WRF-Chem Modeling of Lake Michigan Summertime Ozone Air Quality: Optimization of Meteorology and Its Impact on Air Quality Forecasts

Coastal environments with substantial ozone precursor emissions present an air quality management challenge, in part because of complex wind patterns and shallow stable boundary layers associated with temperature and pressure gradients at the land-water boundary. Both urban and rural regions around Lake Michigan have persistently recorded high ozone concentrations in exceedance of the National Ambient Air Quality Standards (NAAQS). High precursor emissions from large transport, urban, and industrial sources in upwind parts of the Lake Michigan can contribute the high ozone events around the lake. Complex meteorology associated with the land-water interface, particularly in the late spring and early summer when the lake is substantially colder than the surrounding land usually creates an ideal condition for ozone formation over the lake and transport of ozone to the land around the lake.

In this study, we assessed the performance of high-resolution (4km x 4km) Weather Research and Forecasting with Chemistry (WRF-Chem) simulation with National Emission Inventory (NEI-2011) in capturing meteorology and transport of ozone precursors and ozone formation. Measurements used in this study include airborne and ground-based measurements from the Lake Michigan Ozone Study (LMOS 2017), GEOS-16 data processed by Clouds from AVHRR Extended System (CLAVR-x), and MODIS aqua visible images. Model successfully captured the ozone concentration trends and diurnal variability but underestimated the daily maximum ozone concentrations. Model comparison with MODIS Aqua visible images and vertical wind profiles from two stations along the west shore show that the model simulates the lake breeze in-land penetration and timing fairly well. However, it did not resolve the finer scale shallow lake breeze events. The sensitivity of meteorological skill and ozone prediction skill to aspects of the WRF-Chem configuration was tested. Significant improvement in meteorology and ozone was obtained from use of the High-Resolution Rapid Refresh (HRRR) model as initial and boundary condition, the Noah land surface model, and the updated WRF-Chem TUV photolysis option.