عنوان مقاله [English]
In this research, first, the pollutant concentration data was obtained from the air quality control company of Tehran province. Then, a thermodynamic diagram (SKEW-T) was drawn for the vertical survey of the atmosphere using RAOB software and atmospheric data above Mehrabad station. In order to investigate the atmospheric circulations, the corresponding maps were drawn in the Grads software using the database of the European Mesoscale Center (ECMWF). In this research, first, the seasonal trend and the number of contaminated days in the period of 2016-2018 were extracted and analyzed. The findings show a decreasing trend in the concentration of pollutants such as SO2, CO, O3, 2.5 PM and an increasing trend in the concentration of 10 PM and NO2 during the studied period; Then, by determining the days with very intense and pervasive pollution, visual interpretation of the selected samples for each season was done. In the winter and spring seasons, with the influence of the high-pressure cold migrant system on the northern half of Iran, on the surface of the earth and in the middle levels of the Wardspehr, a ridge is drawn from the land of Arabia and Iraq, and according to the high pressure on the surface of the earth, the prevailing conditions at the time of the occurrence of severe pollution and It has been pervasive. In the summer and autumn seasons, it is the same with the establishment of high pressure over the Caspian and the northern belt of the country and the expansion of the low pressure of Pakistan to the southern areas of Alborz and in the middle levels of the Vardspehr with the influence of the shallow trough associated with the low altitude of northern Russia over the research area by creating conditions The calm wind and the decrease in the depth of the boundary layer have provided suitable conditions for increasing the potential of air pollution in Tehran province.