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

L. Kaser, E. G. Patton, G. G. Pfister, A. J. Weinheimer, D. D. Montzka, F. Flocke, A. M. Thompson, R. M. Stauffer, H. S. Halliday

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Ozone concentrations at the Earth’s surface are controlled by meteorological and chemical processes and are a function of advection, entrainment, deposition, and net chemical production/loss. The relative contributions of these processes vary in time and space. Understanding the relative importance of these processes controlling surface ozone concentrations is an essential component for designing effective regulatory strategies. Here we focus on the diurnal cycle of entrainment through atmospheric boundary layer (ABL) growth in the Colorado Front Range. Aircraft soundings and surface observations collected in July/August 2014 during the 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) campaigns and equivalent data simulated by a regional chemical transport model are analyzed. Entrainment through ABL growth is most important in the early morning, fumigating the surface at a rate of ~5 ppbv/h. The fumigation effect weakens near noon and changes sign to become a small dilution effect in the afternoon on the order of 1 ppbv/h. The chemical transport model WRF-Chem (Weather Research and Forecasting Model with chemistry) underestimates ozone at all altitudes during this study on the order of 10–15 ppbv. The entrainment through ABL growth is overestimated by the model in the order of 0.6–0.8 ppbv/h. This results from differences in boundary layer growth in the morning and ozone concentration jump across the ABL top in the afternoon. This implicates stronger modeled fumigation in the morning and weaker modeled dilution after 11:00 LT.

Original languageEnglish (US)
Pages (from-to)6075-6093
Number of pages19
JournalJournal of Geophysical Research
Issue number11
StatePublished - 2017

All Science Journal Classification (ASJC) codes

  • Forestry
  • Aquatic Science
  • Soil Science
  • Water Science and Technology
  • Earth-Surface Processes
  • Geochemistry and Petrology
  • Geophysics
  • Oceanography
  • Palaeontology
  • Ecology
  • Space and Planetary Science
  • Earth and Planetary Sciences (miscellaneous)
  • Atmospheric Science


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