Climatology of aerosol types and their vertical distribution over Iran using CALIOP dataset during 2007–2021

Abstract

The present study uses a Lidar-based aerosol type's extinction coefficient (EC) of the Cloud–Aerosol Lidar with Orthogonal Polarization (CALIOP) on the Cloud–Aerosol Lidar and Infrared Pathfinder Satellite Observation (CALIPSO) mission to investigate the spatio-temporal changes in the vertical cross section of aerosols from 2007 to 2021 in Iran. Aerosol characteristics i.e., the EC values (levels) and frequency are presented in a seasonal time scale. The trend of aerosol types EC in the vertical profile was estimated using Sen's slope estimator. Moreover a Pearson's correlation was employed to assess the link between climatic factors (temperature, pressure and relative humidity) and aerosol types EC. It is found that smoke followed by polluted continental have the largest EC levels than dust and polluted dust. The highest level and frequency of dust EC were observed in summer at an average altitude of 0.7 and 4.5 km, respectively in southern Iran. The highest level and greatest frequency of polluted continental were detected in summer and winter respectively at an altitude of below 2 km in the southern and northern polluted cities of Iran. The highest level and the greatest frequency of polluted dust EC were recorded in summer in the south of Iran at an average altitude of 4.5 km. Both the maximum smoke EC level and frequency were detected in winter and in the south of Iran at an average altitude of 4 km. A significant decreasing (increasing) trend of dust (polluted continental) EC was observed in spring and summer (summer) at an altitude below 5 (3) km in most regions (northern part) of Iran. Polluted dust showed an increasing trend in spring in most regions at an altitude below 5 km. The correlation between climatic factors and aerosol EC varied according to seasons, altitudes, and aerosol type. The common feature was the positive correlation between aerosol types EC and relative humidity in most regions, seasons and altitudes. In the final step, six polluted cities were analyzed for aerosol's trend and the correlations.