Investigating the role of atmospheric circulation patterns in the severe air pollution in Esfahan

In this study, combinated synoptic analysis method was used to identify the role of atmospheric circulation patterns in the occurrence of severe air pollution in Esfahan. To perform the research, data from air pollution stations, digital atmospheric profile data, and HYSPLIT outputs over a 11-year period (2004-2005) were used. The results show that the highly pollutated days of the city of Esfahan can be explained by the four synoptic patterns. The occurrence of days with extremely severe pollution in Esfahan, rather than being rooted in local factors, is due to the interaction of local conditions with atmospheric circulation at the regional scale. In other words, the city of Esfahan will only experience extremely polluted days when the atmospheric circulation of the atmosphere provides conditions for increased concentrations of pollutants. The main causes of the occurrence of days associated with maximum contamination can be attributed to Subtropical high latitude and its progression to higher latitudes. This circulation system contributes to the occurrence of highly polluted days on most days, either directly or in combination with other atmospheric systems.