Meteorology, Emissions, and Grid Resolution: Effects on Discrete and Probabilistic Model Performance

In this study, we analyze the impacts of perturbations in meteorology and emissions and variations in grid resolution on air quality forecast simulations. The meteorological perturbations considered in this study introduce a typical variability of ∼1 °C, 250-500 m, 1 m/s, and 15-30° for temperature, PBL height, wind speed, and wind direction, respectively. The effects of grid resolution are typically smaller and more localized. Results of the air quality simulations show that the perturbations in meteorology tend to have a larger impact on pollutant concentrations than emission perturbations and grid resolution effects. Operational model evaluation results show that the meteorological and grid resolution ensembles impact a wider range of model performance metrics than emission perturbations. Probabilistic model performance was found to vary with exceedance thresholds. The results of this study suggest that meteorological perturbations introduced through ensemble weather forecasts are the most important factor in constructing a model-based O₃ and PM_2.5 ensemble forecasting system.