Modern Urban Living; Air Quality in Two Northern Greek Cities

In this article, we aim to show the capabilities, benefits, as well as restrictions, of three different air quality-related information sources, namely the Sentinel-5Precursor TROPOspheric Monitoring Instrument (TROPOMI) space-born observations, the Multi-Axis Differential Optical Absorption Spectroscopy (MAX-DOAS) ground-based measurements and the LOng Term Ozone Simulation – EURopean Operational Smog (LOTOS-EUROS) chemical transport modelling system simulations. The tropospheric NO2 concentrations between 2018 and 2021 are discussed as air quality indicators for the Greek cities of Thessaloniki and Ioannina. Each dataset was analysed in an autonomous manner and, without disregarding their differences, the common air quality picture that they provide is revealed. All three systems report a clear seasonal pattern, with high NO2 levels during winter-time and lower NO2 levels during summer-time, reflecting the importance of photochemistry in the abatement of this air pollutant. The spatial patterns of the NO2 load also showed, in both space-born observations and model simulations, the undeniable variability of the NO2 load within the urban agglomerations. The diurnal variability was furthermore clearly identified by the ground-based measurements, which also unquestionably revealed a Sunday minimum NO2 load effect, alongside the rest of the sources of air quality information. Within their individual strengths and limitations, the space-born observations, the ground-based measurements and the chemical transport modelling simulations, demonstrate unequivocally their ability to report on the air quality situation in urban locations.