TY - JOUR
T1 - Higher measured than modeled ozone production at increased NOx levels in the Colorado Front Range
AU - Baier, Bianca C.
AU - Brune, William H.
AU - Miller, David O.
AU - Blake, Donald
AU - Long, Russell
AU - Wisthaler, Armin
AU - Cantrell, Christopher
AU - Fried, Alan
AU - Heikes, Brian
AU - Brown, Steven
AU - McDuffie, Erin
AU - Flocke, Frank
AU - Apel, Eric
AU - Kaser, Lisa
AU - Weinheimer, Andrew
N1 - Funding Information:
Acknowledgements. We gratefully acknowledge the entire DISCOVER-AQ and FRAPPÉ teams for the collection of ground and airborne measurement data in this work. We kindly acknowledge Ronald Cohen for the provision of data used in these model studies. PTR-ToF-MS measurements during DISCOVER-AQ were carried out by Philipp Eichler, Tomas Mikoviny, and Markus Müller and were supported by the Austrian Federal Ministry for Transport, Innovation, and Technology (bmvit) through the Austrian Space Applications Programme (ASAP) of the Austrian Research Promotion Agency (FFG). We thank Glenn Wolfe for provision of and help with the MCM model framework, Wendy Go-liff for the provision of RACM2, and Joel Thornton for thoughtful discussions. We also thank the two anonymous reviewers for their useful comments. For the use of the web version of the HYSPLIT model (http://www.ready.noaa.gov), we acknowledge the NOAA Air Resources Laboratory. This work was funded by NASA grants NNX14AR83G and NNX12AB84G.
Publisher Copyright:
© 2017 Author(s).
PY - 2017/9/25
Y1 - 2017/9/25
N2 - 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.
AB - 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.
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U2 - 10.5194/acp-17-11273-2017
DO - 10.5194/acp-17-11273-2017
M3 - Article
AN - SCOPUS:85029918007
VL - 17
SP - 11273
EP - 11292
JO - Atmospheric Chemistry and Physics
JF - Atmospheric Chemistry and Physics
SN - 1680-7316
IS - 18
ER -