Articles | Volume 16, issue 22
Atmos. Chem. Phys., 16, 14463–14474, 2016
Atmos. Chem. Phys., 16, 14463–14474, 2016

Research article 22 Nov 2016

Research article | 22 Nov 2016

Ozone production and its sensitivity to NOx and VOCs: results from the DISCOVER-AQ field experiment, Houston 2013

Gina M. Mazzuca1, Xinrong Ren1,2, Christopher P. Loughner2,3, Mark Estes4, James H. Crawford5, Kenneth E. Pickering1,6, Andrew J. Weinheimer7, and Russell R. Dickerson1 Gina M. Mazzuca et al.
  • 1Department of Atmospheric and Oceanic Science, University of Maryland, College Park, MD 20742, USA
  • 2Air Resources Laboratory, National Oceanic and Atmospheric Administration, College Park, MD 20740, USA
  • 3Earth System Science Interdisciplinary Center, University of Maryland, College Park, MD 20740, USA
  • 4Texas Commission on Environmental Quality, Austin, TX 78711, USA
  • 5NASA Langley Research Center, Hampton, VA 23681, USA
  • 6NASA Goddard Space Flight Center, Greenbelt, MD 20771, USA
  • 7National Center for Atmospheric Research, Boulder, CO 80307, USA

Abstract. An observation-constrained box model based on the Carbon Bond mechanism, version 5 (CB05), was used to study photochemical processes along the NASA P-3B flight track and spirals over eight surface sites during the September 2013 Houston, Texas deployment of the NASA Deriving Information on Surface Conditions from COlumn and VERtically Resolved Observations Relevant to Air Quality (DISCOVER-AQ) campaign. Data from this campaign provided an opportunity to examine and improve our understanding of atmospheric photochemical oxidation processes related to the formation of secondary air pollutants such as ozone (O3). O3 production and its sensitivity to NOx and volatile organic compounds (VOCs) were calculated at different locations and times of day. Ozone production efficiency (OPE), defined as the ratio of the ozone production rate to the NOx oxidation rate, was calculated using the observations and the simulation results of the box and Community Multiscale Air Quality (CMAQ) models. Correlations of these results with other parameters, such as radical sources and NOx mixing ratio, were also evaluated. It was generally found that O3 production tends to be more VOC-sensitive in the morning along with high ozone production rates, suggesting that control of VOCs may be an effective way to control O3 in Houston. In the afternoon, O3 production was found to be mainly NOx-sensitive with some exceptions. O3 production near major emissions sources such as Deer Park was mostly VOC-sensitive for the entire day, other urban areas near Moody Tower and Channelview were VOC-sensitive or in the transition regime, and areas farther from downtown Houston such as Smith Point and Conroe were mostly NOx-sensitive for the entire day. It was also found that the control of NOx emissions has reduced O3 concentrations over Houston but has led to larger OPE values. The results from this work strengthen our understanding of O3 production; they indicate that controlling NOx emissions will provide air quality benefits over the greater Houston metropolitan area in the long run, but in selected areas controlling VOC emissions will also be beneficial.

Short summary
We used a box model to study the sensitivity of ozone production by different precursors within the Houston metro area during NASA's DISCOVER-AQ air quality field mission in 2013. We constrained the box model to observations from the campaign and to a 3-D model for species that were not measured. By focusing our analysis on different locations and times of day within the metro area, we were able to suggest which ozone precursors, if controlled, would have the greatest impact on ozone reduction.
Final-revised paper