Spatial-temporal assessment of air quality in Rome (Italy) based on anemological clustering

The relationship between atmospheric circulation and air pollution is investigated by analysing in-situ mea-surements collected at four monitoring stations located in the coastal area of central Italy over the period 2014-2020. The study is based on the prior identification of three typical circulation patterns, obtained via the k -mean clustering of surface anemological data. The present analysis explores the relation between atmospheric dynamics and concentrations of nitrogen oxides (NO and NO2), NO2/NOx (NOx = NO + NO2), ozone (O3), and particulate matters (PM2.5 and PM10). When local circulation systems prevail, the best air quality conditions are observed, as the onset of the sea breeze permits clean, marine air masses to be advected to the urban area of Rome. On the other hand, when synoptic winds persistently blow from the northeast, the highest concentrations of atmospheric pollutants are recorded. Finally, when both synoptic and local winds blow from the southeast, the complex anemological regime results in low ventilation and quite poor air quality conditions. The largest dif-ferences among clusters are observed during winter, when the north-easterly winds can persist for more than ten consecutive days, with the enhanced atmospheric stability limiting the development of the mixed layer, causing the increase of ground-level pollutants concentration.