George K. Georgiou, The Cyprus Institute, Cyprus

We evaluate the skill of the regional coupled meteorology-atmospheric chemistry WRF/Chem model to perform daily, 3-day air quality forecasts over the Eastern Mediterranean, focusing on Cyprus. Natural (dust, sea-salt, biogenic) emissions are calculated online, while anthropogenic emissions are based on the EDGAR-HTAP global emission inventory. A high spatial (1km) and temporal (hourly) anthropogenic emission inventory is used for the island of Cyprus in the innermost domain. The model skill in forecasting the concentrations of atmospheric pollutants is evaluated using measurements from a network of nine ground stations in Cyprus and compared with the forecasting skill of the EU Copernicus Atmosphere Monitoring Service - CAMS. The WRF/Chem model forecasts surface temperature, pressure, and wind speed accurately, with minor differences in 10m wind speed between model and observations at coastal and mountainous stations attributed to limitations in the representation of the complex topography. Compared to CAMS, the WRF/Chem model predicts with higher accuracy the NO2 mixing ratios at the residential site with a normalized mean bias of 7% during winter and -44% during summer, whereas the corresponding biases for CAMS are -81% and -84%. Due to the high temporal resolution of the anthropogenic emission inventory, the WRF/Chem model captures more accurately the diurnal profiles of NO2 and O3 mixing ratios at the residential site. Background PM2.5 concentrations influenced by long-range transport are overestimated by the WRF/Chem model during winter NMB = 54% whereas the corresponding NMB for CAMS is 11%. Our results support the adoption of regional, on-line coupled air quality models over chemical transport models for real-time air quality forecasts.