Spatio temporal behavior of AOD over Pakistan using MODIS data

Aerosols are solid or liquid particles suspended in the atmosphere coming from both natural and anthropogenic sources, they are distributed through wind currents to the places even where they are not formed. Hence, atmospheric aerosols have varying spatial and temporal concentration on both regional and global scale. They play a very vital role in regulating climate by modifying earth´s radiative budget through the absorption and scattering of solar radiations. Moreover it also affects environmental status of region at both local and regional scale like visibility and air pollution. Satellite remote sensing is a potential source for monitoring air pollution. In order to access aerosol volume concentration over Pakistan at temporal and spatial scale, attribute data from Terra-MODIS satellite for AOD550 nm was downloaded for years 2007-2011. Maps were generated to identify hotspots by using Arc GIS 9.3 for the time scale of 2007-2011. Furthermore, backward trajectories were also calculated from NOAA HYSPLIT model at the height of 500, 1000, and 1500 meter for different locations over Pakistan. It was observed that aerosol concentration of coarse mode particles increases in the season of monsoon due to high dust storm frequency, burning activities in the agricultural fields of Pakistan and India (Indian Gigantic Plain) and due to the transportation of particles from the neighboring countries. It was observed that 2008 was highly polluted year as it had the highest concentration of aerosols throughout the year. Aerosol optical density (AOD) values and visibility was plotted and it was observed that it reduced considerably in years 2007-2011 with increasing AOD concentration.