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Volume 15, issue 9
Atmos. Chem. Phys., 15, 5109–5122, 2015
https://doi.org/10.5194/acp-15-5109-2015
© Author(s) 2015. This work is distributed under
the Creative Commons Attribution 3.0 License.
Atmos. Chem. Phys., 15, 5109–5122, 2015
https://doi.org/10.5194/acp-15-5109-2015
© Author(s) 2015. This work is distributed under
the Creative Commons Attribution 3.0 License.

Research article 06 May 2015

Research article | 06 May 2015

Ozone distributions over southern Lake Michigan: comparisons between ferry-based observations, shoreline-based DOAS observations and model forecasts

P. A. Cleary1, N. Fuhrman1, L. Schulz*,2, J. Schafer3, J. Fillingham3, H. Bootsma3, J. McQueen4, Y. Tang4,**, T. Langel5, S. McKeen6, E. J. Williams6,5, and S. S. Brown5 P. A. Cleary et al.
  • 1University of Wisconsin-Eau Claire, Department of Chemistry, 105 Garfield Ave, Eau Claire, WI 54702, USA
  • 2University of Wisconsin-Parkside, 900 Wood Road, Kenosha, WI 53144, USA
  • 3University of Wisconsin-Milwaukee, School of Freshwater Science, 600 E Greenfield Ave, Milwaukee, WI 53204, USA
  • 4National Centers for Environmental Prediction/Environmental Modeling Center, 5830 University Research Court, College Park, MD 20740, USA
  • 5Chemical Sciences Division, NOAA Earth System Research Laboratory, Boulder, CO 80305, USA
  • 6Cooperative Institute for Research in Environmental Sciences, University of Colorado, Boulder, CO 809309, USA
  • *now at: University of Wisconsin-Madison College of Agricultural Life and Sciences, 1450 Linden Drive, Madison, WI 53706, USA
  • **now at Air Resources Laboratory, NOAA, 5830 University Research Court, College Park, MD 20740, USA

Abstract. Air quality forecast models typically predict large summertime ozone abundances over water relative to land in the Great Lakes region. While each state bordering Lake Michigan has dedicated monitoring systems, offshore measurements have been sparse, mainly executed through specific short-term campaigns. This study examines ozone abundances over Lake Michigan as measured on the Lake Express ferry, by shoreline differential optical absorption spectroscopy (DOAS) observations in southeastern Wisconsin and as predicted by the Community Multiscale Air Quality (CMAQ) model. From 2008 to 2009 measurements of O3, SO2, NO2 and formaldehyde were made in the summertime by DOAS at a shoreline site in Kenosha, WI. From 2008 to 2010 measurements of ambient ozone were conducted on the Lake Express, a high-speed ferry that travels between Milwaukee, WI, and Muskegon, MI, up to six times daily from spring to fall. Ferry ozone observations over Lake Michigan were an average of 3.8 ppb higher than those measured at shoreline in Kenosha, with little dependence on position of the ferry or temperature and with greatest differences during evening and night. Concurrent 1–48 h forecasts from the CMAQ model in the upper Midwestern region surrounding Lake Michigan were compared to ferry ozone measurements, shoreline DOAS measurements and Environmental Protection Agency (EPA) station measurements. The bias of the model O3 forecast was computed and evaluated with respect to ferry-based measurements. Trends in the bias with respect to location and time of day were explored showing non-uniformity in model bias over the lake. Model ozone bias was consistently high over the lake in comparison to land-based measurements, with highest biases for 25–48 h after initialization.

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This study examines ozone mixing ratios over Lake Michigan as measured on the Lake Express ferry, by shoreline differential optical absorption spectroscopy (DOAS) observations in southeastern Wisconsin, and as predicted by the Community Multiscale Air Quality (CMAQ) model. Over water, ozone was determined to be an average of 3.8ppb higher than shoreline observations but overpredicted by the CMAQ model by as much as 11-16ppb midday.
This study examines ozone mixing ratios over Lake Michigan as measured on the Lake Express...
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