Ex-hurricane Ophelia and air quality impacts over Europe in CAMS forecast systems

Within the framework of the Copernicus Atmosphere Monitoring Service (CAMS) element CAMS-84 (Global and regional a posteriori evaluation and quality assurance), we analyze and evaluate the performance of CAMS forecast systems during the passage of ex-hurricane Ophelia in mid-October 2017, carrying Saharan dust and Iberian fire smoke over several Western European regions. To this end, day-1 forecasts from CAMS-global (ECMWF Integrated Forecast System; IFS) and CAMS-regional (ensemble of seven regional air quality models) products are compared against satellite retrievals (MODIS/Terra and Aqua, CALIPSO) and ground-based measurements. The analysis indicates that dust and smoke are injected into the warm sector of Ophelia, lying in the vicinity of the warm and cold front, respectively, gradually affecting the air quality and atmospheric composition over France, the Netherlands and Great Britain. The distinct pattern of enhanced aerosol optical depth (AOD) over Western coastal Europe seen in satellite retrievals is well reproduced by the CAMS near-real time forecast. The observed implications for air quality (PM10 and PM2.5) are satisfactorily forecasted in qualitative terms by both CAMS-global and CAMS-regional systems, while in quantitative terms, the CAMS-regional system exhibits a better performance in predicting surface PM concentrations (higher correlation and lower bias) compared to the global.