A study of trend and seasonality of tropospheric NO2 over Iran by using 14 years of OMI data acquisition

Results of a study on tropospheric NO2 over Iran for a 14 years period have been reported. Monthly averages of tropospheric NO2 concentrations recorded by OMI from Oct 2004 to Mar 2018 have been used. A model including a linear and sinusoidal term is applied to study trend and seasonal behavior of NO2 concentrations. Original 0.125 ×0.125 degree data of OMI have been averaged to get 1 ×1 degree resolution to analyze trends. Trend results with 95% confidence level have been reported. In 27 centers of provinces in Iran, real trends have been detected. By using seasonal analysis, mostly polluted months have been determined for these cities. 2 cities experience most pollution in spring, 3 in summer, 2 in autumn and 24 cities in winter. Pollution source type classification shows 24 urban and 3 soil emission cases for the studied cities. Source type determination was impossible in 4 cities by criteria used in this paper.