Journal cover Journal topic
Atmospheric Chemistry and Physics An interactive open-access journal of the European Geosciences Union
Atmos. Chem. Phys., 17, 11273-11292, 2017
https://doi.org/10.5194/acp-17-11273-2017
© Author(s) 2017. This work is distributed under
the Creative Commons Attribution 3.0 License.
Research article
25 Sep 2017
Higher measured than modeled ozone production at increased NOx levels in the Colorado Front Range
Bianca C. Baier1,a,b, William H. Brune1, David O. Miller1, Donald Blake2, Russell Long3, Armin Wisthaler4,5, Christopher Cantrell6, Alan Fried7, Brian Heikes8, Steven Brown9,10, Erin McDuffie9,10,11, Frank Flocke12, Eric Apel12, Lisa Kaser12, and Andrew Weinheimer12 1Department of Meteorology and Atmospheric Science, The Pennsylvania State University, University Park, PA, USA
2School of Physical Sciences, University of California, Irvine, CA, USA
3US EPA National Exposure Research Lab, Research Triangle Park, NC, USA
4Institute of Ion Physics and Applied Physics, University of Innsbruck, Innsbruck, Austria
5Department of Chemistry, University of Oslo, Oslo, Norway
6Department of Atmospheric and Oceanic Sciences, University of Colorado Boulder, Boulder, CO, USA
7INSTAAR, University of Colorado Boulder, Boulder, CO, USA
8Graduate School of Oceanography, University of Rhode Island, Kingston, RI, USA
9Chemical Sciences Division, NOAA Earth System Research Laboratory, Boulder, CO, USA
10Department of Chemistry and Biochemistry, University of Colorado Boulder, Boulder, CO, USA
11Cooperative Institute for Research in Environmental Sciences, University of Colorado Boulder, Boulder, CO, USA
12Atmospheric Chemistry Observations and Modeling Laboratory, National Center for Atmospheric Research, Boulder, CO, USA
anow at: Cooperative Institute for Research in Environmental Sciences, University of Colorado Boulder, Boulder, CO, USA
bnow at: Global Monitoring Division, NOAA Earth System Research Laboratory, Boulder, CO, USA
Abstract. Chemical models must correctly calculate the ozone formation rate, P(O3), to accurately predict ozone levels and to test mitigation strategies. However, air quality models can have large uncertainties in P(O3) calculations, which can create uncertainties in ozone forecasts, especially during the summertime when P(O3) is high. One way to test mechanisms is to compare modeled P(O3) to direct measurements. During summer 2014, the Measurement of Ozone Production Sensor (MOPS) directly measured net P(O3) in Golden, CO, approximately 25 km west of Denver along the Colorado Front Range. Net P(O3) was compared to rates calculated by a photochemical box model that was constrained by measurements of other chemical species and that used a lumped chemical mechanism and a more explicit one. Median observed P(O3) was up to a factor of 2 higher than that modeled during early morning hours when nitric oxide (NO) levels were high and was similar to modeled P(O3) for the rest of the day. While all interferences and offsets in this new method are not fully understood, simulations of these possible uncertainties cannot explain the observed P(O3) behavior. Modeled and measured P(O3) and peroxy radical (HO2 and RO2) discrepancies observed here are similar to those presented in prior studies. While a missing atmospheric organic peroxy radical source from volatile organic compounds co-emitted with NO could be one plausible solution to the P(O3) discrepancy, such a source has not been identified and does not fully explain the peroxy radical model–data mismatch. If the MOPS accurately depicts atmospheric P(O3), then these results would imply that P(O3) in Golden, CO, would be NOx-sensitive for more of the day than what is calculated by models, extending the NOx-sensitive P(O3) regime from the afternoon further into the morning. These results could affect ozone reduction strategies for the region surrounding Golden and possibly other areas that do not comply with national ozone regulations. Thus, it is important to continue the development of this direct ozone measurement technique to understand P(O3), especially under high-NOx regimes.

Citation: Baier, B. C., Brune, W. H., Miller, D. O., Blake, D., Long, R., Wisthaler, A., Cantrell, C., Fried, A., Heikes, B., Brown, S., McDuffie, E., Flocke, F., Apel, E., Kaser, L., and Weinheimer, A.: Higher measured than modeled ozone production at increased NOx levels in the Colorado Front Range, Atmos. Chem. Phys., 17, 11273-11292, https://doi.org/10.5194/acp-17-11273-2017, 2017.
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Short summary
Ozone production rates were measured using the Measurement of Ozone Production Sensor (MOPS). Measurements are compared to modeled ozone production rates using two different chemical mechanisms. At high nitric oxide levels, observed rates are higher than those modeled, prompting the need to revisit current model photochemistry. These direct measurements can add to our understanding of the ozone chemistry within air quality models and can be used to guide government regulatory strategies.
Ozone production rates were measured using the Measurement of Ozone Production Sensor (MOPS)....
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