Health-related atmospheric aerosol over an urban hotspot in the Mediterranean: model performance and insights for different urban parameterizations during heat stress periods

Fine aerosol particles (PM2.5) in the mediterranean, urban area of Athens (Gr) during a contemporary year free of anthropogenic activity restrictions (2019) is the focus of this study. The numerical atmospheric model system used (WRF/ Episode-CityChem) can describe the local atmospheric conditions (in 1 km resolution), with additional features to represent the urban canyon pollutant dispersion and local photochemistry in the intra-urban scale (100 m resolution). An extensive evaluation of both models’ performance is assessed through comparisons with in situ measurements from multiple National networks, including the weather station network operated by the METEO unit, and the state-of-the-art air pollution equipment by the Ypatia unit at the National Observatory of Athens, as well as the air quality networks of Panacea-RI and of the Greek State. A multi-parametric comparison against measurements gave useful insights and opportunities for optimization of models’ setup. Indicatively, a series of single day meteorological runs would result in atmospheric (both meteorological and air quality) predictions of similar accuracy than the a sequence of 3-day simulations, saving substantial computational time and human effort. Further, a separate evaluation for precipitation-impacted periods was performed, indicating that both the rainy meteorological conditions and the wet deposition processes do not add deviations between aerosol predictions and observations. A similar calculation and finding are seen for African dust events, suggesting the satisfactory treatment of dust at the regional (CAMS) and local (dispersion of transboundary pollution) level in the southeastern Mediterranean. Deviations in air quality performance for day-night and summer-winter time periods, indicated pathways to optimize the configuration of the model system. Last, the study focuses on limited periods of heat when thermal discomfort is induced to the urban population. During such periods, health risk may become more severe due to high concentrations of PM2.5. The investigation of the differential model performance and aerosol load due to the selection of different urban parameterizations (WRF), is currently under study and will be presented during the conference.