Seasonal variation and classification of aerosols over an inland station in India



Aerosols are capable of interfering with the radiation balance and cloud properties of the Earth-atmosphere system. The present study analyses and classifies the aerosol properties over a station, Kanpur, located in the Gangetic plain, which is the area with maximum aerosol loading in Indian subcontinent. Kanpur is one of the highly populated and industrialized cities in north India and is a good source of natural and anthropogenic aerosols. The analysis of aerosol characteristics reveals that aerosol loading is highest during the months of May to June and November to January. Accumulation mode aerosols (mainly of anthropogenic origin) dominate over coarse mode aerosols in the winter and post-monsoon seasons. During the summer, coarse mode aerosols dominate in the atmosphere. A comparison of sunphotometer data with satellite data shows lowest correlation during monsoon season. The satellite derived aerosol optical depth is overestimated during the monsoon season. Atmospheric aerosols are grouped and classified into different clusters according to their optical and microphysical properties. Three clusters were identified and defined according to features of the location and aerosol microphysical properties over the station. The classified clusters are defined as: (1) urban fine aerosols; (2) heavy pollution, and, (3) urban mixed aerosols. Of these heavy pollution episodes occur least and urban fine aerosols are observed at the highest number of occurrence. Wind has significant impact in the determination of local aerosol properties by advection of the particles from other locations and enhancing dust storm activities. Copyright © 2012 Royal Meteorological Society