Spatial Variation of Aerosol Optical Depth and Solar Irradiance over Delhi -NCR During Summer Season

Present study shows the spatial variation of Aerosol Optical Depth (AOD), solar irradiance and their association at the urban and rural sites in Delhi and National Capital Region (NCR) during the summer season of the year 2015. Summer-time AOD data from the NASA’s Terra satellite MODIS sensor has been used to study the spatial distribution of aerosols over Delhi and its surrounding rural area. The ground data for the direct and global solar irradiances was collected over this region at urban and rural locations in Delhi and NCR using a Fieldspec Spectro-radiometer. HYSPLIT model has been used for the air mass trajectory analysis. The AOD values were observed to be higher over Delhi compared to the relatively lower AOD in rural area of NCR. The NCR site observed higher average solar irradiances than Delhi during the summer season. This may be because of the higher aerosol concentration in Delhi as compared to its outskirts. Also, this region is affected by the severe dust storm events during the summer season which further increases the aerosol load in the atmosphere. HYSPLIT results show the influence of western Thar Desert air masses on the Delhi-NCR. Windblown as well anthropogenic aerosols play a major role in scattering and absorption of the incoming solar radiation and hence, in governing the micro-climatology of the region.