RELATIONSHIP OF AIR-QUALITY INDICATORS AND SYNOPTIC-SCALE CIRCULATIONAT 850 HPA OVER ATHENS DURING 1983-1995

The daily relationship between synoptic circulation in the lower tropo sphere and air quality conditions is demonstrated over the Athens Metr opolitan Area (AMA) for the period between 1983 and 1995. This approac h utilises eight distinct synoptic categories at the isobaric level of 850 hPa and air quality indicators with respect to O-3, NO2, CO, SO2 and black smoke (BS). It is demonstrated that high concentrations of p hotochemical pollutants and SO2 are closely related to the synoptic sc ale circulation while CO and BS show a weaker correlation. The most fa vourable synoptic pattern for the accumulation of high concentrations is the open anticyclonic circulation and for the occurrence of extreme events the closed anticyclone. NO2 and BS present the highest frequen cy of severe events. The seasonal analysis reveals that the bad and ex treme air quality conditions due to O-3 and NO2 prevail in the warm se ason while during the cold season CO and SO2 events prevail. The synop tic category representing a combination of high and low pressure syste ms, commonly associated with an intense wind flow over the Aegean Sea in the warm period, seems to favour the accumulation of photochemical pollutants, especially O-3, over the AMA. The converse relationship wa s found for the SO2 case. During cold periods, the synoptic category c haracterised by 'zonal flow' seems to favour the development of bad co nditions for NO2 and particularly CO.