SEASONAL VARIABILITY OF AEROSOL OVER VARIOUS CITIES OF PAKISTAN

This study simulates seasonal and temporal variations in aerosol optical depth (AOD) over various regions of Pakistan using Moderate Resolution Imaging Spectroradiometer (MODIS) data during the period (2001-2011). The obtained result indicated seasonal variation in AOD with high value of 2.3, in summer and low values of 0.2, in winter for the costal part of the region. Angstrom exponent has been found to be high (> 0.61) during winter season, indicating higher abundance of fine particles. The maximum annual mean AOD value of 2.3 with the corresponding Angstrom exponent value of 0.4 was found for Karachi, while the minimum annual mean AOD value < 0.7 with the corresponding Angstrom exponent value of > 0.15 was recorded for the northern region of the country during summer season. The HYSPLIT model showed that air masses arrived Pakistan from Afghanistan, Iran, Thar desert, Saudi Arabia and Sahara deserts, and subsequently passed over the various locations in Pakistan.

Keywords:

Aerosol , AOD , Angstrom Exponent , HYSPLIT , Pakistan