Spatial and temporal characteristics of the relationship between air quality status and mesoscale circulation over an urban Mediterranean basin

The objective of this study is to identify and establish the day-by-day relationship between mesoscale circulation and the air quality status over the Metropolitan area of Athens for a period of 13 years and to further investigate its temporal and spatial variability. Eleven distinct mesoscale patterns are identified using a formulated methodology based on surface wind measurements. The air quality conditions are classified into seven distinct classes according to the method of the Air Quality Indicators for five main pollutants namely, O3, NO2, SO2, CO and black smoke (BS). It was found that severe and bad air quality conditions over specific parts of the examined area are associated with the weak mesoscale patterns of southern direction or calm conditions. The good and moderate conditions are established mainly under northerly airflows. The most serious pollution problem favored even by intense northerly flow is attributed to O3 during the warm period in the northern zone. High concentrations of O3, NO2 and SO2 in the warm period are remarkably related to the pure sea breeze circulation, especially in the central and northern zone.