“Modeled Sensitivity of Tropospheric Ozone to PBL Height in the Great Lakes Region”

High surface ozone concentrations are often observed in the Great Lakes region during the summer season. Distinctive littoral zone meteorology, combined with an abundance of ozone precursor chemicals can result in severe air pollution exceedances. In particular, the east coast of Lake Michigan reports anomalously high surface ozone concentrations compared to the rest of the domain. To better understand the role of the lakes on the production, accumulation, and transport of surface ozone, we present a high resolution modeling case study of a 2012 extreme ozone event over the Great Lakes region. The Weather Research and Forecasting Model coupled with Chemistry (WRF-Chem) is used to simulate this event and investigate the atmospheric processes responsible for the observed ozone concentrations. Results indicate that the shallow daytime planetary boundary layer (PBL) over the lakes is responsible for the unique vertical distribution of ozone, and that the littoral area is highly sensitive to minor changes in PBL height.

Because such research represents the first regional WRF-Chem simulation of its type, this study also includes an evaluation of both NOx input sources from the National Emissions Inventory (NEI-2011), along with model output of ozone concentrations. Overall, the NEI-2011 NOx sources are accurately scaled and WRF-Chem produces reasonably realistic ozone concentrations over the domain when compared to EPA observations. This confirmation, along with the enhanced representation of littoral meteorology effects on ozone accumulation will allow for improved air pollution modeling and ozone air quality forecasts in the Great Lakes region.