A first annual assessment of air quality modeling over Lebanon using WRF/Polyphemus

Air quality is modelled at high resolution over Lebanon (5 × 5 km) and Beirut (1 × 1 km) using the WRF/Polyphemus modeling system for the year 2014. The observation data collected from the recently deployed national air quality monitoring network as well as ground measurement from a long-term campaign are used to evaluate both models performance. Statistical indicators are calculated and compared to a selection of performance criteria from the literature. Accordingly, the modelled results are satisfactory and within the range of the literature for both the meteorological parameters as well as air quality pollutants. For the meteorological model, some biases are observed for the wind components especially during winter, as better statistics are obtained during summer. As for the air quality, the model satisfied commonly used performance criteria for O3 and PM2.5. However, the model underestimates the carbon monoxide values in urban regions and overestimates sulfur dioxide and it appears that these biases results mainly from the emission inventory and the meteorology. Also, EC and OC components of PM_2.5 are evaluated. The results highlight an underestimation of OC, which could relate to the sensitivity of the chemical mechanism to the temperature, the boundary conditions, or the emission inventory.