WRF-Chem Modeling of Summertime Air Pollution in the Northern Great Plains: Chemistry and Aerosol Mechanism Intercomparison

Oil and gas production in the Bakken region increased dramatically during the past decade. A WRF-Chem modeling study of the Northern Great Plains was conducted for a July 2010 baseline scenario prior to the largest of these production increases. Simulations using the RACM-MADE/SORGAM, CBMZ-MOSAIC, and MOZART-MOSAIC chemistry-aerosol mechanisms were compared to each other and against ground level observations. All three gas-aerosol modules produced similar prediction results for O3, and NO2, with moderate correlation to hourly measurements and monthly average values overpredicted by 20% for O3 and underpredicted by 5% for NO2. Monthly average PM2.5 concentrations were relatively accurate, but correlation to hourly measurements was very low and PM2.5 subspecies exhibited high variability with a mix of over and underpredictions depending on the mechanism. Pollutant concentrations were relatively low across the mostly rural study domain, especially in the Bakken region. Results from this work can be used as a basis of comparison for studies of more recent time periods that include increased oil and gas-related emissions.