A NOVEL APPROACH FOR AIR QUALITY TREND STUDIES AND ITS APPLICATION TO EUROPEAN URBAN ENVIRONMENTS

Studying future climatic change effects on atmospheric processes and air quality one should consider the inherent uncertainties in trying to mathematically describe the associated phenomena. When quantifying such processes is more reliable to talk about trends rather than absolute values. Within the objectives of the present study is to provide high space and time resolution concentrations trends for the period 2001-2050, following the moderate Representative Concentration Pathway - RCP4.5, on major air pollutants (PM10, PM2.5, NO2, O3) in Europe, focusing on nine (9) cities i.e. Thessaloniki, Athens, Madrid, Stuttgart, Ljubljana, Brno, Milan, Basel and Copenhagen/Roskilde. To achieve such an objective, a common approach in the past, has been to perform weather and air quality simulations for a complete year but only for a limited number of years. Such an approach has the inherent weakness that the results represent the selected year only and not the neighboring ones due to the high yearly weather variability. The present effort was to come up with a new approach that fulfills the study objectives by introducing proper trend indicators and targeted weather and air quality simulations. Thus, a novel approach based on weather clustering is inaugurated to study climate change effect on air quality levels. The adopted clustering technique has been applied in daily weather data of 50-year period (2001-2050). The clustering exercise results are examined over 5-year periods, instead of one (1) year. The detailed weather data were derived from the Coordinated Regional Climate Downscaling Experiment (CORDEX) provided from the Earth System Grid Federation (ESGF) index nodes. The Regional Climate Model (RCM) INERIS-WRF331F was selected, using the EUR 11 (about 10 km resolution) horizontal domain projection. The detailed atmospheric modeling was performed using WRF-Chem and it has been restricted to cluster representative days in each of the above mentioned 5-years period. The study has provided interesting results on concentrations and heat wave trends revealing among others the correlation between weather patterns with higher heat wave events and elevated O3 concentrations strengthening the hypothesis that the greenhouse effect leads to intensification of the atmospheric photochemical activity