Higher measured than modeled ozone production at increased NO<sub><i>x</i></sub> levels in the Colorado Front Range

Abstract

Abstract. Chemical models must correctly calculate the ozone formation rate, P(O 3 ), to accurately predict ozone levels and to test mitigation strategies. However, air quality models can have large uncertainties in P(O 3 ) calculations, which can create uncertainties in ozone forecasts, especially during the summertime when P(O 3 ) is high. One way to test mechanisms is to compare modeled P(O 3 ) to direct measurements. During summer 2014, the Measurement of Ozone Production Sensor (MOPS) directly measured net P(O 3 ) in Golden, CO, approximately 25 km west of Denver along the Colorado Front Range. Net P(O 3 ) 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(O 3 ) 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(O 3 ) 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(O 3 ) behavior. Modeled and measured P(O 3 ) and peroxy radical (HO 2 and RO 2 ) discrepancies observed here are similar to those presented in prior studies. While a missing atmospheric organic peroxy radical source from volatile organic compounds coemitted with NO could be one plausible solution to the P(O 3 ) 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(O 3 ), then these results would imply that P(O 3 ) in Golden, CO, would be NO x -sensitive for more of the day than what is calculated by models, extending the NO x -sensitive P(O 3 ) regime from the afternoon further into the morning. These results couldPublished by Copernicus Publications on behalf of the European Geosciences Union. 11274 B. C. Baier et al.: Higher measured than modeled ozone production 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(O 3 ), especially under high-NO x regimes.

Wintertime photochemistry in Beijing: Observations of RO<sub>x</sub> radical concentrations in the North China Plain during the BEST-ONE campaign

“…rate during pollution episodes. Similarly, ozone production rates that were directly measured in cities in the US were significantly higher than model calculations for high NO x regimes (Baier et al, 2017;Brune et al, 2016;Cazorla et al, 2012).…”

Atmospheric oxidation in the presence of clouds during the Deep Convective Clouds and Chemistry (DC3) study

“…The photolysis frequency measurements are particularly critical for DC3 because of all the time spent flying around clouds and in the deep convection anvil. A list of these measurements is given in Table 1 and is summarized in Barth et al (2015Barth et al ( , 2016 and Pollack et al (2016). The list of measured chemical species includes CO, CH 4 , N 2 O, NO, NO 2 , O 3 , organic nitrates, alkanes, alkenes, aromatics, aldehydes, alcohols, and peroxides.…”

“…2 Measurement and modeling methods 2.1 The DC3 study Barth et al (2015) provide a detailed description of the objectives, strategy, locations, instrument payloads, and modeling for DC3. DC3 was designed to quantify the link between the properties of deep convective clouds and changes in chemical composition in the troposphere.…”

“…DC3 involved several heavily instrumented aircraft, ground-based dual Doppler radar, lightning mapping arrays, and satellites (Barth et al, 2015). Studies were generally focused on areas in Colorado, Texas/Oklahoma, and Alabama that had dual Doppler radar coverage to quantify cloud properties.…”

The effect of entrainment through atmospheric boundary layer growth on observed and modeled surface ozone in the Colorado Front Range

“…During their 19 September 1979 case study, they report an ozone production rate of 5.1 ppbv/h (2.42 ng m −3 s −1 ) between 10:00 and 12:00 LT over the Colorado Front Range. During DISCOVER‐AQ/FRAPPÉ (Deriving Information on Surface conditions from Column and Vertically Resolved Observations Relevant to Air Quality/Front Range Air Pollution and Photochemistry Éxperiment), Baier et al [] report a measured median ozone production in Golden, CO of 5–10 ppbv/h between 10:00 and 12:00 LT. Many investigators have followed the strategy of Lenschow et al [] to measure all but one term in the budget and infer the residual budget term [e.g., Conley et al , ; Trousdell et al , ].…”