Ensemble Air Quality Forecasting: Effects of Perturbations in Meteorology and Emissions

Model-based air quality forecasts are affected by uncertainties in both meteorology and emissions. In this study, we analyze the impacts of these uncertainties on ozone (O3) forecasts over the Northeastern U.S. during a 45 day period in the summer of 2008. The meteorological uncertainty is prescribed through the use of 12 different weather forecasts from a short-range ensemble forecasting system differing in their initial conditions and physics options. To quantify the effects of emission uncertainties, we computed O3 sensitivities towards variations in anthropogenic NOx and VOC emissions using the Direct Decoupled Method (DDM). Results show that the perturbations in meteorology tend to have a larger impact on O3 forecasts than the emission perturbations considered in this study.