Analysis of NO, NO2, and O3 Between Model Simulations and Ground-Based, Aircraft, and Satellite Observations

Regional air quality model simulations with Community Multiscale Air Quality Modeling System (CMAQ) were evaluated using multiple platforms for a 2-month summer period. In this context, inter-comparisons of the model with available satellite-based observations of NO2, ground-and aircraft-based observations of NO, NO2, NOx, NOy, and O-3 were performed. NO2 comparisons found low biases in CMAQ results when using both ground-and satellite-based observations. Aircraft-based observations, on the other hand, indicated a higher positive bias and error, but the overall NO2 vertical profile was captured well by themodel. The highest correlation was observed with satellite-based NO2 observations indicating that the model and satellite found similar spatial gradients. NO concentrations were underestimated in comparison with both ground- and aircraft-based observations, especially near the surface, indicating the limitations of the model to simulate primary pollutant concentrations at point observations when there are sources nearby. NOy comparisons found positive biases in the model when using both ground-and aircraft-based observations. The main reason for this overestimation was the consistent overestimation of peroxyacyl nitrates (PANs) in CMAQ results. Modeled O-3 concentrations compared well with lowest biases and errors when compared to aircraft-and ground-based observations. The O-3 vertical profile indicated a small positive bias in the model results near the surface similar to the comparison with ground-based observations. However, a negative bias in the model was observed above 2 km. Comparison with aircraft-based observations revealed significant overestimations in PAN and OH concentrations. Overestimation of the modeled OH concentrations is particularly important considering the effect of OH in atmospheric reactions.