2010;Oltmans et al, 2006Oltmans et al, , 2013Cooper et al, 2012;Simon et al, 2015). These studies have focused on a range of spatial scales from global-intercontinental (e.g., Cooper et al, 2014) to urban (e.g., Los Angeles, CA: Pollack et al, 2013).…”

Section: Introductionmentioning

confidence: 99%

Precursor reductions and ground-level ozone in the Continental United States

Hidy¹,

Blanchard²

2015

Journal of the Air & Waste Management Association

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Numerous papers analyze ground-level ozone (O 3 ) trends since the 1980s, but few have linked O 3 trends with observed changes in nitrogen oxide (NO x ) and volatile organic compound (VOC) emissions and ambient concentrations. This analysis of emissions and ambient measurements examines this linkage across the United States on multiple spatial scales from continental to urban. O 3 concentrations follow the general decreases in both NO x and VOC emissions and ambient concentrations of precursors (nitrogen dioxide, NO 2 ; nonmethane organic compounds, NMOCs). Annual fourth-highest daily peak 8-hr average ozone and annual average or 98th percentile daily maximum hourly NO 2 concentrations show a statistically significant (p < 0.05) linear fit whose slope is less than 1:1 and intercept is in the 30 to >50 ppbv range. This empirical relationship is consistent with current understanding of O 3 photochemistry. The linear O 3 -NO 2 relationships found from our multispatial scale analysis can be used to extrapolate the rate of change of O 3 with projected NO x emission reductions, which suggests that future declines in annual fourth-highest daily average 8-hr maximum O 3 concentrations are unlikely to reach 65 ppbv or lower everywhere in the next decade. Measurements do not indicate increased annual reduction rates in (high) O 3 concentrations beyond the multidecadal precursor proportionality, since aggressive measures for NO x and VOC reduction are in place and have not produced an accelerated O 3 reduction rate beyond that prior to the mid-2000s. Empirically estimated changes in O 3 with emissions suggest that O 3 is less sensitive to precursor reductions than is found by the CAMx (v. 6.1) photochemical model. Options for increasing the rate of O 3 change are limited by photochemical factors, including the increase in NO x sensitivity with time (NMOC/NO x ratio increase), increase in O 3 production efficiency at lower NO x concentrations (higher O 3 /NO y ratio), and the presence of natural NO x and NMOC precursors and background O 3 .Implications: This analysis demonstrates empirical relations between O 3 and precursors based on long term trends in U.S. locations. The results indicate that ground-level O 3 concentrations have responded predictably to reductions in VOC and NO x since the 1980s. The analysis reveals linear relations between the highest O 3 and NO 2 concentrations. Extrapolation of the historic trends to the future with expected continued precursor reductions suggest that achieving the 2014 proposed reduction in the U.S. National Ambient Air Quality Standard to a level between 65 and 70 ppbv is unlikely within the next decade. Comparison of measurements with national results from a regulatory photochemical model, CAMx, v. 6.1, suggests that model predictions are more sensitive to emissions changes than the observations would support.

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Ozone Trends Across the United States over a Period of Decreasing NOx and VOC Emissions

Cited by 360 publications

References 24 publications

Tropospheric ozone and its precursors from the urban to the global scale from air quality to short-lived climate forcer

Tropospheric ozone and its precursors from the urban to the global scale from air quality to short-lived climate forcer

Reanalysis of and attribution to near-surface ozone concentrations in Sweden during 1990–2013

Precursor reductions and ground-level ozone in the Continental United States

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