The influence of synoptic-scale circulations on air quality is an area of increasing interest to air quality management. Tehran has long been ranked as one of the world’s most polluted cities. In order to determine the impact of atmospheric circulation patterns on the air pollution, the average daily concentration measurement of Pollution Standard Index (PSI) during 2002 to 2007 is used. The results showed five different circulation patterns result in extreme value of pollution in Tehran. Each synoptic pattern dictates a distinctive air mass affecting concentration and subsidence conditions. The highest value of air pollution observed during the extension of the Azores High pressure over Tehran, covered by a strong ridge on the upper level in 850 and 500 hPa and accompanied by a low thermal pressure in the surface over the Pakistan and Iran
